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Etesami H, Glick BR. Bacterial indole-3-acetic acid: A key regulator for plant growth, plant-microbe interactions, and agricultural adaptive resilience. Microbiol Res 2024; 281:127602. [PMID: 38228017 DOI: 10.1016/j.micres.2024.127602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/02/2024] [Accepted: 01/03/2024] [Indexed: 01/18/2024]
Abstract
Indole-3-acetic acid (IAA), a fundamental phytohormone categorized under auxins, not only influences plant growth and development but also plays a critical role in plant-microbe interactions. This study reviews the role of IAA in bacteria-plant communication, with a focus on its biosynthesis, regulation, and the subsequent effects on host plants. Bacteria synthesize IAA through multiple pathways, which include the indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and several other routes, whose full mechanisms remain to be fully elucidated. The production of bacterial IAA affects root architecture, nutrient uptake, and resistance to various abiotic stresses such as drought, salinity, and heavy metal toxicity, enhancing plant resilience and thus offering promising routes to sustainable agriculture. Bacterial IAA synthesis is regulated through complex gene networks responsive to environmental cues, impacting plant hormonal balances and symbiotic relationships. Pathogenic bacteria have adapted mechanisms to manipulate the host's IAA dynamics, influencing disease outcomes. On the other hand, beneficial bacteria utilize IAA to promote plant growth and mitigate abiotic stresses, thereby enhancing nutrient use efficiency and reducing dependency on chemical fertilizers. Advancements in analytical methods, such as liquid chromatography-tandem mass spectrometry, have improved the quantification of bacterial IAA, enabling accurate measurement and analysis. Future research focusing on molecular interactions between IAA-producing bacteria and host plants could facilitate the development of biotechnological applications that integrate beneficial bacteria to improve crop performance, which is essential for addressing the challenges posed by climate change and ensuring global food security. This integration of bacterial IAA producers into agricultural practice promises to revolutionize crop management strategies by enhancing growth, fostering resilience, and reducing environmental impact.
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Affiliation(s)
- Hassan Etesami
- Soil Science Department, University of Tehran, Tehran, Iran.
| | - Bernard R Glick
- Department of Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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2
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Zhou J, Stringlis IA, Wen J, Liu Y, Xu S, Wang R. Interplay between Amaryllidaceae alkaloids, the bacteriome and phytopathogens in Lycoris radiata. New Phytol 2024; 241:2258-2274. [PMID: 38105545 DOI: 10.1111/nph.19479] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 11/28/2023] [Indexed: 12/19/2023]
Abstract
Alkaloids are a large group of plant secondary metabolites with various structures and activities. It is important to understand their functions in the interplay between plants and the beneficial and pathogenic microbiota. Amaryllidaceae alkaloids (AAs) are unique secondary metabolites in Amaryllidaceae plants. Here, we studied the interplay between AAs and the bacteriome in Lycoris radiata, a traditional Chinese medicinal plant containing high amounts of AAs. The relationship between AAs and bacterial composition in different tissues of L. radiata was studied. In vitro experiments revealed that AAs have varying levels of antimicrobial activity against endophytic bacteria and pathogenic fungi, indicating the importance of AA synthesis in maintaining a balance between plants and beneficial/pathogenic microbiota. Using bacterial synthetic communities with different compositions, we observed a positive feedback loop between bacteria insensitive to AAs and their ability to increase accumulation of AAs in L. radiata, especially in leaves. This may allow insensitive bacteria to outcompete sensitive ones for plant resources. Moreover, the accumulation of AAs enhanced by insensitive bacteria could benefit plants when challenged with fungal pathogens. This study highlights the functions of alkaloids in plant-microbe interactions, opening new avenues for designing plant microbiomes that could contribute to sustainable agriculture.
