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Marchetti R, Bedini E, Gully D, Lanzetta R, Giraud E, Molinaro A, Silipo A. Rhodopseudomonas palustris Strain CGA009 Produces an O-Antigen Built up by a C-4-Branched Monosaccharide: Structural and Conformational Studies. Org Lett 2018; 20:3656-3660. [PMID: 29874087 DOI: 10.1021/acs.orglett.8b01439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Here, the analysis of the peculiar homopolymeric O-chain, isolated from the lipopolysaccharide (LPS) of Rhodopseudomonas palustris strain CGA009, is reported. The O-chain is built up of a novel 4-C-branched sugar (12-deoxy-4- C-(d- altro-5,7,8,9-tetrahydroxyhexyl))-3- O-methyl-d-galactopyranose)) whose structure, absolute configuration, and conformational features were deduced by 2D NMR spectroscopy, optical rotation measurements, and molecular dynamics simulations.
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Belin BJ, Busset N, Giraud E, Molinaro A, Silipo A, Newman DK. Hopanoid lipids: from membranes to plant-bacteria interactions. Nat Rev Microbiol 2018; 16:304-315. [PMID: 29456243 PMCID: PMC6087623 DOI: 10.1038/nrmicro.2017.173] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Lipid research represents a frontier for microbiology, as showcased by hopanoid lipids. Hopanoids, which resemble sterols and are found in the membranes of diverse bacteria, have left an extensive molecular fossil record. They were first discovered by petroleum geologists. Today, hopanoid-producing bacteria remain abundant in various ecosystems, such as the rhizosphere. Recently, great progress has been made in our understanding of hopanoid biosynthesis, facilitated in part by technical advances in lipid identification and quantification. A variety of genetically tractable, hopanoid-producing bacteria have been cultured, and tools to manipulate hopanoid biosynthesis and detect hopanoids are improving. However, we still have much to learn regarding how hopanoid production is regulated, how hopanoids act biophysically and biochemically, and how their production affects bacterial interactions with other organisms, such as plants. The study of hopanoids thus offers rich opportunities for discovery.
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Chaintreuil C, Perrier X, Martin G, Fardoux J, Lewis GP, Brottier L, Rivallan R, Gomez-Pacheco M, Bourges M, Lamy L, Thibaud B, Ramanankierana H, Randriambanona H, Vandrot H, Mournet P, Giraud E, Arrighi JF. Naturally occurring variations in the nod-independent model legume Aeschynomene evenia and relatives: a resource for nodulation genetics. BMC PLANT BIOLOGY 2018; 18:54. [PMID: 29614957 PMCID: PMC5883870 DOI: 10.1186/s12870-018-1260-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2017] [Accepted: 03/06/2018] [Indexed: 05/21/2023]
Abstract
BACKGROUND Among semi-aquatic species of the legume genus Aeschynomene, some have the unique property of being root and stem-nodulated by photosynthetic Bradyrhizobium lacking the nodABC genes necessary for the production of Nod factors. These species provide an excellent biological system with which to explore the evolution of nodulation in legumes. Among them, Aeschynomene evenia has emerged as a model legume to undertake the genetic dissection of the so-called Nod-independent symbiosis. In addition to the genetic analysis of nodulation on a reference line, natural variation in a germplasm collection could also be surveyed to uncover genetic determinants of nodulation. To this aim, we investigated the patterns of genetic diversity in a collection of 226 Nod-independent Aeschynomene accessions. RESULTS A combination of phylogenetic analyses, comprising ITS and low-copy nuclear genes, along with cytogenetic experiments and artificial hybridizations revealed the richness of the Nod-independent Aeschynomene group with the identification of 13 diploid and 6 polyploid well-differentiated taxa. A set of 54 SSRs was used to further delineate taxon boundaries and to identify different genotypes. Patterns of microsatellite diversity also illuminated the genetic basis of the Aeschynomene taxa that were all found to be predominantly autogamous and with a predicted simple disomic inheritance, two attributes favorable for genetics. In addition, taxa displaying a pronounced genetic diversity, notably A. evenia, A. indica and A. sensitiva, were characterized by a clear geographically-based genetic structure and variations in root and stem nodulation. CONCLUSION A well-characterized germplasm collection now exists as a major genetic resource to thoroughly explore the natural variation of nodulation in response to different bradyrhizobial strains. Symbiotic polymorphisms are expected to be found notably in the induction of nodulation, in nitrogen fixation and also in stem nodulation. Subsequent genetic analysis and locus mapping will pave the way for the identification of the underlying genes through forward or reverse genetics. Such discoveries will significantly contribute to our understanding of the molecular mechanisms underpinning how some Aeschynomene species can be efficiently nodulated in a Nod-independent fashion.
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Busset N, Di Lorenzo F, Palmigiano A, Sturiale L, Gressent F, Fardoux J, Gully D, Chaintreuil C, Molinaro A, Silipo A, Giraud E. The Very Long Chain Fatty Acid (C 26:25OH) Linked to the Lipid A Is Important for the Fitness of the Photosynthetic Bradyrhizobium Strain ORS278 and the Establishment of a Successful Symbiosis with Aeschynomene Legumes. Front Microbiol 2017; 8:1821. [PMID: 28983292 PMCID: PMC5613085 DOI: 10.3389/fmicb.2017.01821] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 09/06/2017] [Indexed: 11/13/2022] Open
Abstract
In rhizobium strains, the lipid A is modified by the addition of a very long-chain fatty acid (VLCFA) shown to play an important role in rigidification of the outer membrane, thereby facilitating their dual life cycle, outside and inside the plant. In Bradyrhizobium strains, the lipid A is more complex with the presence of at least two VLCFAs, one covalently linked to a hopanoid molecule, but the importance of these modifications is not well-understood. In this study, we identified a cluster of VLCFA genes in the photosynthetic Bradyrhizobium strain ORS278, which nodulates Aeschynomene plants in a Nod factor-independent process. We tried to mutate the different genes of the VLCFA gene cluster to prevent the synthesis of the VLCFAs, but only one mutant in the lpxXL gene encoding an acyltransferase was obtained. Structural analysis of the lipid A showed that LpxXL is involved in the transfer of the C26:25OH VLCFA to the lipid A but not in the one of the C30:29OH VLCFA which harbors the hopanoid molecule. Despite maintaining the second VLCFA, the ability of the mutant to cope with various stresses (low pH, high temperature, high osmolarity, and antimicrobial peptides) and to establish an efficient nitrogen-fixing symbiosis was drastically reduced. In parallel, we investigated whether the BRADO0045 gene, which encodes a putative acyltransferase displaying a weak identity with the apo-lipoprotein N-acyltransferase Lnt, could be involved in the transfer of the C30:29OH VLCFA to the lipid A. Although the mutant exhibited phenotypes similar to the lpxXL mutant, no difference in the lipid A structure was observed from that in the wild-type strain, indicating that this gene is not involved in the modification of lipid A. Our results advance our knowledge of the biosynthesis pathway and the role of VLCFAs-modified lipid A in free-living and symbiotic states of Bradyrhizobium strains.
