Characterization of the regulatory network of the Type III secretion system in Pseudomonas syringae pv. tomato DC3000

The Type III Secretion System (TTSS) plays an important role in the pathogenicity of many Gram-negative bacteria. Bacteria secrete and translocate virulence proteins directly into the eukaryotic host cells via the TTSS. Little is known about the regulatory network of the TTSS. We designed a novel in vitro genetic screen to characterize the regulatory network of the TTSS in Pseudomonas syringae. Two different approaches were taken. Preliminary results showed that the first method employing IPTG induction of transposon-borne hrpL was not feasible because of inefficient induction of the lac promotor, and a non-functional positive selection gene (sacB) in P.syringae pv. tomato DC3000. A positive control was constructed to optimize conditions for the second method, which employed induction of the genomic hrpL using MMpH5.5. Results from control experiments and preliminary screening indicated that the second method had the potential to succeed in strain P. syringae pv. maculicola ES4326.