title: Characterization of the GntR family regulator HpaR1 of the crucifer black rot pathogen Xanthomonas campestris pathovar campestris.
abstract: The GntR family transcription regulator HpaR1 identified from Xanthomonas campestris pv. campestris has been previously shown to positively regulate the genes responsible for hypersensitive reaction and pathogenicity and to autorepress its own expression. Here, we demonstrated that HpaR1 is a global regulator that positively regulates diverse biological processes, including xanthan polysaccharide production, extracellular enzyme activity, cell motility and tolerance to various stresses. To investigate the regulatory mechanisms of HpaR1, we began with xanthan polysaccharide production, which is governed by a cluster of gum genes. These are directed by the gumB promoter. Disruption of HpaR1 significantly reduced gumB transcription and an electrophoretic mobility shift assay demonstrated that HpaR1 interacts directly with gumB promoter. DNase I footprint analysis revealed that HpaR1 and RNA polymerase were bound to the sequences extending from -21 to +10 and -41 to +29 relative to the transcription initiation site of gumB, respectively. Furthermore, in vitro transcription assays showed that HpaR1 facilitated the binding of RNA polymerase to gumB promoter, leading to an enhancement of its transcription. These results suggest that HpaR1 regulates gumB transcription via a mechanism similar but different to what was found, until now, to only be used by some MerR family transcription activators.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Hui-Zhao
authors.initials: HZ
authors.lastname: Su
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Wu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Yan-Hua
authors.initials: YH
authors.lastname: Qi
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Guo-Fang
authors.initials: GF
authors.lastname: Liu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Guang-Tao
authors.initials: GT
authors.lastname: Lu
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China.
authors.forename: Ji-Liang
authors.initials: JL
authors.lastname: Tang
mesh_terms: D000220:Adaptation, Biological; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005110:Extracellular Space / Q000201:enzymology; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation; D009876:Operon; D010935:Plant Diseases / Q000382:microbiology; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D013312:Stress, Physiological; D014157:Transcription Factors / Q000378:metabolism*; D024363:Transcription Initiation Site; D016959:Xanthomonas campestris / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases; C002563:xanthan gum
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