Regulatory actions of ToxR and CalR on their own genes and type III secretion system 1 in Vibrio parahaemolyticus

// George Osei-Adjei 1, * , He Gao 3, * , Ying Zhang 1 , Lingyu Zhang 1 , Wenhui Yang 2 , Huiying Yang 2 , Zhe Yin 2 , Xinxiang Huang 1 , Yiquan Zhang 1 and Dongsheng Zhou 2 1 School of Medicine, Jiangsu University, Zhenjiang 212013, China 2 State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China 3 State Key Laboratory of Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing 102206, China * These authors have contributed equally to this work Correspondence to: Dongsheng Zhou, email: dongshengzhou1977@gmail.com Yiquan Zhang, email: zhangyiquanq@163.com Xinxiang Huang, email: huxinx@ujs.edu.cn Keywords: Vibrio parahaemolyticus, calR, ToxR, T3SS1 Received: May 10, 2017     Accepted: June 20, 2017     Published: July 22, 2017 ABSTRACT Vibrio parahaemolyticus is the leading cause of seafood-associated gastroenteritis. Type III secretion system 1 (T3SS1) is one of the virulence determinants of this bacteria. T3SS1 expression is regulated by ToxR and CalR. ToxR represses the transcription of T3SS1 genes via activation of CalR, which acts as a transcriptional repressor of T3SS1 genes. However, the transcriptional regulation mechanisms have not been elucidated. As showing in the present work, ToxR binds to the promoter DNA region of calR to activate its transcription. CalR occupies the promoter-proximal regions of each detected target operons in T3SS1 loci to repress their transcription, and thereby inhibiting T3SS1-dependent cytotoxicity. Moreover, a feedback CalR inhibits toxR and its own gene in a direct manner. Collectively, this work reported an interesting gene regulatory network involving the reciprocal regulation of ToxR and CalR, and their regulation on T3SS1 genes transcription in V. parahaemolyticus .