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Berrabah F, Benaceur F, Yin C, Xin D, Magne K, Garmier M, Gruber V, Ratet P. Defense and senescence interplay in legume nodules. Plant Commun 2024; 5:100888. [PMID: 38532645 PMCID: PMC11009364 DOI: 10.1016/j.xplc.2024.100888] [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] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Revised: 02/05/2024] [Accepted: 03/23/2024] [Indexed: 03/28/2024]
Abstract
Immunity and senescence play a crucial role in the functioning of the legume symbiotic nodules. The miss-regulation of one of these processes compromises the symbiosis leading to death of the endosymbiont and the arrest of the nodule functioning. The relationship between immunity and senescence has been extensively studied in plant organs where a synergistic response can be observed. However, the interplay between immunity and senescence in the symbiotic organ is poorly discussed in the literature and these phenomena are often mixed up. Recent studies revealed that the cooperation between immunity and senescence is not always observed in the nodule, suggesting complex interactions between these two processes within the symbiotic organ. Here, we discuss recent results on the interplay between immunity and senescence in the nodule and the specificities of this relationship during legume-rhizobium symbiosis.
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Affiliation(s)
- Fathi Berrabah
- Faculty of Sciences, University Amar Telidji, 03000 Laghouat, Algeria; Research Unit of Medicinal Plants (RUMP), National Center of Biotechnology Research, CRBt, 25000 Constantine, Algeria.
| | - Farouk Benaceur
- Faculty of Sciences, University Amar Telidji, 03000 Laghouat, Algeria; Research Unit of Medicinal Plants (RUMP), National Center of Biotechnology Research, CRBt, 25000 Constantine, Algeria
| | - Chaoyan Yin
- Université Paris-Saclay, CNRS, INRAE, University of Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France; Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Dawei Xin
- Key Laboratory of Soybean Biology in the Chinese Ministry of Education, College of Agriculture, Northeast Agricultural University, Harbin 150030, China
| | - Kévin Magne
- Université Paris-Saclay, CNRS, INRAE, University of Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France; Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Marie Garmier
- Université Paris-Saclay, CNRS, INRAE, University of Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France; Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Véronique Gruber
- Université Paris-Saclay, CNRS, INRAE, University of Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France; Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France.
| | - Pascal Ratet
- Université Paris-Saclay, CNRS, INRAE, University of Evry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France; Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
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2
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Berrabah F, Bernal G, Elhosseyn AS, El Kassis C, L’Horset R, Benaceur F, Wen J, Mysore KS, Garmier M, Gourion B, Ratet P, Gruber V. Insight into the control of nodule immunity and senescence during Medicago truncatula symbiosis. Plant Physiol 2023; 191:729-746. [PMID: 36305683 PMCID: PMC9806560 DOI: 10.1093/plphys/kiac505] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 09/25/2022] [Indexed: 06/16/2023]
Abstract
Medicago (Medicago truncatula) establishes a symbiosis with the rhizobia Sinorhizobium sp, resulting in the formation of nodules where the bacteria fix atmospheric nitrogen. The loss of immunity repression or early senescence activation compromises symbiont survival and leads to the formation of nonfunctional nodules (fix-). Despite many studies exploring an overlap between immunity and senescence responses outside the nodule context, the relationship between these processes in the nodule remains poorly understood. To investigate this phenomenon, we selected and characterized three Medicago mutants developing fix- nodules and showing senescence responses. Analysis of specific defense (PATHOGENESIS-RELATED PROTEIN) or senescence (CYSTEINE PROTEASE) marker expression demonstrated that senescence and immunity seem to be antagonistic in fix- nodules. The growth of senescence mutants on non-sterile (sand/perlite) substrate instead of sterile in vitro conditions decreased nodule senescence and enhanced defense, indicating that environment can affect the immunity/senescence balance. The application of wounding stress on wild-type (WT) fix+ nodules led to the death of intracellular rhizobia and associated with co-stimulation of defense and senescence markers, indicating that in fix+ nodules the relationship between the two processes switches from opposite to synergistic to control symbiont survival during response to the stress. Our data show that the immune response in stressed WT nodules is linked to the repression of DEFECTIVE IN NITROGEN FIXATION 2 (DNF2), Symbiotic CYSTEINE-RICH RECEPTOR-LIKE KINASE (SymCRK), and REGULATOR OF SYMBIOSOME DIFFERENTIATION (RSD), key genes involved in symbiotic immunity suppression. This study provides insight to understand the links between senescence and immunity in Medicago nodules.
