A Distinct QscR Regulon in the Pseudomonas aeruginosa Quorum-Sensing Circuit

Department of Microbiology, University of Washington, Seattle 98195-7242, USA.
Journal of Bacteriology (Impact Factor: 2.81). 06/2006; 188(9):3365-70. DOI: 10.1128/JB.188.9.3365-3370.2006
Source: PubMed


The opportunistic pathogen Pseudomonas aeruginosa possesses two complete acyl-homoserine lactone (acyl-HSL) signaling systems. One system consists of LasI and LasR, which
generate a 3-oxododecanoyl-homoserine lactone signal and respond to that signal, respectively. The other system is RhlI and
RhlR, which generate butanoyl-homoserine lactone and respond to butanoyl-homoserine lactone, respectively. These quorum-sensing
systems control hundreds of genes. There is also an orphan LasR-RhlR homolog, QscR, for which there is no cognate acyl-HSL
synthetic enzyme. We previously reported that a qscR mutant is hypervirulent and showed that QscR transiently represses a few quorum-sensing-controlled genes. To better understand
the role of QscR in P. aeruginosa gene regulation and to better understand the relationship between QscR, LasR, and RhlR control of gene expression, we used
transcription profiling to identify a QscR-dependent regulon. Our analysis revealed that QscR activates some genes and represses
others. Some of the repressed genes are not regulated by the LasR-I or RhlR-I systems, while others are. The LasI-generated
3-oxododecanoyl-homoserine lactone serves as a signal molecule for QscR. Thus, QscR appears to be an integral component of
the P. aeruginosa quorum-sensing circuitry. QscR uses the LasI-generated acyl-homoserine lactone signal and controls a specific regulon that
overlaps with the already overlapping LasR- and RhlR-dependent regulons.

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    • "However, LuxR orphans or solos, i.e., LuxR homologs without the cognate autoinducer synthase LuxI, were also reported, such as SdiA in Salmonella enterica and E. coli (Ahmer et al., 1998; Kanamaru et al., 2000), QscR in P. aeruginosa (Fuqua, 2006) and PluR in Photorhabdus luminescens (Brameyer et al., 2015). These LuxR orphans contain an AHLbinding domain at the N-terminus to bind to endogenous AHLs (Lequette et al., 2006), exogenous AHLs (Yao et al., 2006) or other novel signals (Brameyer et al., 2015) as well as a DNA-binding helix-turn-helix (HTH) domain at the C-terminus. AI-2, which represents a universal " language " to facilitate interspecies communication, is a byproduct of the detoxification of S-adenosylmethionine (SAM), which is catalyzed by Sribosylhomocysteine lyase (LuxS, EC "
    Dataset: Review

    Full-text · Dataset · Jan 2016
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    • "However, a subfamily of luxR-type genes that are not genetically adjacent to a luxI gene, termed solo luxRs (Subramoni and Venturi, 2009a) are widespread in Proteobacteria species (Case et al., 2008; Patankar and González, 2009; Subramoni and Venturi, 2009b). Characterized examples of solo LuxR proteins have a range of ligands; from AHLs produced by non-adjacent luxI genes (Marketon et al., 2003; Lequette et al., 2006; McIntosh et al., 2008), to host derived, non-AHL small molecules (Zhang et al., 2007; Ferluga and Venturi, 2009; Subramoni et al., 2011; González and Venturi, 2013; Patel et al., 2013). In addition, solo LuxR-type regulators can function in the absence of a signal molecule (Cox et al., 1998). "
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