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Songwattana P, Noisangiam R, Teamtisong K, Prakamhang J, Teulet A, Tittabutr P, Piromyou P, Boonkerd N, Giraud E, Teaumroong N. Type 3 Secretion System (T3SS) of Bradyrhizobium sp. DOA9 and Its Roles in Legume Symbiosis and Rice Endophytic Association. Front Microbiol 2017; 8:1810. [PMID: 28979252 PMCID: PMC5611442 DOI: 10.3389/fmicb.2017.01810] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/05/2017] [Indexed: 11/15/2022] Open
Abstract
The Bradyrhizobium sp. DOA9 strain isolated from a paddy field has the ability to nodulate a wide spectrum of legumes. Unlike other bradyrhizobia, this strain has a symbiotic plasmid harboring nod, nif, and type 3 secretion system (T3SS) genes. This T3SS cluster contains all the genes necessary for the formation of the secretory apparatus and the transcriptional activator (TtsI), which is preceded by a nod-box motif. An in silico search predicted 14 effectors putatively translocated by this T3SS machinery. In this study, we explored the role of the T3SS in the symbiotic performance of DOA9 by evaluating the ability of a T3SS mutant (ΩrhcN) to nodulate legumes belonging to Dalbergioid, Millettioid, and Genistoid tribes. Among the nine species tested, four (Arachis hypogea, Vigna radiata, Crotalaria juncea, and Macroptilium atropurpureum) responded positively to the rhcN mutation (ranging from suppression of plant defense reactions, an increase in the number of nodules and a dramatic improvement in nodule development and infection), one (Stylosanthes hamata) responded negatively (fewer nodules and less nitrogen fixation) and four species (Aeschynomene americana, Aeschynomene afraspera, Indigofera tinctoria, and Desmodium tortuosum) displayed no phenotype. We also tested the role of the T3SS in the ability of the DOA9 strain to endophytically colonize rice roots, but detected no effect of the T3SS mutation, in contrast to what was previously reported in the Bradyrhizobium SUTN9-2 strain. Taken together, these data indicate that DOA9 contains a functional T3SS that interferes with the ability of the strain to interact symbiotically with legumes but not with rice.
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Barrière Q, Guefrachi I, Gully D, Lamouche F, Pierre O, Fardoux J, Chaintreuil C, Alunni B, Timchenko T, Giraud E, Mergaert P. Integrated roles of BclA and DD-carboxypeptidase 1 in Bradyrhizobium differentiation within NCR-producing and NCR-lacking root nodules. Sci Rep 2017; 7:9063. [PMID: 28831061 PMCID: PMC5567381 DOI: 10.1038/s41598-017-08830-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/12/2017] [Indexed: 11/09/2022] Open
Abstract
Legumes harbor in their symbiotic nodule organs nitrogen fixing rhizobium bacteria called bacteroids. Some legumes produce Nodule-specific Cysteine-Rich (NCR) peptides in the nodule cells to control the intracellular bacterial population. NCR peptides have antimicrobial activity and drive bacteroids toward terminal differentiation. Other legumes do not produce NCR peptides and their bacteroids are not differentiated. Bradyrhizobia, infecting NCR-producing Aeschynomene plants, require the peptide uptake transporter BclA to cope with the NCR peptides as well as a specific peptidoglycan-modifying DD-carboxypeptidase, DD-CPase1. We show that Bradyrhizobium diazoefficiens strain USDA110 forms undifferentiated bacteroids in NCR-lacking soybean nodules. Unexpectedly, in Aeschynomene afraspera nodules the nitrogen fixing USDA110 bacteroids are hardly differentiated despite the fact that this host produces NCR peptides, suggesting that USDA110 is insensitive to the host peptide effectors and that nitrogen fixation can be uncoupled from differentiation. In agreement with the absence of bacteroid differentiation, USDA110 does not require its bclA gene for nitrogen fixing symbiosis with these two host plants. Furthermore, we show that the BclA and DD-CPase1 act independently in the NCR-induced morphological differentiation of bacteroids. Our results suggest that BclA is required to protect the rhizobia against the NCR stress but not to induce the terminal differentiation pathway.
