title: hpaR, a putative marR family transcriptional regulator, is positively controlled by HrpG and HrpX and involved in the pathogenesis, hypersensitive response, and extracellular protease production of Xanthomonas campestris pathovar campestris.
abstract: The MarR family of transcriptional regulators of bacteria are involved in the regulation of many cellular processes, including pathogenesis. In this work, we have demonstrated genetically that hpaR (hpa, hrp associated), which encodes a putative MarR family regulator, is involved in the hypersensitive response (HR), pathogenicity, and extracellular protease production of the phytopathogenic bacterium Xanthomonas campestris pathovar campestris. A mutation in hpaR resulted in complete loss of virulence in the host plant cabbage, a delayed and weakened HR in the nonhost plant pepper ECW-10R, and an increase in extracellular protease production. Detection of the beta-glucuronidase activity of a plasmid-driven hpaR promoter-gusA reporter revealed that the expression of hpaR is positively controlled by HrpG and HrpX and is suppressed in rich medium while being strongly induced in minimal and hrp-inducing media and inside the host. These findings indicate that hpaR belongs to the hrpG and hrpX regulon and that HrpX regulates the extracellular protease production via hpaR in X. campestris pv. campestris.
authors.affiliation: College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Wei
authors.forename: Dong-Jie
authors.initials: DJ
authors.lastname: Tang
authors.forename: Yong-Qiang
authors.initials: YQ
authors.lastname: He
authors.forename: Jia-Xun
authors.initials: JX
authors.lastname: Feng
authors.forename: Bo-Le
authors.initials: BL
authors.lastname: Jiang
authors.forename: Guang-Tao
authors.initials: GT
authors.lastname: Lu
authors.forename: Baoshan
authors.initials: B
authors.lastname: Chen
authors.forename: Ji-Liang
authors.initials: JL
authors.lastname: Tang
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000502:physiology*; D016959:Xanthomonas campestris / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*
chemical_list: D001426:Bacterial Proteins; C102404:HrpG protein, Xanthomonas campestris; C080371:HrpX protein, Bacteria; D014157:Transcription Factors; D010447:Peptide Hydrolases