Differential binding of LuxR in response to temperature gauges switches virulence gene expression in Vibrio alginolyticus

Abstract

Vibrio pathogens must cope with temperature changes for proper thermo-adaptation and virulence gene expression. LuxR is a quorum-sensing (QS) master regulator of vibrios, playing roles in response to temperature alteration. However, the molecular mechanisms how LuxR is involved in adapting to different temperatures in bacteria have not been precisely elucidated. In this study, using chromatin immunoprecipitation and nucleotide sequencing (ChIP-seq), we identified 272 and 22 enriched loci harboring LuxR-binding peaks at ambient temperature (30 ˚C) and heat shock (42 ˚C) in the Vibrio alginolyticus genome, respectively. Analysis with the MEME (multiple EM for motif elicitation) algorithm indicated that the binding motifs of LuxR varied from temperatures. Three novel binding regions (the promoter of orf00292, orf00397 and fadD) of LuxR were identified and verified that the rising temperature causes the decreasing binding affinity of LuxR to these promoters. Meanwhile, the expression of orf00292, orf00397 and fadD were regulated by LuxR. Moreover, the weak binding of LuxR to the promoter of extracellular protease (Asp) was attributed to the attenuated Asp expression at thermal stress conditions. Taken together, our study demonstrated distinct binding characteristics of LuxR in response to temperature changes, thus highlighting LuxR as a thermo-sensor to switch and control virulence gene expression in V. alginolyticus.