title: Functional analysis of Ralstonia solanacearum PrhG regulating the hrp regulon in host plants.
abstract: Genes in the hrp regulon encode component proteins of the type III secretion system and are essential for the pathogenicity of Ralstonia solanacearum. The hrp regulon is controlled by HrpB. We isolated several genes regulating hrpB expression from the Japanese strain OE1-1 using minitransposon mutagenesis. Among them, we mainly focused on two genes, hrpG and prhG, which are the positive regulators of hrpB. Although the global virulence regulator PhcA negatively regulated hrpG expression via prhIR, it positively regulated prhG expression. We further investigated the contrasting regulation of hrpG and prhG by PhcA and speculated that R. solanacearum may switch from HrpG to PrhG for hrpB activation in a cell density-dependent manner. Although the prhG mutant proliferated similarly to the wild-type in leaf intercellular spaces and in xylem vessels of the host plants, it was less virulent than the wild-type. The expression of the popA operon, which belongs to the hrp regulon, was significantly reduced in the prhG mutant by more than half in the leaf intercellular spaces and more than two-thirds in the xylem vessels when compared with the wild-type.
authors.affiliation: Research Center of Bioenergy and Bioremediation, Southwest University, BeiBei District, Chongqing 400715, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Research Institute of Molecular Genetics, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.affiliation: Laboratory of Plant Pathology and Biotechnology, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yoshimochi
authors.affiliation: Laboratory of Plant Pathology and Biotechnology, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Akinori
authors.initials: A
authors.lastname: Kiba
authors.affiliation: Laboratory of Plant Pathology and Biotechnology, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Hikichi
authors.affiliation: Research Institute of Molecular Genetics, Kochi University, Nankoku, Kochi 783-8502, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Ohnishi
mesh_terms: D000818:Animals; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005786:Gene Expression Regulation; D054884:Host-Pathogen Interactions; D018551:Solanum lycopersicum / Q000382:microbiology; D020050:Mantodea; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000382:microbiology; D043368:Ralstonia solanacearum / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018085:Regulon; D017422:Sequence Analysis, DNA; D011198:Solanum tuberosum / Q000382:microbiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014774:Virulence; D052584:Xylem / Q000382:microbiology
chemical_list: D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D014157:Transcription Factors