Biosynthesis and regulation of two vitellogenins in the fat body and ovaries of Ceratitis capitata (Diptera)

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Abstract
In adult female Ceratitis capitata both fat body and ovaries synthesize two vitellogenins (Vg-1 and Vg-2) with the same molecular masses as the respective vitellins of the eggs. Furthermore, both tissues contain two abundant mRNAs which yield, in a cell-free system, two previtellogenin polypeptides with molecular masses approximately 1,000 daltons higher than the mature Vgs. In vivo and in vitro studies during development suggested co-ordinate synthesis of Vg-1 and Vg-2 in each tissue. Also, at least in the fat body, Vg synthesis appears to be regulated at the level of transcription. Although both Vg-1 and Vg-2 are synthesized in the fat body and ovaries synchronously, their relative synthetic rates differ in the two tissues. The ratio of Vg-1 to Vg-2 synthesis in the fat body is approximately twice the respective ratio in the ovaries. Adult C. capitata males do not synthesize Vgs; however, they do so after treatment with 20-hydroxyecdysone.