Abstract
Abnormal differentiation, mainly double fruiting bodiest was demonstrated to be induced by ultraviolet light (UVC) in a radiation sensitive mutant, γs13. In addition, a number of non-viable spores, the viability of which was measured by plaque forming ability, were produced in γs13 as compared to the wild-type strain, NC4. It was also demonstrated that the uv-sensitivity in cell killing of γs13 spores, most of which were defective at the germination step, was apparently high. From these results, it is possible to propose that the D. discoideum would be a very useful organism for the investigation of the effects of cosmic radiation and low gravity in space. When the difference in the induced frequency of abnormal differentiation does not exist at all between γs13 and NC4, it can be speculated that cosmic radiation and low gravity have no effect on them. When there are differences between γs13 and NC4 , on the other hand, it is possible to speculate that cosmic radiation must induce abnormal differentiation. In the case that normal morphogenesis and cell differentiation are not detected in both strains, the effects of low gravity and other inhibitory factors can not be neglected. Furthermore, a possible study of the effects of cosmic radiation on the viability and germination activity of the spores was proposed.
