title: Multihost experimental evolution of the pathogen Ralstonia solanacearum unveils genes involved in adaptation to plants.
abstract: Ralstonia solanacearum, the causal agent of a lethal bacterial wilt plant disease, infects an unusually wide range of hosts. These hosts can further be split into plants where R. solanacearum is known to cause disease (original hosts) and those where this bacterium can grow asymptomatically (distant hosts). Moreover, this pathogen is able to adapt to many plants as supported by field observations reporting emergence of strains with enlarged pathogenic properties. To investigate the genetic bases of host adaptation, we conducted evolution experiments by serial passages of a single clone of the pathogen on three original and two distant hosts over 300 bacterial generations and then analyzed the whole-genome of nine evolved clones. Phenotypic analysis of the evolved clones showed that the pathogen can increase its fitness on both original and distant hosts although the magnitude of fitness increase was greater on distant hosts. Only few genomic modifications were detected in evolved clones compared with the ancestor but parallel evolutionary changes in two genes were observed in independent evolved populations. Independent mutations in the regulatory gene efpR were selected for in three populations evolved on beans, a distant host. Reverse genetic approaches confirmed that these mutations were associated with fitness gain on bean plants. This work provides a first step toward understanding the within-host evolutionary dynamics of R. solanacearum during infection and identifying bacterial genes subjected to in planta selection. The discovery of EfpR as a determinant conditioning host adaptation of the pathogen illustrates how experimental evolution coupled with whole-genome sequencing is a potent tool to identify novel molecular players involved in central life-history traits.
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.
authors.forename: Alice
authors.initials: A
authors.lastname: Guidot
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.affiliation: UPS-CNRS-ENFA, Laboratoire Évolution et Diversité Biologique (EDB), UMR5174, Université Paul Sabatier, Toulouse, France.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Ferdy
authors.affiliation: UPS-CNRS-ENFA, Laboratoire Évolution et Diversité Biologique (EDB), UMR5174, Université Paul Sabatier, Toulouse, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Thébaud
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Barberis
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Gouzy
authors.affiliation: INRA, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR441, Castanet-Tolosan, France CNRS, Laboratoire des Interactions Plantes-Microorganismes (LIPM), UMR2594, Castanet-Tolosan, France sgenin@toulouse.inra.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Genin
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D019607:Brassicaceae / Q000382:microbiology; D002999:Clone Cells; D007887:Fabaceae / Q000382:microbiology; D005798:Genes, Bacterial; D005809:Genes, Regulator; D016680:Genome, Bacterial; D031314:Geraniaceae / Q000382:microbiology; D058507:Host Specificity; D054884:Host-Pathogen Interactions; D009154:Mutation; D010935:Plant Diseases / Q000382:microbiology; D043368:Ralstonia solanacearum / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D012641:Selection, Genetic; D019657:Solanaceae / Q000382:microbiology; D014774:Virulence
keywords: Ralstonia solanacearum; bacterial plant pathogen; fitness; full genome sequence; in vivo experimental evolution; parallel evolution; reverse genetic; tomato; virulence evolution