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Di Lorenzo F, Palmigiano A, Duda KA, Pallach M, Busset N, Sturiale L, Giraud E, Garozzo D, Molinaro A, Silipo A. Structure of the Lipopolysaccharide from the Bradyrhizobium sp. ORS285 rfaL Mutant Strain. ChemistryOpen 2017; 6:541-553. [PMID: 28794950 PMCID: PMC5542761 DOI: 10.1002/open.201700074] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Indexed: 12/13/2022] Open
Abstract
The importance of the outer membrane and of its main constituent, lipopolysaccharide, in the symbiosis between rhizobia and leguminous host plants has been well studied. Here, the first complete structural characterization of the entire lipopolysaccharide from an O‐chain‐deficient Bradyrhizobium ORS285 rfaL mutant is achieved by a combination of chemical analysis, NMR spectroscopy, MALDI MS and MS/MS. The lipid A structure is shown to be consistent with previously reported Bradyrhizobium lipid A, that is, a heterogeneous blend of penta‐ to hepta‐acylated species carrying a nonstoichiometric hopanoid unit and possessing very‐long‐chain fatty acids ranging from 26:0(25‐OH) to 32:0(31‐OH). The structure of the core oligosaccharide region, fully characterized for the first time here, is revealed to be a nonphosphorylated linear chain with methylated sugar residues, with a heptose residue exclusively present in the outer core region, and with the presence of two singly substituted 3‐deoxy‐d‐manno‐oct‐2‐ulosonic acid (Kdo) residues, one of which is located in the outer core region. The lipid A moiety is linked to the core moiety through an uncommon 4‐substituted Kdo unit.
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Grimaldi-Bensouda L, Rossignol M, Koné-Paut I, Krivitzky A, Lebrun-Frenay C, Clet J, Brassat D, Papeix C, Nicolino M, Benhamou PY, Fain O, Costedoat-Chalumeau N, Courcoux MF, Viallard JF, Godeau B, Papo T, Vermersch P, Bourgault-Villada I, Breart G, Abenhaim L, Abbas F, Abdelmoumni A, Hilliquin P, Requeda E, Adoue D, Brassat D, Agard C, Masseau A, Aladjidi N, Clet J, Fernandes H, Lemasson G, Perel Y, Raymond I, Richer O, Vital A, Allain-Launay E, Bru M, Nicolino M, Thomas C, Altman JJ, Amsallem D, Aras N, Boukari L, Dubrel M, Fain O, Letellier E, Lucidarme N, Mekinian A, Morin AS, Stirnemann J, Atlan C, Audry D, Augustin J, Bakir R, Bartolucci P, Chevalier X, Godeau B, Guillaud C, Khellaf M, Limal N, Lousteau V, Mahevas M, Méliksetyan G, Michel M, Roumier M, Bayart S, Bonnet F, Decaux O, Bekherraz A, Brihaye B, Dachez R, Daugas E, Hayem G, Meyer O, Papo T, Pasqualoni E, Sacre K, Travert F, Bellon H, Beltrand J, Lefrere F, Simon A, Benhamou PY, Benveniste O, Bolgert F, Costedoat-Chalumeau N, De Paz R, Demeret S, Fautrel B, Jacqueminet S, Louapre C, Maillart E, Morel N, Papeix C, Rigabert J, Bensaid P, Berger C, Berquin P, Le Moing AG, Berroir S, Besson G, Boutte C, Casez O, Bonnotte B, Audia S, Bossu-Estour C, Bourgarit A, Dupuy A, Keshmandt H, Bourre B, Brac A, Perrin A, Pondarré C, Villar-Fimbel S, Bruckert I, Cosson A, Magy-Bertrand N, Tisserand G, Camu W, Carlander B, Morales RJ, Cances C, Pasquet M, Castilla Lievre MA, Chabroux S, Charif M, Chatelus E, Sibilia J, Chevrant-Breton J, Clavel S, Bille-Turc F, Cohen J, Courcoux MF, Leverger G, Machet L, Cuisset JM, Cony-Makhoul P, Darsy P, Favre S, Giraud P, Leitenschenck L, Monteiro I, Morati C, DeSeze J, Dinulescu M, Dhaoui T, Dommange-Romero F, Drevard E, Dupuis C, Dumuis ML, Durand JM, Farad S, Lecomte P, Pierre P, Fouyssac F, Gaudin P, Gautier A, Gellen-Dautremer J, Jarrin I, Richette P, Georget E, Gras P, Moreau T, Giraud E, Hacini M, Mayer A, Guillaumat C, Guillaume S, Guitton C, Kone-Paut I, Marsaud C, Rossi L, Guyot MH, Hassler P, Heimfert C, Heinzlef O, Hillion B, Hocquelet C, Husson H, Ichai P, Jeziorski E, Deslandre CJ, Le Guern V, Kamenov K, Kerlan V, Lemoine P, Misery L, Pan-Petesch B, Krivitzky A, Labauge P, Rodier M, Lacade C, Razafimahefa B, Lachgar K, Larmarau MP, Leblanc T, Lebrun-Frenay C, Lefèbvre P, Lejoyeux P, Leske C, Ly K, Magy L, Mansuy S, Marechaud R, Martin Negrier ML, Sole G, Maupetit J, Mazingue F, Mochon S, Moktar B, Morcamp D, Morlet-Barla N, Nicolas G, Pautot V, Pellier I, Verret JL, Outteryck O, Vermersch P, Pallot-Prades B, Paquet JM, Puechal X, Sortais A, Pelletier J, Rico A, Pez D, Stankoff B, Quittet P, Rémy C, Roba E, Rosario H, Roudaut N, Sonnet E, Ruel M, Sebban S, Schaepelynck P, Simonin MJ, Vial C, Viallard JF, Ladedan I, Zenone T. Risk of autoimmune diseases and human papilloma virus (HPV) vaccines: Six years of case-referent surveillance. J Autoimmun 2017; 79:84-90. [DOI: 10.1016/j.jaut.2017.01.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Revised: 12/08/2016] [Accepted: 01/26/2017] [Indexed: 10/20/2022]
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Di Lorenzo F, Palmigiano A, Al Bitar-Nehme S, Sturiale L, Duda KA, Gully D, Lanzetta R, Giraud E, Garozzo D, Bernardini ML, Molinaro A, Silipo A. The Lipid A from Rhodopseudomonas palustris Strain BisA53 LPS Possesses a Unique Structure and Low Immunostimulant Properties. Chemistry 2016; 23:3637-3647. [PMID: 28004420 DOI: 10.1002/chem.201604379] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Indexed: 12/15/2022]
Abstract
The search for novel lipid A analogues from any biological source that can act as antagonists, displaying inhibitory activity towards the production of pro-inflammatory cytokines, or as immunomodulators in mammals, is a very topical issue. To this aim, the structure and immunological properties of the lipopolysaccharide lipid A from the purple nonsulfur bacterium Rhodopseudomonas palustris strain BisA53 have been determined. This lipid A displays a unique structural feature, with a non-phosphorylated skeleton made up of the tetrasaccharide Manp-α-(1→4)-GlcpN3N-β-1→6-GlcpN3N-α-(1→1)-α-GalpA, and four primary amide-linked 14:0(3-OH) and, as secondary O-acyl substituents, a 16:0 and the very long-chain fatty acid 26:0(25-OAc), appended on the GlcpN3N units. This lipid A architecture is definitely rare, so far identified only in the genus Bradyrhizobium. Immunological tests on both murine bone-marrow-derived and human monocyte-derived macrophages revealed an extremely low immunostimulant capability of this LPS lipid A.
