A MADS Box Protein Interacts with a Mating-Type Protein and Is Required for Fruiting Body Development in the Homothallic Ascomycete Sordaria macrospora
التفاصيل البيبلوغرافية
العنوان:
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 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 MCM1 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 MCM1 protein is involved in the transcriptional regulation of mating-type-specific genes as well as in fruiting body development. The regulation of sexual reproduction is one of the central processes in the life cycles of most fungi. Like sex chromosomes in animals and plants, the allele type at the fungal mating-type locus determines sexual compatibility between haploid individuals in fungi (19, 20). The genetic breeding mechanism of fungi in which sexual reproduction only occurs between strains of the opposite mating type is called heterothallism. Strains of heterothallic ascomycetes exist in two mating types; these are termed Mat and Mata in Saccharomyces cerevisiae and MatA and Mata in the filamentous ascomycete Neurospora crassa. The genes that determine the fungal mating type are located at the mating-type loci. In ascomycetes, alternative versions of the mating-type locus on homologous chromosomes are termed idiomorphs and are completely dissimilar in the genes they carry (11, 42, 62). The ascomycetous fungus S. cerevisiae has the best-studied mating system. The MAT idiomorphs encode transcription factors, which in combination with other regulatory proteins are responsible for cell-type-specific gene expression, e.g., the mating-type-specific expression of pheromone and pheromone receptor genes. Each mating-type locus carries two genes: the MAT locus carries MAT1 and MAT2, and the MATa locus carries MATa1 and MATa2 (Fig. 1). The Mat1p protein has been shown to be a transcriptional activator of -specific genes and carries the domain as a DNA-binding motif (4). The gene product of MAT2 is a homeodomain protein and acts as a negative regulator of a-specific genes. In the MATa locus, MATa1 is the only gene to encode a functional protein, Mata1p, which is also a homeodomain transcription factor (14). However, unlike the Mat2p homeodomain protein of
