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Kaziūnienė J, Pini F, Shamshitov A, Razbadauskienė K, Frercks B, Gegeckas A, Mažylytė R, Lapinskienė L, Supronienė S. Genetic Characterization of Rhizobium spp. Strains in an Organic Field Pea ( Pisum sativum L.) Field in Lithuania. PLANTS (BASEL, SWITZERLAND) 2024; 13:1888. [PMID: 39065414 PMCID: PMC11280047 DOI: 10.3390/plants13141888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2024] [Revised: 07/03/2024] [Accepted: 07/06/2024] [Indexed: 07/28/2024]
Abstract
Biological nitrogen fixation in legume plants depends on the diversity of rhizobia present in the soil. Rhizobial strains exhibit specificity towards host plants and vary in their capacity to fix nitrogen. The increasing interest in rhizobia diversity has prompted studies of their phylogenetic relations. Molecular identification of Rhizobium is quite complex, requiring multiple gene markers to be analysed to distinguish strains at the species level or to predict their host plant. In this research, 50 rhizobia isolates were obtained from the root nodules of five different Pisum sativum L. genotypes ("Bagoo", "Respect", "Astronaute", "Lina DS", and "Egle DS"). All genotypes were growing in the same field, where ecological farming practices were applied, and no commercial rhizobia inoculants were used. The influence of rhizobial isolates on pea root nodulation and dry biomass accumulation was determined. 16S rRNA gene, two housekeeping genes recA and atpD, and symbiotic gene nodC were analysed to characterize rhizobia population. The phylogenetic analysis of 16S rRNA gene sequences showed that 46 isolates were linked to Rhizobium leguminosarum; species complex 1 isolate was identified as Rhizobium nepotum, and the remaining 3 isolates belonged to Rahnella spp., Paenarthrobacter spp., and Peribacillus spp. genera. RecA and atpD gene analysis showed that the 46 isolates identified as R. leguminosarum clustered into three genospecies groups (B), (E) and (K). Isolates that had the highest influence on plant dry biomass accumulation clustered into the (B) group. NodC gene phylogenetic analysis clustered 46 R. leguminosarum isolates into 10 groups, and all isolates were assigned to the R. leguminosarum sv. viciae.
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Affiliation(s)
- Justina Kaziūnienė
- Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, LT-58344 Akademija, Lithuania (S.S.)
| | - Francesco Pini
- Department of Biology, University of Bari Aldo Moro, 70125 Bari, Italy
| | - Arman Shamshitov
- Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, LT-58344 Akademija, Lithuania (S.S.)
| | - Kristyna Razbadauskienė
- Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, LT-58344 Akademija, Lithuania (S.S.)
| | - Birutė Frercks
- Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Kaunas Str. 30, LT-54333 Babtai, Lithuania
| | - Audrius Gegeckas
- Life Sciences Center, Institute of Biosciences, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Raimonda Mažylytė
- Life Sciences Center, Institute of Biosciences, Vilnius University, LT-10257 Vilnius, Lithuania
| | - Laura Lapinskienė
- Department of Biology, Faculty of Natural Sciences, Vytautas Magnus University, 53361 Kaunas, Lithuania
| | - Skaidrė Supronienė
- Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry, LT-58344 Akademija, Lithuania (S.S.)
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Zhuang Y, Wang H, Tan F, Wu B, Liu L, Qin H, Yang Z, He M. Rhizosphere metabolic cross-talk from plant-soil-microbe tapping into agricultural sustainability: Current advance and perspectives. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 210:108619. [PMID: 38604013 DOI: 10.1016/j.plaphy.2024.108619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 03/21/2024] [Accepted: 04/08/2024] [Indexed: 04/13/2024]
Abstract
Rhizosphere interactions from plant-soil-microbiome occur dynamically all the time in the "black microzone" underground, where we can't see intuitively. Rhizosphere metabolites including root exudates and microbial metabolites act as various chemical signalings involving in rhizosphere interactions, and play vital roles on plant growth, development, disease suppression and resistance to stress conditions as well as proper soil health. Although rhizosphere metabolites are a mixture from plant roots and soil microbes, they often are discussed alone. As a rapid appearance of various omics platforms and analytical methods, it offers possibilities and opportunities for exploring rhizosphere interactions in unprecedented breadth and depth. However, our comprehensive understanding about the fine-tuning mechanisms of rhizosphere interactions mediated by these chemical compounds still remain clear. Thus, this review summarizes recent advances systemically including the features of rhizosphere metabolites and their effects on rhizosphere ecosystem, and looks forward to the future research perspectives, which contributes to facilitating better understanding of biochemical communications belowground and helping identify novel rhizosphere metabolites. We also address challenges for promoting the understanding about the roles of rhizosphere metabolites in different environmental stresses.
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Affiliation(s)
- Yong Zhuang
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China.
| | - Hao Wang
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - Furong Tan
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - Bo Wu
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - Linpei Liu
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - Han Qin
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - ZhiJuan Yang
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China
| | - Mingxiong He
- Biogas Institute of Ministry of Agriculture and Rural Affairs, Chinese Academy of Agricultural Sciences, 610041, Chengdu, China.
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Cho A, Joshi A, Hur HG, Lee JH. Nodulation Experiment by Cross-Inoculation of Nitrogen-Fixing Bacteria Isolated from Root Nodules of Several Leguminous Plants. J Microbiol Biotechnol 2024; 34:570-579. [PMID: 38213271 PMCID: PMC11016771 DOI: 10.4014/jmb.2310.10025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Revised: 12/13/2023] [Accepted: 12/21/2023] [Indexed: 01/13/2024]
Abstract
Root-nodule nitrogen-fixing bacteria are known for being specific to particular legumes. This study isolated the endophytic root-nodule bacteria from the nodules of legumes and examined them to determine whether they could be used to promote the formation of nodules in other legumes. Forty-six isolates were collected from five leguminous plants and screened for housekeeping (16S rRNA), nitrogen fixation (nifH), and nodulation (nodC) genes. Based on the 16S rRNA gene sequencing and phylogenetic analysis, the bacterial isolates WC15, WC16, WC24, and GM5 were identified as Rhizobium, Sphingomonas, Methylobacterium, and Bradyrhizobium, respectively. The four isolates were found to have the nifH gene, and the study confirmed that one isolate (GM5) had both the nifH and nodC genes. The Salkowski method was used to measure the isolated bacteria for their capacity to produce phytohormone indole acetic acid (IAA). Additional experiments were performed to examine the effect of the isolated bacteria on root morphology and nodulation. Among the four tested isolates, both WC24 and GM5 induced nodulation in Glycine max. The gene expression studies revealed that GM5 had a higher expression of the nifH gene. The existence and expression of the nitrogen-fixing genes implied that the tested strain had the ability to fix the atmospheric nitrogen. These findings demonstrated that a nitrogen-fixing bacterium, Methylobacterium (WC24), isolated from a Trifolium repens, induced the formation of root nodules in non-host leguminous plants (Glycine max). This suggested the potential application of these rhizobia as biofertilizer. Further studies are required to verify the N2-fixing efficiency of the isolates.
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Affiliation(s)
- Ahyeon Cho
- Department of Agricultural Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
| | - Alpana Joshi
- Department of Bioenvironmental Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
- Department of Agriculture Technology & Agri-Informatics, Shobhit Institute of Engineering & Technology, Meerut 250110, India
| | - Hor-Gil Hur
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 61005, Republic of Korea
| | - Ji-Hoon Lee
- Department of Agricultural Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
- Department of Bioenvironmental Chemistry, Jeonbuk National University, Jeonju 54896, Republic of Korea
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4
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Ghosh P, Chakraborty J. Exploring the role of symbiotic modifier peptidases in the legume - rhizobium symbiosis. Arch Microbiol 2024; 206:147. [PMID: 38462552 DOI: 10.1007/s00203-024-03920-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 02/27/2024] [Accepted: 02/28/2024] [Indexed: 03/12/2024]
Abstract
Legumes can establish a mutual association with soil-derived nitrogen-fixing bacteria called 'rhizobia' forming lateral root organs called root nodules. Rhizobia inside the root nodules get transformed into 'bacteroids' that can fix atmospheric nitrogen to ammonia for host plants in return for nutrients and shelter. A substantial 200 million tons of nitrogen is fixed annually through biological nitrogen fixation. Consequently, the symbiotic mechanism of nitrogen fixation is utilized worldwide for sustainable agriculture and plays a crucial role in the Earth's ecosystem. The development of effective nitrogen-fixing symbiosis between legumes and rhizobia is very specialized and requires coordinated signaling. A plethora of plant-derived nodule-specific cysteine-rich (NCR or NCR-like) peptides get actively involved in this complex and tightly regulated signaling process of symbiosis between some legumes of the IRLC (Inverted Repeat-Lacking Clade) and Dalbergioid clades and nitrogen-fixing rhizobia. Recent progress has been made in identifying two such peptidases that actively prevent bacterial differentiation, leading to symbiotic incompatibility. In this review, we outlined the functions of NCRs and two nitrogen-fixing blocking peptidases: HrrP (host range restriction peptidase) and SapA (symbiosis-associated peptidase A). SapA was identified through an overexpression screen from the Sinorhizobium meliloti 1021 core genome, whereas HrrP is inherited extra-chromosomally. Interestingly, both peptidases affect the symbiotic outcome by degrading the NCR peptides generated from the host plants. These NCR-degrading peptidases can shed light on symbiotic incompatibility, helping to elucidate the reasons behind the inefficiency of nitrogen fixation observed in certain groups of rhizobia with specific legumes.
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Affiliation(s)
- Prithwi Ghosh
- Department of Botany, Narajole Raj College, Vidyasagar University, Midnapore, 721211, India.
| | - Joydeep Chakraborty
- School of Plant Sciences and Food Security, Tel Aviv University, Tel-Aviv, Israel
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Knights HE, Ramachandran VK, Jorrin B, Ledermann R, Parsons JD, Aroney STN, Poole PS. Rhizobium determinants of rhizosphere persistence and root colonization. THE ISME JOURNAL 2024; 18:wrae072. [PMID: 38690786 PMCID: PMC11103875 DOI: 10.1093/ismejo/wrae072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 04/16/2024] [Accepted: 04/23/2024] [Indexed: 05/03/2024]
Abstract
Bacterial persistence in the rhizosphere and colonization of root niches are critical for the establishment of many beneficial plant-bacteria interactions including those between Rhizobium leguminosarum and its host legumes. Despite this, most studies on R. leguminosarum have focused on its symbiotic lifestyle as an endosymbiont in root nodules. Here, we use random barcode transposon sequencing to assay gene contributions of R. leguminosarum during competitive growth in the rhizosphere and colonization of various plant species. This facilitated the identification of 189 genes commonly required for growth in diverse plant rhizospheres, mutation of 111 of which also affected subsequent root colonization (rhizosphere progressive), and a further 119 genes necessary for colonization. Common determinants reveal a need to synthesize essential compounds (amino acids, ribonucleotides, and cofactors), adapt metabolic function, respond to external stimuli, and withstand various stresses (such as changes in osmolarity). Additionally, chemotaxis and flagella-mediated motility are prerequisites for root colonization. Many genes showed plant-specific dependencies highlighting significant adaptation to different plant species. This work provides a greater understanding of factors promoting rhizosphere fitness and root colonization in plant-beneficial bacteria, facilitating their exploitation for agricultural benefit.
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Affiliation(s)
- Hayley E Knights
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
| | | | - Beatriz Jorrin
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Raphael Ledermann
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Jack D Parsons
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Samuel T N Aroney
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
| | - Philip S Poole
- Department of Biology, University of Oxford, Oxford OX1 3RB, United Kingdom
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Aoki N, Shimasaki T, Yazaki W, Sato T, Nakayasu M, Ando A, Kishino S, Ogawa J, Masuda S, Shibata A, Shirasu K, Yazaki K, Sugiyama A. An isoflavone catabolism gene cluster underlying interkingdom interactions in the soybean rhizosphere. ISME COMMUNICATIONS 2024; 4:ycae052. [PMID: 38707841 PMCID: PMC11069340 DOI: 10.1093/ismeco/ycae052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/19/2024] [Accepted: 04/03/2024] [Indexed: 05/07/2024]
Abstract
Plant roots secrete various metabolites, including plant specialized metabolites, into the rhizosphere, and shape the rhizosphere microbiome, which is crucial for the plant health and growth. Isoflavones are major plant specialized metabolites found in legume plants, and are involved in interactions with soil microorganisms as initiation signals in rhizobial symbiosis and as modulators of the legume root microbiota. However, it remains largely unknown the molecular basis underlying the isoflavone-mediated interkingdom interactions in the legume rhizosphere. Here, we isolated Variovorax sp. strain V35, a member of the Comamonadaceae that harbors isoflavone-degrading activity, from soybean roots and discovered a gene cluster responsible for isoflavone degradation named ifc. The characterization of ifc mutants and heterologously expressed Ifc enzymes revealed that isoflavones undergo oxidative catabolism, which is different from the reductive metabolic pathways observed in gut microbiota. We further demonstrated that the ifc genes are frequently found in bacterial strains isolated from legume plants, including mutualistic rhizobia, and contribute to the detoxification of the antibacterial activity of isoflavones. Taken together, our findings reveal an isoflavone catabolism gene cluster in the soybean root microbiota, providing molecular insights into isoflavone-mediated legume-microbiota interactions.
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Affiliation(s)
- Noritaka Aoki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tomohisa Shimasaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
- Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Wataru Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Tomoaki Sato
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Masaru Nakayasu
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Akinori Ando
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Shigenobu Kishino
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Jun Ogawa
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan
| | - Sachiko Masuda
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Arisa Shibata
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Ken Shirasu
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, Yokohama, Kanagawa 230-0045, Japan
| | - Kazufumi Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Akifumi Sugiyama
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
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Shumilina J, Soboleva A, Abakumov E, Shtark OY, Zhukov VA, Frolov A. Signaling in Legume-Rhizobia Symbiosis. Int J Mol Sci 2023; 24:17397. [PMID: 38139226 PMCID: PMC10743482 DOI: 10.3390/ijms242417397] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Revised: 11/19/2023] [Accepted: 12/02/2023] [Indexed: 12/24/2023] Open
Abstract
Legumes represent an important source of food protein for human nutrition and animal feed. Therefore, sustainable production of legume crops is an issue of global importance. It is well-known that legume-rhizobia symbiosis allows an increase in the productivity and resilience of legume crops. The efficiency of this mutualistic association strongly depends on precise regulation of the complex interactions between plant and rhizobia. Their molecular dialogue represents a complex multi-staged process, each step of which is critically important for the overall success of the symbiosis. In particular, understanding the details of the molecular mechanisms behind the nodule formation and functioning might give access to new legume cultivars with improved crop productivity. Therefore, here we provide a comprehensive literature overview on the dynamics of the signaling network underlying the development of the legume-rhizobia symbiosis. Thereby, we pay special attention to the new findings in the field, as well as the principal directions of the current and prospective research. For this, here we comprehensively address the principal signaling events involved in the nodule inception, development, functioning, and senescence.
