The effect of beta-ecdysone on protein synthesis in imaginal discs of Drosophila melanogaster cultured in vitro

The effect of ecdysterone and juvenile hormones on protein synthesis and development of imaginal wing discs of Drosophila melanogaster

The effect of ecdysterone and juvenile hormone on protein synthesis and development of imaginal wing discs of Drosophila melanogaster has been studied. It is found that juvenile hormone apparently does not inhibit the synthesis of the ecdysterone-inducible proteins, although wing disc development is inhibited to various extent by different juvenile hormones. It is suggested that the ecdysterone-inducible proteins are not involved directly in the initiation of wing disc evagination, it is possible that some of these proteins are involved in the maintenance of chromatin activities or they are involved in gene activation.

Effect of 20-hydroxyecdysone on protein synthesis in wing discs ofDrosophila melanogaster

Full wing disc evagination requires about 10 h of continuous exposure to 20-hydroxyecdysone. The synthesis of two polypeptides is increased when wing discs are subjected to short exposure (4 h) to the hormone, and their synthesis is dependent on hormone. A second group of proteins increased in synthesis only after longer hormonal treatment (12 h); however, the increased synthesis of these proteins can be induced by withdrawing hormone after short exposure. The results of this study are consistent with the model of sequential gene activation by 20-hydroxyecdysone proposed by Ashburner et al. (1974).

The effects of 20-hydroxyecdysone on the metabolic labeling of membrane proteins in Drosophila imaginal discs

20-Hydroxyecdysone induces evagination of imaginal discs of Drosophila melanogaster cultured in vitro. The possible involvement of cell-surface proteins in this process has prompted us to study the synthesis of membrane proteins in imaginal discs. A procedure is reported for the isolation of membrane vesicle fractions from discs that are enriched for the plasma membrane enzyme, Na+/K+-ATPase, and that label with the surface-labeling reagent [125I]iodosulfanilic acid. 20-Hydroxyecdysone alters the pattern of [35S]methionine incorporation into polypeptides in these membrane vesicle fractions. Increased and decreased incorporation as well as changes in migration on two-dimensional gels of specific polypeptides are caused by the hormone. These changes parallel in time the onset and the continuation of evagination.

Influence of molt cycle and beta-ecdysone on protein synthesis in the chelicerate arthropod, Limulus polyphemus

1. The effect of molt cycle stage and beta-ecdysone on protein synthesis in the horsehoe crab, Limulus polyphemus, was examined. 2. A pronounced decline in protein specific radioactivity after incubation with 14C-leucine was noted in muscle, midgut gland and operculum from postmolt to intermolt to premolt and in gut and gill tissue from intermolt to premolt. 3. beta-Ecdysone injections produced an early stimulation of protein synthesis in the midgut gland followed by strong inhibition within 48 hr. 4. Results are compared with those obtained in mandibulate arthropods.

Pyridine nucleotide metabolism in imaginal discs of Drosophila melanogaster

The pyridine nucleotide metabolism of imaginal discs of Drosophila melanogaster has been studied in vitro by incubating discs with labeled nicotinic acid in the presence and absence of ecdysterone. The major labeled compounds found within the discs are NAD, NADP, and nicotinic acid. There is preferential uptake of nicotinamide over nicotinic acid, although the Priess-Handler pathway is used exclusively. The presence of ecdysterone produces a small increase in the NADP/NAD ratio, and an increase in NAD synthesis, probably to compensate for increased NAD turnover.

The in vitro synthesis and secretion of alpha-ecdysone by the ring glands of the fly, Sarcophaga bullata

The in vitro secretory product of larval Sarcophage bullata ring glands has been identified as 2beta, 3beta, 14alpha, 22R, 25-pentahydroxy-5beta-cholest-7-en-6-one (alpha-ecdysone). Mid to late 3rd instar larval ecdysones were isolated and identified as 2beta, 3beta, 14alpha, 20R, 22R, 25-hexahydroxy-5beta-cholest-7-en-6-one (beta-ecdysone) and alpha-ecdysone at a ratio of 27:1. The low level of alpha-ecdysone in vivo, relative to its exclusive in vitro synthesis and secretion by the ring glands, is a function of the very active C20 hydroxylation mechanism in tissues peripheral to the ring gland. The role of alpha-ecdysone as a prohormone in dipteran metamorphosis is discussed.

Hormonal control of growth and differentiation of insect tissues cultured in vitro

This paper reviews the effects of insect hormones on lepidopteran imaginal discs cultured in vitro. Beta-ecdysone showed that RNA and protein synthesis was required for evagination and cuticle deposition. In particular, studies with actinomycin D and cycloheximide (at nontoxic levels) showed that RNA and protein synthesis during the ecdysone-dependent period was essential for subsequent development. These findings support the hypothesis that stimulation of macromolecular synthesis is fundamental to the action of ecdysone on imaginal discs. The influence of beta-ecdysone on chitin synthesis was also examined. Beta-ecdysone stimulated uptake and incorporation of tritiated-glucosamine by cultured P.interpunctella wing discs. Addition of hexosamines to the culture medium had no influence on ecdysone-induced cuticle deposition, but inhibition of glucose-uptake by cytochalasin B prevented the formation of cuticle. The action of ecdysone on particular enzymes in the chitin pathway remains to be elucidated.timulated both evatination and cuticle deposition of wing discs of Plodia interpunctella(Hubner). However, evagination required a shorter exposure to ecdysone than did cuticle deposition. Cuticle deposition was obtained under the following conditions: (a) a 24-hour pulse of beta-ecdysone (0.5-5.0 mug/ml); (b) continuous treatment with 0.2 mug/ml beta-ecdysone; or (c) continuous treatment with 0.5 to 50.0 mug/ml beta-ecdysone in medium conditioned with larval fat body...

Effect of insect hormones on RNA polymerases of mass-isolated imaginal discs of Drosophila melanogaster cultured in vitro

Four chromatographically separable DNA-dependent RNA polymerases (nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) were partially purified from imaginal discs of Drosophila melanogaster. Their properties are similar to those described for RNA polymerases I and II isolated from other eukaryotes. In vitro incubation of discs with beta-ecdysone, juvenile hormone, or cycloheximide resulted in increased activity of RNA polymerase I. The increase was irreversible with beta-ecdysone incubation and removal but reversible with juvenile hormone incubation and removal. With beta-ecdysone, the rate of the increase in polymerase I activity paralleled the kinetics of ecdysone binding to discs and increases in the rate of precursor incorporation into RNA. A model to explain the increased acticity of RNA polymerase I is presented.