title: Metabolic adaptation of Ralstonia solanacearum during plant infection: a methionine biosynthesis case study.
abstract: MetE and MetH are two distinct enzymes that catalyze a similar biochemical reaction during the last step of methionine biosynthesis, MetH being a cobalamin-dependent enzyme whereas MetE activity is cobalamin-independent. In this work, we show that the last step of methionine synthesis in the plant pathogen Ralstonia solanacearum is under the transcriptional control of the master pathogenicity regulator HrpG. This control is exerted essentially on metE expression through the intermediate regulator MetR. Expression of metE is strongly and specifically induced in the presence of plant cells in a hrpG- and metR-dependent manner. metE and metR mutants are not auxotrophic for methionine and not affected for growth inside the plant but produce significantly reduced disease symptoms on tomato whereas disruption of metH has no impact on pathogenicity. The finding that the pathogen preferentially induces metE expression rather than metH in the presence of plant cells is indicative of a probable metabolic adaptation to physiological host conditions since this induction of metE occurs in an environment in which cobalamin, the required co-factor for MetH, is absent. It also shows that MetE and MetH are not functionally redundant and are deployed during specific stages of the bacteria lifecycle, the expression of metE and metH being controlled by multiple and distinct signals.
authors.affiliation: INRA, UMR441 Laboratoire des Interactions Plantes-Microorganismes (LIPM), Castanet-Tolosan, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Plener
authors.forename: Pierre
authors.initials: P
authors.lastname: Boistard
authors.forename: Adriana
authors.initials: A
authors.lastname: González
authors.forename: Christian
authors.initials: C
authors.lastname: Boucher
authors.forename: Stéphane
authors.initials: S
authors.lastname: Genin
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006710:Homocysteine / Q000235:genetics / Q000378:metabolism; D008715:Methionine / Q000096:biosynthesis* / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D059828:Plant Cells; D010935:Plant Diseases / Q000382:microbiology*; D043368:Ralstonia solanacearum / Q000235:genetics* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014805:Vitamin B 12 / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C058169:MetR protein, Bacteria; D015534:Trans-Activators; D006710:Homocysteine; D008715:Methionine; D008780:Methyltransferases; C121199:methylcobalamin - homocysteine methyltransferase; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D014805:Vitamin B 12