Identification of a putative cognate sensor kinase for the two-component response regulator HrpG, a key regulator controlling the expression of the hrp genes in Xanthomonas campestris pv. campestris

Authors

  • Rui-Fang Li,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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    • Rui-Fang Li and Guang-Tao Lu contributed equally to this work.
  • Guang-Tao Lu,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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    • Rui-Fang Li and Guang-Tao Lu contributed equally to this work.
  • Lei Li,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Hui-Zhao Su,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Guo-fang Feng,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Ya Chen,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Yong-Qiang He,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Bo-Le Jiang,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Dong-Jie Tang,

    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
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  • Ji-Liang Tang

    Corresponding author
    1. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, Nanning, China
    • For correspondence. E-mail jltang@gxu.edu.cn; Tel. (+86) 771 3239566; Fax (+86) 771 3239413.

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Summary

The bacterial phytopathogen Xanthomonas campestris pv. campestris (Xcc) relies on the hrp (hypersensitive response and pathogenicity) genes to cause disease and induce hypersensitive response (HR). The hrp genes of bacterial phytopathogens are divided into two groups. Xcc hrp genes belong to group II. It has long been known that the group II hrp genes are activated by an AraC-type transcriptional regulator whose expression is controlled by a two-component system (TCS) response regulator (named HrpG in Xcc). However, no cognate sensor kinase has yet been identified. Here, we present evidence showing that the Xcc open-reading frame XC_3670 encodes a TCS sensor kinase (named HpaS). Mutation of hpaS almost completely abolished the HR induction and virulence. Bacterial two-hybrid and protein pull-down assays revealed that HpaS physically interacted with HrpG. Phos-tag™ SDS-PAGE analysis showed that mutation in hpaS reduced markedly the phosphorylation of HrpG in vivo. These data suggest that HpaS and HrpG are most likely to form a TCS. We also showed that XC_3669 (named hpaR2), which is adjacent to hpaS and encodes a putative TCS response regulator, is required for full virulence but not HR induction. HpaR2 also physically interacted with HpaS, suggesting that HpaS may also form another TCS with HpaR2.

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