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Affiliation(s)
- Julia Shumilina
- Laboratory of Analytical Biochemistry and Biotechnology, Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia; (J.S.); (A.S.)
| | - Alena Soboleva
- Laboratory of Analytical Biochemistry and Biotechnology, Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia; (J.S.); (A.S.)
- Biological Faculty, Saint Petersburg State University, 199034 St. Petersburg, Russia;
| | - Evgeny Abakumov
- Biological Faculty, Saint Petersburg State University, 199034 St. Petersburg, Russia;
| | - Oksana Y. Shtark
- Laboratory of Genetics of Plant-Microbe Interactions, All-Russia Research Institute for Agricultural Microbiology, 196608 St. Petersburg, Russia; (O.Y.S.); (V.A.Z.)
| | - Vladimir A. Zhukov
- Laboratory of Genetics of Plant-Microbe Interactions, All-Russia Research Institute for Agricultural Microbiology, 196608 St. Petersburg, Russia; (O.Y.S.); (V.A.Z.)
| | - Andrej Frolov
- Laboratory of Analytical Biochemistry and Biotechnology, Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127276 Moscow, Russia; (J.S.); (A.S.)
- Biological Faculty, Saint Petersburg State University, 199034 St. Petersburg, Russia;
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8
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Li Y, Wu Y, Yang Z, Shi R, Zhang L, Feng Z, Wei G, Chou M. The Rpf107 gene, a homolog of LOR, is required for the symbiotic nodulation of Robinia pseudoacacia. PLANTA 2023; 259:6. [PMID: 38001306 DOI: 10.1007/s00425-023-04280-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 11/03/2023] [Indexed: 11/26/2023]
Abstract
MAIN CONCLUSION Rpf107 is involved in the infection process of rhizobia and the maintenance of symbiotic nitrogen fixation in black locust root nodules. The LURP-one related (LOR) protein family plays a pivotal role in mediating plant defense responses against both biotic and abiotic stresses. However, our understanding of its function in the symbiotic interaction between legumes and rhizobia remains limited. Here, Rpf107, a homolog of LOR, was identified in Robinia pseudoacacia (black locust). The subcellular localization of Rpf107 was analyzed, and its function was investigated using RNA interference (RNAi) and overexpression techniques. The subcellular localization assay revealed that Rpf107 was mainly distributed in the plasma membrane and nucleus. Rpf107 silencing prevented rhizobial infection and hampered plant growth. The number of infected cells in the nitrogen fixation zone of the Rpf107-RNAi nodules was also noticeably lower than that in the control nodules. Notably, Rpf107 silencing resulted in bacteroid degradation and the premature aging of nodules. In contrast, the overexpression of Rpf107 delayed the senescence of nodules and prolonged the nitrogen-fixing ability of nodules. These results demonstrate that Rpf107 was involved in the infection of rhizobia and the maintenance of symbiotic nitrogen fixation in black locust root nodules. The findings reveal that a member of the LOR protein family plays a role in leguminous root nodule symbiosis, which is helpful to clarify the functions of plant LOR protein family and fully understand the molecular mechanisms underlying legume-rhizobium symbiosis.
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Affiliation(s)
- Yuanli Li
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Yuanyuan Wu
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
- Xiangyang Public Inspection and Testing Center, No.69, Taiziwan Road, Xiangyang, 441000, Hubei Province, People's Republic of China
| | - Ziyi Yang
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Rui Shi
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Lu Zhang
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Zhao Feng
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Gehong Wei
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China
| | - Minxia Chou
- State Key Laboratory for Crop Stress Resistance and High-Efficiency Production, College of Life Sciences, Northwest A&F University, 3 Taicheng Road, Yangling, 712100, Shaanxi, People's Republic of China.
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9
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Van Cauwenberghe J, Simms EL. How might bacteriophages shape biological invasions? mBio 2023; 14:e0188623. [PMID: 37812005 PMCID: PMC10653932 DOI: 10.1128/mbio.01886-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/10/2023] Open
Abstract
Invasions by eukaryotes dependent on environmentally acquired bacterial mutualists are often limited by the ability of bacterial partners to survive and establish free-living populations. Focusing on the model legume-rhizobium mutualism, we apply invasion biology hypotheses to explain how bacteriophages can impact the competitiveness of introduced bacterial mutualists. Predicting how phage-bacteria interactions affect invading eukaryotic hosts requires knowing the eco-evolutionary constraints of introduced and native microbial communities, as well as their differences in abundance and diversity. By synthesizing research from invasion biology, as well as bacterial, viral, and community ecology, we create a conceptual framework for understanding and predicting how phages can affect biological invasions through their effects on bacterial mutualists.
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Affiliation(s)
- Jannick Van Cauwenberghe
- Institute of Biodiversity, Faculty of Biological Sciences, Cluster of Excellence Balance of the Microverse, Friedrich Schiller University Jena, Jena, Germany
- Department of Integrative Biology, University of California, Berkeley, California, USA
| | - Ellen L. Simms
- Department of Integrative Biology, University of California, Berkeley, California, USA
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Tang Z, Cai S, Liu Y, Li D, Xie F, Lin H, Chen D, Li Y. A Lipopolysaccharide O-Antigen Synthesis Gene in Mesorhizobium huakuii Plays Differentiated Roles in Root Nodule Symbiotic Compatibility with Astragalus sinicus. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2023; 36:623-635. [PMID: 37366577 DOI: 10.1094/mpmi-05-23-0066-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Lipopolysaccharide (LPS) is a ubiquitous microbial-associated molecular pattern. Plants can sense the three components of LPS, including core polysaccharide, lipid A, and O-antigen. LPS biosynthesis is an essential factor for the successful establishment of symbiosis in the rhizobium-legume plant system. The MCHK_1752 gene (Mesorhizobium huakuii 7653R gene) encodes O-antigen polymerase and affects the synthesis of O-antigen. Here, we investigated the symbiotic phenotypes of six Astragalus sinicus accessions inoculated with the MCHK_1752 deletion mutant strain. The results revealed that the MCHK_1752 deletion mutant strain had a suppressing effect on the symbiotic nitrogen fixation of two A. sinicus accessions, a promoting effect in three A. sinicus accessions, and no significant effect in one A. sinicus accessions. In addition, the effect of MCHK_1752 on the phenotype was confirmed by its complementary strains and LPS exogenous application. Deletion of MCHK_1752 showed no effect on the growth of a strain, but affected biofilm formation and led to higher susceptibility to stress in a strain. At the early symbiotic stage, Xinzi formed more infection threads and nodule primordia than Shengzhong under inoculation with the mutant, which might be an important reason for the final symbiotic phenotype. A comparison of early transcriptome data between Xinzi and Shengzhong also confirmed the phenotype at the early symbiotic stage. Our results suggest that O-antigen synthesis genes influence symbiotic compatibility during symbiotic nitrogen fixation. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Zhide Tang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Shuyun Cai
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Yuan Liu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Dongzhi Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Fuli Xie
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Hui Lin
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Dasong Chen
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
| | - Youguo Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, People's Republic of China
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Zhang J, Wang N, Li S, Wang J, Feng Y, Wang E, Li Y, Yang T, Chen W. The Effect of Different Rhizobial Symbionts on the Composition and Diversity of Rhizosphere Microorganisms of Chickpea in Different Soils. PLANTS (BASEL, SWITZERLAND) 2023; 12:3421. [PMID: 37836161 PMCID: PMC10575130 DOI: 10.3390/plants12193421] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 09/22/2023] [Accepted: 09/22/2023] [Indexed: 10/15/2023]
Abstract
BACKGROUND Chickpea (Cicer arietinum L.) is currently the third most important legume crop in the world. It could form root nodules with its symbiotic rhizobia in soils and perform bio-nitrogen fixation. Mesorhizobium ciceri is a prevalent species in the world, except China, where Mesorhizobium muleiense is the main species associated with chickpea. There were significant differences in the competitive ability between M. ciceri and M. muleiense in sterilized and unsterilized soils collected from Xinjiang, China, where chickpea has been grown long term. In unsterilized soils, M. muleiense was more competitive than M. ciceri, while in sterilized soils, the opposite was the case. In addition, the competitive ability of M. ciceri in soils of new areas of chickpea cultivation was significantly higher than that of M. muleiense. It was speculated that there might be some biological factors in Xinjiang soils of China that could differentially affect the competitive nodulation of these two chickpea rhizobia. To address this question, we compared the composition and diversity of microorganisms in the rhizosphere of chickpea inoculated separately with the above two rhizobial species in soils from old and new chickpea-producing regions. RESULTS Chickpea rhizosphere microbial diversity and composition varied in different areas and were affected significantly due to rhizobial inoculation. In general, eight dominant phyla with 34 dominant genera and 10 dominant phyla with 47 dominant genera were detected in the rhizosphere of chickpea grown in soils of Xinjiang and of the new zones, respectively, with the inoculated rhizobia. Proteobacteria and Actinobacteria were dominant at the phylum level in the rhizosphere of all soils. Pseudomonas appeared significantly enriched after inoculation with M. muleiense in soils from Xinjiang, a phenomenon not found in the new areas of chickpea cultivation, demonstrating that Pseudomonas might be the key biological factor affecting the competitive colonization of M. muleiense and M. ciceri there. CONCLUSIONS Different chickpea rhizobial inoculations of M. muleiense and M. ciceri affected the rhizosphere microbial composition in different sampling soils from different chickpea planting areas. Through high throughput sequencing and statistical analysis, it could be found that Pseudomonas might be the key microorganism influencing the competitive nodulation of different chickpea rhizobia in different soils, as it is the dominant non-rhizobia community in Xinjiang rhizosphere soils, but not in other areas.
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Affiliation(s)
- Junjie Zhang
- College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China
- Collaborative Innovation Center for Food Production and Safety of Henan Province, Zhengzhou 450002, China
| | - Nan Wang
- College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China
| | - Shuo Li
- College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China
| | - Jingqi Wang
- College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China
| | - Yufeng Feng
- College of Food and Bioengineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Ciudad de Mexico C.P. 11340, Mexico
| | - Youguo Li
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Tao Yang
- Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Wenfeng Chen
- College of Biological Sciences, Rhizobium Research Center, China Agricultural University, Beijing 100193, China
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12
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Rahman A, Manci M, Nadon C, Perez IA, Farsamin WF, Lampe MT, Le TH, Torres Martínez L, Weisberg AJ, Chang JH, Sachs JL. Competitive interference among rhizobia reduces benefits to hosts. Curr Biol 2023; 33:2988-3001.e4. [PMID: 37490853 DOI: 10.1016/j.cub.2023.06.081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 03/31/2023] [Accepted: 06/29/2023] [Indexed: 07/27/2023]
Abstract
The capacity of beneficial microbes to compete for host infection-and the ability of hosts to discriminate among them-introduces evolutionary conflict that is predicted to destabilize mutualism. We investigated fitness outcomes in associations between legumes and their symbiotic rhizobia to characterize fitness impacts of microbial competition. Diverse Bradyrhizobium strains varying in their capacity to fix nitrogen symbiotically with a common host plant, Acmispon strigosus, were tested in full-factorial coinoculation experiments involving 28 pairwise strain combinations. We analyzed the effects of interstrain competition and host discrimination on symbiotic-interaction outcomes by relativizing fitness proxies to clonally infected and uninfected controls. More than one thousand root nodules of coinoculated plants were genotyped to quantify strain occupancy, and the Bradyrhizobium strain genome sequences were analyzed to uncover the genetic bases of interstrain competition outcomes. Strikingly, interstrain competition favored a fast-growing, minimally beneficial rhizobia strain. Host benefits were significantly diminished in coinoculation treatments relative to expectations from clonally inoculated controls, consistent with competitive interference among rhizobia that reduced both nodulation and plant growth. Competition traits appear polygenic, linked with inter-strain allelopathic interactions in the rhizosphere. This study confirms that competition among strains can destabilize mutualism by favoring microbes that are superior in colonizing host tissues but provide minimal benefits to host plants. Moreover, our findings help resolve the paradox that despite efficient host control post infection, legumes nonetheless encounter rhizobia that vary in their nitrogen fixation.
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Affiliation(s)
- Arafat Rahman
- Institute of Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Max Manci
- Department of Microbiology & Plant Pathology, University of California, Riverside, Riverside, CA 92521, USA
| | - Cassandra Nadon
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Ivan A Perez
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Warisha F Farsamin
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Matthew T Lampe
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Tram H Le
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA
| | - Lorena Torres Martínez
- Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA; Department of Biology, St. Mary's College of Maryland, St. Mary's City, MD 20686, USA
| | - Alexandra J Weisberg
- Department of Botany & Plant Pathology, Oregon State University, Corvallis, OR 97331, USA
| | - Jeff H Chang
- Department of Botany & Plant Pathology, Oregon State University, Corvallis, OR 97331, USA
| | - Joel L Sachs
- Institute of Integrative Genome Biology, University of California, Riverside, Riverside, CA 92521, USA; Department of Microbiology & Plant Pathology, University of California, Riverside, Riverside, CA 92521, USA; Department of Evolution Ecology & Organismal Biology, University of California, Riverside, Riverside, CA 92521, USA.
