FORMATION OF NON-VIABLE SPORES OF DICTYOSTELIUM DISCOIDEUM BY UV-IRRADIATION AND CAFFEINE

Abstract We have characterized the spores formed from amoeboid cells of the wild type strain of Dictyostelium discoideum after UV-irradiation. Cell differentiation in the presence of caffeine after a fluence of 300 J/m² resulted in a population of spores which was 98% non-viable. The UV-irradiation did not affect the conversion of the spores to swollen spores but did affect the conversion of swollen spores to amoeboid cells. When the germination of the spores was done without caffeine, we detected only a small effect on conversion of swollen spores to amoeboid cells and on the beginning of growth. On the other hand, in the presence of caffeine, the spores had a remarkable delay in both. It was also shown that few, if any, pyrimidine dimers exist in the DNA of the non-viable spores. Possible mechanisms of formation of non-viable spores are discussed.