A MADS box protein interacts with a mating-type protein and is required for fruiting body development in the homothallic ascomycete Sordaria macrospora

MADS box transcription factors control diverse developmental processes in plants, metazoans, and fungi. To analyze the involvement of MADS box proteins in fruiting body development of filamentous ascomycetes, we isolated the mcm1 gene from the homothallic ascomycete Sordaria macrospora, which encodes a putative homologue of the Saccharomyces cerevisiae MADS box protein Mcm1p. Deletion of the S. macrospora mcm1 gene resulted in reduced biomass, increased hyphal branching, and reduced hyphal compartment length during vegetative growth. Furthermore, the S. macrospora Delta mcm1 strain was unable to produce fruiting bodies or ascospores during sexual development. A yeast two-hybrid analysis in conjugation with in vitro analyses demonstrated that the S. macrospora MCMI protein can interact with the putative transcription factor SMTA-1, encoded by the S. macrospora mating-type locus. These results suggest that the S. macrospora MCMI protein is involved in the transcriptional regulation of mating-type-specific genes as well as in fruiting body development.