Juvenile hormone signaling during oogenesis in Drosophila melanogaster.

Juvenile hormone (JH) participates both in the control of insect development and the establishment of reproductive maturity. In cultured Drosophila cells and in ovarian nurse cells, JH and its synthetic analog, methoprene, induce the expression of two related genes. These genes encode highly similar amino acid transport proteins that are homologous to transporters found in a variety of eukaryotes. JhI-21 is a novel Drosophila gene, and minidiscs (mnd) is a gene that was identified earlier. Two JH-inducible genes are regulated by different molecular mechanisms; JhI-21 behaves as a secondary JH-responsive gene, while mnd behaves as a primary responsive gene. Both JhI-21 and mnd transcripts show developmental profiles, which are consistent with JH regulation. Following eclosion, transcripts from JhI-21 and mnd are synthesized in ovarian nurse cells and subsequently sequestered in the mature egg. Their ectopic accumulation in ovaries can be induced by topical methoprene application. In apterous (ap4) mutant adults defective in JH secretion, mnd and JhI-21 RNA levels are severely reduced, but normal abundance is rescued to a high degree by topical methoprene treatment. Based on the evidence, we propose that during sexual maturation of Drosophila, JH provides a signal to the ovary that leads to the production of several maternally inherited mRNAs.