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Wongdee J, Songwattana P, Nouwen N, Noisangiam R, Fardoux J, Chaintreuil C, Teaumroong N, Tittabutr P, Giraud E. nifDK Clusters Located on the Chromosome and Megaplasmid of Bradyrhizobium sp. Strain DOA9 Contribute Differently to Nitrogenase Activity During Symbiosis and Free-Living Growth. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:767-773. [PMID: 27603559 DOI: 10.1094/mpmi-07-16-0140-r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Bradyrhizobium sp. strain DOA9 contains two copies of the nifDK genes, nifDKc, located on the chromosome, and nifDKp, located on a symbiotic megaplasmid. Unlike most rhizobia, this bacterium displays nitrogenase activity under both free-living and symbiotic conditions. Transcriptional analysis using gusA reporter strains showed that both nifDK operons were highly expressed under symbiosis, whereas nifDKc was the most abundantly expressed under free-living conditions. During free-living growth, the nifDKp mutation did not affect nitrogenase activity, whereas nitrogenase activity was drastically reduced with the nifDKc mutant. This led us to suppose that nifDKc is the main contributor of nitrogenase activity in the free-living state. In contrast, during symbiosis, no effect of the nifDKc mutation was observed and the nitrogen-fixation efficiency of plants inoculated with the nifDKp mutant was reduced. This suggests that nifDKp plays the main role in nitrogenase enzyme activity during symbiosis. Together, these data suggest that Bradyrhizobium sp. strain DOA9 contains two functional copies of nifDK genes that are regulated differently and that, depending on their lifestyle, contribute differently to nitrogenase activity.
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Chaintreuil C, Gully D, Hervouet C, Tittabutr P, Randriambanona H, Brown SC, Lewis GP, Bourge M, Cartieaux F, Boursot M, Ramanankierana H, D'Hont A, Teaumroong N, Giraud E, Arrighi JF. The evolutionary dynamics of ancient and recent polyploidy in the African semiaquatic species of the legume genus Aeschynomene. THE NEW PHYTOLOGIST 2016; 211:1077-1091. [PMID: 27061605 DOI: 10.1111/nph.13956] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 03/04/2016] [Indexed: 06/05/2023]
Abstract
The legume genus Aeschynomene is notable in the ability of certain semiaquatic species to develop nitrogen-fixing stem nodules. These species are distributed in two clades. In the first clade, all the species are characterized by the use of a unique Nod-independent symbiotic process. In the second clade, the species use a Nod-dependent symbiotic process and some of them display a profuse stem nodulation as exemplified in the African Aeschynomene afraspera. To facilitate the molecular analysis of the symbiotic characteristics of such legumes, we took an integrated molecular and cytogenetic approach to track occurrences of polyploidy events and to analyze their impact on the evolution of the African species of Aeschynomene. Our results revealed two rounds of polyploidy: a paleopolyploid event predating the African group and two neopolyploid speciations, along with significant chromosomal variations. Hence, we found that A. afraspera (8x) has inherited the contrasted genomic properties and the stem-nodulation habit of its parental lineages (4x). This study reveals a comprehensive picture of African Aeschynomene diversification. It notably evidences a history that is distinct from the diploid Nod-independent clade, providing clues for the identification of the specific determinants of the Nod-dependent and Nod-independent symbiotic processes, and for comparative analysis of stem nodulation.
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Nouwen N, Fardoux J, Giraud E. NodD1 and NodD2 Are Not Required for the Symbiotic Interaction of Bradyrhizobium ORS285 with Nod-Factor-Independent Aeschynomene Legumes. PLoS One 2016; 11:e0157888. [PMID: 27315080 PMCID: PMC4912097 DOI: 10.1371/journal.pone.0157888] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 06/06/2016] [Indexed: 11/23/2022] Open
Abstract
Photosynthetic Bradyrhizobium strain ORS285 forms nitrogen-fixing nodules on the roots and stems of tropical aquatic legumes of the Aeschynomene genus. Depending on the Aeschynomene species, this symbiotic interaction does or does not rely on the synthesis of Nod-factors (NFs). However, whether during the interaction of Bradyrhizobium ORS285 with NF-independent Aeschynomene species the nod genes are expressed and if the general regulator NodD plays a symbiotic role is unknown. Expression studies showed that in contrast to the interaction with the NF-dependent Aeschynomene species, A. afraspera, the Bradyrhizobium ORS285 nod genes are not induced upon contact with the NF-independent host plant A. indica. Mutational analysis of the two nodD genes present in ORS285, showed that deletion of nodD1 and nodD2 did not affect the symbiotic interaction between Bradyrhizobium ORS285 and A. indica whereas the deletions had an effect on the symbiotic interaction with A. afraspera plants. In addition, when the expression of nod genes was artificially induced by adding naringenin to the plant growth medium, the nodulation of A. indica by Bradyrhizobium ORS285 is delayed and resulted in lower nodule numbers.
