Studies on nucleic acids in plastids of the pigment mutant C-2A' of Scenedesmus obliquus

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Pigment mutant C-2A' of Scenedesmus obliquus whose chlorophyll formation and chloroplast development are light dependent, was studied for the nucleic acid content of its plastids. The ribosomal RNA of plastids of the achlorophyllous or greened mutant C-2A', did not show any difference from that of the wild type. Incorporation of [5-^3H] uridine into mutant cells was partially inhibited by rifampicin, indicating this part as being plastidial incorporation. Since there were no significant differences in the ribosomal RNA of plastids between the mutant and the wild type of Scenedesmus. the ribosomal system in the plastids of mutant C-2A' seemed not to be affected by the mutation. CsCl gradient patterns of Scenedesmus mutant and wild-type DNA were almost identical with those of Chlorella DNA. A peak at a buoyant density of 1.69 g/cm^3, the same as that of Chlorella chloroplast DNA, could be identified in Scenedesmus also as plastid DNA because it disappeared after prolonged treatment with myxin and hybridized with rifampicin-sensitive pulse-Iabelled RNA. This peak was present to nearly the same degree in the mutant and the wild type, indicating that a larger deficit of plastid DNA did not occur in the mutant. Whether or not the mutation might be localized in the plastid genome is discussed.
日本植物生理学会の論文