The synthesis and properties of polysomal RNA in potato tuber slices during the early stage of aging

摘要

The synthesis, molecular size, and coding properties of polysome-associated polyadenylated RNA[poly(A)(+)RNA]and non-polyadenylated RNA [poly(A)(−)RNA] were investigated in potato tuber discs during the early stage of aging. Tissue discs were labeled for 6 hr with3H-uridine in the presence of 5-fluorouracil to suppress rRNA synthesis, and polysomal RNA was isolated from the discs. Poly(A)(+)RNA accounted for 70%of the radioactivity in polysomal RNA and had a molecular size ranging from 6S to 30S with a peak at about 15S, when measured by formamide-polyacrylamide gel electrophoresis. The rest of the radioactivity was in poly(A)(−)RNA which had nearly the same range in molecular size, but had no conspicuous peaks on the gel. The polysomal RNA could program the synthesis of a wide variety of polypeptides in a cell-free translation system of wheat germ. Seventy percent of the translational capacity of polysomal RNA was attributed to poly(A)(+)RNA. The electrophoretic behaviour of the majority of the products from poly(A)(+)RNA was similar to that of products from poly(A)(−)RNA, but the former could program the synthesis of five polypeptides in addition to those translated from the latter. There was a tendency for poly(A)(−)RNA to be a more efficient messenger for large polyp