Juvenile hormone regulates the expression of the gene encoding ceratotoxin a,an antibacterial peptide from the female reproductive accessory glands of the medfly Ceratitis capitata

Ceratotoxin A is an antibacterial peptide produced by the reproductive female accessory glands of the medfly Ceratitis capitata. To investigate whether ceratotoxin A gene expression was affected by juvenile hormone, which has gonadotropic functions in adult insects, newly emerged female medflies were treated with precocene II, an antiallotropin compound capable of inhibiting juvenile hormone biosynthesis. Daily treatment of newly emerged flies with precocene II blocked ceratotoxin A gene expression in a dose-dependent manner. Ceratotoxin A gene expression could be recovered after withdrawl of precocene II treatment. Moreover, the effect of precocene II on ceratotoxin A gene expression could be countered by simultaneous treatment with methoprene, a juvenile hormone analogue. The effects of precocene II and methoprene treatments on the growth of both ovaries and accessory glands was also investigated. Our data suggest that ceratotoxin A gene expression is modulated by juvenile hormone.     

The effects of precocene II on early adult development in male Locusta

Haemolymph protein synthesis and the accumulation of protein in haemolymph and accessory reproductive gland of normal adult male locusts were compared to that of males treated with precocene II. The precocene-treated insects showed a lower level of protein synthesis in both the fat body (source of haemolymph protein) and accessory reproductive gland. Topical application of juvenile hormone reversed the effects of precocene treatment. It would appear that the observed effects are the result of a reduction in juvenile hormone titre in the treated animals.     

Effects of prococene II on the nutritional physiology of last instar Heliothis zea larvae

When precocene II was fed to last instar larvae of Heliothis zea, it caused significant reductions in the calculated rate of growth, rate of nutrient assimilation, and conversion of ingested and digested food to body mass. No change in the rate of food consumption occurred but respiration was significantly higher. Transport of the nutrient [1-¹⁴C] linoleic acid across midgut tissue was hindered when larvae were fed precocence II. There was also a precocene-induced change in the apical (luminal) morphology of midgut cells, including absence of the glycocalyx and loss of the microvillar absorptive surface. The influence of precocene II on the midgut physiology and metabolic processes in last instar larvae of H. zea may account for the observed reduced growth and delayed development. © 1992 wiley-Liss, Inc.     

Effects of Juvenile Hormone and Precocene on the Reproduction of Brachionus calyciflorus

We studied the effects of juvenile hormone and precocene on reproduction of the rotifer Brachionus calyciflorus. Amictic females of B. calyciflorus that were 2‐4 hours old were exposed to different concentrations of juvenile hormone (0.004, 0.02, 0.1, 0.5, 2.5, 12.5 mg/L) and/or precocene (0.05, 0.25, 0.75, 3.75, 7.5 mg/L) for 24 h. They were then transferred to a new medium without hormone and checked every 2 h during the next 48 h, and thereafter monitored daily until the individual died. Precocene had no effects on the length of the rotifer juvenile period, hatching time of the first neonate, lifetime reproduction, or the mixis ratio. In contrast, juvenile hormone at 0.5, 2.5, and 12.5 mg/L significantly prolonged the juvenile period by 6.1, 9.2, and 8.6%, respectively. When 26‐28‐h‐old amictic females were exposed to the same concentration series of juvenile hormone or precocene, precocene at 3.75 mg/L resulted in an increase in lifetime reproduction of 30.39%. However, at 0.75 and 3.75 mg/L precocene, a significantly lower percentage of mictic females was found, whereas juvenile hormone had no effect on the lifetime reproduction or mixis ratio. The population growth test showed that juvenile hormone had significant effects on the population growth rate and mixis ratio, but no effect on resting egg production. In comparison, precocene had no effect on any of these parameters. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of precocene and methoprene application in young adult Musca autumnalis

Abstract Observations were made on the relative rates of growth among corpora allata, ovarian follicles and fat bodies in diapausing and reproductive Musca autumnalis DeGeer. Rates of corpora allata growth were greater in long-day than in short-day animals. Topically applied precocene II reduced the size of the corpora allata. Two sequential doses of precocene inhibited vitellogenesis. Topically applied methoprene produced vitellogenesis in short-day flies and inhibited development of hypertrophied fat body. This work provides evidence that Juvenile Hormone is the primary agent controlling diapause and non-diapause (vitellogenic) development in the ovaries of face flies.     