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13
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Li Y, Wang C, Zheng L, Ma W, Li M, Guo Z, Zhao Q, Zhang K, Liu R, Liu Y, Tian Z, Bai Y, Zhong Y, Liao H. Natural variation of GmRj2/Rfg1 determines symbiont differentiation in soybean. Curr Biol 2023; 33:2478-2490.e5. [PMID: 37301200 DOI: 10.1016/j.cub.2023.05.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 04/17/2023] [Accepted: 05/16/2023] [Indexed: 06/12/2023]
Abstract
Symbiotic nitrogen fixation (SNF) provides much of the N utilized by leguminous plants throughout growth and development. Legumes may simultaneously establish symbiosis with different taxa of microbial symbionts. Yet, the mechanisms used to steer associations toward symbionts that are most propitious across variations in soil types remain mysterious. Here, we demonstrate that GmRj2/Rfg1 is responsible for regulating symbiosis with multiple taxa of soybean symbionts. In our experiments, the GmRj2/Rfg1SC haplotype favored association with Bradyrhizobia, which is mostly distributed in acid soils, whereas the GmRj2/Rfg1HH haplotype and knockout mutants of GmRj2/Rfg1SC associated equally with Bradyrhizobia and Sinorhizobium. Association between GmRj2/Rfg1 and NopP, furthermore, appeared to be involved in symbiont selection. Furthermore, geographic distribution analysis of 1,821 soybean accessions showed that GmRj2/Rfg1SC haplotypes were enriched in acidic soils where Bradyrhizobia were the dominant symbionts, whereas GmRj2/Rfg1HH haplotypes were most prevalent in alkaline soils dominated by Sinorhizobium, and neutral soils harbored no apparent predilections toward either haplotype. Taken together, our results suggest that GmRj2/Rfg1 regulates symbiosis with different symbionts and is a strong determinant of soybean adaptability across soil regions. As a consequence, the manipulation of the GmRj2/Rfg1 genotype or application of suitable symbionts according to the haplotype at the GmRj2/Rfg1 locus might be suitable strategies to explore for increasing soybean yield through the management of SNF.
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Affiliation(s)
- Yanjun Li
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Cunhu Wang
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Lei Zheng
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Wenjing Ma
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Mingjia Li
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Zilong Guo
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Qingsong Zhao
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Kefei Zhang
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Ran Liu
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
| | - Yucheng Liu
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China
| | - Zhixi Tian
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Innovative Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yang Bai
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China; CAS-JIC Centre of Excellence for Plant and Microbial Science, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongjia Zhong
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
| | - Hong Liao
- Root Biology Center, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China
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14
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A Germin-Like Protein GLP1 of Legumes Mediates Symbiotic Nodulation by Interacting with an Outer Membrane Protein of Rhizobia. Microbiol Spectr 2023; 11:e0335022. [PMID: 36633436 PMCID: PMC9927233 DOI: 10.1128/spectrum.03350-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Rhizobia can infect legumes and induce the coordinated expression of symbiosis and defense genes for the establishment of mutualistic symbiosis. Numerous studies have elucidated the molecular interactions between rhizobia and host plants, which are associated with Nod factor, exopolysaccharide, and T3SS effector proteins. However, there have been relatively few reports about how the host plant recognizes the outer membrane proteins (OMPs) of rhizobia to mediate symbiotic nodulation. In our previous work, a gene (Mhopa22) encoding an OMP was identified in Mesorhizobium huakuii 7653R, whose homologous genes are widely distributed in Rhizobiales. In this study, a germin-like protein GLP1 interacting with Mhopa22 was identified in Astragalus sinicus. RNA interference of AsGLP1 resulted in a decrease in nodule number, whereas overexpression of AsGLP1 increased the number of nodules in the hairy roots of A. sinicus. Consistent symbiotic phenotypes were identified in Medicago truncatula with MtGLPx (refer to medtr7g111240.1, the isogeny of AsGLP1) overexpression or Tnt1 mutant (glpx-1) in symbiosis with Sinorhizobium meliloti 1021. The glpx-1 mutant displayed hyperinfection and the formation of more infection threads but a decrease in root nodules. RNA sequencing analysis showed that many differentially expressed genes were involved in hormone signaling and symbiosis. Taken together, AsGLP1 and its homology play an essential role in mediating the early symbiotic process through interacting with the OMPs of rhizobia. IMPORTANCE This study is the first report to characterize a legume host plant protein to sense and interact with an outer membrane protein (OMP) of rhizobia. It can be speculated that GLP1 plays an essential role to mediate early symbiotic process through interacting with OMPs of rhizobia. The results provide deeper understanding and novel insights into the molecular interactive mechanism of a legume symbiosis signaling pathway in recognition with rhizobial OMPs. Our findings may also provide a new perspective to improve the symbiotic compatibility and nodulation of legume.
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15
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Liu Y, Lin Y, Guan N, Song Y, Li Y, Xie X. A Lipopolysaccharide Synthesis Gene rfaD from Mesorhizobium huakuii Is Involved in Nodule Development and Symbiotic Nitrogen Fixation. Microorganisms 2022; 11:microorganisms11010059. [PMID: 36677351 PMCID: PMC9866225 DOI: 10.3390/microorganisms11010059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Revised: 12/21/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022] Open
Abstract
Rhizobium lipopolysaccharide (LPS) is an important component of the cell wall of gram-negative bacteria and serves as a signal molecule on the surface of rhizobia, participating in the symbiosis during rhizobia-legume interaction. In this study, we constructed a deletion mutant of ADP-L-glycerol-D-mannoheptosyl-6-exoisomerase (rfaD) of Mesorhizobium huakuii 7653R and a functional complementary strain. The results showed that the deletion of rfaD did not affect the free-living growth rate of 7653R, but that it did affect the LPS synthesis and that it increased sensitivity to abiotic stresses. The rfaD promoter-GUS reporter assay showed that the gene was mainly expressed in the infection zone of the mature nodules. The root nodules formation of the rfaD mutant was delayed during symbiosis with the host plant of Astragalus sinicus. The symbiotic phenotype analyses showed that the nodules of A. sinicus lost symbiotic nitrogen fixation ability, when inoculated with the rfaD mutant strain. In conclusion, our results reveal that the 7653R rfaD gene plays a crucial role in the LPS synthesis involved in the symbiotic interaction between rhizobia and A. sinicus. This study also provides new insights into the molecular mechanisms by which the rhizobia regulate their own gene expression and cell wall components enabling nodulation in legumes.
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Affiliation(s)
- Yuan Liu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Ye Lin
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Ning Guan
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuting Song
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
| | - Youguo Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China
- Correspondence: (Y.L.); (X.X.); Tel.: +86-127-8728-1685 (Y.L.); +86-159-1855-2425 (X.X.)
| | - Xianan Xie
- State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Laboratory for Lingnan Modern Agriculture, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China
- Correspondence: (Y.L.); (X.X.); Tel.: +86-127-8728-1685 (Y.L.); +86-159-1855-2425 (X.X.)
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16
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Genome-Wide Association Studies across Environmental and Genetic Contexts Reveal Complex Genetic Architecture of Symbiotic Extended Phenotypes. mBio 2022; 13:e0182322. [PMID: 36286519 PMCID: PMC9765617 DOI: 10.1128/mbio.01823-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A goal of modern biology is to develop the genotype-phenotype (G→P) map, a predictive understanding of how genomic information generates trait variation that forms the basis of both natural and managed communities. As microbiome research advances, however, it has become clear that many of these traits are symbiotic extended phenotypes, being governed by genetic variation encoded not only by the host's own genome, but also by the genomes of myriad cryptic symbionts. Building a reliable G→P map therefore requires accounting for the multitude of interacting genes and even genomes involved in symbiosis. Here, we use naturally occurring genetic variation in 191 strains of the model microbial symbiont Sinorhizobium meliloti paired with two genotypes of the host Medicago truncatula in four genome-wide association studies (GWAS) to determine the genomic architecture of a key symbiotic extended phenotype-partner quality, or the fitness benefit conferred to a host by a particular symbiont genotype, within and across environmental contexts and host genotypes. We define three novel categories of loci in rhizobium genomes that must be accounted for if we want to build a reliable G→P map of partner quality; namely, (i) loci whose identities depend on the environment, (ii) those that depend on the host genotype with which rhizobia interact, and (iii) universal loci that are likely important in all or most environments. IMPORTANCE Given the rapid rise of research on how microbiomes can be harnessed to improve host health, understanding the contribution of microbial genetic variation to host phenotypic variation is pressing, and will better enable us to predict the evolution of (and select more precisely for) symbiotic extended phenotypes that impact host health. We uncover extensive context-dependency in both the identity and functions of symbiont loci that control host growth, which makes predicting the genes and pathways important for determining symbiotic outcomes under different conditions more challenging. Despite this context-dependency, we also resolve a core set of universal loci that are likely important in all or most environments, and thus, serve as excellent targets both for genetic engineering and future coevolutionary studies of symbiosis.
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17
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Hamad HS, Bleih EM, Gewaily EE, Abou Elataa AE, El Sherbiny HA, Abdelhameid NM, Rehan M. Cyanobacteria Application Ameliorates Floral Traits and Outcrossing Rate in Diverse Rice Cytoplasmic Male Sterile Lines. PLANTS (BASEL, SWITZERLAND) 2022; 11:plants11243411. [PMID: 36559523 PMCID: PMC9781212 DOI: 10.3390/plants11243411] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/04/2022] [Accepted: 12/05/2022] [Indexed: 05/14/2023]
Abstract
In rice, cytoplasmic male sterility (CMS) represents an irreplaceable strategy for producing high-yielding hybrid rice based on the commercial exploitation of heterosis. Thereupon, enhancing floral traits and outcrossing rates in CMS lines increase hybrid seed production and ensure global food security. The exogenous application of cyanobacteria could enhance outcrossing rates in CMS lines and, accordingly, hybrid rice seed production. In the present study, we aimed at exploring the impact of cyanobacteria implementation such as Anabaena oryzae, Nostoc muscorum, and their mixture to promote the floral traits, outcrossing rates, and seed production in hybrid rice. The impact of cyanobacteria (Anabaena Oryza (T2), Nostoc muscorum (T3), and their combination (T4) versus the untreated control (T1) was investigated for two years on the growth, floral, and yield traits of five diverse CMS lines, namely IR69625A (L1), IR58025A (L2), IR70368A (L3), G46A (L4), and K17A(L5). The evaluated CMS lines exhibited significant differences in all measured floral traits (days to heading (DTH), total stigma length (TSL), stigma width (SW), duration of spikelet opening (DSO), spikelet opening angle (SOA)). Additionally, L4 displayed the uppermost total stigma length and stigma width, whereas L1 and L5 recorded the best duration of spikelet opening and spikelet opening angle. Notably, these mentioned CMS lines exhibited the highest plant growth and yield traits, particularly under T4 treatment. Strong positive relationships were distinguished between the duration of the spikelet opening, panicle exertion, panicle weight, seed set, grain yield, total stigma length, spikelet opening angle, stigma width, and number of fertile panicles per hill. Cyanobacteria is a potential promising tool to increase floral traits and seed production in hybrid rice.
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Affiliation(s)
- Hassan Sh. Hamad
- Rice Research and Training Department, Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
| | - Eman M. Bleih
- Rice Research and Training Department, Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
| | - Elsayed E. Gewaily
- Rice Research and Training Department, Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
| | - Ahmed E. Abou Elataa
- Rice Research and Training Department, Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
| | - Heba A. El Sherbiny
- Rice Research and Training Department, Field Crops Research Institute, Agricultural Research Center, Kafrelsheikh 33717, Egypt
| | - Noha M. Abdelhameid
- Soil Fertility and Microbiology Department, Desert Research Center (DRC), Cairo 11753, Egypt
| | - Medhat Rehan
- Department of Plant Production and Protection, College of Agriculture and Veterinary Medicine, Qassim University, Buraydah 51452, Saudi Arabia
- Department of Genetics, Faculty of Agriculture, Kafrelsheikh University, Kafr El-Sheikh 33516, Egypt
- Correspondence: or
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18
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Zarrabian M, Montiel J, Sandal N, Ferguson S, Jin H, Lin YY, Klingl V, Marín M, James EK, Parniske M, Stougaard J, Andersen SU. A Promiscuity Locus Confers Lotus burttii Nodulation with Rhizobia from Five Different Genera. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:1006-1017. [PMID: 35852471 DOI: 10.1094/mpmi-06-22-0124-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Legumes acquire access to atmospheric nitrogen through nitrogen fixation by rhizobia in root nodules. Rhizobia are soil-dwelling bacteria and there is a tremendous diversity of rhizobial species in different habitats. From the legume perspective, host range is a compromise between the ability to colonize new habitats, in which the preferred symbiotic partner may be absent, and guarding against infection by suboptimal nitrogen fixers. Here, we investigate natural variation in rhizobial host range across Lotus species. We find that Lotus burttii is considerably more promiscuous than Lotus japonicus, represented by the Gifu accession, in its interactions with rhizobia. This promiscuity allows Lotus burttii to form nodules with Mesorhizobium, Rhizobium, Sinorhizobium, Bradyrhizobium, and Allorhizobium species that represent five distinct genera. Using recombinant inbred lines, we have mapped the Gifu/burttii promiscuity quantitative trait loci (QTL) to the same genetic locus regardless of rhizobial genus, suggesting a general genetic mechanism for symbiont-range expansion. The Gifu/burttii QTL now provides an opportunity for genetic and mechanistic understanding of promiscuous legume-rhizobia interactions. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
- Mohammad Zarrabian
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Jesús Montiel
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
- Center for Genomic Sciences, National Autonomous University of Mexico. Cuernavaca, Mexico
| | - Niels Sandal
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Shaun Ferguson
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Haojie Jin
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Yen-Yu Lin
- Faculty of Biology, University of Munich, Großhaderner Straße 2-4, 82152, Planegg-Martinsried, Germany
| | - Verena Klingl
- Faculty of Biology, University of Munich, Großhaderner Straße 2-4, 82152, Planegg-Martinsried, Germany
| | - Macarena Marín
- Faculty of Biology, University of Munich, Großhaderner Straße 2-4, 82152, Planegg-Martinsried, Germany
| | - Euan K James
- The James Hutton Institute, Invergowrie, Dundee DD2 5DA, U.K
| | - Martin Parniske
- Faculty of Biology, University of Munich, Großhaderner Straße 2-4, 82152, Planegg-Martinsried, Germany
| | - Jens Stougaard
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
| | - Stig U Andersen
- Department of Molecular Biology and Genetics, Aarhus University, Denmark
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Dinkins RD, Hancock JA, Bickhart DM, Sullivan ML, Zhu H. Expression and Variation of the Genes Involved in Rhizobium Nodulation in Red Clover. PLANTS (BASEL, SWITZERLAND) 2022; 11:2888. [PMID: 36365339 PMCID: PMC9655500 DOI: 10.3390/plants11212888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 10/21/2022] [Accepted: 10/25/2022] [Indexed: 06/16/2023]
Abstract
Red clover (Trifolium pratense L.) is an important forage crop and serves as a major contributor of nitrogen input in pasture settings because of its ability to fix atmospheric nitrogen. During the legume-rhizobial symbiosis, the host plant undergoes a large number of gene expression changes, leading to development of root nodules that house the rhizobium bacteria as they are converted into nitrogen-fixing bacteroids. Many of the genes involved in symbiosis are conserved across legume species, while others are species-specific with little or no homology across species and likely regulate the specific plant genotype/symbiont strain interactions. Red clover has not been widely used for studying symbiotic nitrogen fixation, primarily due to its outcrossing nature, making genetic analysis rather complicated. With the addition of recent annotated genomic resources and use of RNA-seq tools, we annotated and characterized a number of genes that are expressed only in nodule forming roots. These genes include those encoding nodule-specific cysteine rich peptides (NCRs) and nodule-specific Polycystin-1, Lipoxygenase, Alpha toxic (PLAT) domain proteins (NPDs). Our results show that red clover encodes one of the highest number of NCRs and ATS3-like/NPDs, which are postulated to increase nitrogen fixation efficiency, in the Inverted-Repeat Lacking Clade (IRLC) of legumes. Knowledge of the variation and expression of these genes in red clover will provide more insights into the function of these genes in regulating legume-rhizobial symbiosis and aid in breeding of red clover genotypes with increased nitrogen fixation efficiency.
