Effects of Combination of Different −10 Hexamers and Downstream Sequences on Stationary-Phase-Specific Sigma Factor ς S -Dependent Transcription in Pseudomonas putida

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Abstract
The main sigma factor activating gene expression, necessary in stationary phase and under stress conditions, is ς S . In contrast to other minor sigma factors, RNA polymerase holoenzyme containing ς S (Eς S ) recognizes a number of promoters which are also recognized by that containing ς 70 (Eς 70 ). We have previously shown that transposon Tn 4652 can activate silent genes in starving Pseudomonas putida cells by creating fusion promoters during transposition. The sequence of the fusion promoters is similar to the ς 70 -specific promoter consensus. The −10 hexameric sequence and the sequence downstream from the −10 element differ among these promoters. We found that transcription from the fusion promoters is stationary phase specific. Based on in vivo experiments carried out with wild-type and rpoS -deficient mutant P. putida , the effect of ς S on transcription from the fusion promoters was established only in some of these promoters. The importance of the sequence of the −10 hexamer has been pointed out in several published papers, but there is no information about whether the sequences downstream from the −10 element can affect ς S -dependent transcription. Combination of the −10 hexameric sequences and downstream sequences of different fusion promoters revealed that ς S -specific transcription from these promoters is not determined by the −10 hexameric sequence only. The results obtained in this study indicate that the sequence of the −10 element influences ς S -specific transcription in concert with the sequence downstream from the −10 box.