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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

Research themes - Symbiotic functions, genome and evolution of rhizobia

Experimental evolution of the plant pathogen Ralstonia solanacearum into a legume symbiont

Rhizobia do not form a homogenous group but are phylogenetically disparate α- and β- proteobacteria that have achieved a nitrogen-fixing symbiosis with legume. 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. To experience this evolutionary scenario we have launched more than 10 years ago an evolution experiment aiming at converting a soil bacterium into a legume symbiont. A chimeric Ralstonia strain was engineered by introducing the symbiotic plasmid of the β-rhizobium model Cupriavidus taiwanensis into the plant pathogen Ralstonia-solanacearum. This chimeric strain is being evolved under legume (M. pudica, the host plant of C. taiwanensis) selection pressure to activate and/or improve competitiveness in nodulation, infection, bacterial maintenance in infected cells and tentatively nitrogen fixation. This project exploits the recent advances in fast genome re-sequencing technology to track genome modifications, both R. solanacearum and C. taiwanensis being completely sequenced. Genomic, cellular and molecular genetics approaches are combined to elucidate the underlying genetic basis of symbiotic adaptation. This project is at the interface of symbiosis and pathogenesis.

Shaping new bacterial symbionts


Our main collaborators are P.M. Delaux (LRSV, Toulouse), J.B. Ferdy (EDB, Toulouse), C. Pouzet and A. Leru (Imaging platform Toulouse), E. Rocha (Pasteur Institute, Paris) and D. Roche (Genoscope-CEA, Evry).

 Current fundings

FRAIB DYNAMIC (2021-2022) Evolutionary dynamics of bacterial adaptation to symbiosis with legumes. Partner: J.B. Ferdy (EDB, Toulouse), 15 k€.

ANR REPLAY (2017-2020) Replaying the evolution of rhizobia: towards a conceptual and practical framework for the design of new nitrogen-fixing plant symbionts. Partners: Genoscope (D. Roche), IP Paris (E. Rocha), 460 k€.