RNA synthesis during germination of UV-irradiated Dictyostelium discoideum spores.

Abstract

UV irradiation to the spores of Dictyostelium discoideum NC4 resulted in a more prolonged delay of amoeba-emergence from swollen spores with increasing UV fluence. During the germination, an inhibition of total RNA synthesis and a shift of stage of maximum RNA synthesis to the later period were observed. The maximum poly(A)+ RNA synthetic activity was found on an early stage of amoeba-emergence prior about 1 h to the beginning of rRNA synthesis in unirradiated spore germination; but, in UV-irradiated spore germination, the stage of maximum poly(A)+ RNA synthesis shifted to the later stage of germination with increasing UV fluence. A decreased synthesis of poly(A)+ RNA and a severe inhibition of rRNA synthesis were observed on UV-irradiated and germinated spores, but no significant inhibition of 4-5 S RNA synthesis was detected. Actinomycin D suppressed almost completely the rRNA synthesis of emerged amoebae but the drug apparently did not affect the emergence of amoebae at any stage of germination. It was postulated that the delay of amoeba-emergence in UV-irradiated spore must be mainly due to the shift of the stage of maximum synthesis of poly(A)+ RNA to the later stage of germination.