Analysis of the organization and expression patterns of the convergent lasR/rsaL gene pair uncovers mutual influence
The two adjacent genes encoding the major quorum sensing regulator, LasR, and its opponent, RsaL, overlap in their coding 3´ends and produce mRNA transcripts with long untranslated 3´ends that overlap with the sense transcripts of the gene on the opposing DNA strand. In this study, we evaluated whether the overlapping genes are involved in mutual regulatory events, such as transcriptional interference and interference by natural antisense transcripts. We introduced various gene expression constructs into a P. aeruginosa PA14 lasR/rsaL double deletion mutant, and found that although complementary RNA is produced, this does not interfere with the sense gene expression levels of lasR and rsaL and does not have functional consequences on down-stream gene regulation. Nevertheless, expression of lasR, but not of rsaL, was shown to be further enhanced if transcription was terminated at the end of the respective gene and no overlapping transcription with the gene on the opposite strand was allowed. Our data indicate that the natural organization with a partial overlap at the 3´ends of the lasR/rsaL genes gives rise to a system of checks and balances to prevent dominant and unilateral control by LasR over the RsaL transcriptional regulator of opposing function. Overall design: RNASeq of different Pseudomonas aeruginosa PA14 lasR and rsaL mutants - planctonic growth in LB medium.