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Bustos-Diaz ED, Cruz-Perez A, Garfias-Gallegos D, D'Agostino PM, Gehringer MM, Cibrian-Jaramillo A, Barona-Gomez F. Phylometagenomics of cycad coralloid roots reveals shared symbiotic signals. Microb Genom 2024; 10:001207. [PMID: 38451250 PMCID: PMC10999742 DOI: 10.1099/mgen.0.001207] [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] [Received: 09/27/2023] [Accepted: 02/09/2024] [Indexed: 03/08/2024] Open
Abstract
Cycads are known to host symbiotic cyanobacteria, including Nostocales species, as well as other sympatric bacterial taxa within their specialized coralloid roots. Yet, it is unknown if these bacteria share a phylogenetic origin and/or common genomic functions that allow them to engage in facultative symbiosis with cycad roots. To address this, we obtained metagenomic sequences from 39 coralloid roots sampled from diverse cycad species and origins in Australia and Mexico. Culture-independent shotgun metagenomic sequencing was used to validate sub-community co-cultures as an efficient approach for functional and taxonomic analysis. Our metanalysis shows a host-independent microbiome core consisting of seven bacterial orders with high species diversity within the identified taxa. Moreover, we recovered 43 cyanobacterial metagenome-assembled genomes, and in addition to Nostoc spp., symbiotic cyanobacteria of the genus Aulosira were identified for the first time. Using this robust dataset, we used phylometagenomic analysis to reveal three monophyletic cyanobiont clades, two host-generalist and one cycad-specific that includes Aulosira spp. Although the symbiotic clades have independently arisen, they are enriched in certain functional genes, such as those related to secondary metabolism. Furthermore, the taxonomic composition of associated sympatric bacterial taxa remained constant. Our research quadruples the number of cycad cyanobiont genomes and provides a robust framework to decipher cyanobacterial symbioses, with the potential of improving our understanding of symbiotic communities. This study lays a solid foundation to harness cyanobionts for agriculture and bioprospection, and assist in conservation of critically endangered cycads.
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Affiliation(s)
- Edder D. Bustos-Diaz
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Irapuato, Guanajuato, Mexico
- Institute of Biology, Leiden University, Netherlands, 2333 BE, Leiden
| | - Arely Cruz-Perez
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Irapuato, Guanajuato, Mexico
| | - Diego Garfias-Gallegos
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Irapuato, Guanajuato, Mexico
| | - Paul M. D'Agostino
- Chair of Technical Biochemistry, Technical University of Dresden, Bergstraße 66, 01069 Dresden, Germany
| | - Michelle M. Gehringer
- Department of Microbiology, University of Kaiserslautern-Landau (RPTU), 67663 Kaiserslautern, Germany
| | - Angelica Cibrian-Jaramillo
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Irapuato, Guanajuato, Mexico
- Naturalis Biodiversity Center, Leiden 2333 CR, Netherlands
| | - Francisco Barona-Gomez
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Cinvestav, Irapuato, Guanajuato, Mexico
- Institute of Biology, Leiden University, Netherlands, 2333 BE, Leiden
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Kipp MA, Stüeken EE, Strömberg CAE, Brightly WH, Arbour VM, Erdei B, Hill RS, Johnson KR, Kvaček J, McElwain JC, Miller IM, Slodownik M, Vajda V, Buick R. Nitrogen isotopes reveal independent origins of N 2-fixing symbiosis in extant cycad lineages. Nat Ecol Evol 2024; 8:57-69. [PMID: 37974002 DOI: 10.1038/s41559-023-02251-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Accepted: 10/17/2023] [Indexed: 11/19/2023]
Abstract
Cycads are ancient seed plants (gymnosperms) that emerged by the early Permian. Although they were common understory flora and food for dinosaurs in the Mesozoic, their abundance declined markedly in the Cenozoic. Extant cycads persist in restricted populations in tropical and subtropical habitats and, with their conserved morphology, are often called 'living fossils.' All surviving taxa receive nitrogen from symbiotic N2-fixing cyanobacteria living in modified roots, suggesting an ancestral origin of this symbiosis. However, such an ancient acquisition is discordant with the abundance of cycads in Mesozoic fossil assemblages, as modern N2-fixing symbioses typically occur only in nutrient-poor habitats where advantageous for survival. Here, we use foliar nitrogen isotope ratios-a proxy for N2 fixation in modern plants-to probe the antiquity of the cycad-cyanobacterial symbiosis. We find that fossilized cycad leaves from two Cenozoic representatives of extant genera have nitrogen isotopic compositions consistent with microbial N2 fixation. In contrast, all extinct cycad genera have nitrogen isotope ratios that are indistinguishable from co-existing non-cycad plants and generally inconsistent with microbial N2 fixation, pointing to nitrogen assimilation from soils and not through symbiosis. This pattern indicates that, rather than being ancestral within cycads, N2-fixing symbiosis arose independently in the lineages leading to living cycads during or after the Jurassic. The preferential survival of these lineages may therefore reflect the effects of competition with angiosperms and Cenozoic climatic change.
