MATING REACTION IN THE YEAST HANSENULA WINGEI

Abstract

Cells of the 2 mating types of Hansenula wingei, a new heterothallic yeast, exhibit a marked agglutination when dense suspensions are mixed. The 2 cell types have a strong attraction for each other which results in deforma-'' tion of the cell walls. This mating reaction markedly increases zygote formation as compared to non-agglutinable strains. A method for quantitating this phenomenon is presented which is based on the fact that when the cells agglutinate, they settle to the bottom of the tube. Suspensions of cells are mixed and centrifuged to deposit the cells in intimate contact. The deposit is then scraped from the bottom and re suspended. If agglutination has occurred, the cells will rapidly settle out on standing, and the degree of agglutination can be measured by making turbidity measurements on the supernatant. Using this procedure, it has been shown that washed cells will not agglutinate unless cations or proteins are added as cofactors. However, cells heated for a short time at 100[degree]C will agglutinate without added cofactors. The mating reaction seems to be intensified by heating. Maximum agglutination occurs over a pH range from 3-9. Reduction in dielectric constant with solvents like dioxane, leads to a reversible inhibition of agglutination, but it is not possible to conclude that the attraction between the 2 cell types is merely electrostatic. The agglutination is highly specific, since a diploid hybrid of the 2 types shows no agglutination with either type.