Comparative studies on pharmacokinetics and metabolism of the anti-juvenile hormone precocene II

The cuticular penetration and pharmacokinetics of the anti-juvenile hormone precocene II were determined in a sensitive species (Oncopeltus fasciatus) and an insensitive species (Heliothis zea). Precocene was sequestered by the fat body and slowly metabolized in Oncopeltus, but rapidly metabolized and excreted in Heliothis. Studies in vitro using inhibitors for cytochrome P-450 and for cyt P-450-NADPH-reductase, confirmed the anticipated detoxification of precocene by a mixed-function oxidase via the 3,4-epoxide. Use of the inhibitors in vivo had no influence on the metabolism of precocene.     

Precocenes as pro-allatocidins in adult female Diploptera punctata: A functional and ultrastructural study

Adult mated females of the viviparous cockroach Diploptera punctata are moderately sensitive to precocenes. Oöcyte growth is inhibited and oviposition is delayed in insects topically treated with precocene II or precocene III. C₁₆ juvenile hormone release by corpora allata of precocene-treated insects is markedly inhibited when compared to corpora allata of acetone-treated controls. Electron microscopy of the corpora allata reveals that precocene treatment results in a disorganisation of the intracellular organelles. Topically applied precocene II reaches a high concentration in the haemolymph (0.5 mM 2 hr after topical application of 250 μg). C₁₆ juvenile hormone release by isolated corpora allata is inhibited by precocenes in vitro; half-maximal inhibition over a 3 hr period is obtained at 0.4 mM precocene II. In vitro inhibition of corpora allata by precocene II concentrations higher than 1 mM rapidly destroys the glands as evidenced by electron microscopy (total disintegration of cellular organelles) and by the virtual cessation of C₁₆ juvenile hormone synthesis by the corpora allata. Inhibition of C₁₆ juvenile hormone release by precocene is time-dependent and is not reversible over the short-term incubation in vitro. This inhibition does not appear to be related to the spontaneous activity of the glands in vitro, and it can be reduced by two epoxidase inhibitors. Precocenes are pro-allatocidins in this species: they are bioactivated within the corpora allata to cytotoxic epoxides.     

Mobilization of carbohydrates in tissues of female silkworms, Bombyx mori, during metamorphosis

The metabolic activity and mobilization of carbohydrates among tissues of female silkworms were examined during metamorphosis by injecting radioactive ¹⁴C-glucose as a tracer. The isotope injected was incorporated into various tissues with varying degrees and reached a relatively stable state in all tissues tested in about 240 min. The metabolic activities analysed by 4 hr pulse labelling were different for different tissues and ages; in glycogen synthetic activity midgut was highest on the day of the larval-pupal ecdysis, the fat body 2 days later, and ovaries a further 4 days later.When the isotope was injected on the day of larval-pupal ecdysis, it was found predominantly in glycogen first in the midgut, then in the fat body, and finally in the ovaries, proceeding through development. The total radioactivity recovered in the glycogen fractions from these tissues was almost constant throughout development. Ovariectomy caused a rise in synthesis of both glycogen and trehalose in the fat body during the second half of development.From these results it is proposed that the dermand of developing ovaries for carbohydrates exerts a controlling influence over mobilization of glycogen in the fat body.     

