ECDYSONE DURING INSECT DEVELOPMENT. 3. ACTIVITIES OF SOME ENZYMES OF TYROSINE METABOLISM IN COMPARISON WITH ECDYSONE TITER DURING THE DEVELOPMENT OF THE BLOWFLY, CALLIPHORA ERYTHROCEPHIA MEIG

Role of ecdysone, pupariation factors, and cyclic AMP in formation and tanning of the puparium of the fleshfly Sarcophaga bullata

Two pupariation factors, anterior retraction factor (ARF) and puparium tanning factor (PTF), are absent from the hemolymph of larvae at the time of tanning accelerated by ARF/PTF, cyclic AMP, or dopamine. ARF and PTF are not involved in derepression of dopa decarboxylase (aromatic L-amino-acid decarboxylase, aromatic L-amino-acid carboxy-lyase, EC 4.1.1.28) synthesis initiated by ecdysone. Tanning is entirely inhibited by injection of two transcriptional inhibitors, actinomycin and BrdUrd, and two translational inhibitors, puromycin and cycloheximide. Retraction activity is more severely inhibited by the transcriptional than by the translational inhibitors. A tanning response is initiated by cyclic AMP in the presence of the transcriptional but not the translational inhibitors. Dihydric tanning substances (dopa, dopamine) initiate tanning in the presence of both types of inhibitors. Release of ARF and PTF from the central nervous system is inhibited by the four inhibitors. ARF totally reverses the inhibitory effects on retraction, whereas PTF does not reverse inhibition of tanning. These data are interpreted to mean that PTF is concerned with the regulation of two components of the tanning response: (i) acceleration of synthesis of a particular protein (associated with the tyrosine hydroxylation complex), and (ii) activation via cyclic AMP of a component of the tyrosine hydroxylating system.

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.

Phenoloxidase activity in Apis mellifera honey bee pupae, and ecdysteroid-dependent expression of the prophenoloxidase mRNA

Phenoloxidase (monophenol, l-dopa: oxygen oxidoreductase, EC 1.14.18.1) is a multicopper oxidase, which plays an important role in melanin synthesis, necessary for defense against intruding microorganisms and parasites, wound healing and cuticle pigmentation. A phenoloxidase from the hemolymph of honey bee pupae exhibited an apparent molecular mass of 70 kDa, as estimated by gel filtration and SDS-PAGE. Optimal pH and temperature were 6.5 and 20 degrees C, respectively. Activity was fully stable for 30 min at 50 degrees C. Like phenoloxidases from the hemolymph of other insects, the honey bee enzyme was activated by trypsin and inhibited by protease inhibitors and phenylthiourea. Only high concentrations of sodium azide effectively inhibited the detected activity. A low concentration (5 microM) of Ca2+, Mg2+, and Mn2+ had a stimulatory effect on the activity. Single Michaelis-Menten curves were observed for l-dopa and dopamine oxidation, but the affinity of the enzyme for dopamine was greater than for L-dopa. Semiquantitative RT-PCR and Southern blot analysis using a 359 bp labeled probe, and quantification of the prophenoloxidase mRNA levels by real-time PCR showed increased amounts of transcripts in hemocytes and integument from young pupae injected with 20-hydroxyecdysone.

Isolation and characterization of a dopa decarboxylase cDNA and the induction of its expression by an insect cytokine, growth-blocking peptide in Pseudaletia separata

Parasitization by the wasp, Cotesia kariyai, elevates the concentration of an insect cytokine, growth-blocking peptide (GBP), in hemolymph of last instar Pseudaletis separata larvae. The increase of epidermal and hemolymph dopamine level is associated with the GBP increase. Both GBP and dopamine disturb host development and metamorphosis (Hayakawa, 1995). Dopa decarboxylase (DDC) converts Dopa to dopamine, and its cDNA was isolated from P. separata, and the deduced amino acid sequence showed that it was highly homologous to other lepidopteran DDCs, showing 96, 90 and 86% identity with those of Mamestra brassicae, Bombyx mori, and Manduca sexta, respectively. A 3.2 kb DDC mRNA transcript was constitutively expressed at low levels in the epidermis, brain-nerve cord and hemocytes, and the expression was enhanced by injection of GBP in these tissues. Detailed characterization of the DDC mRNA expression in the epidermis showed that its expression reached a plateau 3 hr after the injection. DDC activity and DDC protein (55 kDa) level mirrored the mRNA expression. Immunocytochemistry with anti-DDC antibody confirmed that the enhanced DDC expression was localized in the epidermal cells. Dopamine concentration in the epidermis gradually increased and reached maximum 6 hr after the injection. When the epidermis of Day 1 last instar larvae was cultured in vitro in the presence of GBP, DDC mRNA increased, indicating that GBP acted on the epidermal cells directly to induce expression of the DDC gene.

