A σE-Mediated Temperature Gauge Controls a Switch from LuxR-Mediated Virulence Gene Expression to Thermal Stress Adaptation in Vibrio alginolyticus

In vibrios,the expression of virulence factors is often controlled by luxr,the master quorum-sensing regulator. here,we investigate the interplay between luxr and σe,an alternative sigma factor,during the control of virulence-related gene expression and adaptations to temperature elevations in the zoonotic pathogen vibrio alginolyticus. an rpoe null v. alginolyticus mutant was unable to adapt to various stresses and was survival-deficient in fish. in wild type v. alginolyticus,the expression of luxr-regulated virulence factors increased as the temperature was increased from 22°c to 37°c,but mutants lacking σe did not respond to temperature,indicating that σe is critical for the temperature-dependent upregulation of virulence genes. further analyses revealed that σe binds directly to -10 and -35 elements in the luxr promoter that drive its transcription. chip assays showed that σe binds to the promoter regions of luxr,rpoh and rpoe at high temperatures (e.g.,30°c and 37°c). however,at higher temperatures (42°c) that induce thermal stress,σe binding to the luxr promoter decreased,while its binding to the rpoh and rpoe promoters was unchanged. thus,the temperature-dependent binding of σe to distinct promoters appears to underlie a σe-controlled switch between the expression of virulence genes and adaptation to thermal stress. this study illustrates how a conserved temperature response mechanism integrates into quorum-sensing circuits to regulate both virulence and stress adaptation. © 2016 gu et al.