Comparative transcriptomic analysis provides insights into transcription mechanisms of Vibrio parahaemolyticus T3SS during interaction with HeLa cells

Vibrio parahaemolyticus is an important foodborne pathogenic bacterium that harbors the type III secretion system 1 (T3SS1) as an essential virulence factor. However, the pathogenesis and infection mechanism mediated by T3SS1 are not entirely clarified. Similar to previous studies on other T3SS-positive bacteria, the T3SS1 needle is a major extracellular component in V. parahaemolyticus. We recently showed that the needle gene-deletion mutant (ΔvscF) exhibited markedly decreased cytotoxicity and effector translocation during interaction with HeLa cells. To further elucidate the pathogenesis of T3SS1 during host cell infection, bacterial RNA was extracted from wild-type POR-1 and ΔvscF mutants under infected condition for comparative RNA sequencing analysis in HeLa cell. The results showed that 120 differentially expressed genes (DEGs) were identified in the ΔvscF-infected group. These encoded proteins of DEGs, such as VP2088, VP2089, and VP2091, were annotated as ABC transporter system, whereas VP0757, VP1123, and VP1289 may be new transcriptional regulators. In addition, the downregulation of T3SS1 had a positive influence on the expression of T3SS2. Moreover, the transcription of the basal body is unaffected by the needle, and there was a close relation among the tip, translocon, and needle, because bacterial adenylate cyclase two-hybrid system (BACTH system) assay indicated the interaction of VP1656, VP1670, VP1693, and VP1694 (VscF). This study provides insights into transcription mechanism of T3SS1 upon infecting HeLa cell, which is expected to better clarify the T3SS1 virulent mechanism.