TouR-mediated effector-independent growth phase-dependent activation of the sigma54 Ptou promoter of Pseudomonas stutzeri OX1.
Transcription of the catabolic touABCDEF operon, encoding the toluene-o-xylene monooxygenase of Pseudomonas stutzeri OX1, is driven by the sigma(54)-dependent Ptou promoter, whose activity is controlled by the phenol-responsive NtrC-like activator TouR. In this paper we describe for the first time a peculiar characteristic of this system, namely, that Ptou transcription is activated in a growth phase-dependent manner in the absence of genuine effectors of the cognate TouR regulator. This phenomenon, which we named gratuitous activation, was observed in the native strain P. stutzeri OX1, as well as in a Pseudomonas putida PaW340 host harboring the reconstructed tou regulatory circuit. Regulator-promoter swapping experiments demonstrated that the presence of TouR is necessary and sufficient for imposing gratuitous activation on the Ptou promoter, as well as on other sigma(54)-dependent catabolic promoters, whereas the highly similar phenol-responsive activator DmpR is unable to activate the Ptou promoter in the absence of effectors. We show that this phenomenon is specifically triggered by carbon source exhaustion but not by nitrogen starvation. An updated model of the tou regulatory circuit is presented.
Dipartimento di Biologia Strutturale e Funzionale, Università degli Studi di Milano, Milan, Italy.
Dafne
D
Solera
Fabio L G
FL
Arenghi
Tanja
T
Woelk
Enrica
E
Galli
Paola
P
Barbieri
D002244:Carbon / Q000378:metabolism; D003470:Culture Media; D004268:DNA-Binding Proteins / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D044223:Pseudomonas stutzeri / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000378:metabolism*; D014050:Toluene / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D014992:Xylenes / Q000378:metabolism
D003470:Culture Media; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D015534:Trans-Activators; D014992:Xylenes; D014050:Toluene; D002244:Carbon; D010105:Oxygenases; C114360:toluene 2-xylene monooxygenase; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54