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Chaintreuil C, Rivallan R, Bertioli DJ, Klopp C, Gouzy J, Courtois B, Leleux P, Martin G, Rami JF, Gully D, Parrinello H, Séverac D, Patrel D, Fardoux J, Ribière W, Boursot M, Cartieaux F, Czernic P, Ratet P, Mournet P, Giraud E, Arrighi JF. A gene-based map of the Nod factor-independent Aeschynomene evenia sheds new light on the evolution of nodulation and legume genomes. DNA Res 2016; 23:365-76. [PMID: 27298380 PMCID: PMC4991833 DOI: 10.1093/dnares/dsw020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 05/02/2016] [Indexed: 11/13/2022] Open
Abstract
Aeschynomene evenia has emerged as a new model legume for the deciphering of the molecular mechanisms of an alternative symbiotic process that is independent of the Nod factors. Whereas most of the research on nitrogen-fixing symbiosis, legume genetics and genomics has so far focused on Galegoid and Phaseolid legumes, A. evenia falls in the more basal and understudied Dalbergioid clade along with peanut (Arachis hypogaea). To provide insights into the symbiotic genes content and the structure of the A. evenia genome, we established a gene-based genetic map for this species. Firstly, an RNAseq analysis was performed on the two parental lines selected to generate a F2 mapping population. The transcriptomic data were used to develop molecular markers and they allowed the identification of most symbiotic genes. The resulting map comprised 364 markers arranged in 10 linkage groups (2n = 20). A comparative analysis with the sequenced genomes of Arachis duranensis and A. ipaensis, the diploid ancestors of peanut, indicated blocks of conserved macrosynteny. Altogether, these results provided important clues regarding the evolution of symbiotic genes in a Nod factor-independent context. They provide a basis for a genome sequencing project and pave the way for forward genetic analysis of symbiosis in A. evenia.
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Gully D, Gargani D, Bonaldi K, Grangeteau C, Chaintreuil C, Fardoux J, Nguyen P, Marchetti R, Nouwen N, Molinaro A, Mergaert P, Giraud E. A Peptidoglycan-Remodeling Enzyme Is Critical for Bacteroid Differentiation in Bradyrhizobium spp. During Legume Symbiosis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:447-57. [PMID: 26959836 DOI: 10.1094/mpmi-03-16-0052-r] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In response to the presence of compatible rhizobium bacteria, legumes form symbiotic organs called nodules on their roots. These nodules house nitrogen-fixing bacteroids that are a differentiated form of the rhizobium bacteria. In some legumes, the bacteroid differentiation comprises a dramatic cell enlargement, polyploidization, and other morphological changes. Here, we demonstrate that a peptidoglycan-modifying enzyme in Bradyrhizobium strains, a DD-carboxypeptidase that contains a peptidoglycan-binding SPOR domain, is essential for normal bacteroid differentiation in Aeschynomene species. The corresponding mutants formed bacteroids that are malformed and hypertrophied. However, in soybean, a plant that does not induce morphological differentiation of its symbiont, the mutation does not affect the bacteroids. Remarkably, the mutation also leads to necrosis in a large fraction of the Aeschynomene nodules, indicating that a normally formed peptidoglycan layer is essential for avoiding the induction of plant immune responses by the invading bacteria. In addition to exopolysaccharides, capsular polysaccharides, and lipopolysaccharides, whose role during symbiosis is well defined, our work demonstrates an essential role in symbiosis for yet another rhizobial envelope component, the peptidoglycan layer.
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Busset N, De Felice A, Chaintreuil C, Gully D, Fardoux J, Romdhane S, Molinaro A, Silipo A, Giraud E. The LPS O-Antigen in Photosynthetic Bradyrhizobium Strains Is Dispensable for the Establishment of a Successful Symbiosis with Aeschynomene Legumes. PLoS One 2016; 11:e0148884. [PMID: 26849805 PMCID: PMC4743980 DOI: 10.1371/journal.pone.0148884] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2015] [Accepted: 01/25/2016] [Indexed: 11/18/2022] Open
Abstract
The photosynthetic bradyrhizobia are able to use a Nod-factor independent process to induce nitrogen-fixing nodules on some semi-aquatic Aeschynomene species. These bacteria display a unique LPS O-antigen composed of a new sugar, the bradyrhizose that is regarded as a key symbiotic factor due to its non-immunogenic character. In this study, to check this hypothesis, we isolated mutants affected in the O-antigen synthesis by screening a transposon mutant library of the ORS285 strain for clones altered in colony morphology. Over the 10,000 mutants screened, five were selected and found to be mutated in two genes, rfaL, encoding for a putative O-antigen ligase and gdh encoding for a putative dTDP-glucose 4,6-dehydratase. Biochemical analysis confirmed that the LPS of these mutants completely lack the O-antigen region. However, no effect of the mutations could be detected on the symbiotic properties of the mutants indicating that the O-antigen region of photosynthetic Bradyrhizobium strains is not required for the establishment of symbiosis with Aeschynomene.
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Okazaki S, Tittabutr P, Teulet A, Thouin J, Fardoux J, Chaintreuil C, Gully D, Arrighi JF, Furuta N, Miwa H, Yasuda M, Nouwen N, Teaumroong N, Giraud E. Rhizobium-legume symbiosis in the absence of Nod factors: two possible scenarios with or without the T3SS. THE ISME JOURNAL 2016; 10:64-74. [PMID: 26161635 PMCID: PMC4681849 DOI: 10.1038/ismej.2015.103] [Citation(s) in RCA: 91] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 04/28/2015] [Accepted: 05/08/2015] [Indexed: 02/07/2023]
Abstract
The occurrence of alternative Nod factor (NF)-independent symbiosis between legumes and rhizobia was first demonstrated in some Aeschynomene species that are nodulated by photosynthetic bradyrhizobia lacking the canonical nodABC genes. In this study, we revealed that a large diversity of non-photosynthetic bradyrhizobia, including B. elkanii, was also able to induce nodules on the NF-independent Aeschynomene species, A. indica. Using cytological analysis of the nodules and the nitrogenase enzyme activity as markers, a gradient in the symbiotic interaction between bradyrhizobial strains and A. indica could be distinguished. This ranged from strains that induced nodules that were only infected intercellularly to rhizobial strains that formed nodules in which the host cells were invaded intracellularly and that displayed a weak nitrogenase activity. In all non-photosynthetic bradyrhizobia, the type III secretion system (T3SS) appears required to trigger nodule organogenesis. In contrast, genome sequence analysis revealed that apart from a few exceptions, like the Bradyrhizobium ORS285 strain, photosynthetic bradyrhizobia strains lack a T3SS. Furthermore, analysis of the symbiotic properties of an ORS285 T3SS mutant revealed that the T3SS could have a positive or negative role for the interaction with NF-dependent Aeschynomene species, but that it is dispensable for the interaction with all NF-independent Aeschynomene species tested. Taken together, these data indicate that two NF-independent symbiotic processes are possible between legumes and rhizobia: one dependent on a T3SS and one using a so far unknown mechanism.
