The Effects of Juvenile Hormone on Imaginal Discs of Drosophila In Vitro: The Role of the Inhibition of Protein Synthesis

Abstract

We have been studying the genetic, molecular and developmental processes involved in the evagination of imaginal discs of Drosophila melanogaster. These studies have been facilitated, on the one hand, by the fact that evagination occurs in vitro in a variety of culture media in response to ecdysones (Mandaron, 1973; Chihara et al., 1972; Fristrom et al., 1973; Milner and Sang, 1974), and, on the other hand, by the availability of large numbers of imaginal discs (600,000–800,000 per day) isolated by a preparative procedure (Fristrom, 1972). Thus we have the advantage of both defined in vitro conditions and sufficient material for biochemical analysis. The morphology of an unevaginated and fully evaginated leg disc is compared in Fig. 1. Ecdysone-induced evagination is inhibited by all three of the known, naturally occurring juvenile hormones (JHs) and some, but not all, juvenile hormone analogs (Siegel and Fristrom, in press). In addition to inhibiting evagination, juvenile hormone also inhibits, under some conditions, DNA synthesis (Logan et al., 1975), RNA synthesis (Chihara and Fristrom, 1973) and protein synthesis, and affects some membrane properties (e.g., uridine transport, Chihara and Fristrom, 1973).