Genetic analysis of developmental stages of the cellular slime mold Dictyostelium purpureum.

71 Mutants of Dictyostelium purpureum, unable to carry out normal development, were isolated. These mutants fall into three phenotypic classes. The mutants of the first class do not aggregate. Those of the second class develop a little further and form conical aggregates. The mutants of the third class progress still further, and the conical aggregates are transformed into finger-shaped masses, but no fruiting bodies are formed. Mutants of each class were able to form fruiting bodies when mixed with mutants of other classes. Pairs of mutants belonging to the same class, however, never responded synergistically. This result indicates the presence of three distinct developmental stages in the process of the fruiting-body formation. Experiments with actinomycin D suggested that genes controlling the developmental process of D. purpureum were divided into three groups which were identical to those identified by the analysis of synergism.