TetR Family Member PsrA Directly Binds the Pseudomonas rpoS and psrA Promoters

Abstract

We have previously described a Pseudomonas gene, psrA, which enhances transcription of the rpoS sigma factor gene at stationary phase. We present molecular data which demonstrate that in Pseudomonas putida PsrA binds specifically to the rpoS and psrA promoters in DNA regions having similar palindromic sequences, C/GAAAC N 2-4 GTTTG/C, where N is any nucleotide. The position of the initiation of transcription was determined for both promoters, and PsrA binds from positions ؊59 to ؊35 in the rpoS promoter and from ؊18 to ؉20 in the psrA promoter with respect to the ؉1 transcription site. Expression studies with a psrA-lacZ transcriptional fusion in wild-type and psrA::Tn5 knockout mutants revealed that psrA was under additional control in response to growth phase. A model for the role of PsrA in the regulation of rpoS and psrA is presented.

Regulatory roles of psrA and rpoS in phenazine-1-carboxamide synthesis by Pseudomonas chlororaphis PCL1391

“…It was previously shown for P. putida that PsrA regulates the expression of rpoS (Kojic & Venturi, 2001) by binding to its promoter (Kojic et al, 2002). Our results indicate a similar regulation in PCL1391.…”

“…The organization of the rpoS gene in strain PCL1391 is comparable to that observed in other pseudomonads (Fujita et al, 1994;Heeb & Haas, 2001;Kojic et al, 1999Kojic et al, , 2002Ramos-González & Molin, 1998). A substantial difference is the presence of a putative transposase downstream of rpoS in PCL1391, whereas in many other Pseudomonas spp.…”

“…In addition a sequence (GA-AACTGCACTTTG) was identified close to the ATG codon in the promoter of the PCL1391 rpoS homologous gene, identical to the PsrA binding box consensus of P. putida (Kojic et al, 2002).…”

“…The psrA gene of Pseudomonas putida was shown to regulate the transcription of the rpoS gene (Kojic & Venturi, 2001) by directly binding to the rpoS promoter (Kojic et al, 2002). rpoS encodes the stationary-phase alternative sigma factor s s , which is responsible for the switch in gene expression occurring upon exposure of cells to starvation and/ or various stresses (Lange & Hengge-Aronis, 1991).…”

Evolutionary convergence in experimental Pseudomonas populations

“…However, given the extreme molecular parallelism observed combined with the lack of mutations in amiC (which causes a similar phenotype (Uehara et al, 2010)), it is conceivable that the adaptive contribution is not directly related to loss of nlpD activity. Instead, effects maybe attributable to changes in expression of rpoS, which in Pseudomonas putida reportedly harbours a promoter in the nlpD open reading frame, with a transcriptional start site six base pairs downstream of the nlpD mutation (Kojic et al, 2002). Effects on rpoS expression may thus constrain the mutational target and explain the parallelism.…”