A Novel MFS Transporter Gene Is Important for Hyphal Morphology, Conidiation, and Pathogenicity in .

is a widely distributed fungus attacking many cruciferous species. To investigate pathogenic mechanisms of the pathogen on the host , we screened and obtained a virulence-deficient mutant Ch-1-T513 in a T-DNA insertion mutant library of The mutant Ch-1-T513 produced yellow colony centers with distorted multi-branching hyphal tips as well as producing few conidia. Heavily swollen hyphae in the mutant could be observed, and intra-hyphal hyphae were found to be formed in the balloon-shaped hyphae. The mutant failed to produce lesions on 12-day-old seedlings, and invasive hyphae did not differentiate into large primary and thin secondary hyphae after appressorial formation on leaves, but formed abundant bulbous hyphae in epidermal cells. Southern blot analysis showed Ch-1-T513 had double-site T-DNA integrations. The mutant had insertions upstream of genes for a major facilitator superfamily (MFS) transporter, and an aldo/keto reductase, . Complementation experiments by transforming genomic sequences from a wild-type strain into the insertion mutant demonstrated that is involved in the Ch-1-T513 phenotype. The complementation strain C-ChMfs1-1 exhibited normal hyphal morphology, conidiation, and pathogenicity identical to the wild-type. The results demonstrate that is involved in intra-hyphal hyphae production, conidiation, and pathogenicity in To our knowledge, this is the first report of a MFS transporter gene in a phytopathogenic fungus associated with intra-hyphal hyphae formation, playing a key role in infection of its plant host.