title: Bacterial RuBisCO is required for efficient Bradyrhizobium/Aeschynomene symbiosis.
abstract: Rhizobia and legume plants establish symbiotic associations resulting in the formation of organs specialized in nitrogen fixation. In such organs, termed nodules, bacteria differentiate into bacteroids which convert atmospheric nitrogen and supply the plant with organic nitrogen. As a counterpart, bacteroids receive carbon substrates from the plant. This rather simple model of metabolite exchange underlies symbiosis but does not describe the complexity of bacteroids' central metabolism. A previous study using the tropical symbiotic model Aeschynomene indica/photosynthetic Bradyrhizobium sp. ORS278 suggested a role of the bacterial Calvin cycle during the symbiotic process. Herein we investigated the role of two RuBisCO gene clusters of Bradyrhizobium sp. ORS278 during symbiosis. Using gene reporter fusion strains, we showed that cbbL1 but not the paralogous cbbL2 is expressed during symbiosis. Congruently, CbbL1 was detected in bacteroids by proteome analysis. The importance of CbbL1 for symbiotic nitrogen fixation was proven by a reverse genetic approach. Interestingly, despite its symbiotic nitrogen fixation defect, the cbbL1 mutant was not affected in nitrogen fixation activity under free living state. This study demonstrates a critical role for bacterial RuBisCO during a rhizobia/legume symbiotic interaction.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, SupAgro/Institut National de la Recherche Agronomique/Université Montpellier 2/Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Montpellier, France. benjamin.gourion@isv.cnrs-gif.fr
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gourion
authors.forename: Nathanaël
authors.initials: N
authors.lastname: Delmotte
authors.forename: Katia
authors.initials: K
authors.lastname: Bonaldi
authors.forename: Nico
authors.initials: N
authors.lastname: Nouwen
authors.forename: Julia A
authors.initials: JA
authors.lastname: Vorholt
authors.forename: Eric
authors.initials: E
authors.lastname: Giraud
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D020369:Bradyrhizobium / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D004591:Electrophoresis, Polyacrylamide Gel; D007887:Fabaceae / Q000378:metabolism* / Q000382:microbiology; D015971:Gene Expression Regulation, Enzymologic; D054884:Host-Pathogen Interactions; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics / Q000378:metabolism*; D053204:Root Nodules, Plant / Q000378:metabolism / Q000382:microbiology; D013559:Symbiosis; D053719:Tandem Mass Spectrometry
chemical_list: D001426:Bacterial Proteins; D007527:Isoenzymes; D021122:Protein Subunits; D012273:Ribulose-Bisphosphate Carboxylase