Promoter specificity elements in Pseudomonas aeruginosa quorum-sensing-controlled genes

The LasR-dependent and RhIR-dependent quorum-sensing systems are global regulators of gene expression in Pseudomonas aeruginosa. Previous studies have demonstrated that promoter elements of the quorum-sensing-controlled genes lasB and hcnABC are important in density-dependent regulation. We have identified LasR- and RhIR-dependent determinants in promoters of quorum-sensing-control led genes qsc102, qsc117 (acpP), and qsc131 (phzA to -G) by in silico, deletion, point-mutational, and primer extension analyses. Each of these genes (in addition to lasI and rsaL) is activated by LasR, and qsc117 and qsc131 also respond to RhIR. Point mutations in the promoters of the LasR-specific gene, qsc102, relax specificity so that this promoter can respond to RhIR in addition to LasR. Our findings indicate that quorum-sensing-controlled promoters in P. aeruginosa are either specific for LasR or respond to both LasR and RhIR and that critical bases in the promoter elements determine specificity.