RNA synthesised during oogenesis and early embryogenesis in an insect egg (Euscelis plebejus)

RNA labelled during oogenesis or early embryogenesis was isolated from eggs of the leaf hopperEuscelis plebejus. The polyadenylated RNA fraction deposited during early oogenesis accounted for approximately 2.7% of the total RNA content of the newly laid egg. This fraction differed significantly in molecular weight (15-32 S) from poly(A)-containing RNA synthesised between early cleavage and early germ anlage stages (4-20S). Locally injected³H-uridine spread through the egg within approximately 3 h. A considerable fraction (25-35%) of label injected as³H-uridine during early cleavage was recovered in DNA at subsequent stages (10-20 h later); labelled RNA was not found prior to the cellular blastoderm stage. When the yolk-endoplasm was separated from the blastoderm cells, only the latter contained demonstrable amounts of RNA synthesised by the embryo. Of the precursor incorporated into embryonic RNA, approximately 10% was found in the polyadenylated fraction at the early blastoderm stage, but only 3% at the early germ anlage stage. No differences in size distribution of polyadenylated RNA were evident between anterior and posterior halves of the early germ anlage stage.