Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: March 24, 2008
Publication Date: June 1, 2008
Citation: Swingle, B.M., Schneider, D.J. 2008. Characterization of the Promoter Motif Regulated by PSPTO_1209 a FecI-like ECF Sigma Factor of Pseudomonas syringae pv. tomato DC3000. American Society for Microbiology. H-039:p.128. Technical Abstract: Pseudomanads are renowned for their capacity to adapt to diverse environments, a fact that is reflected in the fraction of their genomes dedicated to encoding transcription regulators. Members of the Pseudomonas genus include species that are adapted to pathogenic and symbiotic lifestyles in association with animals, plants and insects as well as free living in soil and water. With the recent completion of genome sequences from several pseudomonad species, we now have the ability to make global genome comparisons to examine how orthologous regulators have been adapted to solve niche specific challenges. Examination of pseudomonad genome sequences revealed that these organisms are endowed with overlapping sets of orthologous sigma factors. We are focused on the subset of sigma factors that have been classified as being involved with iron uptake or metaloregulation based on their sequence similarity to FecI, which regulates iron citrate uptake in Escherichia coli. These regulators are members of the group IV or extracytoplasmic function (ECF) sigma factors and function by altering the promoter specificity of RNA polymerase in response to specific environmental stimuli. We are currently working to characterize the promoter motif recognized by the gene product of PSPTO_1209, a member of this class of sigma factor from Pseudomonas syringae pv. tomato DC3000. We are using conventional molecular techniques to identify nucleotides within promoters that are important for PSPTO_1209 mediated differential regulation. This information has been used to train computational models in order to (1) summarize the relative conservation within a 30 bp region of the promoter and (2) as a tool to identify other sequences with similarity to the characterized promoters. We are testing the hypothesis that some of the sequences identified by the computational models will function as bona fide promoters and will be useful to predict regulon members for PSPTO_1209 and orthologous sigma factors in related pseudomonads. Furthermore, comparisons of the regulon members will then be used to generate predictions regarding the species-specific role of each sigma factor.