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Affiliation(s)
- Jiayu Zhou
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, 210014, Nanjing, China
| | - Ioannis A Stringlis
- Plant-Microbe Interactions, Department of Biology, Science4Life, Utrecht University, P.O. Box 800.56, 3508 TB, Utrecht, the Netherlands
- Laboratory of Plant Pathology, Agricultural University of Athens, 75 Iera Odos St., 11855, Athens, Greece
| | - Jian Wen
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, 210014, Nanjing, China
| | - Yifang Liu
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, 210014, Nanjing, China
| | - Sheng Xu
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, 210014, Nanjing, China
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, 210014, Nanjing, China
| | - Ren Wang
- Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, 210014, Nanjing, China
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, 210014, Nanjing, China
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3
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Chen L, Liu Y. The Function of Root Exudates in the Root Colonization by Beneficial Soil Rhizobacteria. Biology (Basel) 2024; 13:95. [PMID: 38392313 PMCID: PMC10886372 DOI: 10.3390/biology13020095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 01/26/2024] [Accepted: 01/31/2024] [Indexed: 02/24/2024]
Abstract
Soil-beneficial microbes in the rhizosphere play important roles in improving plant growth and health. Root exudates play key roles in plant-microbe interactions and rhizobacterial colonization. This review describes the factors influencing the dynamic interactions between root exudates and the soil microbiome in the rhizosphere, including plant genotype, plant development, and environmental abiotic and biotic factors. We also discuss the roles of specific metabolic mechanisms, regulators, and signals of beneficial soil bacteria in terms of colonization ability. We highlight the latest research progress on the roles of root exudates in regulating beneficial rhizobacterial colonization. Organic acids, amino acids, sugars, sugar alcohols, flavonoids, phenolic compounds, volatiles, and other secondary metabolites are discussed in detail. Finally, we propose future research objectives that will help us better understand the role of root exudates in root colonization by rhizobacteria and promote the sustainable development of agriculture and forestry.
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Affiliation(s)
- Lin Chen
- National Permanent Scientific Research Base for Warm Temperate Zone Forestry of Jiulong Mountain, Experimental Center of Forestry in North China, Chinese Academy of Forestry, Beijing 102300, China
| | - Yunpeng Liu
- State Key Laboratory of Efficient Utilization of Arid and Semi-Arid Arable Land in Northern China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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4
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Li H, Song K, Zhang X, Wang D, Dong S, Liu Y, Yang L. Application of Multi-Perspectives in Tea Breeding and the Main Directions. Int J Mol Sci 2023; 24:12643. [PMID: 37628823 PMCID: PMC10454712 DOI: 10.3390/ijms241612643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Revised: 07/29/2023] [Accepted: 08/08/2023] [Indexed: 08/27/2023] Open
Abstract
Tea plants are an economically important crop and conducting research on tea breeding contributes to enhancing the yield and quality of tea leaves as well as breeding traits that satisfy the requirements of the public. This study reviews the current status of tea plants germplasm resources and their utilization, which has provided genetic material for the application of multi-omics, including genomics and transcriptomics in breeding. Various molecular markers for breeding were designed based on multi-omics, and available approaches in the direction of high yield, quality and resistance in tea plants breeding are proposed. Additionally, future breeding of tea plants based on single-cellomics, pangenomics, plant-microbe interactions and epigenetics are proposed and provided as references. This study aims to provide inspiration and guidance for advancing the development of genetic breeding in tea plants, as well as providing implications for breeding research in other crops.
