title: A proteomic approach of bradyrhizobium/aeschynomene root and stem symbioses reveals the importance of the fixA locus for symbiosis.
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.
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland. nathanael.delmotte@gmail.com.
authors.forename: Nathanael
authors.initials: N
authors.lastname: Delmotte
authors.affiliation: Institut des Sciences du Végétal, CNRS, 91198 Gif sur Yvette, France. samuel.mondy@isv.cnrs-gif.fr.
authors.forename: Samuel
authors.initials: S
authors.lastname: Mondy
authors.affiliation: Institut des Sciences du Végétal, CNRS, 91198 Gif sur Yvette, France. alunni@isv.cnrs-gif.fr.
authors.forename: Benoit
authors.initials: B
authors.lastname: Alunni
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR IRD/SupAgro/INRA/UM2/CIRAD, F-34398 Montpellier, France. joel.fardoux@ird.fr.
authors.forename: Joel
authors.initials: J
authors.lastname: Fardoux
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR IRD/SupAgro/INRA/UM2/CIRAD, F-34398 Montpellier, France. clemence.chaintreuil@ird.fr.
authors.forename: Clémence
authors.initials: C
authors.lastname: Chaintreuil
authors.affiliation: Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zurich, Vladimir-Prelog-Weg 4, 8093 Zurich, Switzerland. vorholt@micro.biol.ethz.ch.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Vorholt
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, UMR IRD/SupAgro/INRA/UM2/CIRAD, F-34398 Montpellier, France. eric.giraud@ird.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Giraud
authors.affiliation: Institut des Sciences du Végétal, CNRS, 91198 Gif sur Yvette, France. benjamin.gourion@isv.cnrs-gif.fr.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gourion
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020369:Bradyrhizobium / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D007887:Fabaceae / Q000382:microbiology / Q000502:physiology*; D016680:Genome, Bacterial / Q000235:genetics; D054884:Host-Pathogen Interactions; D009154:Mutation; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000382:microbiology / Q000502:physiology*; D018547:Plant Stems / Q000382:microbiology / Q000502:physiology*; D040901:Proteomics / Q000379:methods; D053204:Root Nodules, Plant / Q000382:microbiology / Q000502:physiology; D013559:Symbiosis / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins