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RpoS induces expression of the Vibrio anguillarum quorum-sensing regulator VanT

Antony Croxatto

Chang Chen

Department of Molecular Biology, Umeå University, S-901 87 Umeå, Sweden

Correspondence
Debra L. Milton
Debra.Milton{at}molbiol.umu.se

In vibrios, regulation of the Vibrio harveyi-like LuxR transcriptional activators occurs post-transcriptionally via small regulatory RNAs (sRNAs) that destabilize the luxR mRNA at a low cell population, eliminating expression of LuxR. Expression of the sRNAs is modulated by the vibrio quorum-sensing phosphorelay systems. However, vanT mRNA, which encodes a LuxR homologue in Vibrio anguillarum, is abundant at low and high cell density, indicating that VanT expression may be regulated via additional mechanisms. In this study, Western analyses showed that VanT was expressed throughout growth with a peak of expression during late exponential growth. VanO induced partial destabilization of vanT mRNA via activation of at least one Qrr sRNA. Interestingly, the sigma factor RpoS significantly stabilized vanT mRNA and induced VanT expression during late exponential growth. This induction was in part due to RpoS repressing expression of Hfq, an RNA chaperone. RpoS is not part of the quorum-sensing regulatory cascade since RpoS did not regulate expression or activity of VanO, and RpoS was not regulated by VanO or VanT. VanT and RpoS were needed for survival following UV irradiation and for pigment and metalloprotease production, suggesting that RpoS works with the quorum-sensing systems to modulate expression of VanT, which regulates survival and stress responses.

Present address: Center for Research on Intracellular Bacteria (CRIB), Institute for Microbiology, University of Lausanne, Switzerland.

Present address: Guangdong Province, South China Sea Institute of Oceanology, Xinggang Xi Lu, 164, 510301 Guangzhou, China.

The GenBank/EMBL/DDBJ accession numbers for the sequences of rpoS and hfq are EU330190 and EU330191, respectively.