Deletion of the Ustilago maydis ortholog of the Aspergillus sporulation regulator medA affects mating and virulence through pheromone response

Mating of compatible haploid cells of Ustilago maydis is essential for infection and disease development in the host. For mating and subsequent filamentous growth and pathogenicity, the transcription factor, prf1 is necessary. Prf1 is in turn regulated by the cAMP and MAPK pathways and other regulators like rop1 and hap1. Here we describe the identification of another putative Prf1 regulator, med1, the ortholog of the Aspergillus nidulans medusa (medA) transcription factor and show that it is required for mating and full virulence in U. maydis. med1 deletion mutants show both pre- and post-mating defects and are unresponsive to external pheromone. The expression of prf1 is down-regulated in Δmed1 compared to the wild type, suggesting that med1 is upstream of prf1. Additionally, indicative of a role in secondary metabolism regulation, deletion of the med1 gene de-represses the production of glycolipids in U. maydis.

► Ustilago maydis Med1 is 57% identical with Aspergillus regulator MedAp. ► The med1 gene is required for mating and filamentation in vitro. ► The Δmed1 mutant is unable to produce conjugation tubes in response to pheromones. ► Expression of mating associated genes was comparatively down-regulated in Δmed1. ► The Δmed1 mutants are pathogenic even though significantly reduced in virulence.