20-Hydroxyecdysone stimulates the accumulation of translatable yolk polypeptide gene transcript in adult male Drosophila melanogaster.

Yolk polypeptide (YP) synthesis is hormonally stimulated during maturation of adult female Drosophila melanogaster. Synthesis of the three YPs is sex specific and occurs in fat body cells and follicle cells of adult females. However, males have been shown to produce YPs when treated with the steroid hormone 20-hydroxyecdysone (20-HE). By using a cell-free translation system as an assay for YP mRNA, we found that 20-HE also causes the accumulation of translatable YP message in males. In addition, hybridization of cloned copies of genes for both YP1 and YP3 to total RNA from males showed that 20-HE caused the appearance of YP gene transcripts in males. Eight hours after treatment of males with 20-HE, YP gene transcript levels had increased at least 25-fold to approximately 2.7 x 10(6) copies of YP1 gene transcript per adult male fly. In normal adult females, there were 42 x 10(6) copies per fly by 24 hr. There was neither detectable YP synthesis nor translatable YP gene transcript in either normal 1- to 3-day-old males or 24-hr-old males treated with a juvenile hormone analogue. This evidence shows that 20-HE acts to regulate the levels of translatable YP mRNA in male Drosophila.