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Affiliation(s)
- Michael A Kipp
- Department of Earth & Space Sciences, University of Washington, Seattle, WA, USA.
- Virtual Planetary Laboratory, NASA Astrobiology Institute, Seattle, WA, USA.
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
- Division of Earth and Climate Sciences, Nicholas School of the Environment, Duke University, Durham, NC, USA.
| | - Eva E Stüeken
- Virtual Planetary Laboratory, NASA Astrobiology Institute, Seattle, WA, USA
- School of Earth & Environmental Sciences, University of St. Andrews, St. Andrews, UK
| | - Caroline A E Strömberg
- Department of Biology, University of Washington, Seattle, WA, USA
- Burke Museum of Natural History and Culture, Seattle, WA, USA
| | | | - Victoria M Arbour
- Department of Knowledge, Royal BC Museum, Victoria, British Columbia, Canada
| | - Boglárka Erdei
- Botanical Department, Hungarian Natural History Museum, Budapest, Hungary
| | - Robert S Hill
- School of Biological Sciences and the Environment Institute, University of Adelaide, Adelaide, South Australia, Australia
| | - Kirk R Johnson
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Jiří Kvaček
- Department of Palaeontology, National Museum, Prague, Czech Republic
| | - Jennifer C McElwain
- Department of Botany, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Ian M Miller
- National Geographic Society, Washington, DC, USA
| | - Miriam Slodownik
- School of Biological Sciences and the Environment Institute, University of Adelaide, Adelaide, South Australia, Australia
| | - Vivi Vajda
- Research Division, Swedish Museum of Natural History, Stockholm, Sweden
- Department of Geology, Lund University, Lund, Sweden
| | - Roger Buick
- Department of Earth & Space Sciences, University of Washington, Seattle, WA, USA
- Virtual Planetary Laboratory, NASA Astrobiology Institute, Seattle, WA, USA
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Chatterjee P, Schafran P, Li FW, Meeks JC. Nostoc Talks Back: Temporal Patterns of Differential Gene Expression During Establishment of Anthoceros-Nostoc Symbiosis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:917-932. [PMID: 35802132 DOI: 10.1094/mpmi-05-22-0101-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Endosymbiotic associations between hornworts and nitrogen-fixing cyanobacteria form when the plant is limited for combined nitrogen (N). We generated RNA-seq data to examine temporal gene expression patterns during the culturing of N-starved Anthoceros punctatus in the absence and the presence of symbiotic cyanobacterium Nostoc punctiforme. In symbiont-free A. punctatus gametophytes, N starvation caused downregulation of chlorophyll content and chlorophyll fluorescence characteristics as well as transcription of photosynthesis-related genes. This downregulation was reversed in A. punctatus cocultured with N. punctiforme, corresponding to the provision by the symbiont of N2-derived NH4+, which commenced within 5 days of coculture and reached a maximum by 14 days. We also observed transient increases in transcription of ammonium and nitrate transporters in a N. punctiforme-dependent manner as well as that of a SWEET transporter that was initially independent of N2-derived NH4+. The temporal patterns of differential gene expression indicated that N. punctiforme transmits signals that impact gene expression to A. punctatus both prior to and after its provision of fixed N. This study is the first illustrating the temporal patterns of gene expression during establishment of an endosymbiotic nitrogen-fixing association in this monophyletic evolutionary lineage of land plants. [Formula: see text] Copyright © 2022 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)
- Poulami Chatterjee
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, U.S.A
| | - Peter Schafran
- Boyce Thompson Institute, Ithaca, NY 14853, U.S.A
- Plant Biology Section, Cornell University, Ithaca, NY 14953, U.S.A
| | - Fay-Wei Li
- Boyce Thompson Institute, Ithaca, NY 14853, U.S.A
