Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
Nucleic Acids Res. 2018 Nov 16;46(20):10619-10634. doi: 10.1093/nar/gky717.
During growth on chitinous surfaces in its natural aquatic environment Vibrio cholerae develops natural competence for transformation and kills neighboring non-immune bacteria using a type VI secretion system (T6SS). Activation of these two phenotypes requires the chitin-induced regulator TfoX, but also integrates signals from quorum sensing via the intermediate regulator QstR, which belongs to the LuxR-type family of regulators. Here, we define the QstR regulon using RNA sequencing. Moreover, by mapping QstR binding sites using chromatin immunoprecipitation coupled with deep sequencing we demonstrate that QstR is a transcription factor that binds upstream of the up- and down-regulated genes. Like other LuxR-type family transcriptional regulators we show that QstR function is dependent on dimerization. However, in contrast to the well-studied LuxR-type biofilm regulator VpsT of V. cholerae, which requires the second messenger c-di-GMP, we show that QstR dimerization and function is c-di-GMP independent. Surprisingly, although ComEA, which is a periplasmic DNA-binding protein essential for transformation, is produced in a QstR-dependent manner, QstR-binding was not detected upstream of comEA suggesting the existence of a further regulatory pathway. Overall, these results provide detailed insights into the function of a key regulator of natural competence and type VI secretion in V. cholerae.
在其天然水生环境的几丁质表面生长时，霍乱弧菌会发展出天然转化能力，并利用一种 VI 型分泌系统（T6SS）杀死邻近的非免疫细菌。这两种表型的激活需要几丁质诱导调节因子 TfoX，但也整合了来自群体感应的信号，通过中间调节因子 QstR，属于 LuxR 型调节因子家族。在这里，我们使用 RNA 测序定义了 QstR 调控子。此外，通过使用染色质免疫沉淀结合深度测序来绘制 QstR 结合位点，我们证明 QstR 是一种转录因子，它在上调基因和下调基因的上游结合。像其他 LuxR 型家族转录调节因子一样，我们表明 QstR 的功能依赖于二聚化。然而，与研究得很好的霍乱弧菌的 LuxR 型生物膜调节因子 VpsT 不同，它需要第二信使 c-di-GMP，我们表明 QstR 二聚化和功能与 c-di-GMP 无关。令人惊讶的是，尽管 ComEA 是一种对转化至关重要的周质 DNA 结合蛋白，但它是以 QstR 依赖的方式产生的，然而在 comEA 的上游没有检测到 QstR 结合，这表明存在进一步的调节途径。总的来说，这些结果提供了霍乱弧菌天然感受态和 VI 型分泌关键调节因子功能的详细见解。