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Affiliation(s)
- Randy D. Dinkins
- Forage-Animal Production Research Unit, USDA-ARS, Lexington, KY 40506, USA
| | - Julie A. Hancock
- College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY 40508, USA
| | | | | | - Hongyan Zhu
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA
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Sato Y, Wippler J, Wentrup C, Ansorge R, Sadowski M, Gruber-Vodicka H, Dubilier N, Kleiner M. Fidelity varies in the symbiosis between a gutless marine worm and its microbial consortium. MICROBIOME 2022; 10:178. [PMID: 36273146 PMCID: PMC9587655 DOI: 10.1186/s40168-022-01372-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Accepted: 09/15/2022] [Indexed: 05/30/2023]
Abstract
BACKGROUND Many animals live in intimate associations with a species-rich microbiome. A key factor in maintaining these beneficial associations is fidelity, defined as the stability of associations between hosts and their microbiota over multiple host generations. Fidelity has been well studied in terrestrial hosts, particularly insects, over longer macroevolutionary time. In contrast, little is known about fidelity in marine animals with species-rich microbiomes at short microevolutionary time scales, that is at the level of a single host population. Given that natural selection acts most directly on local populations, studies of microevolutionary partner fidelity are important for revealing the ecological and evolutionary processes that drive intimate beneficial associations within animal species. RESULTS In this study on the obligate symbiosis between the gutless marine annelid Olavius algarvensis and its consortium of seven co-occurring bacterial symbionts, we show that partner fidelity varies across symbiont species from strict to absent over short microevolutionary time. Using a low-coverage sequencing approach that has not yet been applied to microbial community analyses, we analysed the metagenomes of 80 O. algarvensis individuals from the Mediterranean and compared host mitochondrial and symbiont phylogenies based on single-nucleotide polymorphisms across genomes. Fidelity was highest for the two chemoautotrophic, sulphur-oxidizing symbionts that dominated the microbial consortium of all O. algarvensis individuals. In contrast, fidelity was only intermediate to absent in the sulphate-reducing and spirochaetal symbionts with lower abundance. These differences in fidelity are likely driven by both selective and stochastic forces acting on the consistency with which symbionts are vertically transmitted. CONCLUSIONS We hypothesize that variable degrees of fidelity are advantageous for O. algarvensis by allowing the faithful transmission of their nutritionally most important symbionts and flexibility in the acquisition of other symbionts that promote ecological plasticity in the acquisition of environmental resources. Video Abstract.
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Affiliation(s)
- Yui Sato
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany.
| | - Juliane Wippler
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
| | - Cecilia Wentrup
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
| | - Rebecca Ansorge
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
- Gut Microbes and Health Programme, Quadram Institute Bioscience, Norwich, NR4 7UQ, UK
| | - Miriam Sadowski
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
| | - Harald Gruber-Vodicka
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany
| | - Nicole Dubilier
- Max Planck Institute for Marine Microbiology, Celsiusstr. 1, D-28359, Bremen, Germany.
| | - Manuel Kleiner
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA.
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21
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Bouhnik O, Alami S, Lamin H, Lamrabet M, Bennis M, Ouajdi M, Bellaka M, Antri SE, Abbas Y, Abdelmoumen H, Bedmar EJ, Idrissi MME. The Fodder Legume Chamaecytisus albidus Establishes Functional Symbiosis with Different Bradyrhizobial Symbiovars in Morocco. MICROBIAL ECOLOGY 2022; 84:794-807. [PMID: 34625829 DOI: 10.1007/s00248-021-01888-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 09/29/2021] [Indexed: 06/13/2023]
Abstract
In this work, we analyzed the symbiotic performance and diversity of rhizobial strains isolated from the endemic shrubby legume Chamaecytisus albidus grown in soils of three different agroforestry ecosystems representing arid and semi-arid forest areas in Morocco. The analysis of the rrs gene sequences from twenty-four representative strains selected after REP-PCR fingerprinting showed that all the strains belong to the genus Bradyrhizobium. Following multi-locus sequence analysis (MLSA) using the rrs, gyrB, recA, glnII, and rpoB housekeeping genes, five representative strains, CA20, CA61, CJ2, CB10, and CB61 were selected for further molecular studies. Phylogenetic analysis of the concatenated glnII, gyrB, recA, and rpoB genes showed that the strain CJ2 isolated from Sahel Doukkala soil is close to Bradyrhizobium canariense BTA-1 T (96.95%); that strains CA20 and CA61 isolated from the Amhach site are more related to Bradyrhizobium valentinum LmjM3T, with 96.40 and 94.57% similarity values; and that the strains CB10 and CB60 isolated from soil in the Bounaga site are more related to Bradyrhizobium murdochi CNPSo 4020 T and Bradyrhizobium. retamae Ro19T, with which they showed 95.45 and 97.34% similarity values, respectively. The phylogenetic analysis of the symbiotic genes showed that the strains belong to symbiovars lupini, genistearum, and retamae. All the five strains are able to nodulate Lupinus luteus, Retama monosperma, and Cytisus monspessilanus, but they do not nodulate Glycine max and Phaseolus vulgaris. The inoculation tests showed that the strains isolated from the 3 regions improve significantly the plant yield as compared to uninoculated plants. However, the strains of Bradyrhizobium sp. sv. retamae isolated from the site of Amhach were the most performing. The phenotypic analysis showed that the strains are able to use a wide range of carbohydrates and amino acids as sole carbon and nitrogen source. The strains isolated from the arid areas of Bounaga and Amhach were more tolerant to salinity and drought stress than strains isolated in the semi-arid area of Sahel Doukkala.
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Affiliation(s)
- Omar Bouhnik
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco.
| | - Soufiane Alami
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
| | - Hanane Lamin
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
| | - Mouad Lamrabet
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
| | - Meryeme Bennis
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
| | - Mohammed Ouajdi
- Centre de Recherche Forestière, Département Des Eaux Et Forêts, Avenue Omar Ibn El KhattabAgdal, BP 763, 10050, Rabat, Morocco
| | - Mhammed Bellaka
- Centre de Recherche Forestière, Département Des Eaux Et Forêts, Avenue Omar Ibn El KhattabAgdal, BP 763, 10050, Rabat, Morocco
| | - Salwa El Antri
- Centre de Recherche Forestière, Département Des Eaux Et Forêts, Avenue Omar Ibn El KhattabAgdal, BP 763, 10050, Rabat, Morocco
| | - Younes Abbas
- Faculté Polydiciplinaire, Université Sultan Moulay Slimane, Beni Mellal, Morocco
| | - Hanaa Abdelmoumen
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
| | - Eulogio J Bedmar
- Departamento de Microbiología del Suelo y Sistemas Simbióticos Estación Experimental del Zaidín, CSIC Apartado Postal 419, Granada, 18008, Spain
| | - Mustapha Missbah El Idrissi
- Centre de Biotechnologies Végétale Et Microbienne, Biodiversité Et Environnement, Faculté Des Sciences, Université Mohammed V de Rabat, 4, Avenue Ibn Battouta, Agdal, BP 1014 RP, Rabat, Morocco
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22
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Velandia K, Reid JB, Foo E. Right time, right place: The dynamic role of hormones in rhizobial infection and nodulation of legumes. PLANT COMMUNICATIONS 2022; 3:100327. [PMID: 35605199 PMCID: PMC9482984 DOI: 10.1016/j.xplc.2022.100327] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 03/24/2022] [Accepted: 04/13/2022] [Indexed: 06/15/2023]
Abstract
Many legume plants form beneficial associations with rhizobial bacteria that are hosted in new plant root organs, nodules, in which atmospheric nitrogen is fixed. This association requires the precise coordination of two separate programs, infection in the epidermis and nodule organogenesis in the cortex. There is extensive literature indicating key roles for plant hormones during nodulation, but a detailed analysis of the spatial and temporal roles of plant hormones during the different stages of nodulation is required. This review analyses the current literature on hormone regulation of infection and organogenesis to reveal the differential roles and interactions of auxin, cytokinin, brassinosteroids, ethylene, and gibberellins during epidermal infection and cortical nodule initiation, development, and function. With the exception of auxin, all of these hormones suppress infection events. By contrast, there is evidence that all of these hormones promote nodule organogenesis, except ethylene, which suppresses nodule initiation. This differential role for many of the hormones between the epidermal and cortical programs is striking. Future work is required to fully examine hormone interactions and create a robust model that integrates this knowledge into our understanding of nodulation pathways.
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Affiliation(s)
- Karen Velandia
- Discipline of Biological Sciences, School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia
| | - James B Reid
- Discipline of Biological Sciences, School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia
| | - Eloise Foo
- Discipline of Biological Sciences, School of Natural Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia.
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23
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Burghardt LT, Epstein B, Hoge M, Trujillo DI, Tiffin P. Host-Associated Rhizobial Fitness: Dependence on Nitrogen, Density, Community Complexity, and Legume Genotype. Appl Environ Microbiol 2022; 88:e0052622. [PMID: 35852362 PMCID: PMC9361818 DOI: 10.1128/aem.00526-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 06/24/2022] [Indexed: 11/20/2022] Open
Abstract
The environmental context of the nitrogen-fixing mutualism between leguminous plants and rhizobial bacteria varies over space and time. Variation in resource availability, population density, and composition likely affect the ecology and evolution of rhizobia and their symbiotic interactions with hosts. We examined how host genotype, nitrogen addition, rhizobial density, and community complexity affected selection on 68 rhizobial strains in the Sinorhizobium meliloti-Medicago truncatula mutualism. As expected, host genotype had a substantial effect on the size, number, and strain composition of root nodules (the symbiotic organ). The understudied environmental variable of rhizobial density had a stronger effect on nodule strain frequency than the addition of low nitrogen levels. Higher inoculum density resulted in a nodule community that was less diverse and more beneficial but only in the context of the more selective host genotype. Higher density resulted in more diverse and less beneficial nodule communities with the less selective host. Density effects on strain composition deserve additional scrutiny as they can create feedback between ecological and evolutionary processes. Finally, we found that relative strain rankings were stable across increasing community complexity (2, 3, 8, or 68 strains). This unexpected result suggests that higher-order interactions between strains are rare in the context of nodule formation and development. Our work highlights the importance of examining mechanisms of density-dependent strain fitness and developing theoretical predictions that incorporate density dependence. Furthermore, our results have translational relevance for overcoming establishment barriers in bioinoculants and motivating breeding programs that maintain beneficial plant-microbe interactions across diverse agroecological contexts. IMPORTANCE Legume crops establish beneficial associations with rhizobial bacteria that perform biological nitrogen fixation, providing nitrogen to plants without the economic and greenhouse gas emission costs of chemical nitrogen inputs. Here, we examine the influence of three environmental factors that vary in agricultural fields on strain relative fitness in nodules. In addition to manipulating nitrogen, we also use two biotic variables that have rarely been examined: the rhizobial community's density and complexity. Taken together, our results suggest that (i) breeding legume varieties that select beneficial strains despite environmental variation is possible, (ii) changes in rhizobial population densities that occur routinely in agricultural fields could drive evolutionary changes in rhizobial populations, and (iii) the lack of higher-order interactions between strains will allow the high-throughput assessments of rhizobia winners and losers during plant interactions.
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Affiliation(s)
- Liana T. Burghardt
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
- Plant Science Department, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Brendan Epstein
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Michelle Hoge
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
| | - Diana I. Trujillo
- Department of Plant Pathology, University of Minnesota, St. Paul, Minnesota, USA
| | - Peter Tiffin
- Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA
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24
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Legume plant defenses and nutrients mediate indirect interactions between soil rhizobia and chewing herbivores. Basic Appl Ecol 2022. [DOI: 10.1016/j.baae.2022.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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25
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Kajihara KT, Egan CP, Swift SOI, Wall CB, Muir CD, Hynson NA. Core arbuscular mycorrhizal fungi are predicted by their high abundance-occupancy relationship while host-specific taxa are rare and geographically structured. THE NEW PHYTOLOGIST 2022; 234:1464-1476. [PMID: 35218016 DOI: 10.1111/nph.18058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 02/16/2022] [Indexed: 06/14/2023]
Abstract
Habitat restoration may depend on the recovery of plant microbial symbionts such as arbuscular mycorrhizal (AM) fungi, but this requires a better understanding of the rules that govern their community assembly. We examined the interactions of soil and host-associated AM fungal communities between remnant and restored patches of subtropical montane forests. While AM fungal richness did not differ between habitat types, community membership did and was influenced by geography, habitat and host. These differences were largely driven by rare host-specific AM fungi that displayed near-complete turnover between forest types, while core AM fungal taxa were highly abundant and ubiquitous. The bipartite networks in the remnant forest were more specialized and hosts more specific than in the restored forest. Host-associated AM fungal communities nested within soil communities in both habitats, but only significantly so in the restored forest. Our results provide evidence that restored and remnant forests harbour the same core fungal symbionts, while rare host-specific taxa differ, and that geography, host identity and taxonomic resolution strongly affect the observed distribution patterns of these fungi. We suggest that host-specific interactions with AM fungi, as well as spatial processes, should be explicitly considered to effectively re-establish target host and symbiont communities.