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Affiliation(s)
| | | | | | | | | | | | - Long Yang
- College of Plant Protection and Agricultural Big-Data Research Center, Shandong Agricultural University, Tai’an 271018, China
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Martins SJ, Pasche J, Silva HAO, Selten G, Savastano N, Abreu LM, Bais HP, Garrett KA, Kraisitudomsook N, Pieterse CMJ, Cernava T. The Use of Synthetic Microbial Communities to Improve Plant Health. Phytopathology 2023; 113:1369-1379. [PMID: 36858028 DOI: 10.1094/phyto-01-23-0016-ia] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Despite the numerous benefits plants receive from probiotics, maintaining consistent results across applications is still a challenge. Cultivation-independent methods associated with reduced sequencing costs have considerably improved the overall understanding of microbial ecology in the plant environment. As a result, now, it is possible to engineer a consortium of microbes aiming for improved plant health. Such synthetic microbial communities (SynComs) contain carefully chosen microbial species to produce the desired microbiome function. Microbial biofilm formation, production of secondary metabolites, and ability to induce plant resistance are some of the microbial traits to consider when designing SynComs. Plant-associated microbial communities are not assembled randomly. Ecological theories suggest that these communities have a defined phylogenetic organization structured by general community assembly rules. Using machine learning, we can study these rules and target microbial functions that generate desired plant phenotypes. Well-structured assemblages are more likely to lead to a stable SynCom that thrives under environmental stressors as compared with the classical selection of single microbial activities or taxonomy. However, ensuring microbial colonization and long-term plant phenotype stability is still one of the challenges to overcome with SynComs, as the synthetic community may change over time with microbial horizontal gene transfer and retained mutations. Here, we explored the advances made in SynCom research regarding plant health, focusing on bacteria, as they are the most dominant microbial form compared with other members of the microbiome and the most commonly found in SynCom studies.
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Affiliation(s)
- Samuel J Martins
- Department of Plant Pathology, University of Florida, Gainesville, FL, 32611, U.S.A
| | - Josephine Pasche
- Department of Plant Pathology, University of Florida, Gainesville, FL, 32611, U.S.A
| | - Hiago Antonio O Silva
- Department of Plant Pathology, University of Florida, Gainesville, FL, 32611, U.S.A
- Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - Gijs Selten
- Plant-Microbe Interactions, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Noah Savastano
- Department of Plant and Soil Sciences, 311 AP Biopharma, University of Delaware, Newark, DE 19713, U.S.A
| | - Lucas Magalhães Abreu
- Departamento de Fitopatologia, Universidade Federal de Viçosa, Viçosa, MG 36570-900, Brazil
| | - Harsh P Bais
- Department of Plant and Soil Sciences, 311 AP Biopharma, University of Delaware, Newark, DE 19713, U.S.A
| | - Karen A Garrett
- Department of Plant Pathology, University of Florida, Gainesville, FL, 32611, U.S.A
| | | | - Corné M J Pieterse
- Plant-Microbe Interactions, Department of Biology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Tomislav Cernava
- Institute of Environmental Biotechnology, Graz University of Technology, Graz, 8020, Austria
- School of Biological Sciences, Faculty of Environmental and Life Sciences, University of Southampton, Southampton, SO17 1BJ, U.K
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Nazaret F, Alloing G, Mandon K, Frendo P. MarR Family Transcriptional Regulators and Their Roles in Plant-Interacting Bacteria. Microorganisms 2023; 11:1936. [PMID: 37630496 PMCID: PMC10458429 DOI: 10.3390/microorganisms11081936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/25/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023] Open
Abstract
The relationship between plants and associated soil microorganisms plays a major role in ecosystem functioning. Plant-bacteria interactions involve complex signaling pathways regulating various processes required by bacteria to adapt to their fluctuating environment. The establishment and maintenance of these interactions rely on the ability of the bacteria to sense and respond to biotic and abiotic environmental signals. In this context, MarR family transcriptional regulators can use these signals for transcriptional regulation, which is required to establish adapted responses. MarR-like transcriptional regulators are essential for the regulation of the specialized functions involved in plant-bacteria interactions in response to a wide range of molecules associated with the plant host. The conversion of environmental signals into changes in bacterial physiology and behavior allows the bacteria to colonize the plant and ensure a successful interaction. This review focuses on the mechanisms of plant-signal perception by MarR-like regulators, namely how they (i) allow bacteria to cope with the rhizosphere and plant endosphere, (ii) regulate the beneficial functions of Plant-Growth-Promoting Bacteria and (iii) regulate the virulence of phytopathogenic bacteria.
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Affiliation(s)
| | | | | | - Pierre Frendo
- Université Côte d’Azur, INRAE, CNRS, ISA, 06903 Sophia Antipolis, France; (F.N.); (G.A.); (K.M.)
