Electrophoretic analysis of newly synthesized and stored maternal RNA during oogenesis ofCalliphora erythrocephala (Dipt.).

Ovaries ofC. erythrocephala synthesize large amounts of poly(A) and poly(A) RNA during early and middle stages of oogenesis as shown by labelling withH-uridine in vivo. After incubation for 1 h, a striking difference in the electrophoretic pattern of newly synthesized labelled poly(A) RNA and the poly(A) RNA present in sufficient amounts for optical density measurements (steady state poly(A) RNA) was observed. During early and mid-oogenesis, in the poly(A) RNA fraction, ≧4S predominantly mature rRNA, 5S RNA and tRNA were labelled. These fractions were no longer synthesized during late oogenesis, whereas poly(A) RNA was labelled continously During oogenesis stage specific differences in the size distribution of newly synthesized and steady state poly(A) RNA were not obvious. However, different sizes of labelled poly(A) RNA species were detected in 0-2h old preblastoderm embryos, after injection ofH-uridine into females either 3-4 days (stage 3-4 of oogenesis) or 24 h before oviposition (stage 5-6 of oogenesis). This difference in RNA synthesis was related to the presence of active nurse cell nuclei. The poly(A) RNA fraction represents about 2-3% of the total RNA in both ovaries and freshly laid eggs as judged by measurements of optical density and radioactivity bound to oligo(dT). The length of poly(A)-segments in ovarian poly(A) RNA varied from about 30 to 200 nucleotides.