- Plant Biology Section, Cornell University, Ithaca, NY 14953, U.S.A
| | - John C Meeks
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA 95616, U.S.A
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Novel metabolic interactions and environmental conditions mediate the boreal peatmoss-cyanobacteria mutualism. THE ISME JOURNAL 2022; 16:1074-1085. [PMID: 34845335 PMCID: PMC8941135 DOI: 10.1038/s41396-021-01136-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 09/24/2021] [Accepted: 10/01/2021] [Indexed: 11/18/2022]
Abstract
Interactions between Sphagnum (peat moss) and cyanobacteria play critical roles in terrestrial carbon and nitrogen cycling processes. Knowledge of the metabolites exchanged, the physiological processes involved, and the environmental conditions allowing the formation of symbiosis is important for a better understanding of the mechanisms underlying these interactions. In this study, we used a cross-feeding approach with spatially resolved metabolite profiling and metatranscriptomics to characterize the symbiosis between Sphagnum and Nostoc cyanobacteria. A pH gradient study revealed that the Sphagnum–Nostoc symbiosis was driven by pH, with mutualism occurring only at low pH. Metabolic cross-feeding studies along with spatially resolved matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) identified trehalose as the main carbohydrate source released by Sphagnum, which were depleted by Nostoc along with sulfur-containing choline-O-sulfate, taurine and sulfoacetate. In exchange, Nostoc increased exudation of purines and amino acids. Metatranscriptome analysis indicated that Sphagnum host defense was downregulated when in direct contact with the Nostoc symbiont, but not as a result of chemical contact alone. The observations in this study elucidated environmental, metabolic, and physiological underpinnings of the widespread plant–cyanobacterial symbioses with important implications for predicting carbon and nitrogen cycling in peatland ecosystems as well as the basis of general host-microbe interactions.
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Kipp MA, Stüeken EE, Gehringer MM, Sterelny K, Scott JK, Forster PI, Strömberg CAE, Buick R. Exploring cycad foliage as an archive of the isotopic composition of atmospheric nitrogen. GEOBIOLOGY 2020; 18:152-166. [PMID: 31769156 DOI: 10.1111/gbi.12374] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/16/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
Molecular nitrogen (N2 ) constitutes the majority of Earth's modern atmosphere, contributing ~0.79 bar of partial pressure (pN2 ). However, fluctuations in pN2 may have occurred on 107 -109 year timescales in Earth's past, perhaps altering the isotopic composition of atmospheric nitrogen. Here, we explore an archive that may record the isotopic composition of atmospheric N2 in deep time: the foliage of cycads. Cycads are ancient gymnosperms that host symbiotic N2 -fixing cyanobacteria in modified root structures known as coralloid roots. All extant species of cycads are known to host symbionts, suggesting that this N2 -fixing capacity is perhaps ancestral, reaching back to the early history of cycads in the late Paleozoic. Therefore, if the process of microbial N2 fixation records the δ15 N value of atmospheric N2 in cycad foliage, the fossil record of cycads may provide an archive of atmospheric δ15 N values. To explore this potential proxy, we conducted a survey of wild cycads growing in a range of modern environments to determine whether cycad foliage reliably records the isotopic composition of atmospheric N2 . We find that neither biological nor environmental factors significantly influence the δ15 N values of cycad foliage, suggesting that they provide a reasonably robust record of the δ15 N of atmospheric N2 . Application of this proxy to the record of carbonaceous cycad fossils may not only help to constrain changes in atmospheric nitrogen isotope ratios since the late Paleozoic, but also could shed light on the antiquity of the N2 -fixing symbiosis between cycads and cyanobacteria.