Juvenile Hormone Stimulation of Oocyte Development and Embryogenesis in the Parthenogenetic Ovaries of an Aphid,Aphis fabae

Summary

The parthenogenetic ovaries of the black bean aphid, Aphis fabae, contain developing embryos. When reared at 15°C in long days (LD 16:8) oocyte development begins within the ovaries of the largest embryos of a fourth instar mother 24–48 hr after her ecdysis from the third instar. Starvation, decapitation and precocene III treatment inhibit embryonic oocyte development; juvenile hormone treatment reverses this inhibition. A method for the in vitro culture of embryos is described and under these conditions juvenile hormone again stimulates oogenesis. Embryogénie growth in vivo, as measured by the increase in length of the oldest daughter embryos, is also stimulated by juvenile hormone treatment. The results are discussed in relation to other roles proposed for juvenile hormone in aphid development.     

Morphogenetic effects of precocenes on three aphid species

The disruptive effects of precocenes I, II and III on metamorphosis were assessed in apterous viviparae of Acyrthosiphon pisum, Aphis fabae and Megoura viciae. Prenatally applied precocene I had no effect, precocene II caused supernumerary moulting (metathetely) in M. viciae but precocene III induced both precocious adult development (prothetely) and metathetely in all three species. the latter compound also promoted precocious adult development in alate virginoparae, males and ovipara-producers of M. viciae. However, gynoparae of A. fabae, and oviparae of M. viciae and A. pisum were resistant to this action. When topically applied to young adults of A. fabae or M. viciae none of the precocenes caused alate progeny to be produced but all did so in A. pisum. However, the previous supposition that precocene II promotes wing development because it decreases juvenile hormone titres should be viewed with caution as: (a) Precocene II was more potent than precocenes I and III when inducing wing formation but did not provoke precocious adult development, an overt indication of low juvenile hormone titres. (b) Precocene I and III were equally effective in inducing alate progeny but only the latter provoked precocious adult development. (c) Attempts to prevent or reduce the alata-inducing property of precocene II with juvenile hormone I were unsuccessful.     

Some effects of allatectomy in the female tsetse,Glossina austeni

The effects of juvenile hormone on the milk gland, ovaries, and fat body of adult female G. austeni were studied by allatectomy and hormone replacement therapy. In the absence of juvenile hormone, milk synthesis is slow, leading to the production, in a few cases, of small larvae over a prolonged inter-larval period. In most cases, no viable larva is produced and the fat body hypertrophies. Replacement of the corpus allatum with C₁₆JH leads to a rapid synthesis of milk, production of normal-sized larvae and a reversal of the effect on the fat body. It is therefore suggested that the milk gland activity is directly influenced by JH. Allatectomy in most cases also results in only one egg being matured. The others do not enter vitellogenesis. Similarly, this effect on the ovaries can be reversed by topical application of C₁₆JH.     

Age-dependent physiological responses of last instarHelicoverpa zea larvae to oral and topical application of precocene II

Newly-ecdysed last instar larvae ofH. zea grouped into 100-, 200-, 300-, or 400-mg categories were fed diet containing precocene II or given precocene II topically on the abdomen. The time for larvae to reach a maximal weight, time to pupation, growth rate, and the amount of precocene II excreted were calculated. Younger larvae of lower weights, which were fed or topically treated with precocene II required more time to reach their maximal weight, had a lower maximal weight, a lower growth rate, and required more time to pupate than control larvae. Older larvae represented by the largest weight category were less sensitive to precocene II, had a shorter delay in reaching maximal weight, and a shorter delay in the time to pupation than control larvae; larvae in the largest weight category that were fed precocene II also had smaller decreases in the growth rate. Growth rate declines for larvae given topical doses of precocene II, however, were largest for the oldest larvae. All larvae given a single topical dose excreted precocene II for several days and were most efficient at eliminating smaller doses; larger, older larvae excreted more precocene II than smaller, younger larvae. Age-dependent responses to precocene II indicate that growth and metabolic processes, as well as xenobiotic metabolism, change in last instar larvae.     