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Fabre S, Gully D, Poitout A, Patrel D, Arrighi JF, Giraud E, Czernic P, Cartieaux F. Nod Factor-Independent Nodulation in Aeschynomene evenia Required the Common Plant-Microbe Symbiotic Toolkit. PLANT PHYSIOLOGY 2015; 169:2654-64. [PMID: 26446590 PMCID: PMC4677901 DOI: 10.1104/pp.15.01134] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/04/2015] [Indexed: 05/06/2023]
Abstract
Nitrogen fixation in the legume-rhizobium symbiosis is a crucial area of research for more sustainable agriculture. Our knowledge of the plant cascade in response to the perception of bacterial Nod factors has increased in recent years. However, the discovery that Nod factors are not involved in the Aeschynomene-Bradyrhizobium spp. interaction suggests that alternative molecular dialogues may exist in the legume family. We evaluated the conservation of the signaling pathway common to other endosymbioses using three candidate genes: Ca(2+)/Calmodulin-Dependent Kinase (CCaMK), which plays a central role in cross signaling between nodule organogenesis and infection processes; and Symbiosis Receptor Kinase (SYMRK) and Histidine Kinase1 (HK1), which act upstream and downstream of CCaMK, respectively. We showed that CCaMK, SYMRK, and HK1 are required for efficient nodulation in Aeschynomene evenia. Our results demonstrate that CCaMK and SYMRK are recruited in Nod factor-independent symbiosis and, hence, may be conserved in all vascular plant endosymbioses described so far.
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Guefrachi I, Pierre O, Timchenko T, Alunni B, Barrière Q, Czernic P, Villaécija-Aguilar JA, Verly C, Bourge M, Fardoux J, Mars M, Kondorosi E, Giraud E, Mergaert P. Bradyrhizobium BclA Is a Peptide Transporter Required for Bacterial Differentiation in Symbiosis with Aeschynomene Legumes. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:1155-66. [PMID: 26106901 DOI: 10.1094/mpmi-04-15-0094-r] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Nodules of legume plants are highly integrated symbiotic systems shaped by millions of years of evolution. They harbor nitrogen-fixing rhizobium bacteria called bacteroids. Several legume species produce peptides called nodule-specific cysteine-rich (NCR) peptides in the symbiotic nodule cells which house the bacteroids. NCR peptides are related to antimicrobial peptides of innate immunity. They induce the endosymbionts into a differentiated, enlarged, and polyploid state. The bacterial symbionts, on their side, evolved functions for the response to the NCR peptides. Here, we identified the bclA gene of Bradyrhizobium sp. strains ORS278 and ORS285, which is required for the formation of differentiated and functional bacteroids in the nodules of the NCR peptide-producing Aeschynomene legumes. The BclA ABC transporter promotes the import of NCR peptides and provides protection against the antimicrobial activity of these peptides. Moreover, BclA can complement the role of the related BacA transporter of Sinorhizobium meliloti, which has a similar symbiotic function in the interaction with Medicago legumes.
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Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK. Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens. mBio 2015. [PMID: 26489859 DOI: 10.1128/mbio.01251-1215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
UNLABELLED A better understanding of how bacteria resist stresses encountered during the progression of plant-microbe symbioses will advance our ability to stimulate plant growth. Here, we show that the symbiotic system comprising the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens and the legume Aeschynomene afraspera requires hopanoid production for optimal fitness. While methylated (2Me) hopanoids contribute to growth under plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. In contrast, synthesis of extended (C35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low pH, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene. Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean. This difference is likely related to the presence of cysteine-rich antimicrobial peptides in Aeschynomene nodules that induce drastic modification in bacterial morphology and physiology. The study of hopanoid mutants in plant symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage. IMPORTANCE Because bradyrhizobia provide fixed nitrogen to plants, this work has potential agronomical implications. An understanding of how hopanoids facilitate bacterial survival in soils and plant hosts may aid the engineering of more robust agronomic strains, especially relevant in regions that are becoming warmer and saline due to climate change. Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history. This is the first study to uncover roles for 2Me- and C35 hopanoids in the context of an ecological niche that captures many of the stressful environmental conditions thought to be important during (2Me)-hopane deposition. Though much remains to be done to determine whether the conditions present within the plant host are shared with niches of relevance to the rock record, our findings represent an important step toward identifying conserved mechanisms whereby hopanoids contribute to fitness.
