NUCLEIC ACID AND PROTEIN SYNTHESIS IN THE DEVELOPING OOCYTES OF THE BUDDING FORM OF THE SYLLID, AUTOLYTUS EDWARSI (CLASS POLYCHAETA)

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Abstract
Incorporation of tritiated uridine, thymidine, and phenylalanine into nucleic acids and proteins was studied in the developing oocytes of stolons produced by asexual budding in Autolytus edwarsi. Radioautographs indicate that RNA is synthesized mainly in the nucleolus of developing oocytes from which it migrates to non-nucleolar regions of the nucleus and then to the cytoplasm. Incorporation of uridine-H3 into the nucleolus is extremely rapid while transfer of RNA to the cytoplasm is a relatively slow process in these eggs. Fully grown oocytes at metaphse I (the stage at which Autolytus eggs are fertilizable) do not incorporate uridine-H3 indicating that no significant synthesis of RNA is occurring at the close of the growth period of oogenesis. Phenylalanine-H3 was not incorporated more rapidly into the nucleolus, results indicating that all parts of developing eggs (nucleoli, non-nucleolar regions of the nucleus, and cytoplasm) are synthesizing protein. Fully grown oocytes in metaphase I, however, are synthesizing little, if any, protein. In contrast to ripe eggs, cleavage stages are synthesizing proteins, particularly in nuclear and spindle regions. These results suggest that in Autolytus eggs the proteins for the mitotic spindles are being synthesized during cleavage whereas the proteins for the meiotic spindles are synthesized prior to the maturation divisions. Thymidine-H3 was not incorporated into developing oocytes indicating that no significant DNA synthesis was occurring. Radioautographs and cyto-chemical tests indicate that DNA is diffusely distributed in the germinal vesicle of Autolytus edwarsi. Presumably in this species, DNA is synthesized very early in oogenesis.