Attempts to Isolate Mutants of Dictyostelium discoideum Which Express α-Mannosidase-2 Constitutively

Evidence was sought for gene-specific negative regulatory element of Dictyostelium discoideum similar to the repressor/operator systems that control some operons in rpkaryotes and their viruses. Mutants of D. discoideum that constitutively express the stage specific enzyme α-mannosidase-2 could provide such evidence. Reconstruction experiments demonstrated that the screening technique developed would detect mutants of that type. Over 2 × 105 surviovors of heavily mutagenized cell populations were grown and their progeny tested. No mutants of the desired type were obtained. The possible implications of this finding are discussed.