Identification and characterization of an aromatic amino acid decarboxylase from the filarial nematode, Dirofilaria immitis

A novel secreted aromatic amino acid decarboxylase-like molecule was identified in the excretory/secretory products of L3/L4 larvae as well as in an extract of adult Dirofilaria immitis. The secretion of the enzyme was developmentally regulated. Peak enzyme activities were detected in the culture medium before and after the molting of L3 larvae in vitro. The enzyme was purified from D. immitis adult extracts and the excretory/secretory products of L3/L4 larvae using different chromatographic methods followed by isoelectric focusing and SDS-PAGE. The enzyme has a molecular mass of 48 kDa and a pI of 5.6, and shows a specific enzymatic activity towards the aromatic amino acid substrates phenylalanine, tyrosine and tryptophan. The enzyme's activity did not show an absolute requirement for exogenous pyridoxal-5-phosphate. However, addition of pyridoxal-5-phosphate at 5 microM in the reaction increased the enzyme activity greatly. The enzyme had the ability to catalyze the formation of dopamine from L-dopa. Studies on the effects of inhibitors on the enzyme activity showed that the enzyme was sensitive to Pefabloc and p-chloromercuribenzoic acid, but not to diisopropyl flurophosphate. The Km values of the enzyme for H-Phe-AMC, H-Tyr-AMC and H-Trp-AMC were calculated to be 32.1 microM, 35.1 microM and 29.1 microM, respectively.

Two different cDNAs code for L-DOPA decarboxylase in the white prepuparium and eclosion developmental stages of the insect Ceratitis capitata1

In insects the DOPA decarboxylase gene (Ddc) is expressed in the epidermis where dopamine derivatives promote cuticle sclerotization and the central nervous system participating in the synthesis of serotonin and dopamine. The temporal course of Ddc enzyme activity during the white prepuparium and eclosion developmental stages primarily reflects this role. Here we report that a cDNA clone for l-DOPA decarboxylase (EC 4.1.1.28) has been isolated from the white puparium stage of the insect Ceratitis capitata, the cDNA sequence has been determined and it corresponds to an mRNA of 1341 base pairs. The comparison of this cDNA sequence with that of the eclosion stage which has been previously isolated in our laboratory revealed that the cDNA from the eclosion stage codes for protein consisting of 431 amino acid (aa) residues whereas that from the white prepuparium stage for protein of 425 aa residues. In addition there is a region of 33 aa residues close to the N-terminal region of the deduced protein in which marked differences in the aa composition are observed. This result was further confirmed by Northern blot analysis in which mRNAs isolated from both developmental stages were only hybridized with their respective polymerase chain reaction synthesized stage specific probes. These results suggest that during development of the insect C. capitata two different mRNAs are produced at the white prepuparium and the eclosion stages, giving rise to two protein isoforms presumably in response to different signals.

cDNA cloning of L-dopa decarboxylase from the eclosion stage of the insect Ceratitis capitata. Evolutionary relationship to other species decarboxylases

The cDNA encoding the L-dopa decarboxylase (ddc) from the eclosion stage of the insect Ceratitis capitata was isolated by PCR and a molecular cloning strategy. The isolated cDNA clone encoded a protein of 431 amino acids with a calculated molecular weight of 47,843 Da. Northern blot analysis of poly(A)+ RNA showed an approximately 2 kb transcript. The deduced protein sequence shares a high percentage of homology with Ddc protein sequences of other species. Furthermore, the molecular weight of the deduced protein agreed well with that of the purified Ddc from the same insect. Data base search revealed significant and extensive sequence similarities among prokaryotic and eukaryotic PLP-dependent decarboxylases including Ceratitis capitata and bacterial histidine decarboxylase (HDC), strongly suggesting an ancient and common origin for all PLP-dependent decarboxylases.

