The σ-factor FliA, ppGpp and DksA coordinate transcriptional control of the aer2 gene of Pseudomonas putida

Abstract

Here the s-factor requirement for transcription of three similar, but differentially regulated, aer genes of Pseudomonas putida KT2440 is investigated. Previous work has shown that the three Aer proteins, like chemoreceptors, colocalize to a single pole in a CheA-dependent manner. Lack of Aer2 - the most abundant of these three proteins - mediates defects in metabolism-dependent taxis and aerotaxis, while lack of Aer1 or Aer3 has no apparent phenotype. We show, using wild-type and mutant P. putida derivatives combined with P. putida reconstituted FliA- (σ 28) and σ 70-dependent in vitro transcription assays, that transcription of aer2 is coupled to motility through the flagella σ-factor FliA, while σ 70 is responsible for transcription of aer1 and aer3. By comparing activities of the wild-type and mutant forms of the aer2 promoter, we present evidence (i) that transcription from FliAdependent Paer2 is enhanced by changes towards the Escherichia coli consensus for FliA promoters rather than towards that of P. putida, (ii) that the nature of the AT-rich upstream region is important for both output and σ 70 discrimination of this promoter, and (iii) that Paer2 output is directly stimulated by the bacterial alarmone ppGpp and its cofactor DksA. © 2010 Society for Applied Microbiology and Blackwell Publishing Ltd.