title: Genome-wide analysis of gene expression in Ralstonia solanacearum reveals that the hrpB gene acts as a regulatory switch controlling multiple virulence pathways.
abstract: A 70-mer oligonucleotide-based DNA microarray covering 5,074 of the 5,120 predicted genes from Ralstonia solanacearum has been generated and used to investigate the repertoire of genes that are under the control of the transcription activator HrpB, which governs pathogenicity in this plant pathogenic bacterium. This study identified 143 hrpB up-regulated genes and 50 hrpB down-regulated genes. In addition to extending the repertoire of type III effector proteins with 26 new candidates, this work demonstrates that the hrpB regulon extends beyond type III secretion system-related functions to include a number of genes governing chemotaxy, biosynthesis or catabolism of various low-molecular-weight chemical compounds, and siderophore production and uptake. The presence of several transcripttional regulators and a cluster of genes predicted to encode the synthesis of an acylhomoserine lactone together with the absence of a consensus hrpII box in the promoter of a significant proportion of the hrpB-regulated genes suggest that, for some genes, hrpB regulation might be indirect. Altogether, the data indicate that hrpB acts as a master regulatory gene governing a physiological swing associated with the shift from saprophytic to parasitic life.
authors.affiliation: Laboratoire des Interactions Plantes-Microorganismes, INRA-CNRS, UMR2594, BP 52627, 31326 Castanet tolosan Cedex, France.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Occhialini
authors.forename: Sébastien
authors.initials: S
authors.lastname: Cunnac
authors.forename: Nancie
authors.initials: N
authors.lastname: Reymond
authors.forename: Stéphane
authors.initials: S
authors.lastname: Genin
authors.forename: Christian
authors.initials: C
authors.lastname: Boucher
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D016680:Genome, Bacterial; D005810:Multigene Family; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000382:microbiology; D010944:Plants / Q000382:microbiology*; D043368:Ralstonia solanacearum / Q000235:genetics* / Q000472:pathogenicity*; D018085:Regulon; D014157:Transcription Factors / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C079047:hrpB protein, Ralstonia solanacearum