Hormonal control of vitellogenin mRNA levels in the male and female housefly, Musca domestica

Abstract

The temporal changes and hormonal control of vitellogenin gene transcript (vitellogenin mRNA) levels in the female and male housefly, Musca domestica, were investigated during the first cycle of oögenesis by Northern blot analysis using housefly vitellogenin cDNA as a probe. The vitellogenin mRNA in the ovary and fat body in female flies accumulated in a stage-dependent fashion in parallel with the change of vitellogenin concentration in the haemolymph during egg formation. No vitellogenin mRNA was detected in the fat body of male flies. The accumulation of vitellogenin mRNA in the decapitated females of autogenous strain (in which vitellogenesis had been prevented by decapitation at the pre-vitellogenic stage) was accelerated by administration of 20-hydroxyecdysone in a dose-dependent manner. The male flies of the same strain, however, were about 100 times less sensitive to 20-hydroxyecdysone than the female flies. The time at which 20-hydroxyecdysone stimulates the vitellogenin gene was slower in males than in females. Furthermore, 20-hydroxyecdysone activated the vitellogenin gene not only in the fat body of males and females but also in the ovary of females. The vitellogenin gene expression in male flies was not affected by any dose of juvenile hormone analogue (methoprene). The female flies, however, responded to juvenile hormone analogue, though its efficacy on the induction of vitellogenin gene expression was lower and the lag time for induction was longer than those observed with the 20-hydroxyecdysone-treated female flies. The response of the ovary to juvenile hormone analogue was much stronger than that of the fat body. These results clearly indicate that the accumulation of vitellogenin mRNA in the housefly takes place in a sex-, stage- and tissue-specific fashion during the normal gonotropic cycle, and that the effect of ecdysteroid is more pronounced than that of juvenile hormone on the induction of vitellogenin gene transcription.