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Ma Y, Li X, Wang F, Zhang L, Zhou S, Che X, Yu D, Liu X, Li Z, Sun H, Yu G, Zhang H. Structural and biochemical characterization of the key components of an auxin degradation operon from the rhizosphere bacterium Variovorax. PLoS Biol 2023; 21:e3002189. [PMID: 37459330 PMCID: PMC10374108 DOI: 10.1371/journal.pbio.3002189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 07/27/2023] [Accepted: 06/08/2023] [Indexed: 07/29/2023] Open
Abstract
Plant-associated bacteria play important regulatory roles in modulating plant hormone auxin levels, affecting the growth and yields of crops. A conserved auxin degradation (iad) operon was recently identified in the Variovorax genomes, which is responsible for root growth inhibition (RGI) reversion, promoting rhizosphere colonization and root growth. However, the molecular mechanism underlying auxin degradation by Variovorax remains unclear. Here, we systematically screened Variovorax iad operon products and identified 2 proteins, IadK2 and IadD, that directly associate with auxin indole-3-acetic acid (IAA). Further biochemical and structural studies revealed that IadK2 is a highly IAA-specific ATP-binding cassette (ABC) transporter solute-binding protein (SBP), likely involved in IAA uptake. IadD interacts with IadE to form a functional Rieske non-heme dioxygenase, which works in concert with a FMN-type reductase encoded by gene iadC to transform IAA into the biologically inactive 2-oxindole-3-acetic acid (oxIAA), representing a new bacterial pathway for IAA inactivation/degradation. Importantly, incorporation of a minimum set of iadC/D/E genes could enable IAA transformation by Escherichia coli, suggesting a promising strategy for repurposing the iad operon for IAA regulation. Together, our study identifies the key components and underlying mechanisms involved in IAA transformation by Variovorax and brings new insights into the bacterial turnover of plant hormones, which would provide the basis for potential applications in rhizosphere optimization and ecological agriculture.
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Affiliation(s)
- Yongjian Ma
- State Key Laboratory of Experimental Hematology, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Haihe Laboratory of Cell Ecosystem, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
| | - Xuzichao Li
- State Key Laboratory of Experimental Hematology, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Haihe Laboratory of Cell Ecosystem, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
| | - Feng Wang
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Lingling Zhang
- State Key Laboratory of Experimental Hematology, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Haihe Laboratory of Cell Ecosystem, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
| | - Shengmin Zhou
- YDS Pharmatech, Albany, New York, United States of America
| | - Xing Che
- YDS Pharmatech, Albany, New York, United States of America
| | - Dehao Yu
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Medical University; Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, China
| | - Xiang Liu
- State Key Laboratory of Medicinal Chemical Biology, Frontiers Science Center for Cell Responses, College of Life Sciences, Nankai University, Tianjin, China
| | - Zhuang Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan, China
| | - Huabing Sun
- The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Tianjin Medical University; Tianjin Key Laboratory on Technologies Enabling Development of Clinical Therapeutics and Diagnostics, School of Pharmacy, Tianjin Medical University, Tianjin, China
| | - Guimei Yu
- State Key Laboratory of Experimental Hematology, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Haihe Laboratory of Cell Ecosystem, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
| | - Heng Zhang
- State Key Laboratory of Experimental Hematology, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), The Province and Ministry Co-sponsored Collaborative Innovation Center for Medical Epigenetics, Haihe Laboratory of Cell Ecosystem, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
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Krell T, Gavira JA, Roca A, Matilla MA. The emerging role of auxins as bacterial signal molecules: Potential biotechnological applications. Microb Biotechnol 2023. [PMID: 37466451 PMCID: PMC10364314 DOI: 10.1111/1751-7915.14235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Accepted: 02/01/2023] [Indexed: 07/20/2023] Open
Abstract
Microorganisms are exposed in their natural niches to a wide diversity of signal molecules. Specific detection of these signals results in alterations in microbial metabolism and physiology. Auxins like indole-3-acetic acid are key phytohormones that regulate plant growth and development. Nonetheless, auxin biosynthesis is not restricted to plants but is ubiquitous in all kingdoms of life. This wide phylogenetic distribution of auxins production, together with the diversity of regulated cellular processes, have made auxins key intra- and inter-kingdom signal molecules in life modulating, for example microbial physiology, metabolism and virulence. Despite their increasing importance as global signal molecules, the mechanisms by which auxins perform their regulatory functions in microorganisms are largely unknown. In this article, we outline recent research that has advanced our knowledge of the mechanisms of bacterial auxin perception. We also highlight the potential applications of this research in aspects such as antibiotic production, biosensor design, plant microbiome engineering and antivirulence therapies.
