title: GsmR, a response regulator with an HD-related output domain in Xanthomonas campestris, is positively controlled by Clp and is involved in the expression of genes responsible for flagellum synthesis.
abstract: In prokaryotes, two-component signal transduction systems, consisting of a histidine kinase and a response regulator, play a critical role in regulating a range of cellular functions. A recent study suggests that XCC3315, a response regulator with a CheY-like receiver domain attached to an uncharacterized HD-related output domain (HDOD domain), plays a role in the general stress response of the Gram-negative bacterium Xanthomonas campestris pv. campestris (Xcc), the causal agent of black rot in cruciferous plants. Here, we demonstrated genetically that XCC3315, designated as gsmR (general stress and motility regulator), is involved in the expression of genes responsible for flagellum synthesis, including rpoN2, flhF, flhB, and fliC. Site-directed mutagenesis revealed that Glu9 and Arg100 in the receiver domain and Gly205, Asp263, His287, Trp298 and His311 in the HDOD are critical amino acids for GsmR function in cell motility regulation. The gsmR transcription initiation site was mapped. Promoter analysis and gel retardation assay revealed that the expression of gsmR is positively controlled by the global transcriptional regulator Clp in a direct manner, and is subject to catabolite repression. Our findings not only extend the previous work on Clp regulation to show that it influences the expression of gsmR in Xcc, but are also the first to characterize the expression of this response regulator gene in this phytopathogen. Furthermore, GsmR is the first HDOD-containing protein of bacteria in which key amino acids have been experimentally identified and characterized.
authors.affiliation: Department of Biomedical Sciences, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Yu-Fan
authors.initials: YF
authors.lastname: Liu
authors.forename: Chao-Tsai
authors.initials: CT
authors.lastname: Liao
authors.forename: Wan-Ling
authors.initials: WL
authors.lastname: Song
authors.forename: Pei-Chi
authors.initials: PC
authors.lastname: Hsu
authors.forename: Shin-Chiao
authors.initials: SC
authors.lastname: Du
authors.forename: Hsueh-Hsia
authors.initials: HH
authors.lastname: Lo
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Hsiao
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D017124:Conserved Sequence; D005407:Flagella / Q000235:genetics / Q000378:metabolism*; D005408:Flagellin; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009596:Nitrophenols / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000737:chemistry; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D040681:Structural Homology, Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016959:Xanthomonas campestris / Q000166:cytology / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C436751:Clp protein, Xanthomonas campestris; D009596:Nitrophenols; D009943:Organophosphorus Compounds; D014157:Transcription Factors; D005408:Flagellin; C008644:nitrophenylphosphate; D010744:Phosphoric Monoester Hydrolases