Mitogen-Activated Protein Kinase CsPMK1 Is Essential for Pepper Fruit Anthracnose by .

The phytopathogenic fungus , belonging to the species complex, causes severe anthracnose disease on several fruits, including chili pepper (). However, the molecular mechanisms underlying the development and pathogenicity of are unclear. The conserved Fus3/Kss1-related MAPK regulates fungal development and pathogenicity. Here, the role of , orthologous to , was characterized by phenotypic comparison of a target deletion mutant (). The mycelial growth and conidiation of were normal compared to that of the wild type. produced morphologically abnormal conidia, which were delayed in conidial germination. Germinated conidia of failed to develop appressoria on inductive surfaces of hydrophobic coverslips and host plants. was completely defective in infectious growth, which may result from failure to suppress host immunity. Furthermore, was impaired in nuclear division and lipid mobilization during appressorium formation, in response to a hydrophobic surface. CsPMK1 was found to interact with CsHOX7, a homeobox transcription factor essential for appressorium formation, a yeast two-hybridization analysis. Taken together, these findings suggest that is required for fungal development, stress adaptation, and pathogenicity of .