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Affiliation(s)
- Tino Krell
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - José A Gavira
- Laboratory of Crystallographic Studies, IACT (CSIC-UGR), Armilla, Spain
| | - Amalia Roca
- Department of Microbiology, Facultad de Farmacia, Universidad de Granada, Granada, Spain
| | - Miguel A Matilla
- Department of Biotechnology and Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
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Carrillo‐Carrasco VP, Hernandez‐Garcia J, Mutte SK, Weijers D. The birth of a giant: evolutionary insights into the origin of auxin responses in plants. EMBO J 2023; 42:e113018. [PMID: 36786017 PMCID: PMC10015382 DOI: 10.15252/embj.2022113018] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 01/20/2023] [Accepted: 01/25/2023] [Indexed: 02/15/2023] Open
Abstract
The plant signaling molecule auxin is present in multiple kingdoms of life. Since its discovery, a century of research has been focused on its action as a phytohormone. In land plants, auxin regulates growth and development through transcriptional and non-transcriptional programs. Some of the molecular mechanisms underlying these responses are well understood, mainly in Arabidopsis. Recently, the availability of genomic and transcriptomic data of green lineages, together with phylogenetic inference, has provided the basis to reconstruct the evolutionary history of some components involved in auxin biology. In this review, we follow the evolutionary trajectory that allowed auxin to become the "giant" of plant biology by focusing on bryophytes and streptophyte algae. We consider auxin biosynthesis, transport, physiological, and molecular responses, as well as evidence supporting the role of auxin as a chemical messenger for communication within ecosystems. Finally, we emphasize that functional validation of predicted orthologs will shed light on the conserved properties of auxin biology among streptophytes.
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Affiliation(s)
| | | | - Sumanth K Mutte
- Laboratory of BiochemistryWageningen UniversityWageningenthe Netherlands
| | - Dolf Weijers
- Laboratory of BiochemistryWageningen UniversityWageningenthe Netherlands
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Gavira JA, Rico-Jiménez M, Ortega Á, Petukhova NV, Bug DS, Castellví A, Porozov YB, Zhulin IB, Krell T, Matilla MA. Emergence of an Auxin Sensing Domain in Plant-Associated Bacteria. mBio 2023; 14:e0336322. [PMID: 36602305 DOI: 10.1128/mbio.03363-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Bacteria have evolved a sophisticated array of signal transduction systems that allow them to adapt their physiology and metabolism to changing environmental conditions. Typically, these systems recognize signals through dedicated ligand binding domains (LBDs) to ultimately trigger a diversity of physiological responses. Nonetheless, an increasing number of reports reveal that signal transduction receptors also bind antagonists to inhibit responses mediated by agonists. The mechanisms by which antagonists block the downstream signaling cascade remain largely unknown. To advance our knowledge in this field, we used the LysR-type transcriptional regulator AdmX as a model. AdmX activates the expression of an antibiotic biosynthetic cluster in the rhizobacterium Serratia plymuthica. AdmX specifically recognizes the auxin phytohormone indole-3-acetic acid (IAA) and its biosynthetic intermediate indole-3-pyruvic acid (IPA) as signals. However, only IAA, but not IPA, was shown to regulate antibiotic production in S. plymuthica. Here, we report the high-resolution structures of the LBD of AdmX in complex with IAA and IPA. We found that IAA and IPA compete for binding to AdmX. Although IAA and IPA binding does not alter the oligomeric state of AdmX, IPA binding causes a higher degree of compactness in the protein structure. Molecular dynamics simulations revealed significant differences in the binding modes of IAA and IPA by AdmX, and the inspection of the three-dimensional structures evidenced differential agonist- and antagonist-mediated structural changes. Key residues for auxin binding were identified and an auxin recognition motif defined. Phylogenetic clustering supports the recent evolutionary