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Affiliation(s)
- Fathi Berrabah
- Faculty of Sciences, Department of Biology, Amar Telidji University, 03000 Laghouat, Algeria
- Research Unit of Medicinal Plants (RUMP), National Center of Biotechnology Research, CRBt, 25000 Constantine, Algeria
| | - Gautier Bernal
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Ait-Salem Elhosseyn
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Cyrille El Kassis
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Roxane L’Horset
- Pôle de Protection des Plantes, UMR PVBMT, 97410 Saint-Pierre, Réunion, France
| | - Farouk Benaceur
- Faculty of Sciences, Department of Biology, Amar Telidji University, 03000 Laghouat, Algeria
- Research Unit of Medicinal Plants (RUMP), National Center of Biotechnology Research, CRBt, 25000 Constantine, Algeria
| | - Jiangqi Wen
- The Institute of Agricultural Biosciences, Oklahoma State University, Ardmore, Oklahoma 73401, USA
| | - Kirankumar S Mysore
- The Institute of Agricultural Biosciences, Oklahoma State University, Ardmore, Oklahoma 73401, USA
| | - Marie Garmier
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Benjamin Gourion
- LIPME, Université de Toulouse, INRAE, CNRS, 31320 Castanet-Tolosan, France
| | - Pascal Ratet
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
| | - Véronique Gruber
- Université Paris-Saclay, CNRS, INRAE, Université d’Évry, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
- Université Paris Cité, Institute of Plant Sciences Paris-Saclay (IPS2), 91190 Gif-sur-Yvette, France
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Abstract
Plants of the legume family host massive intracellular bacterial populations in the tissues of specialized organs, the nodules. In these organs, the bacteria, named rhizobia, can fix atmospheric nitrogen and transfer it to the plant. This special metabolic skill provides to the legumes an advantage when they grow on nitrogen-scarce substrates. While packed with rhizobia, the nodule cells remain alive, metabolically active, and do not develop defense reactions. Here, we review our knowledge on the control of plant immunity during the rhizobia-legume symbiosis. We present the results of an evolutionary process that selected both divergence of microbial-associated molecular motifs and active suppressors of immunity on the rhizobial side and, on the legume side, active mechanisms that contribute to suppression of immunity.
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Affiliation(s)
- Fathi Berrabah
- 1 Laboratory of Exploration and Valorization of Steppic Ecosystems, Faculty of Nature and Life Sciences, University of Ziane Achour, 17000 Djelfa, Algeria
| | - Pascal Ratet
- 2 Institute of Plant Sciences Paris-Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Bâtiment 630, 91405 Orsay, France
- 3 Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, 91405, Orsay, France; and
| | - Benjamin Gourion
- 4 LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
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Berrabah F, Balliau T, Aït-Salem EH, George J, Zivy M, Ratet P, Gourion B. Control of the ethylene signaling pathway prevents plant defenses during intracellular accommodation of the rhizobia. New Phytol 2018; 219:310-323. [PMID: 29668080 DOI: 10.1111/nph.15142] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 02/28/2018] [Indexed: 05/11/2023]
Abstract
Massive intracellular populations of symbiotic bacteria, referred to as rhizobia, are housed in legume root nodules. Little is known about the mechanisms preventing the development of defense in these organs although genes such as SymCRK and DNF2 of the model legume Medicago truncatula are required for this control after rhizobial internalization in host nodule cells. Here we investigated the molecular basis of the symbiotic control of immunity. Proteomic analysis was performed to compare functional (wild-type) and defending nodules (symCRK). Based on the results, the control of plant immunity during the functional step of the symbiosis was further investigated by biochemical and pharmacological approaches as well as by transcript and histology analysis. Ethylene was identified as a potential signal inducing plant defenses in symCRK nodules. Involvement of this phytohormone in symCRK and dnf2-developed defenses and in the death of intracellular rhizobia was confirmed. This negative effect of ethylene depended on the M. truncatula sickle gene and was also observed in the legume Lotus japonicus. Together, these data indicate that prevention of ethylene-triggered defenses is crucial for the persistence of endosymbiosis and that the DNF2 and SymCRK genes are required for this process.
