Annotation of Schizophyllum commune mating-type loci reveals distinct patterns of evolution

Schizophyllum commune is a mushroom-forming fungus that has long-served as a model system for investigating the molecular control of development through study of its complex mating system. The products of the genes encoded within the mating-type loci interact in non-self combinations to activate the initial events of sexual development. Recently, this fungus has also been noted for a high level of sequence diversity between strains which is hypothesized to be due to a high mutation rate and inefficient DNA repair mechanism. The A mating type loci, that partially control sexual development, stand out even in this highly diverse fungus as extreme outliers in low sequence identity between strains, leading to a hypothesis that this area is under selection for both sequence divergence at the nucleotide level and conservation of function at the protein level. Annotation and sequence comparison of the A-alpha mating-type loci in the twenty strains for which genomic sequences are available reveal a distinct pattern of sequence identity between strains differing in mating-type and a confirm an abrupt boundary in sequence identity between strains at the borders of the mating-type regions. We are expanding our methods of analysis to provide further information on the nature of sequence evolution between strains at the A-alpha mating-type locus