Distinct Function of Mediator Subunits in Fungal Development, Stress Response, and Secondary Metabolism in Maize Pathogen .

Mediator is a nucleus-localized, multisubunit protein complex highly conserved across eukaryotes. It interacts with RNA polymerase II transcription machinery as well as various transcription factors to regulate gene expression. However, systematic characterization of the Mediator complex has not been performed in filamentous fungi. In our study, the goal was to investigate key biological functions of Mediator subunits in a mycotoxigenic plant pathogen . Although there is some level of divergence in the constituent subunits, the overall structure was conserved between and . We generated 11 Mediator subunit deletion mutants and characterized vegetative growth, conidia formation, environmental stress response, carbon and fatty acid use, virulence, and fumonisin B (FB) biosynthesis. Each Mediator subunit deletion mutant showed deficiencies in at least three of the phenotypes tested, suggesting that each subunit has different principal functions in development, metabolism, and virulence. The deletion of led to increased FB production, and we confirmed that FvMed1 is transported from the nucleus to the cytoplasm under fumonisin-producing conditions. Taken together, our study characterized various important functional roles for Mediator subunits in and suggests that select subunits can perform unique cytoplasmic functions independent of the core Mediator in fungal nucleus.