Disease relevance of rhlR

• Genes involved in rhamnolipid synthesis (rhlAB) and regulation (rhlI and rhlR) in Pseudomonas aeruginosa are characterized, and expression of rhlAB in heterologous hosts is discussed [1].
• By using lacZ transcriptional fusions in both homologous (P. aeruginosa) and heterologous (Escherichia coli) genetic backgrounds we provide evidence that (i) lasR is expressed constitutively throughout the growth cycle, (ii) rhlR expression is regulated by LasR/OdDHL, and (iii) that RhlR/BHL regulates rhll [2].
• The remainder of the clinical isolates and the lasR or rhlR mutant strains caused severe keratitis [3].
• Nucleotide sequence analysis revealed an open reading frame (rhlR) encoding a putative 27.6-kDa protein (RhlR) with homology to autoinducer-responsive regulators of quorum sensing systems such as LuxR of Vibrio fischeri and LasR of P. aeruginosa [4].

High impact information on rhlR

• Single cosmid clones capable of restoring rhamnolipid synthesis in the mutant strains were isolated and further subcloned and sequenced, resulting in the identification of two genes (rhlAB) which are organized as an operon upstream of the previously identified rhlR regulatory gene [5].
• Addition of synthetic autoinducers partially restored the expression of the trancriptional activator-encoding genes lasR and rhlR but not that of the autoinducer synthase-encoding gene lasI [6].
• We demonstrate that the phosphate regulon is involved in the transcriptional activation of rhlR and the augmentation of PQS and pyocyanin production under phosphate limitation [7].
• Rapid growth of the flagellate on rhlR/lasR mutant biofilms indicated a key role of quorum sensing in the upregulation of lethal factors and in grazing protection of late biofilms [8].
• Without OprF, bacteria grow extremely poorly because they lack nitrite reductase activity while lacking rhlR or rhlI forces bacteria to undergo metabolic suicide by overproduction of nitric oxide [9].

Biological context of rhlR

• The nucleotide sequence of the complementing 2-kb fragment was determined, and a single open reading frame (rhlR) of 723 bp specifying a putative 28-kDa protein (RhlR) was identified [10].
• Expression of the lasR and rhlR regulator genes was not affected in the nfxC type mutant [11].
• In order to define the role of PQS in the P. aeruginosa quorum-sensing cascade, lacZ gene fusions were used to determine the effect of PQS on the transcription of the quorum-sensing system genes lasR, lasI, rhlR, and rhlI [12].
• Here, the rhlR promoter region has been characterized and shown to present four different transcription start sites, two of which are included in the upstream gene (rhlB) coding region [13].
• In this work, P. aeruginosa PAO1 and its rhlI and rhlR null mutants were used to study the degradation and synthesis kinetics of the rhl system's autoinducer PAI2 (N-butanoyl-homoserine lactone) [14].

Associations of rhlR with chemical compounds

• Compared with the wild type, the rhlR and rhlI mutants both showed defects in the production of elastase, LasA protease, rhamnolipid, and pyocyanin [4].
• Multiple plasmid-based rhlR gene copies had a stimulating effect on the growth of the P. aeruginosa wild-type strain in hexadecane-containing minimal medium, on rhamnolipid production, and on the production of pyocyanin chromophores [10].

Regulatory relationships of rhlR

• We have also mapped the transcriptional start site for pqsR and found that the transcription of pqsR is positively regulated by lasR and negatively regulated by rhlR [15].

Other interactions of rhlR

• METHODS: Expression of the quorum-sensing regulatory genes lasR and rhlR was assessed by real time RT-PCR [16].
• This rpoS mutant showed elevated levels of rhlI (but not rhlR) transcription, elevated levels of the RhlI-generated acylhomoserine lactone quorum-sensing signal, and elevated levels of RhlR-RhlI-regulated gene transcription [17].
• GFP was produced in sand culture, indicating that the rhlR and pra genes are both transcribed in unsaturated porous media [18].

Analytical, diagnostic and therapeutic context of rhlR

• Further sequence analysis downstream of rhlR revealed an independently transcribed gene (rhlI) that encodes a putative 22.2-kDa protein with homology to members of the family of autoinducer synthetases, such as LuxI of V. fischeri and LasI of P. aeruginosa [4].
• With the use of DNA mobility shift assays and beta-galactosidase reporter fusions, we have studied the regulation of pqsR and its relationship to pqsA, lasR, and rhlR [15].

References