Mapping of the Cryptococcus neoformans MATα Locus: Presence of Mating Type-Specific Mitogen-Activated Protein Kinase Cascade Homologs

In this study we investigated the relationship between the MATα locus of Cryptococcus neoformans and several MATα-specific mitogen-activated protein (MAP) kinase signal transduction cascade genes, including STE12α, STE11α, and STE20α. To resolve the location of the genes, we screened a cosmid library of the MATα strain B-4500 (JEC21), which was chosen for the C. neoformans genome project. We isolated several overlapping cosmids spanning a region of about 71 kb covering the entire MATα locus. It was found that STE12α, STE11α, and STE20α are imbedded within the locus rather than closely linked to the locus. Furthermore, three copies of MFα, the mating type α-pheromone gene, a MATα-specific myosin gene, and a pheromone receptor (CPRα) were identified within the locus. We created a physical map, based on the restriction enzyme BamHI, and identified both borders of the MATα locus. The MATα locus of C. neoformans is approximately 50 kb in size and is one of the largest mating type loci reported among fungi with a one-locus, two-allele mating system.