emergence of this motif specifically in plant-associated enterobacteria. IMPORTANCE Although antagonists were found to bind different bacterial signal transduction receptors, we are still at the early stages of understanding the molecular details by which these molecules exert their inhibitory effects. Here, we provide insight into the structural changes resulting from the binding of an agonist and an antagonist to a sensor protein. Our data indicate that agonist and antagonist recognition is characterized by small conformational differences in the LBDs that can be efficiently transmitted to the output domain to modulate the final response. LBDs are subject to strong selective pressures and are rapidly evolving domains. An increasing number of reports support the idea that environmental factors drive the evolution of sensor domains. Given the recent evolutionary history of AdmX homologs, as well as their narrow phyletic distribution within plant-associated bacteria, our results are in accordance with a plant-mediated evolutionary process that resulted in the emergence of receptor proteins that specifically sense auxin phytohormones.
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Poupin MJ, Ledger T, Roselló-Móra R, González B. The Arabidopsis holobiont: a (re)source of insights to understand the amazing world of plant-microbe interactions. Environ Microbiome 2023; 18:9. [PMID: 36803555 PMCID: PMC9938593 DOI: 10.1186/s40793-023-00466-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Accepted: 01/19/2023] [Indexed: 06/18/2023]
Abstract
As holobiont, a plant is intrinsically connected to its microbiomes. However, some characteristics of these microbiomes, such as their taxonomic composition, biological and evolutionary role, and especially the drivers that shape them, are not entirely elucidated. Reports on the microbiota of Arabidopsis thaliana first appeared more than ten years ago. However, there is still a lack of a comprehensive understanding of the vast amount of information that has been generated using this holobiont. The main goal of this review was to perform an in-depth, exhaustive, and systematic analysis of the literature regarding the Arabidopsis-microbiome interaction. A core microbiota was identified as composed of a few bacterial and non-bacterial taxa. The soil (and, to a lesser degree, air) were detected as primary microorganism sources. From the plant perspective, the species, ecotype, circadian cycle, developmental stage, environmental responses, and the exudation of metabolites were crucial factors shaping the plant-microbe interaction. From the microbial perspective, the microbe-microbe interactions, the type of microorganisms belonging to the microbiota (i.e., beneficial or detrimental), and the microbial metabolic responses were also key drivers. The underlying mechanisms are just beginning to be unveiled, but relevant future research needs were identified. Thus, this review provides valuable information and novel analyses that will shed light to deepen our understanding of this plant holobiont and its interaction with the environment.
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Affiliation(s)
- M J Poupin
- Laboratorio de Bioingeniería, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, 7941169, Santiago, Chile
- Center of Applied Ecology and Sustainability (CAPES), Santiago, Chile
- Millennium Nucleus for the Development of Super Adaptable Plants (MN-SAP), Santiago, Chile
| | - T Ledger
- Laboratorio de Bioingeniería, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, 7941169, Santiago, Chile
- Center of Applied Ecology and Sustainability (CAPES), Santiago, Chile
- Millennium Nucleus for the Development of Super Adaptable Plants (MN-SAP), Santiago, Chile
| | - R Roselló-Móra
- Marine Microbiology Group, Department of Animal and Microbial Biodiversity, Mediterranean Institute for Advanced Studies (IMEDEA UIB-CSIC), Illes Balears, Majorca, Spain
| | - B González
- Laboratorio de Bioingeniería, Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, 7941169, Santiago, Chile.
- Center of Applied Ecology and Sustainability (CAPES), Santiago, Chile.
- Millennium Nucleus for the Development of Super Adaptable Plants (MN-SAP), Santiago, Chile.
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