COMPARISON OF ECDYSTEROID PRODUCTION IN DROSOPHILA AND MANDUCA - PHARMACOLOGY AND CROSS-SPECIES NEURAL REACTIVITY

In both Manduca sexta and Drosophila melanogaster, metamorphic events are driven by ecdysteroids whose production in prothoracic gland (PGs) is stimulated periodically by neural factors. Differences in the life cycle of moths and flies have made it difficult to compare the regula tion of ecdysteroid biosynthesis in these two species. As in Manduca, al least two neural factors in the larval Drosophila BVG complex were separable by molecular weight, and they stimulated increased ecdystero id biosynthesis from the ring gland, a composite organ that includes P C cells. Drosophila neural extracts accelerated ecdysteroid biosynthes is in Manduca PGs and, conversely, partially purified Manduca PTTH pre parations elevated ecdysteroid biosynthesis in Drosophila ring glands, suggesting that the two species may share structurally similar protho racicotropic factors. Drosophila ring glands required the presence of calcium ions to respond to neural extracts, but the phosphodiesterase inhibitor MIX and cAMP analogues exerted little, if any, positive effe ct on production. Mean ecdysteroid production rates of BVG-ring gland complexes taken from Drosophila larvae during various phases of the wa ndering period were often submaximal and highly variable, suggesting t hat they fluctuate widely prior to pupariation. Based on available dat a in Drosophila and the Manduca model for the control of ecdysteroid b iosynthesis, a developmental scheme for neuroendocrine control in Dros ophila is proposed. (C) 1995 Wiley-Liss, Inc.