Purification and characterisation of L-DOPA decarboxylase from pharate pupae of Ceratitis capitata. A comparison with the enzyme purified from the white prepupae

In this paper we describe the purification of L-DOPA decarboxylase (DDC) to homogeneity from the developmental stage just before the eclosion (pharate pupae) of Ceratitis capitata. The enzyme was found to have a mol wt of approximately 100,000 and to be composed of two identical subunits (50,000 mol wt each). Polyclonal antibodies raised against the isolated enzyme reacted with the 50,000 dalton subunit and precipitated enzyme activity. Furthermore, properties of the enzyme isolated from the pharate pupa stage, were compared with those of DDC purified from the white prepupa stage with respect to substrate specificity, response to polyclonal antibodies, behaviour towards different cations and dependence of enzyme activity on the concentration of pyridoxal phosphate.

Regulation of dopa decarboxylase gene expression in the larval epidermis of the tobacco hornworm by 20-hydroxyecdysone and juvenile hormone

Dopa decarboxylase (DDC) which converts dopa to dopamine is important for cuticular melanization and sclerotization in insects. An antibody to Drosophila DDC was found to precipitate both DDC activity and a 49-kDa polypeptide synthesized by the epidermis of molting Manduca larvae. Using the Drosophila DDC gene, we isolated the Manduca DDC gene which on hybrid selection produced a 49-kDa translation product precipitable by the Drosophila DDC antibody. The 3.1-kb DDC mRNA appeared 12 hr after head capsule slippage (HCS) and reached maximal levels 7 hr later. Peak expression was twofold higher in melanizing allatectomized larvae and could be depressed to normal levels by application of 0.1 micrograms juvenile hormone I at HCS. Infusion of 1 microgram/hr 20-hydroxyecdysone (20-HE) for 18 hr beginning 2 hr after HCS or addition of 1 microgram/ml 20-HE to the culture medium for 24 hr prevented the normal increase in DDC mRNA. When Day 2 fourth instar epidermis was explanted before the molting ecdysteroid rise and cultured with 1-3 micrograms/ml 20-HE for 17 hr and then for 24 hr in hormone-free medium, DDC expression was three- to fourfold higher than that in epidermis cultured in the absence of hormone. Twelve or more hours of incubation with 20-HE was required for an increase in DDC mRNA, but continuous exposure to 20-HE prevented the increase. In all cultures an initial rapid increase in DDC mRNA was observed which decayed with time in vitro and apparently was associated with the wound response. Thus, ecdysteroid during a larval molt is necessary to program the later expression of DDC, but the subsequent decline of the ecdysteroid is required for this expression to occur.

Some aspects on L-dopa decarboxylase and p-tyrosine decarboxylase in the central nervous and peripheral tissues of the American cockroach Periplaneta americana

1. Aromatic amino acid decarboxylase activities toward L-DOPA (L-3,4-dihydroxyphenylalanine), 5-HTP (5-hydroxytryptophan) and p-tyrosine in different tissues of the sclerotized and newly ecdysed cockroach were analyzed. 2. The ratios of enzyme activity with regard to L-DOPA and p-tyrosine varied considerably in the tissues and between the two different growth stages. 3. A DOPA decarboxylase and a p-tyrosine decarboxylase were separated by gel filtration and ion exchange chromatography. 4. The optimal pH requirement for both enzymes was 7.5 with the exception of the one decarboxylating 5-HTP. 5. The molecular weights of the cockroach brain DOPA decarboxylase and tyrosine decarboxylase were estimated to be 120,000 and 100,000, respectively. 6. Unlike the mammalian aromatic amino acid decarboxylase, the cockroach DOPA decarboxylase cannot be activated by a small amount of benzene. 7. An increase of over 50-fold of DOPA decarboxylase activity and a 50% reduction of tyrosine decarboxylase activity in the epidermal tissue of the newly ecdysed animals was observed. 8. In the fully sclerotized cockroach, a reversible endogenous inhibitor(s) of DOPA decarboxylase in the integument was observed, suggesting that the DOPA decarboxylase is suppressed in the epidermal tissues when ecdysis does not occur.