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Affiliation(s)
- Kacie T Kajihara
- Pacific Biosciences Research Center, University of Hawai'i at Mānoa, 1993 East-West Road, Honolulu, HI, 96822, USA
| | - Cameron P Egan
- Pacific Biosciences Research Center, University of Hawai'i at Mānoa, 1993 East-West Road, Honolulu, HI, 96822, USA
- Department of Biology, Okanagan College, 1000 KLO Road, Kelowna, BC, VIY 4X8, Canada
| | - Sean O I Swift
- Pacific Biosciences Research Center, University of Hawai'i at Mānoa, 1993 East-West Road, Honolulu, HI, 96822, USA
| | - Christopher B Wall
- Pacific Biosciences Research Center, University of Hawai'i at Mānoa, 1993 East-West Road, Honolulu, HI, 96822, USA
- Biological Sciences, University of California San Diego, 9500 Gilman Dr, La Jolla, CA, 92093, USA
| | - Christopher D Muir
- School of Life Sciences, University of Hawai'i at Mānoa, 2538 McCarthy Mall, Honolulu, HI, 96822, USA
| | - Nicole A Hynson
- Pacific Biosciences Research Center, University of Hawai'i at Mānoa, 1993 East-West Road, Honolulu, HI, 96822, USA
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26
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Dependence on Nitrogen Availability and Rhizobial Symbiosis of Different Accessions of Trifolium fragiferum, a Crop Wild Relative Legume Species, as Related to Physiological Traits. PLANTS 2022; 11:plants11091141. [PMID: 35567142 PMCID: PMC9099520 DOI: 10.3390/plants11091141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 04/11/2022] [Accepted: 04/20/2022] [Indexed: 11/17/2022]
Abstract
Biological nitrogen fixation by legume-rhizobacterial symbiosis in temperate grasslands is an important source of soil nitrogen. The aim of the present study was to characterize the dependence of different accessions of T. fragiferum, a rare crop wild relative legume species, from their native rhizobia as well as additional nitrogen fertilization in controlled conditions. Asymbiotically cultivated, mineral-fertilized T. fragiferum plants gradually showed signs of nitrogen deficiency, appearing as a decrease in leaf chlorophyll concentration, leaf senescence, and a decrease in growth rate. The addition of nitrogen, and the inoculation with native rhizobia, or both treatments significantly prevented the onset of these symptoms, leading to both increase in plant shoot biomass as well as an increase in tissue concentration of N. The actual degree of each type of response was genotype-specific. Accessions showed a relatively similar degree of dependence on nitrogen (70–95% increase in shoot dry mass) but the increase in shoot dry mass by inoculation with native rhizobia ranged from 27 to 85%. In general, there was no correlation between growth stimulation and an increase in tissue N concentration by the treatments. The addition of N or rhizobial inoculant affected mineral nutrition at the level of both macronutrient and micronutrient concentration in different plant parts. In conclusion, native rhizobial strains associated with geographically isolated accessions of T. fragiferum at the northern range of distribution of the species represent a valuable resource for further studies aimed at the identification of salinity-tolerant N2-fixing bacteria for the needs of sustainable agriculture, as well as in a view of understanding ecosystem functioning at the level of plant-microorganism interactions.
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Nakei MD, Venkataramana PB, Ndakidemi PA. Soybean-Nodulating Rhizobia: Ecology, Characterization, Diversity, and Growth Promoting Functions. FRONTIERS IN SUSTAINABLE FOOD SYSTEMS 2022. [DOI: 10.3389/fsufs.2022.824444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The worldwide increase in population continues to threaten the sustainability of agricultural systems since agricultural output must be optimized to meet the global rise in food demand. Sub-Saharan Africa (SSA) is among the regions with a fast-growing population but decreasing crop productivity. Pests and diseases, as well as inadequate nitrogen (N) levels in soils, are some of the biggest restrictions to agricultural production in SSA. N is one of the most important plant-limiting elements in agricultural soils, and its deficit is usually remedied by using nitrogenous fertilizers. However, indiscriminate use of these artificial N fertilizers has been linked to environmental pollution calling for alternative N fertilization mechanisms. Soybean (Glycine max) is one of the most important legumes in the world. Several species of rhizobia from the four genera, Bardyrhizobium, Rhizobium, Mesorhizobium, and Ensifer (formerly Sinorhizobium), are observed to effectively fix N with soybean as well as perform various plant-growth promoting (PGP) functions. The efficiency of the symbiosis differs with the type of rhizobia species, soybean cultivar, and biotic factors. Therefore, a complete understanding of the ecology of indigenous soybean-nodulating rhizobia concerning their genetic diversity and the environmental factors associated with their localization and dominance in the soil is important. This review aimed to understand the potential of indigenous soybean-nodulating rhizobia through a synthesis of the literature regarding their characterization using different approaches, genetic diversity, symbiotic effectiveness, as well as their functions in biological N fixation (BNF) and biocontrol of soybean soil-borne pathogens.
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28
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Crosbie DB, Mahmoudi M, Radl V, Brachmann A, Schloter M, Kemen E, Marín M. Microbiome profiling reveals that Pseudomonas antagonises parasitic nodule colonisation of cheater rhizobia in Lotus. THE NEW PHYTOLOGIST 2022; 234:242-255. [PMID: 35067935 DOI: 10.1111/nph.17988] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
Nodule microbiota are dominated by symbiotic nitrogen-fixing rhizobia, however, other non-rhizobial bacteria also colonise this niche. Although many of these bacteria harbour plant-growth-promoting functions, it is not clear whether these less abundant nodule colonisers impact root-nodule symbiosis. We assessed the relationship between the nodule microbiome and nodulation as influenced by the soil microbiome, by using a metabarcoding approach to characterise the communities inside nodules of healthy and starved Lotus species. A machine learning algorithm and network analyses were used to identify nodule bacteria of interest, which were re-inoculated onto plants in controlled conditions to observe their potential functionality. The nodule microbiome of all tested species differed according to inoculum, but only that of Lotus burttii varied with plant health. Amplicon sequence variants representative of Pseudomonas species were the most indicative non-rhizobial signatures inside healthy L. burttii nodules and negatively correlated with Rhizobium sequences. A representative Pseudomonas isolate co-colonised nodules infected with a beneficial Mesorhizobium, but not with an ineffective Rhizobium isolate and another even reduced the number of ineffective nodules induced on Lotus japonicus. Our results show that nodule endophytes influence the overall outcome of the root-nodule symbiosis, albeit in a plant host-specific manner.
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Affiliation(s)
| | - Maryam Mahmoudi
- Microbial Interactions in Plant Ecosystems, Centre for Plant Molecular Biology, University of Tübingen, Tübingen, 72076, Germany
| | - Viviane Radl
- Comparative Microbiome Analysis, Helmholtz Centre for Environmental Health, Oberschleissheim, 85764, Germany
| | | | - Michael Schloter
- Comparative Microbiome Analysis, Helmholtz Centre for Environmental Health, Oberschleissheim, 85764, Germany
- Chair for Soil Science, Technical University of Munich, Freising, 85354, Germany
| | - Eric Kemen
- Microbial Interactions in Plant Ecosystems, Centre for Plant Molecular Biology, University of Tübingen, Tübingen, 72076, Germany
| | - Macarena Marín
- Genetics, Biocentre, LMU Munich, Martinsried, 82152, Germany
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29
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Sui X, Guan K, Chen Y, Xue R, Li A. A Legume Host Benefits More from Arbuscular Mycorrhizal Fungi Than a Grass Host in the Presence of a Root Hemiparasitic Plant. Microorganisms 2022; 10:microorganisms10020440. [PMID: 35208894 PMCID: PMC8880661 DOI: 10.3390/microorganisms10020440] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/26/2022] [Accepted: 02/03/2022] [Indexed: 02/06/2023] Open
Abstract
In nature, most plants parasitized by root hemiparasites are also colonized by mutualistic arbuscular mycorrhizal (AM) fungi, highlighting the prevalence of this tripartite interaction. AM colonization is generally found to improve the growth of parasitized legumes but has little impact on grass hosts parasitized by root hemiparasites, and the underlying mechanisms are still unclear. In this study, we conducted a pot experiment to test the influence of AM fungus (Glomus mosseae) on the growth and photosynthesis of leguminous Trifolium repens and gramineous Elymus nutans in the presence of a root hemiparasitic plant (Pedicularis kansuensis). The results showed that inoculation with AM fungi significantly improved the growth performance of parasitized legumes via enhancing their nutrient status and photosynthetic capacity, even though a larger P. kansuensis parasitized the legume host in the AM treatment. In contrast, AM colonization slightly improved the shoot DW of grass hosts by suppressing haustoria formation and the growth of P. kansuensis. Our results demonstrated that legume hosts benefit more from AM inoculation than grass hosts in the presence of hemiparasitic plants, and set out the various mechanisms. This study provides new clues for parsing the tritrophic interaction of AM fungi, parasitic plants, and host plants.
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Affiliation(s)
- Xiaolin Sui
- Yunnan Key Laboratory for Wild Plant Resources, Department of Economic Plants and Biotechnology, Chinese Academy of Sciences, Kunming 650201, China; (X.S.); (K.G.); (Y.C.); (R.X.)
- Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
| | - Kaiyun Guan
- Yunnan Key Laboratory for Wild Plant Resources, Department of Economic Plants and Biotechnology, Chinese Academy of Sciences, Kunming 650201, China; (X.S.); (K.G.); (Y.C.); (R.X.)
- Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
- Key Laboratory of Biogeography and Bioresource in Arid Land, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China
| | - Yan Chen
- Yunnan Key Laboratory for Wild Plant Resources, Department of Economic Plants and Biotechnology, Chinese Academy of Sciences, Kunming 650201, China; (X.S.); (K.G.); (Y.C.); (R.X.)
- Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
| | - Ruijuan Xue
- Yunnan Key Laboratory for Wild Plant Resources, Department of Economic Plants and Biotechnology, Chinese Academy of Sciences, Kunming 650201, China; (X.S.); (K.G.); (Y.C.); (R.X.)
- Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
| | - Airong Li
- Yunnan Key Laboratory for Wild Plant Resources, Department of Economic Plants and Biotechnology, Chinese Academy of Sciences, Kunming 650201, China; (X.S.); (K.G.); (Y.C.); (R.X.)
- Yunnan Key Laboratory for Fungal Diversity and Green Development, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China
- Correspondence: ; Tel.: +86-0871-65225907
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30
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Metallothionein1A Regulates Rhizobial Infection and Nodulation in Phaseolus vulgaris. Int J Mol Sci 2022; 23:ijms23031491. [PMID: 35163415 PMCID: PMC8836284 DOI: 10.3390/ijms23031491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 02/04/2023] Open
Abstract
Metallothioneins (MTs) constitute a heterogeneous family of ubiquitous metal ion-binding proteins. In plants, MTs participate in the regulation of cell growth and proliferation, protection against heavy metal stress, oxidative stress responses, and responses to pathogen attack. Despite their wide variety of functions, the role of MTs in symbiotic associations, specifically nodule-fabacean symbiosis, is poorly understood. Here, we analyzed the role of the PvMT1A gene in Phaseolus vulgaris-Rhizobium tropici symbiosis using bioinformatics and reverse genetics approaches. Using in silico analysis, we identified six genes encoding MTs in P. vulgaris, which were clustered into three of the four classes described in plants. PvMT1A transcript levels were significantly higher in roots inoculated with R. tropici at 7 and 30 days post inoculation (dpi) than in non-inoculated roots. Functional analysis showed that downregulating PvMT1A by RNA interference (RNAi) reduced the number of infection events at 7 and 10 dpi and the number of nodules at 14 and 21 dpi. In addition, nodule development was negatively affected in PvMT1A:RNAi transgenic roots, and these nodules displayed a reduced nitrogen fixation rate at 21 dpi. These results strongly suggest that PvMT1A plays an important role in the infection process and nodule development in P. vulgaris during rhizobial symbiosis.
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Maitra S, Brestic M, Bhadra P, Shankar T, Praharaj S, Palai JB, Shah MMR, Barek V, Ondrisik P, Skalický M, Hossain A. Bioinoculants-Natural Biological Resources for Sustainable Plant Production. Microorganisms 2021; 10:51. [PMID: 35056500 PMCID: PMC8780112 DOI: 10.3390/microorganisms10010051] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 12/21/2021] [Accepted: 12/23/2021] [Indexed: 11/22/2022] Open
Abstract
Agricultural sustainability is of foremost importance for maintaining high food production. Irresponsible resource use not only negatively affects agroecology, but also reduces the economic profitability of the production system. Among different resources, soil is one of the most vital resources of agriculture. Soil fertility is the key to achieve high crop productivity. Maintaining soil fertility and soil health requires conscious management effort to avoid excessive nutrient loss, sustain organic carbon content, and minimize soil contamination. Though the use of chemical fertilizers have successfully improved crop production, its integration with organic manures and other bioinoculants helps in improving nutrient use efficiency, improves soil health and to some extent ameliorates some of the constraints associated with excessive fertilizer application. In addition to nutrient supplementation, bioinoculants have other beneficial effects such as plant growth-promoting activity, nutrient mobilization and solubilization, soil decontamination and/or detoxification, etc. During the present time, high energy based chemical inputs also caused havoc to agriculture because of the ill effects of global warming and climate change. Under the consequences of climate change, the use of bioinputs may be considered as a suitable mitigation option. Bioinoculants, as a concept, is not something new to agricultural science, however; it is one of the areas where consistent innovations have been made. Understanding the role of bioinoculants, the scope of their use, and analysing their performance in various environments are key to the successful adaptation of this technology in agriculture.
