Protection of spores from ultraviolet-C irradiation by auto-fluorescent substances in the spore mass of the cellular slime mold Dictyostelium discoideum

In this study, native spores surrounded by fluorescent substances in the spore mass of Dictyostelium discoideum were found to be resistant to relatively strong ultraviolet-C (UV-C) irradiation (2880 J/m2). The remaining emergency activity of the native mass of spores was over 80% even after exposure to strong UV-C irradiation (2880 J/m2). In contrast, the washed spores were very sensitive to weak UV-C irradiation (144 J/m2). The mass of spores in the fruiting body formed by amoebae with a low concentration of fluorescent substances was less resistant to UV-C than that in the fruiting body formed by normally grown amoebae. Based on the remaining emergency activity of washed spores with appropriate lumazine solution, the concentration of fluorescent substances in the native mass of spores was estimated to be equivalent to approximately 5 mmol/L of lumazine.