Genetic control of cell type and complex organization of the mating type locus in the yeast Pichia pinus.

Genetic mechanisms of switching the mating type locus MAT1 in the homothallic yeast Pichia pinus were studied. By analysis of mutations affecting MAT1 complex structural and functional organization of this locus was shown. The existence of two functional regions in MAT1 is postulated. Region I controls mating ability of haploid cells, determines the neutrality of heterozygous cells and regulates the work of Region II. Region II controls meiosis and/or sporulation in the cultures heterozygous for Region I as well as controls switching MAT1 ⇋ MAT1α in haploid cells.