Hormonal regulation of dopa decarboxylase during a larval molt

Cuticular sclerotization in insects requires dopamine derivatives and thus the presence of dopa decarboxylase (DDC), the enzyme which converts dopa to dopamine. During the last half of the larval molt of the tobacco hornworm, Manduca sexta, beginning at 16 hr after head capsule slippage, the epidermal DDC activity increased fourfold. By contrast, allatectomized larvae which were destined to produce a melanized cuticle showed a sevenfold increase. This increase in DDC activity was prevented by infusion of 20-hydroxyecdysone (20HE) into the larva, indicating that the fall of the ecdysteroid titer is necessary for the increase. In vitro 20HE also prevented the increase in a dose-dependent manner when the epidermis was explanted at 16 hr after head capsule slippage but had less effect on epidermis explanted 3 hr later. Both 5 micrograms/ml alpha-amanitin and 100 micrograms/ml cycloheximide also prevented the increase. Application of juvenile hormone I showed that the critical period for determination of the level of the later increase in DDC activity was about 4 hr after head capsule slippage at the peak of the ecdysteroid titer. Apparently then the rise and fall of ecdysteroid regulate different aspects of DDC synthesis, the rise determining its later appearance and the fall timing this appearance.

Induction of translatable mRNA for dopa decarboxylase in Drosophila: an early response to ecdysterone

Ecdysteroid titer and dopa decarboxylase (aromatic-L-amino-acid carboxy-lyase, EC 4.1.1.28) activity were determined throughout the life cycle of Drosophila melanogaster. Five peaks in the amount of hormone were observed, which preceeded five dopa decarboxylase peaks by times ranging from 5 to 58 hr. Late in the third instar the hormone and enzyme maxima are nearly coincident. The increase in enzyme activity observed at this time is paralleled by an increase in translatable dopa decarboxylase mRNA. To obtain evidence that ecdysterone induces the appearance of this mRNA we made use of the temperature-sensitive ecd1 mutant. Garen et al. [Garen, A., Kauvar, L. & Lepesant, J.-A. (1977) Proc. Natl, Acad. Sci. USA 74, 5099-5103] have shown that when third instar mutant larvae are kept at 29 degrees C, the ecdysteroid titer remains low. In such larvae we show that the normal increase in dopa decarboxylase activity fails to appear, and no translatable dopa decarboxylase mRNA can be detected. Exogenous feeding of ecdysterone to these larvae results in a rapid synthesis of dopa decarboxylase in the epidermal cells. In addition, a parallel increase in translatable dopa decarboxylase mRNA occurs, which may be a primary response of these target cells to ecdysterone.

Purification of prophenoloxidase in the haemolymph of Calliphora vicina (R. & D.)

An improved method for the purification of prophenoloxidase is described. The proenzyme was purified 400 fold in homogenous form. The purity was tested by disc-electrophoresis and the molecular weight was found to be 87 000 in comparison to the mobility of marker enzymes, which were run simultaneously in SDS-gel electrophoresis. The proenzyme was denatured at 80 degrees C and maximum conversion into active state was found between 40 and 50 degrees C.

Evidence of hormonal control of the nucleolar activity in Sciara ocellaris

The nucleolus organizing region in the salivary gland of Sciara ocellaris becomes gradually less active as the larvae approach pupation. The cytological visible condensation of the nucleolar puff is paralleled by a decrease in the incorporation of [3H]-uridine into the ribosomal RNA. Alterations in the nucleolar behavior were brought about by extirpation of the neuroendocrine glands at six stages of development. There is a 'critical stage' during the 7th day of the 4th instar when the hormonal stimulus for pupation occurs. If the ligature is performed before this stage the NOR remains expanded and the larval-pupal ecdysis is inhibited; if done later on the NOR condenses at a normal rate and the ligated larvae mount to head-less pupae. These results suggest that inhibition of rRNA synthesis and consequent condensation of the NOR is under the control of the moulting hormone.