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Kulkarni G, Busset N, Molinaro A, Gargani D, Chaintreuil C, Silipo A, Giraud E, Newman DK. Specific hopanoid classes differentially affect free-living and symbiotic states of Bradyrhizobium diazoefficiens. mBio 2015; 6:e01251-15. [PMID: 26489859 PMCID: PMC4620461 DOI: 10.1128/mbio.01251-15] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/17/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED A better understanding of how bacteria resist stresses encountered during the progression of plant-microbe symbioses will advance our ability to stimulate plant growth. Here, we show that the symbiotic system comprising the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens and the legume Aeschynomene afraspera requires hopanoid production for optimal fitness. While methylated (2Me) hopanoids contribute to growth under plant-cell-like microaerobic and acidic conditions in the free-living state, they are dispensable during symbiosis. In contrast, synthesis of extended (C35) hopanoids is required for growth microaerobically and under various stress conditions (high temperature, low pH, high osmolarity, bile salts, oxidative stress, and antimicrobial peptides) in the free-living state and also during symbiosis. These defects might be due to a less rigid membrane resulting from the absence of free or lipidA-bound C35 hopanoids or the accumulation of the C30 hopanoid diploptene. Our results also show that C35 hopanoids are necessary for symbiosis only with the host Aeschynomene afraspera but not with soybean. This difference is likely related to the presence of cysteine-rich antimicrobial peptides in Aeschynomene nodules that induce drastic modification in bacterial morphology and physiology. The study of hopanoid mutants in plant symbionts thus provides an opportunity to gain insight into host-microbe interactions during later stages of symbiotic progression, as well as the microenvironmental conditions for which hopanoids provide a fitness advantage. IMPORTANCE Because bradyrhizobia provide fixed nitrogen to plants, this work has potential agronomical implications. An understanding of how hopanoids facilitate bacterial survival in soils and plant hosts may aid the engineering of more robust agronomic strains, especially relevant in regions that are becoming warmer and saline due to climate change. Moreover, this work has geobiological relevance: hopanes, molecular fossils of hopanoids, are enriched in ancient sedimentary rocks at discrete intervals in Earth history. This is the first study to uncover roles for 2Me- and C35 hopanoids in the context of an ecological niche that captures many of the stressful environmental conditions thought to be important during (2Me)-hopane deposition. Though much remains to be done to determine whether the conditions present within the plant host are shared with niches of relevance to the rock record, our findings represent an important step toward identifying conserved mechanisms whereby hopanoids contribute to fitness.
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Czernic P, Gully D, Cartieaux F, Moulin L, Guefrachi I, Patrel D, Pierre O, Fardoux J, Chaintreuil C, Nguyen P, Gressent F, Da Silva C, Poulain J, Wincker P, Rofidal V, Hem S, Barrière Q, Arrighi JF, Mergaert P, Giraud E. Convergent Evolution of Endosymbiont Differentiation in Dalbergioid and Inverted Repeat-Lacking Clade Legumes Mediated by Nodule-Specific Cysteine-Rich Peptides. PLANT PHYSIOLOGY 2015; 169:1254-65. [PMID: 26286718 PMCID: PMC4587450 DOI: 10.1104/pp.15.00584] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 08/17/2015] [Indexed: 05/21/2023]
Abstract
Nutritional symbiotic interactions require the housing of large numbers of microbial symbionts, which produce essential compounds for the growth of the host. In the legume-rhizobium nitrogen-fixing symbiosis, thousands of rhizobium microsymbionts, called bacteroids, are confined intracellularly within highly specialized symbiotic host cells. In Inverted Repeat-Lacking Clade (IRLC) legumes such as Medicago spp., the bacteroids are kept under control by an arsenal of nodule-specific cysteine-rich (NCR) peptides, which induce the bacteria in an irreversible, strongly elongated, and polyploid state. Here, we show that in Aeschynomene spp. legumes belonging to the more ancient Dalbergioid lineage, bacteroids are elongated or spherical depending on the Aeschynomene spp. and that these bacteroids are terminally differentiated and polyploid, similar to bacteroids in IRLC legumes. Transcriptome, in situ hybridization, and proteome analyses demonstrated that the symbiotic cells in the Aeschynomene spp. nodules produce a large diversity of NCR-like peptides, which are transported to the bacteroids. Blocking NCR transport by RNA interference-mediated inactivation of the secretory pathway inhibits bacteroid differentiation. Together, our results support the view that bacteroid differentiation in the Dalbergioid clade, which likely evolved independently from the bacteroid differentiation in the IRLC clade, is based on very similar mechanisms used by IRLC legumes.
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Arrighi JF, Chaintreuil C, Cartieaux F, Cardi C, Rodier-Goud M, Brown SC, Boursot M, D'Hont A, Dreyfus B, Giraud E. Radiation of the Nod-independent Aeschynomene relies on multiple allopolyploid speciation events. THE NEW PHYTOLOGIST 2014; 201:1457-1468. [PMID: 24237245 DOI: 10.1111/nph.12594] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 10/08/2013] [Indexed: 06/02/2023]
Abstract
• The semi-aquatic legumes belonging to the genus Aeschynomene constitute a premium system for investigating the origin and evolution of unusual symbiotic features such as stem nodulation and the presence of a Nod-independent infection process. This latter apparently arose in a single Aeschynomene lineage. But how this unique Nod-independent group then radiated is not yet known. • We have investigated the role of polyploidy in Aeschynomene speciation via a case study of the pantropical A. indica and then extended the analysis to the other Nod-independent species. For this, we combined SSR genotyping, genome characterization through flow cytometry, chromosome counting, FISH and GISH experiments, molecular phylogenies using ITS and single nuclear gene sequences, and artificial hybridizations. • These analyses demonstrate the existence of an A. indica polyploid species complex comprising A. evenia (C. Wright) (2n = 2x = 20), A. indica L. s.s. (2n = 4x = 40) and a new hexaploid form (2n = 6x = 60). This latter contains the two genomes present in the tetraploid (A. evenia and A. scabra) and another unidentified genome. Two other species, A. pratensis and A. virginica, are also shown to be of allopolyploid origin. • This work reveals multiple hybridization/polyploidization events, thus highlighting a prominent role of allopolyploidy in the radiation of the Nod-independent Aeschynomene.
