GENETIC INTERACTIONS IN SOMATIC INTERMATING TYPE HYBRIDS OF THE ZYGOMYCETE ABSIDIA-GLAUCA

Protoplasts of auxotrophic mutants of the heterothallic zygomycete Absidia glauca were efficiently fused by electrofusion. Fusion heterokaryons between the complementary mating types, which grew prototrophically, were selected. Among 72 fusion colonies which were further analysed, 11 did not only grow prototrophically but also combined both mating types as they formed zygotes within the same mycelium. These homothallic hybrids possessed two sets of rDNA repeats originating from the complementary mating types. Those fusion colonies which gave only a (+) type mating reaction, synthesized a 15 kDa (+) type-specific surface protein; fusion colonies which mated as (-) type, did not produce this surface protein. In homothallic fusion products no expression of the (+) type-specific protein could be detected. Single spore derivatives of fusion colonies in general show the phenotype of only one fusion partner, but in some cases prototrophic recombinants were obtained. This system opens up the possibility for genetic analysis of an organism with inefficient meiotic system, lacking a natural parasexual cycle. © 1990 Springer-Verlag.