Vfr targets promoter of genes encoding methyl-accepting chemotaxis protein in Pseudomonas syringae pv. tabaci 6605

Virulence factor regulator (Vfr) is an indispensable transcription factor in the expression of virulence in the phytopathogenic bacteria Pseudomonassyringae. However, the function of Vfr is not known so far. The deletion of vfr resulted in the loss of surface swarming motility and reduced the virulence in P. syringae pv. tabaci (Pta) 6605. In order to identify the target genes of Vfr, we screened the sequences that bind to Vfr by chromatin immune precipitation (ChIP) and sequencing methods using the closely related bacterium P. syringae pv. syringae (Pss) B728a. For this purpose we first generated a strain that possesses the recombinant gene vfr::FLAG in Pss B728a, and performed ChIP using an anti-FLAG antibody. Immunoprecipitated DNA was purified and sequenced with Illumina HiSeq. The Vfr::FLAG-specific peaks were further subjected to an electrophoresis mobility-shift assay, and the promoter regions of locus tag for Psyr_0578 , Psyr_1776, and Psyr_2237 were identified as putative target genes of Vfr. These genes encode plant pathogen–specific methyl-accepting chemotaxis proteins (Mcp). These mcp genes seem to be involved in the Vfr-regulated expression of virulence.