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Delmotte N, Mondy S, Alunni B, Fardoux J, Chaintreuil C, Vorholt JA, Giraud E, Gourion B. A proteomic approach of bradyrhizobium/aeschynomene root and stem symbioses reveals the importance of the fixA locus for symbiosis. Int J Mol Sci 2014; 15:3660-70. [PMID: 24590127 PMCID: PMC3975360 DOI: 10.3390/ijms15033660] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 02/14/2014] [Accepted: 02/14/2014] [Indexed: 11/28/2022] Open
Abstract
Rhizobia are soil bacteria that are able to form symbiosis with plant hosts of the legume family. These associations result in the formation of organs, called nodules in which bacteria fix atmospheric nitrogen to the benefit of the plant. Most of our knowledge on the metabolism and the physiology of the bacteria during symbiosis derives from studying roots nodules of terrestrial plants. Here we used a proteomics approach to investigate the bacterial physiology of photosynthetic Bradyrhizobium sp. ORS278 during the symbiotic process with the semi aquatical plant Aeschynomene indica that forms root and stem nodules. We analyzed the proteomes of bacteria extracted from each type of nodule. First, we analyzed the bacteroid proteome at two different time points and found only minor variation between the bacterial proteomes of 2-week- and 3-week-old nodules. High conservation of the bacteroid proteome was also found when comparing stem nodules and root nodules. Among the stem nodule specific proteins were those related to the phototrophic ability of Bradyrhizobium sp. ORS278. Furthermore, we compared our data with those obtained during an extensive genetic screen previously published. The symbiotic role of four candidate genes which corresponding proteins were found massively produced in the nodules but not identified during this screening was examined. Mutant analysis suggested that in addition to the EtfAB system, the fixA locus is required for symbiotic efficiency.
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Chaintreuil C, Arrighi JF, Giraud E, Miché L, Moulin L, Dreyfus B, Munive-Hernández JA, Villegas-Hernandez MDC, Béna G. Evolution of symbiosis in the legume genus Aeschynomene. THE NEW PHYTOLOGIST 2013; 200:1247-59. [PMID: 23879229 DOI: 10.1111/nph.12424] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 06/24/2013] [Indexed: 05/22/2023]
Abstract
Legumes in the genus Aeschynomene form nitrogen-fixing root nodules in association with Bradyrhizobium strains. Several aquatic and subaquatic species have the additional capacity to form stem nodules, and some of them can symbiotically interact with specific strains that do not produce the common Nod factors synthesized by all other rhizobia. The question of the emergence and evolution of these nodulation characters has been the subject of recent debate. We conducted a molecular phylogenetic analysis of 38 different Aeschynomene species. The phylogeny was reconstructed with both the chloroplast DNA trnL intron and the nuclear ribosomal DNA ITS/5.8S region. We also tested 28 Aeschynomene species for their capacity to form root and stem nodules by inoculating different rhizobial strains, including nodABC-containing strains (ORS285, USDA110) and a nodABC-lacking strain (ORS278). Maximum likelihood analyses resolved four distinct phylogenetic groups of Aeschynomene. We found that stem nodulation may have evolved several times in the genus, and that all Aeschynomene species using a Nod-independent symbiotic process clustered in the same clade. The phylogenetic approach suggested that Nod-independent nodulation has evolved once in this genus, and should be considered as a derived character, and this result is discussed with regard to previous experimental studies.
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Podlešáková K, Fardoux J, Patrel D, Bonaldi K, Novák O, Strnad M, Giraud E, Spíchal L, Nouwen N. Rhizobial synthesized cytokinins contribute to but are not essential for the symbiotic interaction between photosynthetic Bradyrhizobia and Aeschynomene legumes. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1232-8. [PMID: 23777431 DOI: 10.1094/mpmi-03-13-0076-r] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Cytokinins (CK) play an important role in the formation of nitrogen-fixing root nodules. It has been known for years that rhizobia secrete CK in the extracellular medium but whether they play a role in nodule formation is not known. We have examined this question using the photosynthetic Bradyrhizobium sp. strain ORS285 which is able to nodulate Aeschynomene afraspera and A. indica using a Nod-dependent or Nod-independent symbiotic process, respectively. CK profiling showed that the most abundant CK secreted by Bradyrhizobium sp. strain ORS285 are the 2MeS (2-methylthiol) derivatives of trans-zeatin and isopentenyladenine. In their pure form, these CK can activate legume CK receptors in vitro, and their exogenous addition induced nodule-like structures on host plants. Deletion of the miaA gene showed that transfer RNA degradation is the source of CK production in Bradyrhizobium sp. strain ORS285. In nodulation studies performed with A. indica and A. afraspera, the miaA mutant had a 1-day delay in nodulation and nitrogen fixation. Moreover, A. indica plants formed considerably smaller but more abundant nodules when inoculated with the miaA mutant. These data show that CK produced by Bradyrhizobium sp. strain ORS285 are not the key signal triggering nodule formation during the Nod-independent symbiosis but they contribute positively to nodule development in Aeschynomene plants.
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MESH Headings
- Acetylene/metabolism
- Bradyrhizobium/genetics
- Bradyrhizobium/metabolism
- Bradyrhizobium/physiology
- Cytokinins/metabolism
- Cytokinins/pharmacology
- Dose-Response Relationship, Drug
- Ethylenes/metabolism
- Fabaceae/drug effects
- Fabaceae/growth & development
- Fabaceae/metabolism
- Fabaceae/microbiology
- Genes, Reporter
- Nitrogen Fixation
- Nitrogenase
- Phylogeny
- Plant Growth Regulators/metabolism
- Plant Growth Regulators/pharmacology
- Plant Proteins/genetics
- Plant Proteins/metabolism
- Plant Root Nodulation
- Plant Roots/drug effects
- Plant Roots/growth & development
- Plant Roots/metabolism
- Plant Roots/microbiology
- RNA, Plant/genetics
- RNA, Plant/metabolism
- RNA, Transfer/genetics
- RNA, Transfer/metabolism
- Root Nodules, Plant/drug effects
- Root Nodules, Plant/growth & development
- Root Nodules, Plant/metabolism
- Root Nodules, Plant/microbiology
- Sequence Deletion
- Signal Transduction
- Symbiosis
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