XrvB regulates the type III secretion system by directly repressing hrpG transcription in Xanthomonas oryzae pv. oryzicola

文献类型： 外文期刊

第一作者： Peng, Jian-Ling

作者： Peng, Jian-Ling;Shi, Jia-Feng;Ye, Wen-Xin;Su, Qian;Tang, Ji-Liang;Lu, Guang-Tao;Ma, Zeng-Feng;Zhou, Xiao-Long;Zhu, Gui-Ning;Li, Rui-Fang

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关键词： Xanthomonas oryzae; T3SS; hrp genes; H-NS protein; Xrv protein

期刊名称：PHYTOPATHOLOGY RESEARCH （ 影响因子：3.4； 五年影响因子：4.2 ）

ISSN： 2096-5362

年卷期： 2023 年 5 卷 1 期

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收录情况： SCI

摘要： Xrv proteins are a group of regulators in Xanthomonas spp., belonging to the histone-like nucleoid-structuring (H-NS) proteins of Gram-negative bacteria. The rice bacterial leaf streak pathogen Xanthomonas oryzae pv. oryzicola (Xoc) harbors three Xrv proteins, the XrvA, XrvB, and XrvC. Here, we report that in Xoc, the XrvB but not XrvA and XrvC is involved in negative regulation of the type III secretion system (T3SS) encoded by hrp genes. As with other Xanthomonas spp., the T3SS is an essential virulence determinant of Xoc and the expression of the hrp genes in Xoc is controlled by the HrpG/HrpX regulatory cascade. HrpG positively regulates the expression of HrpX, which in turn activates the transcription of the hrp genes. We provide evidences to demonstrate that the XrvB binds to the promoter region of hrpG and represses its transcription. Furthermore, we found that XrvB production was induced in the Xoc cells cultured in a nutrient-rich medium compared to a hrp-inducing minimal medium. We also found that in Xoc, the hrpG expression level is inversely correlated with the content of XrvB, and XrvB occupancy at hrpG promoter region is positively correlated with XrvB levels. Our data suggest that XrvB is a determinative factor controlling the expression levels of HrpG. In addition, mutation analysis revealed that the Xoc XrvB also plays positive roles in regulating bacterial growth, cell motility, and stress tolerance. Our findings provide important insights into the molecular mechanism of T3SS expression regulation in Xoc.

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