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24, chemin de Borde Rouge –Auzeville – CS52627
31326 Castanet Tolosan CEDEX - France

Dernière mise à jour : Mai 2018


Laboratory of Plant-Microbe Interactions - LIPM

Laboratory of Plant-Microbe Interactions

Symbiotic functions, genome and evolution of rhizobia


Our team is interested in molecular and evolutionary mechanisms underlying rhizobium-legume symbiosis. On the plant side, the ability to establish nitrogen-fixing root nodule symbiosis is restricted to 10 plant families scattered within the Fabales, Fagales, Cucurbitales and Rosales (FaFaCuRo). Phylogenomic studies suggest that this symbiotic ability results from a single gain before the radiation of the FaFaCuRo followed by multiple independent losses in many descendant lineages of Fagales, Cucurbitales and Rosales while it was mostly conserved in Fabales (also called legumes). On bacterial side, rhizobia do not form a homogenous group but belong to more than a dozen of different genera and hundreds of species among α- and β- proteobacteria. How rhizobia have emerged is a fascinating, but only partly documented, question. Ample evidence supports the view that rhizobia have evolved through horizontal transfer of key symbiotic functions into diverse soil bacteria followed by subsequent recipient genome adaptation under selection in the host plant environment. Post-transfer adaptation steps as well as genetic predispositions, if they exist, required to successfully convert a soil bacterium into an efficient legume symbiont, are not known.

Our work aims at understanding the emergence and evolution of these mutualistic interactions by focusing on two questions i) how the symbiotic capacity disseminate to so many different genera of bacteria, and ii) what are the molecular events that have accompanied the genesis of this symbiosis on the plant side? To answer these questions we use the model Cupriavidus taiwanensis – Mimosa pudica, a symbiotic interaction that emerged relatively recently (ca. 12 to 16 MYA) and representative of symbioses from the Mimosoideae subclade. Our approaches range from molecular genetics and genomics to experimental evolution and modeling.

images groupe Catherine MASSON

images groupe Catherine MASSON