ABSTRACT

Shigella is an intracellular pathogen that primarily infects the human colon and causes shigellosis. Shigella virulence relies largely on the type III secretion system (T3SS) and secreted effectors. VirF, the master Shigella virulence regulator, is essential for the expression of T3SS-related genes. In this study, we found that YhjC, a LysR-type transcriptional regulator, is required for Shigella virulence through activating the transcription of virF. Pathogenicity of the yhjC mutant, including colonization in the colons of guinea pigs as well as its ability for host cell adhesion and invasion, was significantly lowered. Expression levels of virF and nearly all VirF-dependent genes were downregulated by yhjC deletion, indicating that YhjC can activate virF transcription. Electrophoretic mobility shift assay analysis demonstrated that YhjC could bind directly to the virF promoter region. Therefore, YhjC is a novel virulence regulator that positively regulates the virF expression and promotes Shigella virulence. Additionally, genome-wide expression analysis identified the presence of other genes in the large virulence plasmid and a genome exhibiting differential expression in response to yhjC deletion, with 169 downregulated and 99 upregulated genes, indicating that YhjC also functioned as a global regulatory factor.

摘要

志贺氏菌是一种细胞内病原体，主要感染人类结肠并引起志贺氏菌病。志贺氏菌的毒力主要依赖于 III 型分泌系统 (T3SS) 和分泌的效应器。VirF 是主要的志贺氏菌毒力调节剂，对 T3SS 相关基因的表达至关重要。在这项研究中，我们发现 YhjC 是一种 LysR 型转录调节因子，通过激活virF的转录，志贺氏菌的毒力是必需的。yhjC突变体的致病性，包括在豚鼠结肠中的定植以及其对宿主细胞粘附和侵袭的能力，显着降低。virF的表达水平并且几乎所有的 VirF 依赖基因都被yhjC缺失下调，表明 YhjC 可以激活virF转录。电泳迁移率变动分析表明，YhjC 可以直接与virF启动子区域结合。因此，YhjC 是一种新型的毒力调节剂，可正向调节virF的表达，促进志贺氏菌的毒力。此外，全基因组表达分析确定了大毒力质粒中其他基因的存在，以及响应yhjC缺失而表现出差异表达的基因组，其中 169 个下调和 99 个上调基因，表明 YhjC 也起到全局调节因子的作用。