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Affiliation(s)
- Michael A Kipp
- Department of Earth & Space Sciences, University of Washington, Seattle, WA, USA
- Virtual Planetary Laboratory - NASA Nexus for Exoplanet System Science, Seattle, WA, USA
| | - Eva E Stüeken
- Virtual Planetary Laboratory - NASA Nexus for Exoplanet System Science, Seattle, WA, USA
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, UK
| | - Michelle M Gehringer
- Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Kim Sterelny
- School of Philosophy, Australian National University, Canberra, ACT, Australia
- School of History, Philosophy, Political Science & International Relations, Victoria University of Wellington, Wellington, New Zealand
| | - John K Scott
- CSIRO Land and Water, Wembley, WA, Australia
- School of Biological Sciences, The University of Western Australia, Crawley, WA, Australia
| | - Paul I Forster
- Department of Environment & Science, Queensland Herbarium, Toowong, Qld, Australia
| | - Caroline A E Strömberg
- Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, WA, USA
| | - Roger Buick
- Department of Earth & Space Sciences, University of Washington, Seattle, WA, USA
- Virtual Planetary Laboratory - NASA Nexus for Exoplanet System Science, Seattle, WA, USA
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6
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Suárez-Moo PDJ, Vovides AP, Griffith MP, Barona-Gómez F, Cibrián-Jaramillo A. Unlocking a high bacterial diversity in the coralloid root microbiome from the cycad genus Dioon. PLoS One 2019; 14:e0211271. [PMID: 30726265 PMCID: PMC6364921 DOI: 10.1371/journal.pone.0211271] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2018] [Accepted: 01/10/2019] [Indexed: 12/21/2022] Open
Abstract
Cycads are among the few plants that have developed specialized roots to host nitrogen-fixing bacteria. We describe the bacterial diversity of the coralloid roots from seven Dioon species and their surrounding rhizosphere and soil. Using 16S rRNA gene amplicon sequencing, we found that all coralloid roots are inhabited by a broad diversity of bacterial groups, including cyanobacteria and Rhizobiales among the most abundant groups. The diversity and composition of the endophytes are similar in the six Mexican species of Dioon that we evaluated, suggesting a recent divergence of Dioon populations and/or similar plant-driven restrictions in maintaining the coralloid root microbiome. Botanical garden samples and natural populations have a similar taxonomic composition, although the beta diversity differed between these populations. The rhizosphere surrounding the coralloid root serves as a reservoir and source of mostly diazotroph and plant growth-promoting groups that colonize the coralloid endosphere. In the case of cyanobacteria, the endosphere is enriched with Nostoc spp and Calothrix spp that are closely related to previously reported symbiont genera in cycads and other early divergent plants. The data reported here provide an in-depth taxonomic characterization of the bacterial community associated with coralloid root microbiome. The functional aspects of the endophytes, their biological interactions, and their evolutionary history are the next research step in this recently discovered diversity within the cycad coralloid root microbiome.
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Affiliation(s)
- Pablo de Jesús Suárez-Moo
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav-IPN), Irapuato, Guanajuato, Mexico
| | - Andrew P. Vovides
- Instituto de Ecología, A.C., Red de Ecología Evolutiva, Xalapa, Veracruz, Mexico
| | - M. Patrick Griffith
- Montgomery Botanical Center, Coral Gables, Miami, Florida, United States of America
| | - Francisco Barona-Gómez
- Evolution of Metabolic Diversity Laboratory, Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav-IPN), Irapuato, Guanajuato, Mexico
| | - Angélica Cibrián-Jaramillo
- Ecological and Evolutionary Genomics Laboratory, Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (Cinvestav-IPN), Irapuato, Guanajuato, Mexico
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7
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Highly diverse endophytes in roots of Cycas bifida (Cycadaceae), an ancient but endangered gymnosperm. J Microbiol 2018; 56:337-345. [PMID: 29721831 DOI: 10.1007/s12275-018-7438-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Revised: 02/11/2018] [Accepted: 02/27/2018] [Indexed: 10/17/2022]
Abstract
As an ancient seed plant, cycads are one of the few gymnosperms that develop a root symbiosis with cyanobacteria, which has allowed cycads to cope with harsh geologic and climatic conditions during the evolutionary process. However, the endophytic microbes in cycad roots remain poorly identified. In this study, using next-generation sequencing techniques, we investigated the microbial diversity and composition of both the coralloid and regular roots of Cycas bifida (Dyer) K.D. Hill. Highly diverse endophytic communities were observed in both the coralloid and regular roots. Of the associated bacteria, the top five families were the Nostocaceae, Sinobacteraceae, Bradyrhizobiaceae, Bacillaceae, and Hyphomicrobiaceae. The Nectriaceae, Trichocomaceae, and Incertae sedis were the predominant fungal families in all root samples. A significant difference in the endophytic bacterial community was detected between coralloid roots and regular roots, but no difference was observed between the fungal communities in the two root types. Cyanobacteria were more dominant in coralloid roots than in regular roots. The divergence of cycad root structures and the modified physiological processes may have contributed to the abundance of cyanobionts in coralloid roots. Consequently, the colonization of cyanobacteria inhibits the assemblage of other endophytes. Our results contribute to an understanding of the species diversity and composition of the cycad-endophyte microbiome and provide an abbreviated list of potential ecological roles of the core microbes present.
