Differential and temporal expression of the vitellogenin genes in Drosophila grimshawi

The three vitellogenin transcripts from Drosophila grimshawi have an average size of 1,600 nucleotides as determined using denaturing electrophoretic conditions. Southern analysis showed that the large quantity of vitellogenin mRNAs in adult female fat body cells is not a reflection of specific gene amplification. The quantitative differences in mRNA accumulation between fat body and follicle cells, which are in concert with the onset of their translation, indicate that vitellogenin synthesis entails the regulated expression of individual genes. The expression of the vitellogenin genes during follicle development is stage specific: V1 and V2 expression starts at late stage 7, while V3 is delayed by one stage. Maximum transcription of all three genes occurs at stage 10 whereas at stage 12 none of the transcripts is present. These results suggest that, either there is more than one regulatory signal, or there is one to which each gene reacts differently. Surprisingly, in male fat body cells a V2 transcript has been detected which is also present in the poly(A)+RNA fraction: the function and the purpose of this particular vitellogenin mRNA in male fat body cells are unknown. Neither of the other two vitellogenin transcripts have been detected in male fat body cells.