THE CRYPTOCOCCUS-NEOFORMANS STE12-ALPHA GENE - A PUTATIVE SACCHAROMYCES-CEREVISIAE STE12 HOMOLOG THAT IS MATING-TYPE SPECIFIC

Cryptococcus neoformans possesses two mating types, MAT alpha and MAT alpha. alpha-Cells are more virulent than a-cells and are also, unlike a-cells, capable of producing extensive hyphae in the haploid phase, The molecular analysis of hyphae production in C. neoformans has resul ted in the identification of a gene which displays substantial similar ity to other fungal STE12 genes, including the presence of a highly co nserved homeodomain. Overexpression of the C. neoformans gene resulted in poor growth, altered morphology and the presence of hyphal project ions, phenotypes reported in similar studies of the Saccharomyces cere visiae STE12 gene, Overexpression was also found to induce MF alpha, a pheromone, and CNLAC1, a confirmed C. neoformans virulence gene. The C. neoformans STE12 alpha gene, however, has one striking difference f rom other fungal STE12 genes; it is found only in alpha-cells, The exi stence of STE12 alpha. in C. neoformans suggests that this fungus has elements of a conserved MAP kinase cascade, which may be organized in a novel manner.