Sexual behavior and its pheromonal regulation in ascosporogenous yeasts.

We reviewed our investigations on sexual behaviors and interactions including sexual cell agglutination and pheromone action mainly in non-conventional yeasts, Hansenula anomala, H. wingei, Pichia amethionina, P. heedi, P. opuntiae, Saccharomyces kluyveri, S. globsus, S. exiguus, Saccharomycodes ludwigii. The techniques and genetic models including the cassette model and alpha 1-alpha 2 hypothesis which had been developed largely in S. cerevisiae were applicable to these yeasts in principle. The sexual agglutination was distinctly species-specific while sex pheromones were cross-reactive beyond species' barriers. The successful induction of heterothallic strains from homothallic strains in S. exiguus by mutagenesis enabled to the subsequent biochemical and genetical analysis of sexual behavior in the yeast. The phylogenetic consideration on sex differentiation is also included.