PMID:9294432

Citation	Pearson, JP, Pesci, EC and Iglewski, BH (1997) Roles of Pseudomonas aeruginosa las and rhl quorum-sensing systems in control of elastase and rhamnolipid biosynthesis genes. J. Bacteriol. 179:5756-67
Abstract	Two quorum-sensing systems (las and rhl) regulate virulence gene expression in Pseudomonas aeruginosa. The las system consists of a transcriptional activator, LasR, and LasI, which directs the synthesis of the autoinducer N-(3-oxododecanoyl) homoserine lactone (PAI-1). Induction of lasB (encoding elastase) and other virulence genes requires LasR and PAI-1. The rhl system consists of a putative transcriptional activator, RhlR, and RhlI, which directs the synthesis of N-butyryl homoserine lactone (PAI-2). Rhamnolipid production in P. aeruginosa has been reported to require both the rhl system and rhlAB (encoding a rhamnosyltransferase). Here we report the generation of a delta lasI mutant and both delta lasI delta rhlI and delta lasR rhlR::Tn501 double mutants of strain PAO1. Rhamnolipid production and elastolysis were reduced in the delta lasI single mutant and abolished in the double-mutant strains. rhlAB mRNA was not detected in these strains at mid-logarithmic phase but was abundant in the parental strain. Further RNA analysis of the wild-type strain revealed that rhlAB is organized as an operon. The rhlAB transcriptional start was mapped, and putative sigma 54 and sigma 70 promoters were identified upstream. To define components required for rhlAB expression, we developed a bioassay in Escherichia coli and demonstrated that PAI-2 and RhlR are required and sufficient for expression of rhlA. To characterize the putative interaction between PAI-2 and RhlR, we demonstrated that [3H]PAI-2 binds to E. coli cells expressing RhlR and not to those expressing LasR. Finally, the specificity of the las and rhl systems was examined in E. coli bioassays. The las system was capable of mildly activating rhlA, and similarly, the rhl system partly activated lasB. However; these effects were much less than the activation of rhlA by the rhl system and lasB by the las system. The results presented here further characterize the roles of the rhl and las quorum-sensing systems in virulence gene expression.
Links	PubMed PMC179464
Keywords	Bacterial Proteins/genetics; Bacterial Proteins/physiology; Binding Sites; DNA, Bacterial/genetics; DNA-Binding Proteins/metabolism; DNA-Binding Proteins/physiology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes; Genes, Bacterial; Glycolipids/biosynthesis; Hexosyltransferases/genetics; Homoserine/analogs & derivatives; Homoserine/metabolism; Lactones/metabolism; Operon; Pancreatic Elastase/genetics; Promoter Regions, Genetic; Pseudomonas aeruginosa/enzymology; RNA, Bacterial/genetics; Rhamnose; Sigma Factor/physiology; Signal Transduction; Trans-Activators/physiology; Transcription, Genetic
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
PSEAE:LASR		GO:0010468: regulation of gene expression	ECO:0000314:		P		Table 3 shows that lasB9-lacZ expression in PAI-1 (50 nM) in the presence of LasR was greatly amplified.	complete CACAO 5028
PSEAE:LASR	involved_in	GO:0010468: regulation of gene expression	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
PSEAE:RHLR	involved_in	GO:0010467: gene expression	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
PSEAE:RHLR		GO:0010467: gene expression	ECO:0000315:		P		Figure 4A shows that RhlR was needed for the expression of rhlA9-lacZ in E. coli DH5a(pECP61.5)	complete CACAO 5026

References

See Help:References for how to manage references in GONUTS.