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Title: Identification and Characterization of iron-responsive regulatory elements in Pseudomonas syringae pv tomato DC3000

item Bronstein, Philip
item Filiatrault, Melanie
item Cartinhour, Samuel

Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/20/2008
Publication Date: 6/1/2008
Citation: Bronstein, P., Filiatrault, M.J., Cartinhour, S.W. 2008. Identification and Characterization of iron-responsive regulatory elements in Pseudomonas syringae pv tomato DC3000. American Society for Microbiology Meeting.

Interpretive Summary:

Technical Abstract: Pseudomonas syringae pv. tomato DC3000 (DC3000) is a model bacterial pathogen of tomato and Arabidopsis thaliana. This bacterium must sense and respond to a variety of environmental signals and understanding how the bacterium integrates these signals into a physiological response is central to our understanding of this pathogen. One important micronutrient for all biological organisms is iron. We evaluated the global transcriptional response of DC3000 in iron-replete and iron-limiting conditions at different time points during the exponential growth phase using Affymetrix-style oligo arrays and related the samples to the intracellular iron levels. Stringent statistical analysis of differential regulation between the various time points and clustering of the responses allowed us to identify groups of transcripts that showed similar regulatory patterns. Included in these iron-responsive transcripts are at least 12 putative regulatory elements including sigma factors, two component regulatory systems, and small RNAs. We identified potential targets for the regulatory elements by looking at the transcripts that clustered similarly. One differentially expressed novel regulator appears to be a hybrid sigma/anti-sigma factor-like protein. This gene is also found in Pseudomonas syringae B278a. We constructed an insertion mutant in this gene and evaluated the transcriptional activity of putative regulated genes under iron-replete and iron-limiting conditions by qRT-PCR. We also evaluated the transcriptional activity of genes we hypothesized to be regulated by two iron-responsive small RNAs by over-expressing prrF1 or prrF2 in DC3000. From this study we conclude that iron in an important mediator of gene expression, which acts as a signal for many regulatory cascades, in the plant pathogen P. syringae pv. tomato DC3000.