AUTHOR=Zhang Yiquan , Hu Lingfei , Osei-Adjei George , Zhang Ying , Yang Wenhui , Yin Zhe , Lu Renyun , Sheng Xiumei , Yang Ruifu , Huang Xinxiang , Zhou Dongsheng 

TITLE=Autoregulation of ToxR and Its Regulatory Actions on Major Virulence Gene Loci in Vibrio parahaemolyticus

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00291

DOI=10.3389/fcimb.2018.00291

ISSN=2235-2988

ABSTRACT=<p><italic>Vibrio parahaemolyticus</italic>, the leading causative agent of seafood-associated gastroenteritis, harbors two major virulence gene loci T3SS1 and Vp-PAI (T3SS2 and <italic>tdh2</italic>). ToxR is a virulence regulator of vibrios. Cell density-dependent transcriptional pattern of <italic>toxR</italic> and its regulatory actions on T3SS1 and Vp-PAI have been previously reported, but the detailed regulatory mechanisms are still obscure. In the present work, we showed that the highest transcription level of <italic>toxR</italic> occurs at an OD<sub>600</sub> = 0.2–0.4, which may be due to the subtle repression of ToxR and the quorum-sensing (QS) master regulator AphA. We also showed that ToxR is involved in regulating the mouse lethality, enterotoxicity, cytotoxicity, and hemolytic activity of <italic>V. parahaemolyticus</italic>. ToxR binds to the multiple promoter-proximal DNA regions within the T3SS1 locus to repress their transcription. In addition, ToxR occupies the multiple promoter-proximal DNA regions of Vp-PAI locus to activate their transcription. Thus, ToxR regulates the multiple virulence phenotypes via directly acting on the T3SS1 and Vp-PAI genes. Data presented here provide a deeper understanding of the regulatory patterns of ToxR in <italic>V. parahaemolyticus</italic>.</p>