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Affiliation(s)
- Fathi Berrabah
- Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Batiment 630, Orsay, 91405, France
- Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, Orsay, 91405, France
| | - Thierry Balliau
- INRA, PAPPSO, UMR Génétique Quantitative et Évolution - Le Moulon, INRA/Université Paris-Sud/CNRS/AgroParisTech, Université Paris-Saclay, Gif-sur-Yvette, F-91190, France
| | - El Hosseyn Aït-Salem
- Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Batiment 630, Orsay, 91405, France
- Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, Orsay, 91405, France
| | - Jeoffrey George
- Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Batiment 630, Orsay, 91405, France
- Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, Orsay, 91405, France
| | - Michel Zivy
- CNRS, PAPPSO, UMR Génétique Quantitative et Évolution - Le Moulon, INRA/Université Paris-Sud/CNRS/AgroParisTech, Université Paris-Saclay, Gif-sur-Yvette, F-91190, France
| | - Pascal Ratet
- Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Batiment 630, Orsay, 91405, France
- Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, Orsay, 91405, France
| | - Benjamin Gourion
- Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Batiment 630, Orsay, 91405, France
- Institute of Plant Sciences Paris-Saclay IPS2, Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, Orsay, 91405, France
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Berrabah F, Ratet P, Gourion B. Multiple steps control immunity during the intracellular accommodation of rhizobia. J Exp Bot 2015; 66:1977-85. [PMID: 25682610 PMCID: PMC4378630 DOI: 10.1093/jxb/eru545] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 12/15/2014] [Accepted: 12/16/2014] [Indexed: 05/20/2023]
Abstract
Medicago truncatula belongs to the legume family and forms symbiotic associations with nitrogen fixing bacteria, the rhizobia. During these interactions, the plants develop root nodules in which bacteria invade the plant cells and fix nitrogen for the benefit of the plant. Despite massive infection, legume nodules do not develop visible defence reactions, suggesting a special immune status of these organs. Some factors influencing rhizobium maintenance within the plant cells have been previously identified, such as the M. truncatula NCR peptides whose toxic effects are reduced by the bacterial protein BacA. In addition, DNF2, SymCRK, and RSD are M. truncatula genes required to avoid rhizobial death within the symbiotic cells. DNF2 and SymCRK are essential to prevent defence-like reactions in nodules after bacteria internalization into the symbiotic cells. Herein, we used a combination of genetics, histology and molecular biology approaches to investigate the relationship between the factors preventing bacterial death in the nodule cells. We show that the RSD gene is also required to repress plant defences in nodules. Upon inoculation with the bacA mutant, defence responses are observed only in the dnf2 mutant and not in the symCRK and rsd mutants. In addition, our data suggest that lack of nitrogen fixation by the bacterial partner triggers bacterial death in nodule cells after bacteroid differentiation. Together our data indicate that, after internalization, at least four independent mechanisms prevent bacterial death in the plant cell. These mechanisms involve successively: DNF2, BacA, SymCRK/RSD and bacterial ability to fix nitrogen.
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Affiliation(s)
- Fathi Berrabah
- Institut des Sciences du Végétal, CNRS, Saclay Plant Sciences, Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Pascal Ratet
- Institut des Sciences du Végétal, CNRS, Saclay Plant Sciences, Avenue de la Terrasse, 91198 Gif sur Yvette, France
| | - Benjamin Gourion
- Institut des Sciences du Végétal, CNRS, Saclay Plant Sciences, Avenue de la Terrasse, 91198 Gif sur Yvette, France
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Gourion B, Berrabah F, Ratet P, Stacey G. Rhizobium-legume symbioses: the crucial role of plant immunity. Trends Plant Sci 2015; 20:186-94. [PMID: 25543258 DOI: 10.1016/j.tplants.2014.11.008] [Citation(s) in RCA: 166] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Revised: 11/16/2014] [Accepted: 11/21/2014] [Indexed: 05/03/2023]
Abstract
New research results have significantly revised our understanding of the rhizobium-legume infection process. For example, Nod factors (NFs), previously thought to be absolutely essential for this symbiosis, were shown to be dispensable under particular conditions. Similarly, an NF receptor, previously considered to be solely involved in symbiosis, was shown to function during plant pathogen infections. Indeed, there is a growing realization that plant innate immunity is a crucial component in the establishment and maintenance of symbiosis. We review here the factors involved in the suppression of plant immunity during rhizobium-legume symbiosis, and we attempt to place this information into context with the most recent and sometimes surprising research results.
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Affiliation(s)
- Benjamin Gourion
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique (CNRS), Saclay Plant Sciences, Avenue de la terrasse, 91198 Gif-sur-Yvette CEDEX, France.
