Analyses of Two Oxidase Homologs in the Plant Pathogenic Fungus, Vertcillium dahliae

The plant pathogenic fungus, Verticillium dahliae, is a cause of Verticillium wilt, a disease of world-wide importance on over 200 plant species. V. dahliae can survive for 10-15 years in the absence of a host, and is cross-pathogenic on many plants, including those grown in crop rotations, making control of this pathogen difficult.  The fungus survives in the soil, penetrates the plant roots, and colonizes the plant vascular system, leading to typical symptoms of vascular discoloration and leaf wilt.  Verticillium wilt on lettuce was first reported in the mid 1990s, and has since spread throughout the lettuce production region of central coastal California. Verticillium wilt can be devastating on lettuce, and entire fields have been lost to the disease.  An understanding of the genetic basis for pathogenicity may lead to the development of control strategies alternative to expensive soil fumigation.  In this study, we are analyzing two oxidase-encoding genes identified in V. dahliae that share homology to genes required for pathogenesis in other fungi.  These oxidases may participate in the production of reactive oxygen species that are important for cellular differentiation necessary for pathogenesis. We are employing the One Step Construction of Agrobacterium-recombination ready plasmids (OSCAR) system and Agrobacterium tumefaciens-mediated transformation for targeted gene deletion of two oxidases in the fungus to facilitate functional characterization of these genes. We anticipate that deletion of one or both of these oxidases will affect the ability of V. dahliae to colonize lettuce.