Mating-type differentiation in ascosporogenous yeasts on the basis of mating-type-specific substances responsible for sexual cell-cell recognition

Abstract

Sexual agglutination occurred only between cells of opposite mating types of the same species in all the Sacharomyces, Hansenula, Saccharomycodes, and Pichia yeasts tested. We succeeded in solubilizing the sex-specific glycoprotein, cell wall agglutination substance responsible for sexual agglutinability by briefly autoclaving these yeasts. The agglutination substances of all the above yeasts were univalent and sensitive to the enzyme pronase. The formation of complementary complexes was observed only between agglutination substances of opposite mating types of the same species. In general, the agglutination substance of one mating type was more resistant to heat treatment at 100°C in 3% acetic acid and more sensitive to 5% 2-mercaptoethanol treatment than the agglutination substance of the other mating type in these yeasts. On the basis of these results together with the pheromone response and production, we expect that almost all ascosporogenous yeasts can be classified into the two mating types corresponding to a and α mating types in Saccharomyces cerevisiae, respectively.