Cells of Schizosaccharomyces pombe undergo mating and meiosis when starved for a nitrogen source. In this process a P and and M cell first mate to generate a diploid zygote, which subsequently enters meiosis and sporulates. The P mating type is controlled by the mat1-Pc gene at the mating type locus, together with a gene called map1. We show that these two functions are required for expression of the P-specific gene map3. We have cloned the map1 gene and show that it encodes a putative MADS-box containing transcription factor related to mammalian Serum Response Factor (SRF) and Saccharomyces cerevisiae MCM1. The Mat1-Pc protein contains a motif characteristic for proteins that interact with MADS-box factors, suggesting that Mat-Pc and Map1 may form a heterodimer that activates the P-specific map3 gene.