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Affiliation(s)
- Sagar Maitra
- Department of Agronomy, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakheundi 761 211, India; (S.M.); (T.S.); (S.P.); (J.B.P.)
| | - Marian Brestic
- Department of Plant Physiology, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 01 Nitra, Slovakia;
- Department of Botany and Plant Physiology, Faculty of Agrobiology, Food, and Natural Resources, Czech University of Life Sciences Prague, Kamycka 129, 165 00 Prague, Czech Republic;
| | - Preetha Bhadra
- Department of Biotechnology, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakheundi 761 211, India;
| | - Tanmoy Shankar
- Department of Agronomy, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakheundi 761 211, India; (S.M.); (T.S.); (S.P.); (J.B.P.)
| | - Subhashisa Praharaj
- Department of Agronomy, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakheundi 761 211, India; (S.M.); (T.S.); (S.P.); (J.B.P.)
| | - Jnana Bharati Palai
- Department of Agronomy, M.S. Swaminathan School of Agriculture, Centurion University of Technology and Management, Paralakheundi 761 211, India; (S.M.); (T.S.); (S.P.); (J.B.P.)
| | | | - Viliam Barek
- Department of Water Resources and Environmental Engineering, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 01 Nitra, Slovakia;
| | - Peter Ondrisik
- Department of Plant Physiology, Slovak University of Agriculture, Tr. A. Hlinku 2, 949 01 Nitra, Slovakia;
| | - Milan Skalický
- Department of Botany and Plant Physiology, Faculty of Agrobiology, Food, and Natural Resources, Czech University of Life Sciences Prague, Kamycka 129, 165 00 Prague, Czech Republic;
| | - Akbar Hossain
- Bangladesh Wheat and Maize Research Institute, Dinajpur 5200, Bangladesh;
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Liu Y, Ma B, Chen W, Schlaeppi K, Erb M, Stirling E, Hu L, Wang E, Zhang Y, Zhao K, Lu Z, Ye S, Xu J. Rhizobium Symbiotic Capacity Shapes Root-Associated Microbiomes in Soybean. Front Microbiol 2021; 12:709012. [PMID: 34925249 PMCID: PMC8678110 DOI: 10.3389/fmicb.2021.709012] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 11/09/2021] [Indexed: 12/26/2022] Open
Abstract
Root-microbiome interactions are of central importance for plant performance and yield. A distinctive feature of legumes is that they engage in symbiosis with N2-fixing rhizobia. If and how the rhizobial symbiotic capacity modulates root-associated microbiomes are still not yet well understood. We determined root-associated microbiomes of soybean inoculated with wild type (WT) or a noeI mutant of Bradyrhizobium diazoefficiens USDA 110 by amplicon sequencing. UPLC-MS/MS was used to analyze root exudates. The noeI gene is responsible for fucose-methylation of Nod factor secreted by USDA 110 WT strain. Soybean roots inoculated with the noeI mutant showed a significant decrease in nodulation and root-flavonoid exudation compared to roots inoculated with WT strain. The noeI mutant-inoculated roots exhibited strong changes in microbiome assembly in the rhizosphere and rhizoplane, including reduced diversity, changed co-occurrence interactions and a substantial depletion of root microbes. Root exudates and soil physiochemical properties were significantly correlated with microbial community shift in the rhizosphere between different rhizobial treatments. These results illustrate that rhizobial symbiotic capacity dramatically alters root-associated microbiomes, in which root exudation and edaphic patterns play a vital role. This study has important implications for understanding the evolution of plant-microbiome interactions.
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Affiliation(s)
- Yuanhui Liu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China
| | - Bin Ma
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China
| | - Wenfeng Chen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences and Rhizobium Research Center, China Agricultural University, Ministry of Agriculture Key Laboratory of Soil Microbiology, Beijing, China
| | - Klaus Schlaeppi
- Department of Environmental Sciences, University of Basel, Basel, Switzerland.,Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Matthias Erb
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Erinne Stirling
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China.,Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, China.,Acid Sulfate Soils Centre, School of Biological Sciences, The University of Adelaide, Adelaide, SA, Australia
| | - Lingfei Hu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Entao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México City, México
| | - Yunzeng Zhang
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou, China
| | - Kankan Zhao
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Zhijiang Lu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Shudi Ye
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
| | - Jianming Xu
- Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.,Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou, China
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Nelson JM, Hauser DA, Li FW. The diversity and community structure of symbiotic cyanobacteria in hornworts inferred from long-read amplicon sequencing. AMERICAN JOURNAL OF BOTANY 2021; 108:1731-1744. [PMID: 34533221 DOI: 10.1002/ajb2.1729] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 05/16/2021] [Accepted: 05/17/2021] [Indexed: 06/13/2023]
Abstract
PREMISE Nitrogen-fixing endosymbioses with cyanobacteria have evolved independently in five very different plant lineages. Expanding knowledge of these symbioses promises to improve the understanding of symbiosis evolution and broaden the toolkit for agricultural engineering to reduce artificial fertilizer use. Here we focused on hornworts, a bryophyte lineage in which all members host cyanobacteria, and investigated factors shaping the diversity of their cyanobiont communities. METHODS We sampled hornworts and adjacent soils in upstate New York throughout the hornwort growing season. We included all three sympatric hornwort species in the area, allowing us to directly compare partner selectivity. To profile cyanobacteria communities, we established a metabarcoding protocol targeting rbcL-X with PacBio long reads. RESULTS The hornwort cyanobionts detected were phylogenetically diverse, including clades that do not contain other known plant symbionts. We found significant overlap between hornwort cyanobionts and soil cyanobacteria, a pattern not previously reported in other plant-cyanobacteria symbioses. Cyanobiont communities differed between host plants only centimeters apart, but we did not detect an effect of sampling time or host species on the cyanobacterial community structure. CONCLUSIONS This study expands the phylogenetic diversity of known symbiotic cyanobacteria. Our analyses suggest that hornwort cyanobionts have a tight connection to the soil background, and we found no evidence that time within growing season, host species, or distance at the scale of meters strongly govern cyanobacteria community assembly. This study provides a critical foundation for further study of the ecology, evolution, and interaction dynamics of plant-cyanobacteria symbiosis.
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Affiliation(s)
| | | | - Fay-Wei Li
- Boyce Thompson Institute, Ithaca, NY, USA
- Plant Biology Section, Cornell University, Ithaca, NY, USA
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Thilakarathna MS, Cope KR. Split-root assays for studying legume-rhizobia symbioses, rhizodeposition, and belowground nitrogen transfer in legumes. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:5285-5299. [PMID: 33954584 DOI: 10.1093/jxb/erab198] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 05/03/2021] [Indexed: 06/12/2023]
Abstract
Split-root assays have been used widely in studies focused on understanding the complex regulatory mechanisms in legume-rhizobia symbioses, root nitrogen rhizodeposition, and belowground nitrogen transfer, and the effects of different biotic/abiotic factors on this symbiotic interaction. This assay allows a plant to have a root system that is physically divided into two distinct sections that are both still attached to a common shoot. Thus, each root section can be treated separately to monitor local and systemic plant responses. Different techniques are used to establish split-root assemblies, including double-pot systems, divided growth pouches, elbow root assembly, twin-tube systems, a single pot or chamber with a partition in the center, and divided agar plates. This review is focused on discussing the various types of split-root assays currently used in legume-based studies, and their associated advantages and limitations. Furthermore, this review also focuses on how split-root assays have been used for studies on nitrogen rhizodeposition, belowground nitrogen transfer, systemic regulation of nodulation, and biotic and abiotic factors affecting legume-rhizobia symbioses.
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Affiliation(s)
- Malinda S Thilakarathna
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada
| | - Kevin R Cope
- Biology and Microbiology Department, South Dakota State University, Brookings, SD, USA
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Hailu Gunnabo A, Geurts R, Wolde-meskel E, Degefu T, E. Giller K, van Heerwaarden J. Phylogeographic distribution of rhizobia nodulating common bean (Phaseolus vulgaris L.) in Ethiopia. FEMS Microbiol Ecol 2021; 97:fiab046. [PMID: 33724341 PMCID: PMC8016211 DOI: 10.1093/femsec/fiab046] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Accepted: 03/13/2021] [Indexed: 11/19/2022] Open
Abstract
Rhizobia are soilborne bacteria that form symbiotic relations with legumes and fix atmospheric nitrogen. The nitrogen fixation potential depends on several factors such as the type of host and symbionts and on environmental factors that affect the distribution of rhizobia. We isolated bacteria nodulating common bean in Southern Ethiopia to evaluate their genetic diversity and phylogeography at nucleotide, locus (gene/haplotype) and species levels of genetic hierarchy. Phylogenetically, eight rhizobial genospecies (including previous collections) were determined that had less genetic diversity than found among reference strains. The limited genetic diversity of the Ethiopian collections was due to absence of many of the Rhizobium lineages known to nodulate beans. Rhizobium etli and Rhizobiumphaseoli were predominant strains of bean-nodulating rhizobia in Ethiopia. We found no evidence for a phylogeographic pattern in strain distribution. However, joint analysis of the current and previous collections revealed differences between the two collections at nucleotide level of genetic hierarchy. The differences were due to genospecies Rhizobium aethiopicum that was only isolated in the earlier collection.
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Affiliation(s)
- Ashenafi Hailu Gunnabo
- Plant Production Systems Group, Wageningen University & Research, Wageningen, Gelderland, The Netherlands, Postal code: 6708 PB
| | - Rene Geurts
- Laboratory of Molecular Biology, Department of Plant Sciences, Wageningen University & Research, Wageningen, Gelderland, The Netherlands, Postal code: 6708 PB
| | - Endalkachew Wolde-meskel
- World Agroforestry Centre (ICRAF), c/o ILRI Campus, Gurd Shola PO Box 5689, Addis Ababa, 4 Ethiopia
| | - Tulu Degefu
- International Crops Research Institute for the Semi-Arid Tropics, c/o ILRI Campus, Gurd Shola PO Box 5689, Addis Ababa, Ethiopia
| | - Ken E. Giller
- Plant Production Systems Group, Wageningen University & Research, Wageningen, Gelderland, The Netherlands, Postal code: 6708 PB
| | - Joost van Heerwaarden
- Plant Production Systems Group, Wageningen University & Research, Wageningen, Gelderland, The Netherlands, Postal code: 6708 PB
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Haskett TL, Tkacz A, Poole PS. Engineering rhizobacteria for sustainable agriculture. THE ISME JOURNAL 2021; 15:949-964. [PMID: 33230265 PMCID: PMC8114929 DOI: 10.1038/s41396-020-00835-4] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 10/29/2020] [Accepted: 11/05/2020] [Indexed: 02/06/2023]
Abstract
Exploitation of plant growth promoting (PGP) rhizobacteria (PGPR) as crop inoculants could propel sustainable intensification of agriculture to feed our rapidly growing population. However, field performance of PGPR is typically inconsistent due to suboptimal rhizosphere colonisation and persistence in foreign soils, promiscuous host-specificity, and in some cases, the existence of undesirable genetic regulation that has evolved to repress PGP traits. While the genetics underlying these problems remain largely unresolved, molecular mechanisms of PGP have been elucidated in rigorous detail. Engineering and subsequent transfer of PGP traits into selected efficacious rhizobacterial isolates or entire bacterial rhizosphere communities now offers a powerful strategy to generate improved PGPR that are tailored for agricultural use. Through harnessing of synthetic plant-to-bacteria signalling, attempts are currently underway to establish exclusive coupling of plant-bacteria interactions in the field, which will be crucial to optimise efficacy and establish biocontainment of engineered PGPR. This review explores the many ecological and biotechnical facets of this research.
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Affiliation(s)
- Timothy L. Haskett
- grid.4991.50000 0004 1936 8948Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB UK
| | - Andrzej Tkacz
- grid.4991.50000 0004 1936 8948Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB UK
| | - Philip S. Poole
- grid.4991.50000 0004 1936 8948Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB UK
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Aghdam SA, Brown AMV. Deep learning approaches for natural product discovery from plant endophytic microbiomes. ENVIRONMENTAL MICROBIOME 2021; 16:6. [PMID: 33758794 PMCID: PMC7972023 DOI: 10.1186/s40793-021-00375-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Accepted: 02/21/2021] [Indexed: 05/10/2023]
Abstract
Plant microbiomes are not only diverse, but also appear to host a vast pool of secondary metabolites holding great promise for bioactive natural products and drug discovery. Yet, most microbes within plants appear to be uncultivable, and for those that can be cultivated, their metabolic potential lies largely hidden through regulatory silencing of biosynthetic genes. The recent explosion of powerful interdisciplinary approaches, including multi-omics methods to address multi-trophic interactions and artificial intelligence-based computational approaches to infer distribution of function, together present a paradigm shift in high-throughput approaches to natural product discovery from plant-associated microbes. Arguably, the key to characterizing and harnessing this biochemical capacity depends on a novel, systematic approach to characterize the triggers that turn on secondary metabolite biosynthesis through molecular or genetic signals from the host plant, members of the rich 'in planta' community, or from the environment. This review explores breakthrough approaches for natural product discovery from plant microbiomes, emphasizing the promise of deep learning as a tool for endophyte bioprospecting, endophyte biochemical novelty prediction, and endophyte regulatory control. It concludes with a proposed pipeline to harness global databases (genomic, metabolomic, regulomic, and chemical) to uncover and unsilence desirable natural products. SUPPLEMENTARY INFORMATION The online version contains supplementary material available at 10.1186/s40793-021-00375-0.
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Affiliation(s)
- Shiva Abdollahi Aghdam
- Department of Biological Sciences, Texas Tech University, 2901 Main St, Lubbock, TX 79409 USA
| | - Amanda May Vivian Brown
- Department of Biological Sciences, Texas Tech University, 2901 Main St, Lubbock, TX 79409 USA
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Interactive Effects of Scion and Rootstock Genotypes on the Root Microbiome of Grapevines (Vitis spp. L.). APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11041615] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Diversity and community structure of soil microorganisms are increasingly recognized as important contributors to sustainable agriculture and plant health. In viticulture, grapevine scion cultivars are grafted onto rootstocks to reduce the incidence of the grapevine pest phylloxera. However, it is unknown to what extent this practice influences root-associated microbial communities. A field survey of bacteria in soil surrounding the roots (rhizosphere) of 4 cultivars × 4 rootstock combinations was conducted to determine whether rootstock and cultivar genotypes are important drivers of rhizosphere community diversity and composition. Differences in α-diversity was highly dependent on rootstock–cultivar combinations, while bacterial community structure primarily clustered according to cultivar differences, followed by differences in rootstocks. Twenty-four bacterial indicator genera were significantly more abundant in one or more cultivars, while only thirteen were found to be specifically associated with one or more rootstock genotypes, but there was little overlap between cultivar and rootstock indicator genera. Bacterial diversity in grafted grapevines was affected by both cultivar and rootstock identity, but this effect was dependent on which diversity measure was being examined (i.e., α- or β-diversity) and specific rootstock–cultivar combinations. These findings could have functional implications, for instance, if specific combinations varied in their ability to attract beneficial microbial taxa which can control pathogens and/or assist plant performance.