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9
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Jasper DA. Beneficial Soil Microorganisms of the Jarrah Forest and Their Recovery in Bauxite Mine Restoration in Southwestern Australia. Restor Ecol 2007. [DOI: 10.1111/j.1526-100x.2007.00295.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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10
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Physiological Adaptations in Nitrogen-fixing Nostoc–Plant Symbiotic Associations. MICROBIOLOGY MONOGRAPHS 2007. [DOI: 10.1007/7171_2007_101] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Meeks JC. Molecular mechanisms in the nitrogen-fixing Nostoc-bryophyte symbiosis. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2006; 41:165-96. [PMID: 16623394 DOI: 10.1007/3-540-28221-1_9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Affiliation(s)
- John C Meeks
- Section of Microbiology, University of California, Davis, CA 95616, USA.
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12
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Root-based N2-fixing symbioses: Legumes, actinorhizal plants, Parasponia sp. and cycads. PLANT ECOPHYSIOLOGY 2005. [DOI: 10.1007/1-4020-4099-7_3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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13
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Meeks JC, Elhai J. Regulation of cellular differentiation in filamentous cyanobacteria in free-living and plant-associated symbiotic growth states. Microbiol Mol Biol Rev 2002; 66:94-121; table of contents. [PMID: 11875129 PMCID: PMC120779 DOI: 10.1128/mmbr.66.1.94-121.2002] [Citation(s) in RCA: 313] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Certain filamentous nitrogen-fixing cyanobacteria generate signals that direct their own multicellular development. They also respond to signals from plants that initiate or modulate differentiation, leading to the establishment of a symbiotic association. An objective of this review is to describe the mechanisms by which free-living cyanobacteria regulate their development and then to consider how plants may exploit cyanobacterial physiology to achieve stable symbioses. Cyanobacteria that are capable of forming plant symbioses can differentiate into motile filaments called hormogonia and into specialized nitrogen-fixing cells called heterocysts. Plant signals exert both positive and negative regulatory control on hormogonium differentiation. Heterocyst differentiation is a highly regulated process, resulting in a regularly spaced pattern of heterocysts in the filament. The evidence is most consistent with the pattern arising in two stages. First, nitrogen limitation triggers a nonrandomly spaced cluster of cells (perhaps at a critical stage of their cell cycle) to initiate differentiation. Interactions between an inhibitory peptide exported by the differentiating cells and an activator protein within them causes one cell within each cluster to fully differentiate, yielding a single mature heterocyst. In symbiosis with plants, heterocyst frequencies are increased 3- to 10-fold because, we propose, either differentiation is initiated at an increased number of sites or resolution of differentiating clusters is incomplete. The physiology of symbiotically associated cyanobacteria raises the prospect that heterocyst differentiation proceeds independently of the nitrogen status of a cell and depends instead on signals produced by the plant partner.
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Affiliation(s)
- John C Meeks
- Section of Microbiology, University of California, Davis, California 95616, USA.