| | - Fathi Berrabah
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique (CNRS), Saclay Plant Sciences, Avenue de la terrasse, 91198 Gif-sur-Yvette CEDEX, France
| | - Pascal Ratet
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique (CNRS), Saclay Plant Sciences, Avenue de la terrasse, 91198 Gif-sur-Yvette CEDEX, France
| | - Gary Stacey
- Divisions of Plant Science and Biochemistry, National Center for Soybean Biotechnology, C.S. Bond Life Science Center, University of Missouri, Columbia, MO 65203, USA
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Berrabah F, Bourcy M, Eschstruth A, Cayrel A, Guefrachi I, Mergaert P, Wen J, Jean V, Mysore KS, Gourion B, Ratet P. A nonRD receptor-like kinase prevents nodule early senescence and defense-like reactions during symbiosis. New Phytol 2014; 203:1305-1314. [PMID: 24916161 DOI: 10.1111/nph.12881] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 04/30/2014] [Indexed: 05/11/2023]
Abstract
Rhizobia and legumes establish symbiotic interactions leading to the production of root nodules, in which bacteria fix atmospheric nitrogen for the plant's benefit. This symbiosis is efficient because of the high rhizobia population within nodules. Here, we investigated how legumes accommodate such bacterial colonization. We used a reverse genetic approach to identify a Medicago truncatula gene, SymCRK, which encodes a cysteine-rich receptor-like kinase that is required for rhizobia maintenance within the plant cells, and performed detailed phenotypic analyses of the corresponding mutant. The Medicago truncatula symCRK mutant developed nonfunctional and necrotic nodules. A nonarginine asparate (nonRD) motif, typical of receptors involved in innate immunity, is present in the SymCRK kinase domain. Similar to the dnf2 mutant, bacteroid differentiation defect, defense-like reactions and early senescence were observed in the symCRK nodules. However, the dnf2 and symCRK nodules differ by their degree of colonization, which is higher in symCRK. Furthermore, in contrast to dnf2, symCRK is not a conditional mutant. These results suggest that in M. truncatula at least two genes are involved in the symbiotic control of immunity. Furthermore, phenotype differences between the two mutants suggest that two distinct molecular mechanisms control suppression of plant immunity during nodulation.
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Affiliation(s)
- Fathi Berrabah
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Marie Bourcy
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Alexis Eschstruth
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Anne Cayrel
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Ibtissem Guefrachi
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Peter Mergaert
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Jiangqi Wen
- Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, 73401, USA
| | - Viviane Jean
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Kirankumar S Mysore
- Plant Biology Division, The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK, 73401, USA
| | - Benjamin Gourion
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
| | - Pascal Ratet
- Institut des sciences du végétal, CNRS, Saclay Plant Sciences, Avenue de la terrasse, 91198, Gif Sur Yvette, France
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Berrabah F, Bourcy M, Cayrel A, Eschstruth A, Mondy S, Ratet P, Gourion B. Growth conditions determine the DNF2 requirement for symbiosis. PLoS One 2014; 9:e91866. [PMID: 24632747 PMCID: PMC3954807 DOI: 10.1371/journal.pone.0091866] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 02/17/2014] [Indexed: 11/18/2022] Open
Abstract
Rhizobia and legumes are able to interact in a symbiotic way leading to the development of root nodules. Within nodules, rhizobia fix nitrogen for the benefit of the plant. These interactions are efficient because spectacularly high densities of nitrogen fixing rhizobia are maintained in the plant cells. DNF2, a Medicago truncatula gene has been described as required for nitrogen fixation, bacteroid's persistence and to prevent defense-like reactions in the nodules. This manuscript shows that a Rhizobium mutant unable to differentiate is not sufficient to trigger defense-like reactions in this organ. Furthermore, we show that the requirement of DNF2 for effective symbiosis can be overcome by permissive growth conditions. The dnf2 knockout mutants grown in vitro on agarose or Phytagel as gelling agents are able to produce nodules fixing nitrogen with the same efficiency as the wild-type. However, when agarose medium is supplemented with the plant defense elicitor ulvan, the dnf2 mutant recovers the fix- phenotype. Together, our data show that plant growth conditions impact the gene requirement for symbiotic nitrogen fixation and suggest that they influence the symbiotic suppression of defense reactions in nodules.
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Affiliation(s)
- Fathi Berrabah
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
| | - Marie Bourcy
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
| | - Anne Cayrel
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
| | - Alexis Eschstruth
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
| | - Samuel Mondy
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
| | - Pascal Ratet
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
- * E-mail:
| | - Benjamin Gourion
- Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Gif sur Yvette, France
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9
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Abstract
Medicago truncatula and Sinorhizobium meliloti form a symbiotic association resulting in the formation of nitrogen-fixing nodules. In this organ, symbiotic cells contain large numbers of bacteroids. Remarkably, this chronic infection does not trigger visible defense reactions. Despite the importance of this phenomenon for potential transfer of the symbiotic capacity to non-legume plants, the molecular mechanisms underlying this tolerance are not understood. We have characterized the dnf2 M. truncatula mutant blocked in the symbiotic process after bacterial infection of the symbiotic cells. Nodules formed by the mutant contain only few layers of infected cells. Furthermore, they exhibit defense-like reactions which clearly contrast with premature senescence frequently observed during inefficient symbioses. This atypical phenotype raises DNF2 as an exciting starting point to investigate the molecular basis of symbiotic repression of plant defenses.
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Affiliation(s)
- Marie Bourcy
- Institut des Sciences du Végétal; CNRS; Gif-sur-Yvette, France
| | - Fathi Berrabah
- Institut des Sciences du Végétal; CNRS; Gif-sur-Yvette, France
| | - Pascal Ratet
- Institut des Sciences du Végétal; CNRS; Gif-sur-Yvette, France
- Correspondence to: Pascal Ratet,
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