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Vandana UK, Rajkumari J, Singha LP, Satish L, Alavilli H, Sudheer PD, Chauhan S, Ratnala R, Satturu V, Mazumder PB, Pandey P. The Endophytic Microbiome as a Hotspot of Synergistic Interactions, with Prospects of Plant Growth Promotion. BIOLOGY 2021; 10:101. [PMID: 33535706 PMCID: PMC7912845 DOI: 10.3390/biology10020101] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 01/28/2021] [Accepted: 01/29/2021] [Indexed: 12/16/2022]
Abstract
The plant root is the primary site of interaction between plants and associated microorganisms and constitutes the main components of plant microbiomes that impact crop production. The endophytic bacteria in the root zone have an important role in plant growth promotion. Diverse microbial communities inhabit plant root tissues, and they directly or indirectly promote plant growth by inhibiting the growth of plant pathogens, producing various secondary metabolites. Mechanisms of plant growth promotion and response of root endophytic microorganisms for their survival and colonization in the host plants are the result of complex plant-microbe interactions. Endophytic microorganisms also assist the host to sustain different biotic and abiotic stresses. Better insights are emerging for the endophyte, such as host plant interactions due to advancements in 'omic' technologies, which facilitate the exploration of genes that are responsible for plant tissue colonization. Consequently, this is informative to envisage putative functions and metabolic processes crucial for endophytic adaptations. Detection of cell signaling molecules between host plants and identification of compounds synthesized by root endophytes are effective means for their utilization in the agriculture sector as biofertilizers. In addition, it is interesting that the endophytic microorganism colonization impacts the relative abundance of indigenous microbial communities and suppresses the deleterious microorganisms in plant tissues. Natural products released by endophytes act as biocontrol agents and inhibit pathogen growth. The symbiosis of endophytic bacteria and arbuscular mycorrhizal fungi (AMF) affects plant symbiotic signaling pathways and root colonization patterns and phytohormone synthesis. In this review, the potential of the root endophytic community, colonization, and role in the improvement of plant growth has been explained in the light of intricate plant-microbe interactions.
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Affiliation(s)
- Udaya Kumar Vandana
- Department of Biotechnology, Assam University Silchar, Assam 788011, India; (U.K.V.); (P.B.M.)
| | - Jina Rajkumari
- Department of Microbiology, Assam University Silchar, Assam 788011, India; (J.R.); (L.P.S.)
| | - L. Paikhomba Singha
- Department of Microbiology, Assam University Silchar, Assam 788011, India; (J.R.); (L.P.S.)
| | - Lakkakula Satish
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering and the Ilse Katz Center for Meso and Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel;
- The Albert Katz International School for Desert Studies, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Hemasundar Alavilli
- Department of Biochemistry and Molecular Biology, College of Medicine, Korea Molecular Medicine and Nutrition Research Institute, Korea University, Seoul 02841, Korea;
| | - Pamidimarri D.V.N. Sudheer
- Amity Institute of Biotechnology, Amity University Chhattisgarh, Raipur 493225, India; (P.D.V.N.S.); (S.C.)
| | - Sushma Chauhan
- Amity Institute of Biotechnology, Amity University Chhattisgarh, Raipur 493225, India; (P.D.V.N.S.); (S.C.)
| | - Rambabu Ratnala
- TATA Institute for Genetics and Society, Bangalore 560065, India;
| | - Vanisri Satturu
- Institute of Biotechnology, Professor Jayashankar Telangana State Agricultural University, Rajendranagar, Hyderabad 500030, India;
| | - Pranab Behari Mazumder
- Department of Biotechnology, Assam University Silchar, Assam 788011, India; (U.K.V.); (P.B.M.)
| | - Piyush Pandey
- Department of Microbiology, Assam University Silchar, Assam 788011, India; (J.R.); (L.P.S.)
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Zhou Z, Yu M, Ding G, Gao G, He Y. Diversity and structural differences of bacterial microbial communities in rhizocompartments of desert leguminous plants. PLoS One 2020; 15:e0241057. [PMID: 33351824 PMCID: PMC7755220 DOI: 10.1371/journal.pone.0241057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 10/07/2020] [Indexed: 11/18/2022] Open
Abstract
By assessing diversity variations of bacterial communities under different rhizocompartment types (i.e., roots, rhizosphere soil, root zone soil, and inter-shrub bulk soil), we explore the structural difference of bacterial communities in different root microenvironments under desert leguminous plant shrubs. Results will enable the influence of niche differentiation of plant roots and root soil on the structural stability of bacterial communities under three desert leguminous plant shrubs to be examined. High-throughput 16S rRNA genome sequencing was used to characterize diversity and structural differences of bacterial microbes in the rhizocompartments of three xeric leguminous plants. Results from this study confirm previous findings relating to niche differentiation in rhizocompartments under related shrubs, and they demonstrate that diversity and structural composition of bacterial communities have significant hierarchical differences across four rhizocompartment types under leguminous plant shrubs. Desert leguminous plants showed significant hierarchical filtration and enrichment of the specific bacterial microbiome across different rhizocompartments (P < 0.05). The dominant bacterial microbiome responsible for the differences in microbial community structure and composition across different niches of desert leguminous plants mainly consisted of Proteobacteria, Actinobacteria, and Bacteroidetes. All soil factors of rhizosphere and root zone soils, except for NO3-N and TP under C. microphylla and the two Hedysarum spp., recorded significant differences (P < 0.05). Moreover, soil physicochemical factors have a significant impact on driving the differentiation of bacterial communities under desert leguminous plant shrubs. By investigating the influence of niches on the structural difference of soil bacterial communities with the differentiation of rhizocompartments under desert leguminous plant shrubs, we provide data support for the identification of dominant bacteria and future preparation of inocula, and provide a foundation for further study of the host plants-microbial interactions.
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Affiliation(s)
- Ziyuan Zhou
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
| | - Minghan Yu
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- * E-mail: (MY); (GD)
| | - Guodong Ding
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- * E-mail: (MY); (GD)
| | - Guanglei Gao
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
| | - Yingying He
- Yanchi Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
- Key Laboratory of State Forestry Administration on Soil and Water Conservation, Beijing Forestry University, Beijing, P. R. China
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Fine-Scale Patterns of Genetic Structure in the Host Plant Chamaecrista fasciculata (Fabaceae) and Its Nodulating Rhizobia Symbionts. PLANTS 2020; 9:plants9121719. [PMID: 33297297 PMCID: PMC7762326 DOI: 10.3390/plants9121719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 11/30/2020] [Accepted: 12/03/2020] [Indexed: 01/04/2023]
Abstract
In natural plant populations, a fine-scale spatial genetic structure (SGS) can result from limited gene flow, selection pressures or spatial autocorrelation. However, limited gene flow is considered the predominant determinant in the establishment of SGS. With limited dispersal ability of bacterial cells in soil and host influence on their variety and abundance, spatial autocorrelation of bacterial communities associated with plants is expected. For this study, we collected genetic data from legume host plants, Chamaecrista fasciculata, their Bradyrhizobium symbionts and rhizosphere free-living bacteria at a small spatial scale to evaluate the extent to which symbiotic partners will have similar SGS and to understand how plant hosts choose among nodulating symbionts. We found SGS across all sampled plants for both the host plants and nodulating rhizobia, suggesting that both organisms are influenced by similar mechanisms structuring genetic diversity or shared habitat preferences by both plants and microbes. We also found that plant genetic identity and geographic distance might serve as predictors of nodulating rhizobia genetic identity. Bradyrhizobium elkanii was the only type of rhizobia found in nodules, which suggests some level of selection by the host plant.
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42
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Yang LL, Jiang Z, Li Y, Wang ET, Zhi XY. Plasmids Related to the Symbiotic Nitrogen Fixation Are Not Only Cooperated Functionally but Also May Have Evolved over a Time Span in Family Rhizobiaceae. Genome Biol Evol 2020; 12:2002-2014. [PMID: 32687170 PMCID: PMC7719263 DOI: 10.1093/gbe/evaa152] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2020] [Indexed: 12/17/2022] Open
Abstract
Rhizobia are soil bacteria capable of forming symbiotic nitrogen-fixing nodules associated with leguminous plants. In fast-growing legume-nodulating rhizobia, such as the species in the family Rhizobiaceae, the symbiotic plasmid is the main genetic basis for nitrogen-fixing symbiosis, and is susceptible to horizontal gene transfer. To further understand the symbioses evolution in Rhizobiaceae, we analyzed the pan-genome of this family based on 92 genomes of type/reference strains and reconstructed its phylogeny using a phylogenomics approach. Intriguingly, although the genetic expansion that occurred in chromosomal regions was the main reason for the high proportion of low-frequency flexible gene families in the pan-genome, gene gain events associated with accessory plasmids introduced more genes into the genomes of nitrogen-fixing species. For symbiotic plasmids, although horizontal gene transfer frequently occurred, transfer may be impeded by, such as, the host’s physical isolation and soil conditions, even among phylogenetically close species. During coevolution with leguminous hosts, the plasmid system, including accessory and symbiotic plasmids, may have evolved over a time span, and provided rhizobial species with the ability to adapt to various environmental conditions and helped them achieve nitrogen fixation. These findings provide new insights into the phylogeny of Rhizobiaceae and advance our understanding of the evolution of symbiotic nitrogen fixation.
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Affiliation(s)
- Ling-Ling Yang
- Yunnan Institute of Microbiology, School of Life Sciences, Yunnan University, Kunming, Yunnan, PR China
| | - Zhao Jiang
- Yunnan Institute of Microbiology, School of Life Sciences, Yunnan University, Kunming, Yunnan, PR China
| | - Yan Li
- Key Laboratory of Coastal Biology and Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong, PR China
| | - En-Tao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City D.F., México
| | - Xiao-Yang Zhi
- Yunnan Institute of Microbiology, School of Life Sciences, Yunnan University, Kunming, Yunnan, PR China
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43
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Compton KK, Hildreth SB, Helm RF, Scharf BE. An Updated Perspective on Sinorhizobium meliloti Chemotaxis to Alfalfa Flavonoids. Front Microbiol 2020; 11:581482. [PMID: 33193213 PMCID: PMC7644916 DOI: 10.3389/fmicb.2020.581482] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 09/30/2020] [Indexed: 12/25/2022] Open
Abstract
The symbiotic interaction between leguminous plants and their cognate rhizobia allows for the fixation of gaseous dinitrogen into bioavailable ammonia. The perception of host-derived flavonoids is a key initial step for the signaling events that must occur preceding the formation of the nitrogen-fixing organ. Past work investigating chemotaxis – the directed movement of bacteria through chemical gradients – of Bradyrhizobium japonicum, Rhizobium leguminosarum, and Rhizobium meliloti discovered chemotaxis to various organic compounds, but focused on chemotaxis to flavonoids because of their relevance to the symbiosis biochemistry. The current work sought to replicate and further examine Sinorhizobium (Ensifer) meliloti chemotaxis to the flavonoids previously thought to act as the principal attractant molecules prior to the initial signaling stage. Exudate from germinating alfalfa seedlings was analyzed for composition and quantities of different flavonoid compounds using mass spectrometry. The abundance of four prevalent flavonoids in germinating alfalfa seed exudates (SEs) was at a ratio of 200:5:5:1 for hyperoside, luteolin, luteolin-7-glucoside, and chrysoeriol. Using quantitative chemotaxis capillary assays, we did not detect chemotaxis of motile S. meliloti cells to these, and two other flavonoids identified in seed exudates. In support of these findings, the flavonoid fraction of seed exudates was found to be an insignificant attractant relative to the more hydrophilic fraction. Additionally, we observed that cosolvents commonly used to dissolve flavonoids confound the results. We propose that the role flavonoids play in S. meliloti chemotaxis is insignificant relative to other components released by alfalfa seeds.
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Affiliation(s)
- K Karl Compton
- Department of Biological Sciences, Life Sciences I, Virginia Tech, Blacksburg, VA, United States
| | - Sherry B Hildreth
- Department of Biological Sciences, Life Sciences I, Virginia Tech, Blacksburg, VA, United States
| | - Richard F Helm
- Department of Biochemistry, Fralin Life Science Institute, Virginia Tech, Blacksburg, VA, United States
| | - Birgit E Scharf
- Department of Biological Sciences, Life Sciences I, Virginia Tech, Blacksburg, VA, United States
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Paulitsch F, Delamuta JRM, Ribeiro RA, da Silva Batista JS, Hungria M. Phylogeny of symbiotic genes reveals symbiovars within legume-nodulating Paraburkholderia species. Syst Appl Microbiol 2020; 43:126151. [PMID: 33171385 DOI: 10.1016/j.syapm.2020.126151] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 10/01/2020] [Accepted: 10/02/2020] [Indexed: 10/23/2022]
Abstract
Bacteria belonging to the genus Paraburkholderia are capable of establishing symbiotic relationships with plants belonging to the Fabaceae (=Leguminosae) family and fixing the atmospheric nitrogen in specialized structures in the roots called nodules, in a process known as biological nitrogen fixation (BNF). In the nodulation and BNF processes several bacterial symbiotic genes are involved, but the relations between symbiotic, core genes and host specificity are still poorly studied and understood in Paraburkholderia. In this study, eight strains of nodulating nitrogen-fixing Paraburkholderia isolated in Brazil, together with described species and other reference strains were used to infer the relatedness between core (16S rDNA, recA) and symbiotic (nod, nif, fix) genes. The diversity of genes involved in the nodulation (nodAC) and nitrogen fixation (nifH) abilities was investigated. Only two groups, one containing three Paraburkholderia species symbionts of Mimosa, and another one with P. ribeironis strains presented similar phylogenetic patterns in the analysis of core and symbiotic genes. In three other groups events of horizontal gene transfer of symbiotic genes were detected. Paraburkholderia strains with available genomes were used in the complementary analysis of nifHDK and fixABC and confirmed well-defined phylogenetic positions of symbiotic genes. In all analyses of nod, nif and fix genes the strains were distributed into five clades with high bootstrap support, allowing the proposal of five symbiovars in nodulating nitrogen-fixing Paraburkholderia, designated as mimosae, africana, tropicalis, atlantica and piptadeniae. Phylogenetic inferences within each symbiovar are discussed.