Antijuvenile influence of the precocene on the development of adult antennae in the large fruit-tree tortrix Archips podana Scop. (Lepidoptera: Tortricidae)

The influence of precocene II, an antijuvenile agent, on the development of adult antennae in the large fruit-tree tortrix A. podana Scop. was demonstrated. Treatment of the fifth instar larvae and prepupae with different doses of precocene proved to cause different sensitivity of the specimens to the juvenile hormone deficit. Treatment with 450 and 600 ??g precocene per specimen during the first days after ecdysis to the fifth instar caused the death of larvae. Treatment with 300, 450, and 600 ??g per specimen on the third day of the fifth instar larvae and prepupae caused a delay in the development of adult antennae. The results are discussed with respect to the role of the juvenile hormone in the development of imaginal structures during metamorphosis.     

Factors influencing juvenile hormone esterase activity in the wax moth, Galleria mellonella

The effects of juvenile hormone, antiallatotropins, selected surgical procedures and starvation on the juvenile hormone esterase levels in Galleria larvae and pupae were investigated. JH reduced JH esterase activity in larvae but induced the enzyme in 1-day-old pupae. In vitro studies confirmed that the peak of synthesis and/or release of JH esterase from the fat body of last instar larvae occurred 4 days after ecdysis. These studies also showed that fat body from JH-treated larvae released much less enzyme than controls. Antiallatotropins, precocene 2 and ZR 2646 also reduced JH esterase levels in larvae, but ZR 2646 induced JH esterase in pupae. In starved larvae, JH esterase did not increase during the first five days. A minimum of 36 hr of feeding was necessary for the larval esterase activity to increase on schedule on day 4 of the last larval stadium. When day-l larvae were ligated behind the head or the prothorax, they had lower JH esterase levels and yet showed a slight increase in the enzyme when the larvae reached the age of 4 days. The significance of these results is discussed in relation to the possible control of esterase activity during metamorphosis.     

The effects of juvenile hormone, 20-hydroxyecdysone and precocene II on activity of corpora allata and the mode of negative-feedback regulation of these glands in the adult Colorado potato beetle

When the titre of juvenile hormone III in female Leptinotarsa decemlineata was elevated by the implantation of supernumerary corpora allata or by the injection of the hormone, the rate of endogenous hormone production by the host glands was significantly restrained, as determined by the short-term in vitro radiochemical assay. From denervation studies, it is suggested that during phases of elevated juvenile hormone titre, the corpus allatum activity is regulated via humoral as well as neural factors requiring intact nerve connections. Restrainment of gland activity appears to be mainly via the neural pathway. Isolated corpora allata were not influenced by 10^?5 M juvenile hormone III added to the incubation medium in vitro.Studies with farnesenic acid revealed that the final two enzymatic steps in the biosynthetic pathway of juvenile hormone are also diminished during prolonged neural inhibition of the corpora allata.20-Hydroxyecdysone and precocene II had no apparent effect on the corpus allatum activity of Leptinotarsa decemlineata.     

Precocene I and II inhibition of vitellogenic oöcyte development in Drosophila melanogaster

Adult female Drosophila melanogaster were exposed to precocene I and II, antiallatropin compounds which result in juvenile hormone deficiency in many insects. The presence of juvenile hormone in Drosophila adults was evaluated by examining vitellogenic oöcyte development, a process regulated by juvenile hormone in these flies. Both precocenes reduced the number of vitellogenic oöcytes present 43 hr after exposure in a dose-dependent manner. Precocene I was effective when applied to either newly eclosed females prior to vitellogenic oöcyte development or to gravid females. Precocene I was also effective in decapitated females, indicating that the action of the compound is not mediated by the brain. Corpus allatum volume, presumably a reflection of secretory activity, increased between 0 and 24 hr after eclosion in control females but not in precocene-treated females even after 48 hr. However, when females were removed from precocene medium, gland volumes increased within 48 hr to approximately those of control flies. This result is consistent with the reversibility of the precocene effect on Drosophila adults. These results suggest that precocene acts on the corpus allatum of Drosophila adult females to produce juvenile hormone deficiency.     