Translation of mRNA for 3,4-dihydroxyphenylalanine decarboxylase isolated from epidermis tissue of Calliphora vicina R. -D. in a heterologous system. Dependence of mRNA concentration on the insect steroid hormone ecdysone

RNA was isolated from the epidermis of Calliphora vicina larvae by phenol--chloroform extraction. The RN A sedimenting in sucrose gradients between 5 and 18 S was submitted to chromatography on oligo(dT)-cellulose columns. The fraction binding to the oligo(dT) is able to stimulate protein synthesis in a system consisting of mouse liverribosomal subunits, pH-5 factors from rat liver and initiation factors from rabbit reticulocytes. Optimal Mg2+ concentration for the translation of insect mRNA is 3.5 mM, that of K+ 76 MM. Initiation factors prepared from epidermis of Calliphora larvae are less efficient in the translation of insect mRNA than initiation factors isolated from reticulocytes. The pH-5 fraction from epidermis inhibits protein synthesis independent of the source of the mRNA fraction used. One of the proteins synthesized in the reconstituted system under the direction of insect mRNA has been identified as 3,4-dihydroxyphenylalanine (DOPA) decarboxylase by immunoprecipitation with specific antiserum against DOPA decarboxylase and comigration in dodecylsulphate-acrylamide electrophoresis with pure DOPA decarboxylase. Both mRNA from white prepupae and from 6--7-days-old larvae contain sequences coding for DOPA decarboxylase. However, white prepupae contains 3--4 times more DOPA decarboxylase-mRNA than 6--7-days-old larvae. The content of DOPA decarboxylase mRNA is proportional to the amount of active DOPA decarboxylase molecules present in the animals from which the mRNA was isolated.

Induction of dopa (3,4-dihydroxyphenylalanine) decarboxylase in blowfly integument by ecdysone. A demonstration of synthesis of the enzyme de novo

The activity of the enzyme dopa (3,4-dihydroxyphenylalanine) decarboxylase, present in the epidermis cells of blowfly larvae, increases during the late third instar under the influence of the steroid hormone, ecdysone. By using the double-labelling technique and immune precipitation with univalent antibody to dopa decarboxylase, we demonstrated that the increase in enzyme activity was due to a stimulation of synthesis of enzyme molecules de novo. In this respect, the action of ecdysone is similar to the action of other steroid hormones.

3,4-Dihydroxyphenylalanine (dopa) decarboxylase activity in the arthropod nervous system

1. When homogenates of brains from mature adult locusts (Locusta migratoria) were incubated with l-3-(3,4-dihydroxyphenyl)[3-(14)C]alanine the major radioactive metabolite was dopamine, suggesting the presence of a dopa (3,4-dihydroxyphenylalanine) decarboxylase. 2. Decarboxylation of l-dopa by this tissue, measured under optimum conditions by a radiochemical method, was 21mumol of CO(2)/h per g wet wt. Apparent decarboxylation of l-tyrosine proceeded at 0.34mumol of CO(2)/h per g wet wt. There was no detectable decarboxylation of l-tryptophan, l-histidine or l-phenylalanine. 3. Dopa decarboxylase activity was found in all major regions of the ventral nerve cord of the mature locust (range: 4-7mumol of CO(2)/h per g wet wt.) but was low or absent in thoracic peripheral nerve. 4. Marked decarboxylation of l-dopa was found in homogenates of brains of four other species of insects, and in brain and ventral nerve cord, but not in the claw nerve, of the crayfish. 5. The activity of the locust brain enzyme may be slightly lower at the time of imaginal ecdysis than during the mature period. By contrast, the dopa decarboxylase that produces dopamine as an intermediate in cuticle biosynthesis is known to be high in activity at the time of ecdysis and low in activity during the intermoult stages.

Ovarian maturation in stable flies: inhibition by 20-hydroxyecdysone

The steroid 20-hydroxyeedysone when given by mouth inhibits ovarian maturation in the stable fly, Stomoxys calcitrans (L.). by preventing lipid synthesis flecessary foir vitellogenlesis in the developing oocyte.