Mapping of the Cryptococcus neoformans MAT alpha locus: Presence of matingtype-specific mitogen-activated protein kinase cascade homologs

In this study we investigated the relationship between the MAT alpha locus of Cryptococcus neoformans and several MAT alpha-specific mitogen-activated protein (MAP) kinase signal transduction cascade genes, including STE12 al pha, STE11 alpha, and STE20 alpha. To resolve the location of the genes, we screened a cosmid library of the MAT alpha strain B-4500 (JEC21), which wa s chosen for the C. neoformans genome project. We isolated several overlapp ing cosmids spanning a region of about 71 kb covering the entire MAT alpha locus. It was found that STE12 alpha, STE11 alpha, and STE20 alpha are imbe dded within the locus rather than closely linked to the locus. Furthermore, three copies of MF alpha, the mating type alpha-pheromone gene, a MAT alph a-specific myosin gene, and a pheromone receptor (CPR alpha) were identifie d within the locus. We created a physical map, based on the restriction enz yme BamHI, and identified both borders of the MAT alpha locus. The MAT alph a locus of C. neoformans is approximately 50 kb in size and is one of the l argest mating type loci reported among fungi with a one-locus, two-allele m ating system.