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15
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Canini A, Caiola MG. Characterization of gonidial zone ofCycas revolutacoralloid roots by means of microelectrodes. FEMS Microbiol Lett 1993. [DOI: 10.1111/j.1574-6968.1993.tb06146.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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16
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Ornithine cycle inNostoc PCC 73102: Stimulation of in vitro ornithine carbamoyl transferase activity by addition of arginine. Curr Microbiol 1993. [DOI: 10.1007/bf01577339] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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17
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Abstract
Gunnera L. develops a complex and intimate symbiosis with N2 -fixing cyanobacteria of the genus Nostoc, which renders the plant independent of combined nitrogen. The Nostoc-Gunnera symbiosis exhibits unique features compared to other cyanobacterial-plant symbioses: it is for example the only one that involves a flowering plant (angiosperm), the cyanobacterium infects specialized gland organs located on the stems of the host and once it has passed into the interior of the gland the cyanobacterium also enters the Gunnera cells where it starts to differentiate the highest frequency of heterocysts (the N2 -fixing cells) recorded in any cyanobacterial population. Gunnera has attracted scientific attention also for the following reasons: the genus has a peculiar geographic distribution of its subgenera and species in the Southern Hemisphere. It differs morphologically and anatomically from related plants and also shows an anomalous polystelic vascular system (polystely). This review gives an updated account of present knowledge concerning the Nostoc-Gunnera symbiosis. Emphasis will be on the development of the symbiotic tissue (the gland), the structure and function of the prokaryotic N2 -fixing cyanobacterium, the infection process and on the relationship between the pro- and eukaryotic partners prior to and following the establishment of symbiosis. CONTENTS Summary 379 I. Introduction 379 II. The Gunner a plant 380 III. The microsymbiont(s) 383 IV. The symbiosis 384 V. The gland 385 VI. The infection process 388 VII. Specificity 391 VIII. Impacts on the cyanobiont 392 IX. N2 fixation and release 393 X. Photosynthesis 396 XI. Concluding remarks 397 Acknowledgements 398 References 398.
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Affiliation(s)
- B Bergman
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
| | - C Johansson
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
| | - E Söderbäck
- Department of Botany, Stockholm University, S-106 91 Stockholm, Sweden
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18
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Smith SE, Smith FA. Structure and function of the interfaces in biotrophic symbioses as they relate to nutrient transport. THE NEW PHYTOLOGIST 1990; 114:1-38. [PMID: 33874304 DOI: 10.1111/j.1469-8137.1990.tb00370.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
In this review we compare the structure and function of the interfaces between symbionts in biotrophic associations. The emphasis is on biotrophic fungal parasites and on mycorrhizas, although necrotrophic parasitic associations and the Rhizobium/legume symbiosis are mentioned briefly. We take as a starting point the observations that in the parasitic associations nutrient transport is polarized towards the parasite, whereas in mutualistic associations it is bidirectional. The structure and function of the interfaces are then compared. An important common feature is that in nearly all cases the heterotrophic symbiont (whether mutualistic or parasitic) is located topologically outside the cytoplasm of the host cells, in an apoplastic compartment. This means that nutrient movements across the interface must involve transport into and out of this apoplastic region through membranes of both organisms. Basic principles of membrane transport in uninfected cells are briefly reviewed to set the scene for a discussion of transport mechanisms which may operate in parasitic and mycorrhizal symbioses. The presence and possible roles of ATPases associated with membranes at the interfaces are discussed. We conclude that cytochemical techniques (used to demonstrate the activity of these enzymes) need to he extended and complemented by biochemical and biophysical studies in order to confirm that the activity is due to transport ATPases. Nevertheless, the distribution of activity appears to he in accord with polarized transport mechanisms in some pathogens and with bidirectional transport in mycorrhizas. The absence of ATPases on many fungal membranes needs re-examination. We emphasize that transport mechanisms between mycorrhizal symbionts cannot be viewed simply as the exchange of carbon for phosphate. Additional features include provision for transport of carbon and nitrogen as amino acids or amides and for ions such as K+ and H+ involved in the maintenance of charge balance and pH regulation, processes which also occur in parasitic associations. Interplant transport of nutrients via mycorrhizal hyphae is discussed in the context of these complexities. Some suggestions for the directions of future work are made. CONTENTS Summary 1 I. Introduction 2 II. The availability of nutrients to the symbionts 3 III. Structure of interfaces between symbionts 4 IV. Identity of nutrients transferred: an overview 12 V. Membrane transport: basic principles 14 VI. Transport at the interface of biotrophic symbioses 15 VII. Regulation of pH in biotrophic symbioses 25 VIII. Conclusions: 26.
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Affiliation(s)
- S E Smith
- Departments of Agricultural Biochemistry (Waite Agricultural Research Institute), The University of Adelaide, Adelaide, South Australia, Australia, 5001
| | - F A Smith
- Departments of Botany, The University of Adelaide, Adelaide, South Australia, Australia, 5001
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