CqsA/LuxS-HapR Quorum sensing circuit modulates type VI secretion system VflT6SS2 in Vibrio fluvialis
CqsA/LuxS-HapR Quorum sensing circuit modulates type VI secretion system VflT6SS2 in Vibrio fluvialis
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CqsA/LuxS-HapR 群体感应电路调节河流弧菌中的 VI 型分泌系统 VflT6SS2
DOI：
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发表时间：
2021
期刊：
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通讯作者：
Weili Liang
中科院分区：
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作者：
Xiaoshu Liu;Jingjing Pan;He Gao;Yu Han;Anran Zhang;Yuanming Huang;Ping Liu;Biao Kan;Weili Liang
流感弧菌是一种日益严重威胁公共卫生的新兴肠道病原体。目前已鉴定出两种群体感应系统VfqI-VfqR和CqsA/LuxS-HapR，以及两种VI型分泌系统VflT6SS1和VflT6SS2。这两个系统之间是否存在关联尚不清楚。在本研究中，我们发现CqsA/LuxS-HapR电路调节器LuxO抑制VflT6SS2，而HapR激活VflT6SS2。LuxO的作用在低细胞密度时更为明显，并且依赖于hapr。hapR的缺失可抑制Hcp的表达，减轻其抑菌力。然而，这些效应被表达hapr的质粒所挽救。报告融合分析表明，HapR是VflT6SS2启动子活性所必需的。对主要簇启动子的序列检测发现了两个潜在的Motif 1 HapR结合位点，并通过电泳迁移转移试验（EMSA）和dna酶I足迹试验证实了它们与HapR的结合。同时，在孤儿簇的tssD2_a （hcpA）和tssD2_b （hcpB）启动子区域发现了两个单Motif 2位点，它们与HapR的亲和力较低，保守性较差。总之，我们的研究表明，CqsA/LuxS-HapR QS操纵V. fluvialis中的VflT6SS2，这一发现将增强我们对微生物中T6SS和QS之间可能的串扰的理解。
Vibrio fluvialis is an emerging enteric pathogen of increasing public health threat. Two quorum sensing (QS) systems, VfqI-VfqR and CqsA/LuxS-HapR, and two type VI secretion systems (T6SSs), VflT6SS1 and VflT6SS2, have been identified in V. fluvialis. Whether there exists any correlation between the two systems is unclear. In this study, we found that CqsA/LuxS-HapR circuit regulator LuxO represses while HapR activates VflT6SS2. The effect of LuxO is more pronounced at low cell density and is HapR-dependent. Deletion of hapR abolished Hcp expression and alleviated antibacterial virulence. However, these effects were rescued by HapR-expressing plasmid. Reporter fusion analyses showed that HapR is required for the promoter activities of VflT6SS2. Sequence inspection of the major cluster promoter revealed two potential Motif 1 HapR binding sites, and their bindings to HapR were confirmed by both electrophoretic mobility shift assay (EMSA) and DNase I footprinting assay. Meanwhile, two single Motif 2 sites were identified in tssD2_a (hcpA) and tssD2_b (hcpB) promoter regions of the orphan cluster which are less conserved and displayed lower affinities to HapR. Together, our study demonstrated that CqsA/LuxS-HapR QS manipulate VflT6SS2 in V. fluvialis, and this finding will enhance our understanding of possible crosstalk between T6SS and QS in microbes.