The appearance of dopa decarboxylase activity in imaginal discs of Sarcophaga bullata, undergoing development in vitro

Dopa decarboxylase: a model gene-enzyme system for studying development, behavior, and systematics

Throughout its long evolutionary history, the Dopa decarboxylase gene (Ddc) has acquired a variety of functions in insects. The enzyme (DDC) catalyzes the production of the neural transmitters dopamine and serotonin. Not surprisingly, evidence of the enzyme's involvement in the behavior of insects is beginning to accumulate. In addition, DDC plays a role in wound healing, parasite defense, pigmentation, and cuticle hardening. A high degree of sequence conservation has allowed comparisons of the Ddc-coding regions from various insects, facilitating a number of recent studies on insect systematics. This review outlines the diverse functions of Ddc and illustrates how studies of this model system address many questions on insect neurobiology, developmental biology, and systematics.

Isolation and characterization of the dopa decarboxylase gene of Drosophila melanogaster

We have isolated chromosomal deoxyribonucleic acid clones containing the Drosophila dopa decarboxylase gene. We describe an isolation procedure which can be applied to other nonabundantly expressed Drosophila genes. The dopa decarboxylase gene lies within or very near polytene chromosome band 37C1-2. The gene is interrupted by at least one intron, and the primary mode of regulation is pretranslational. At least two additional sequences hybridized by in vivo ribonucleic acid-derived probes are found within a 35-kilobase region surrounding the gene. The developmental profile of ribonucleic acid transcribed from one of these regions differs from that of the dopa decarboxylase transcript.

Developmental control of transduced dopa decarboxylase genes in D. melanogaster

Seventeen new euchromatic integration sites of the dopa-decarboxylase gene (Ddc) have been generated using p-mediated transduction. The developmental expression of the integrated genes was examined by monitoring the embryonic induction of dopa decarboxylase enzyme activity (DDC) and by monitoring the developmental pattern of DDC activity from late third instar to eclosion. The majority of inserts are regulated correctly within about 30% of controls. Several cases of multiple insertion events were recovered and these show correspondingly elevated levels of activity and are regulated normally. The pattern of expression of one insert (15C) falls outside the normal range. Multiple copies of transduced Ddc genes are used to test for effects of elevated gene dose on levels of expression. One insert on the X chromosome shows little or no dosage compensation. Possible reasons for the differences between the regulation of transduced genes in Drosophila and the regulation of transformed genes in mammalian systems are discussed.

The cuticle genes of drosophila: a developmentally regulated gene cluster

A 36 kilobase (kb) DNA segment of the Drosophila genome that contains several larval cuticle protein genes has been cloned and characterized. This segment maps at chromosomal locus 44D. It contains five genes, all of which are expressed at the same time of Drosophila development. Four of the genes are clustered within 7.9 kb of DNA and are abundantly expressed as poly(A)RNA in the epidermis of late third instar larvae but are not abundantly expressed in other developmental stages. A fifth gene lies 8 kb away from this cluster and is expressed at a much lower level in late third instar larval poly(A) RNA. Three of the four abundantly expressed genes have been shown to code for larval cuticle proteins; less decisive evidence indicates that the fourth gene also probably codes for a larval cuticle protein. Some of the genes are related in DNA sequence, and the proteins encoded in the cluster are related immunologically. Thus the cuticle genes encoded by the segment at 44D are members of a family of genes of common ancestry, which share the same pattern of developmental expression and reside in a small segment of the Drosophila genome.

Isolation and characterization of the dopa decarboxylase gene of Drosophila melanogaster

We have isolated chromosomal deoxyribonucleic acid clones containing the Drosophila dopa decarboxylase gene. We describe an isolation procedure which can be applied to other nonabundantly expressed Drosophila genes. The dopa decarboxylase gene lies within or very near polytene chromosome band 37C1-2. The gene is interrupted by at least one intron, and the primary mode of regulation is pretranslational. At least two additional sequences hybridized by in vivo ribonucleic acid-derived probes are found within a 35-kilobase region surrounding the gene. The developmental profile of ribonucleic acid transcribed from one of these regions differs from that of the dopa decarboxylase transcript.

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...