Low doses of the pesticide lindane induce protein release by the fat body of female cockroach Blaberus craniifer (Dictyoptera)

In the ovoviviparous cockroach Blaberus craniifer, low doses of the pesticide lindane (1-6 microg/g of body mass) have been implicated in the enhancement of ovarian growth and vitellogenesis onset in headless female ovaries. In order to investigate lindane effects on protein release by the fat body, we used antibodies raised against egg proteins to quantify protein levels in fat body, hemolymph and ovaries of treated-fed or -decapitated females 3- or 5-days -old. In vitro assays used fat body in Grace's medium to quantify the protein amount released in the medium. Individual data for each treatment were related to their corresponding control in paired series. In vivo, ovarian enhanced protein content was linked to an enhanced protein secretion by the fat body. This was ascertained in vitro by high levels of released protein in the medium containing lindane (1 microM) by fat body from females, but not from males. This effect was inhibited by EDTA, a calcium chelator. The present results confirmed that low doses of lindane (about 3 microg/g of body mass) acted as a juvenile hormone analogue, at the level of the ovaries, by enhancing protein uptake, and also at the level of the fat body, by triggering protein release. This property is calcium-dependent.     

The Use of Yolk Protein Variations in Drosophila Species to Analyse the Control of Vitellogenesis

The yolk proteins of many insects, including Drosophila , are synthesised in the fat body of adult females and are transported through the haemolymph to be accumulated in the oocytes. We have used differences in the size and number of yolk polypeptides in different species of Drosophila to investigate the role of the ovary and of juvenile hormone in vitellogenesis.
The yolk proteins of eight species of Drosophila were compared with those of Drosophila melanogaster . Only Drosophila simulans had three yolk polypeptides of similar molecular weight to the three polypeptides in D. melanogaster and gave a high degree of cross reactivity with antibody raised against the yolk proteins of D. melanogaster . All other species had one to three bands on a sodium dodecyl sulphate gel representing the yolk polypeptides; they are between 44,000 and 49,500 daltons in molecular weight, showing weak cross reactivity with anti- D. melanogaster yolk antibody. Interspecies ovary transplants established that males of D. arizonensis and D.pseudoobscura which supported vitellogenesis of D. melanogaster ovaries, did so by permitting the implanted ovaries to synthesise their own yolk proteins. The synthetic juvenile hormone, ZR515, was unable to induce ovaries, which failed to develop in other species of males, to undergo vitellogenesis. In females, however, ZR515 was able to induce uptake of the yolk proteins of some of the species into the D. melanogaster donor ovaries, which had failed to develop in the absence of hormone. These interspecies differences in the yolk proteins have therefore been used to investigate the control of vitellogenesis and the role of juvenile hormone in this process in Drosophila .     

Tissue-specific regulation of juvenile hormone esterase gene expression by 20-hydroxyecdysone and juvenile hormone in Bombyx mori

Juvenile hormone esterase (JHE) is the primary juvenile hormone (JH) metabolic enzyme in insects and plays important roles in the regulation of molt and metamorphosis. We investigated its mRNA expression profiles and hormonal control in Bombyx mori larvae. JHE mRNA was expressed at the end of the 4th and 5th (last) larval instars in the midgut and in all the three (anterior, middle, posterior) parts of the silk gland. In the fat body, JHE expression peaked twice in the 5th instar, at wandering and before pupation, while it gradually decreased through the 4th instar. When 20-hydroxyecdysone (20E) was injected into mid-5th instar larvae, JHE mRNA expression was induced in the anterior silk gland but suppressed in the fat body. Topical application of a juvenile hormone analog fenoxycarb to early-5th instar larvae induced JHE expression in both tissues. In the anterior silk gland, JHE expression was accelerated and strengthened by 20E plus fenoxycarb treatments compared with 20E or fenoxycarb single treatment, indicating positive interaction of 20E and JH. JHE mRNA is thus expressed in tissue-specific manners under the control of ecdysteroids and JH.