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Affiliation(s)
- Fabiane Paulitsch
- Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil; Departamento de Microbiologia, Universidade Estadual de Londrina, C.P. 10011, 86057-970 Londrina, Paraná, Brazil; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, SBN, Quadra 2, Bloco L, Lote 06, Edifício Capes, 70.040-020 Brasília, Distrito Federal, Brazil.
| | - Jakeline Renata Marçon Delamuta
- Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil; Conselho Nacional de Desenvolvimento Científico e Tecnológico, SHIS QI 1 Conjunto B, Blocos A, B, C e D, Lago Sul, 71605-001 Brasília, Distrito Federal, Brazil.
| | - Renan Augusto Ribeiro
- Conselho Nacional de Desenvolvimento Científico e Tecnológico, SHIS QI 1 Conjunto B, Blocos A, B, C e D, Lago Sul, 71605-001 Brasília, Distrito Federal, Brazil.
| | - Jesiane Stefania da Silva Batista
- Departamento de Biologia Estrutural, Molecular e Genética, Universidade Estadual de Ponta Grossa, Avenida General Carlos Cavalcanti, 4748 - Uvaranas, C.P. 6001, Ponta Grossa, PR 84030‑900, Brazil.
| | - Mariangela Hungria
- Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil; Departamento de Microbiologia, Universidade Estadual de Londrina, C.P. 10011, 86057-970 Londrina, Paraná, Brazil; Conselho Nacional de Desenvolvimento Científico e Tecnológico, SHIS QI 1 Conjunto B, Blocos A, B, C e D, Lago Sul, 71605-001 Brasília, Distrito Federal, Brazil.
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45
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Brown SP, Grillo MA, Podowski JC, Heath KD. Soil origin and plant genotype structure distinct microbiome compartments in the model legume Medicago truncatula. MICROBIOME 2020; 8:139. [PMID: 32988416 PMCID: PMC7523075 DOI: 10.1186/s40168-020-00915-9] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 09/01/2020] [Indexed: 05/20/2023]
Abstract
BACKGROUND Understanding the genetic and environmental factors that structure plant microbiomes is necessary for leveraging these interactions to address critical needs in agriculture, conservation, and sustainability. Legumes, which form root nodule symbioses with nitrogen-fixing rhizobia, have served as model plants for understanding the genetics and evolution of beneficial plant-microbe interactions for decades, and thus have added value as models of plant-microbiome interactions. Here we use a common garden experiment with 16S rRNA gene amplicon and shotgun metagenomic sequencing to study the drivers of microbiome diversity and composition in three genotypes of the model legume Medicago truncatula grown in two native soil communities. RESULTS Bacterial diversity decreased between external (rhizosphere) and internal plant compartments (root endosphere, nodule endosphere, and leaf endosphere). Community composition was shaped by strong compartment × soil origin and compartment × plant genotype interactions, driven by significant soil origin effects in the rhizosphere and significant plant genotype effects in the root endosphere. Nevertheless, all compartments were dominated by Ensifer, the genus of rhizobia that forms root nodule symbiosis with M. truncatula, and additional shotgun metagenomic sequencing suggests that the nodulating Ensifer were not genetically distinguishable from those elsewhere in the plant. We also identify a handful of OTUs that are common in nodule tissues, which are likely colonized from the root endosphere. CONCLUSIONS Our results demonstrate strong host filtering effects, with rhizospheres driven by soil origin and internal plant compartments driven by host genetics, and identify several key nodule-inhabiting taxa that coexist with rhizobia in the native range. Our results set the stage for future functional genetic experiments aimed at expanding our pairwise understanding of legume-rhizobium symbiosis toward a more mechanistic understanding of plant microbiomes. Video Abstract.
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Affiliation(s)
- Shawn P. Brown
- Department of Plant Biology, University of Illinois, 505 S. Goodwin Ave, Urbana, IL 61801 USA
- Department of Biological Sciences, The University of Memphis, 3774 Walker Ave, Memphis, TN 38152 USA
- Center for Biodiversity Research, The University of Memphis, 3774 Walker Ave, Memphis, TN 38152 USA
| | - Michael A. Grillo
- Department of Plant Biology, University of Illinois, 505 S. Goodwin Ave, Urbana, IL 61801 USA
- Department of Biology, Loyola University Chicago, 1032 W. Sheridan Rd, Chicago, IL 60618 USA
| | - Justin C. Podowski
- Department of Plant Biology, University of Illinois, 505 S. Goodwin Ave, Urbana, IL 61801 USA
- Department of Geophysical Sciences, University of Chicago, 5734 S Ellis Ave, Chicago, IL 60637 USA
| | - Katy D. Heath
- Department of Plant Biology, University of Illinois, 505 S. Goodwin Ave, Urbana, IL 61801 USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois, 1206 W. Gregory Dr, Urbana, IL 61801 USA
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46
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Papik J, Folkmanova M, Polivkova-Majorova M, Suman J, Uhlik O. The invisible life inside plants: Deciphering the riddles of endophytic bacterial diversity. Biotechnol Adv 2020; 44:107614. [PMID: 32858117 DOI: 10.1016/j.biotechadv.2020.107614] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 07/14/2020] [Accepted: 08/15/2020] [Indexed: 10/25/2022]
Abstract
Endophytic bacteria often promote plant growth and protect their host plant against pathogens, herbivores, and abiotic stresses including drought, increased salinity or pollution. Current agricultural practices are being challenged in terms of climate change and the ever-increasing demand for food. Therefore, the rational exploitation of bacterial endophytes to increase the productivity and resistance of crops appears to be very promising. However, the efficient and larger-scale use of bacterial endophytes for more effective and sustainable agriculture is hindered by very little knowledge on molecular aspects of plant-endophyte interactions and mechanisms driving bacterial communities in planta. In addition, since most of the information on bacterial endophytes has been obtained through culture-dependent techniques, endophytic bacterial diversity and its full biotechnological potential still remain highly unexplored. In this study, we discuss the diversity and role of endophytic populations as well as complex interactions that the endophytes have with the plant and vice versa, including the interactions leading to plant colonization. A description of biotic and abiotic factors influencing endophytic bacterial communities is provided, along with a summary of different methodologies suitable for determining the diversity of bacterial endophytes, mechanisms governing the assembly and structure of bacterial communities in the endosphere, and potential biotechnological applications of endophytes in the future.
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Affiliation(s)
- Jakub Papik
- University of Chemistry and Technology, Prague, Faculty of Food and Biochemical Technology, Department of Biochemistry and Microbiology, Prague, Czech Republic
| | - Magdalena Folkmanova
- University of Chemistry and Technology, Prague, Faculty of Food and Biochemical Technology, Department of Biochemistry and Microbiology, Prague, Czech Republic
| | - Marketa Polivkova-Majorova
- University of Chemistry and Technology, Prague, Faculty of Food and Biochemical Technology, Department of Biochemistry and Microbiology, Prague, Czech Republic
| | - Jachym Suman
- University of Chemistry and Technology, Prague, Faculty of Food and Biochemical Technology, Department of Biochemistry and Microbiology, Prague, Czech Republic
| | - Ondrej Uhlik
- University of Chemistry and Technology, Prague, Faculty of Food and Biochemical Technology, Department of Biochemistry and Microbiology, Prague, Czech Republic.
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47
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Liu J, Yu X, Qin Q, Dinkins RD, Zhu H. The Impacts of Domestication and Breeding on Nitrogen Fixation Symbiosis in Legumes. Front Genet 2020; 11:00973. [PMID: 33014021 PMCID: PMC7461779 DOI: 10.3389/fgene.2020.00973] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 07/31/2020] [Indexed: 01/12/2023] Open
Abstract
Legumes are the second most important family of crop plants. One defining feature of legumes is their unique ability to establish a nitrogen-fixing root nodule symbiosis with soil bacteria known as rhizobia. Since domestication from their wild relatives, crop legumes have been under intensive breeding to improve yield and other agronomic traits but with little attention paid to the belowground symbiosis traits. Theoretical models predict that domestication and breeding processes, coupled with high−input agricultural practices, might have reduced the capacity of crop legumes to achieve their full potential of nitrogen fixation symbiosis. Testing this prediction requires characterizing symbiosis traits in wild and breeding populations under both natural and cultivated environments using genetic, genomic, and ecological approaches. However, very few experimental studies have been dedicated to this area of research. Here, we review how legumes regulate their interactions with soil rhizobia and how domestication, breeding and agricultural practices might have affected nodulation capacity, nitrogen fixation efficiency, and the composition and function of rhizobial community. We also provide a perspective on how to improve legume-rhizobial symbiosis in sustainable agricultural systems.
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Affiliation(s)
- Jinge Liu
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Xiaocheng Yu
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Qiulin Qin
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Randy D Dinkins
- Forage-Animal Production Research Unit, United States Department of Agriculture-Agricultural Research Service, Lexington, KY, United States
| | - Hongyan Zhu
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
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48
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Forrester NJ, Rebolleda-Gómez M, Sachs JL, Ashman TL. Polyploid plants obtain greater fitness benefits from a nutrient acquisition mutualism. THE NEW PHYTOLOGIST 2020; 227:944-954. [PMID: 32248526 DOI: 10.1111/nph.16574] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 03/20/2020] [Indexed: 06/11/2023]
Abstract
Polyploidy is a key driver of ecological and evolutionary processes in plants, yet little is known about its effects on biotic interactions. This gap in knowledge is especially profound for nutrient acquisition mutualisms, despite the fact that they regulate global nutrient cycles and structure ecosystems. Generalism in mutualistic interactions depends on the range of potential partners (niche breadth), the benefits obtained and ability to maintain benefits across a variety of partners (fitness plasticity). Here, we determine how each of these is influenced by polyploidy in the legume-rhizobium mutualism. We inoculated a broad geographic sample of natural diploid and autotetraploid alfalfa (Medicago sativa) lineages with a diverse panel of Sinorhizobium bacterial symbionts. To analyze the extent and mechanism of generalism, we measured host growth benefits and functional traits. Autotetraploid plants obtained greater fitness enhancement from mutualistic interactions and were better able to maintain this across diverse rhizobial partners (i.e. low plasticity in fitness) relative to diploids. These benefits were not attributed to increases in niche breadth, but instead reflect increased rewards from investment in the mutualism. Polyploid plants displayed greater generalization in bacterial mutualisms relative to diploids, illustrating another axis of advantage for polyploids over diploids.
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Affiliation(s)
- Nicole J Forrester
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA, 15260, USA
| | - Maria Rebolleda-Gómez
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA, 15260, USA
| | - Joel L Sachs
- Department of Evolution, Ecology, and Organismal Biology, University of California, 3401 Watkins Drive, Riverside, CA, 92521, USA
| | - Tia-Lynn Ashman
- Department of Biological Sciences, University of Pittsburgh, 4249 Fifth Ave., Pittsburgh, PA, 15260, USA
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49
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Han Q, Ma Q, Chen Y, Tian B, Xu L, Bai Y, Chen W, Li X. Variation in rhizosphere microbial communities and its association with the symbiotic efficiency of rhizobia in soybean. THE ISME JOURNAL 2020; 14:1915-1928. [PMID: 32336748 PMCID: PMC7367843 DOI: 10.1038/s41396-020-0648-9] [Citation(s) in RCA: 106] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 03/19/2020] [Accepted: 03/25/2020] [Indexed: 01/06/2023]
Abstract
Rhizobia-legume symbiosis is an important type of plant-microbe mutualism; however, the establishment of this association is complicated and can be affected by many factors. The soybean rhizosphere has a specific microbial community, yet whether these organisms affect rhizobial nodulation has not been well investigated. Here, we analyzed the compositions and relationships of soybean rhizocompartment microbiota in three types of soil. First, we found that the rhizosphere community composition of soybean varied significantly in different soils, and the association network between rhizobia and other rhizosphere bacteria was examined. Second, we found that some rhizosphere microbes were correlated with the composition of bradyrhizobia and sinorhizobia in nodules. We cultivated 278 candidate Bacillus isolates from alkaline soil. Finally, interaction and nodulation assays showed that the Bacillus cereus group specifically promotes and suppresses the growth of sinorhizobia and bradyrhizobia, respectively, and alleviates the effects of saline-alkali conditions on the nodulation of sinorhizobia as well as affecting its colonization in nodules. Our findings demonstrate a crucial role of the bacterial microbiota in shaping rhizobia-host interactions in soybean, and provide a framework for improving the symbiotic efficiency of this system of mutualism through the use of synthetic bacterial communities.
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Affiliation(s)
- Qin Han
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China
| | - Qun Ma
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China
| | - Yong Chen
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China
| | - Bing Tian
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China
| | - Lanxi Xu
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China
| | - Yang Bai
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Wenfeng Chen
- State Key Laboratory of Agrobiotechnology, College of Biological Sciences and Rhizobium Research Center, China Agricultural University, Beijing, 100193, China.
| | - Xia Li
- State Key Laboratory of Agricultural Microbiology, College of Plant Science and Technology, Huazhong Agricultural University, No. 1 Shizishan Road, Hongshan District, Wuhan, 430070, Hubei, China.
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50
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Younginger BS, Friesen ML. Connecting signals and benefits through partner choice in plant-microbe interactions. FEMS Microbiol Lett 2020; 366:5626345. [PMID: 31730203 DOI: 10.1093/femsle/fnz217] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 10/17/2019] [Indexed: 12/20/2022] Open
Abstract
Stabilizing mechanisms in plant-microbe symbioses are critical to maintaining beneficial functions, with two main classes: host sanctions and partner choice. Sanctions are currently presumed to be more effective and widespread, based on the idea that microbes rapidly evolve cheating while retaining signals matching cooperative strains. However, hosts that effectively discriminate among a pool of compatible symbionts would gain a significant fitness advantage. Using the well-characterized legume-rhizobium symbiosis as a model, we evaluate the evidence for partner choice in the context of the growing field of genomics. Empirical studies that rely upon bacteria varying only in nitrogen-fixation ability ignore host-symbiont signaling and frequently conclude that partner choice is not a robust stabilizing mechanism. Here, we argue that partner choice is an overlooked mechanism of mutualism stability and emphasize that plants need not use the microbial services provided a priori to discriminate among suitable partners. Additionally, we present a model that shows that partner choice signaling increases symbiont and host fitness in the absence of sanctions. Finally, we call for a renewed focus on elucidating the signaling mechanisms that are critical to partner choice while further aiming to understand their evolutionary dynamics in nature.
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Affiliation(s)
- Brett S Younginger
- Department of Plant Pathology, Washington State University, PO Box 646430, 345 Johnson Hall, Pullman, WA 99164, USA
| | - Maren L Friesen
- Department of Plant Pathology, Washington State University, PO Box 646430, 345 Johnson Hall, Pullman, WA 99164, USA.,Department of Crop and Soil Sciences, Washington State University, PO Box 646420, 115 Johnson Hall, Pullman, WA 99164, USA
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