Sexuality in the cellular slime mold Dictyostelium giganteum

By pairing of strains of Dictyostelium giganteum in various combinations this species was shown to be heterothallic. Four mating types were identified. Some strains could not be assigned a mating type and others showed no mating reaction. No self-compatible strains were found. Mutations were introduced in several strains and genetic crosses were performed. The results of these crosses show that mating and macrocyst formation are controlled by a single locus-multiple allele incompatibility system. The results also support the view that the myxamoebae that emerge upon germination of the macrocysts are the products of meiosis.