title: Role of methylotrophy during symbiosis between Methylobacterium nodulans and Crotalaria podocarpa.
abstract: Some rare leguminous plants of the genus Crotalaria are specifically nodulated by the methylotrophic bacterium Methylobacterium nodulans. In this study, the expression and role of bacterial methylotrophy were investigated during symbiosis between M. nodulans, strain ORS 2060T, and its host legume, Crotalaria podocarpa. Using lacZ fusion to the mxaF gene, we showed that the methylotroph genes are expressed in the root nodules, suggesting methylotrophic activity during symbiosis. In addition, loss of the bacterial methylotrophic function significantly affected plant development. Indeed, inoculation of M. nodulans nonmethylotroph mutants in C. podocarpa decreased the total root nodule number per plant up to 60%, decreased the whole-plant nitrogen fixation capacity up to 42%, and reduced the total dry plant biomass up to 46% compared with the wild-type strain. In contrast, inoculation of the legume C. podocarpa with nonmethylotrophic mutants complemented with functional mxa genes restored the symbiotic wild phenotype. These results demonstrate the key role of methylotrophy during symbiosis between M. nodulans and C. podocarpa.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, UMR 113 AgroM/CIRAD/INRA/IRD/UMII, TA 10/J, Campus International de Baillarguet, Montpellier, France. jourand@mpl.ird.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Jourand
authors.forename: Adeline
authors.initials: A
authors.lastname: Renier
authors.forename: Sylvie
authors.initials: S
authors.lastname: Rapior
authors.forename: Sergio
authors.initials: S
authors.lastname: Miana de Faria
authors.forename: Yves
authors.initials: Y
authors.lastname: Prin
authors.forename: Antoine
authors.initials: A
authors.lastname: Galiana
authors.forename: Eric
authors.initials: E
authors.lastname: Giraud
authors.forename: Bernard
authors.initials: B
authors.lastname: Dreyfus
mesh_terms: D029864:Crotalaria / Q000502:physiology*; D005816:Genetic Complementation Test; D020580:Methylobacterium / Q000235:genetics / Q000502:physiology*; D018517:Plant Roots / Q000382:microbiology; D013559:Symbiosis