Identification of Verticillium virulence factors using proteomics

The soil-borne fungus Verticillium dahliae is one of the most notorious plant pathogens that causes vascular wilt diseases on over 200 dicotelydenous plant species. Despite its economic importance, little is known about the mechanisms that enable this fungus to infect such a wide array of host plants. It is generally accepted that the in planta secreted pathogen proteins (secretome) contains effectors that determine pathogenicity. To identify V. dahliae pathogenicity determinants, we performed proteomic analyses on V. dahliae grown in vitro in the presence and absence of tomato xylem fluid. In total 404 proteins were detected in Verticillium cultures without xylem fluid whereas the number of proteins detected in the presence of xylem fluid was increased to 489. We also analyzed the secretome of V. dahliae grown solely on tomato xylem fluid and identified 392 proteins. The V. dahliae genome is predicted to encode 780 secretome proteins. Only about 37 % of the proteins detected in the MS analyses contain a signal peptide for secretion. These proteins potentially determine the outcome of Verticillium- host interaction and are candidates for functional analysis