Identification of gonadotropic and antigonadotropic factors from the nervous part of the corpora cardiaca in the African locust

Summary

The nervous part of the locust corpora cardiaca (NCC) was extracted using 70% methanol and subjected to fast protein liquid chromatography (FPLC). Twenty fractions were collected and injected into females from the end of the IIIrd larval instar to day-12 of the adult life to screen the effects on metamorphosis, body pigmentation, and oocyte growth. The rate of juvenile hormone (JH) biosynthesis by the corpora allata of injected animals was evaluated in vitro. One fraction was found to stimulate ovarian maturation, and 3 to delay oocyte growth. None of them disturbed (i) either metamorphosis and body color (which are JH dependent), or (ii) rate of JH biosynthesis. Of the 3 fractions which inhibited ovarian maturation, 2 of them were identified as the neuroparsins A and B. The results clearly illustrate that antagonist factors from the brain are involved in the regulation of ovarian maturation in the locust.     

Endocrine changes in maturing primary queens of Zootermopsis angusticollis

Termite queens are highly specialized for reproduction, but little is known about the endocrine mechanisms regulating this ability. We studied changes in the endocrinology and ovarian maturation in primary reproductive females of the dampwood termite Zootermopsis angusticollis following their release from inhibitory stimuli produced by mature queens. Winged alates were removed from their natal nest, manually dewinged, then paired in an isolated nest with a reproductive male. Development was tracked by monitoring ovarian development, in vitro rates of juvenile hormone (JH) production by corpora allata, and hemolymph titers of JH and ecdysteroids. The production rate and titer of JH were positively correlated with each other but negatively correlated with ecdysteroid titer. Four days after disinhibition, JH release and titer decreased while ecdysteroid titer increased. The new levels persisted until day 30, after which JH increased and ecdysteroids decreased. Fully mature queens had the highest rates of JH production, the lowest ecdysteroid titers, and the greatest number of functional ovarioles. The results support the hypothesis that JH plays a dual role in termite queens depending on their stage of development; an elevated JH titer in immature alates may maintain reproductive inhibition, but an elevated JH titer in mature queens may stimulate ovarian activity. The decline in JH production and the elevation in ecdysteroid titer correspond to a period of physiological reorganization and activation. The specific function of ecdysteroids is unknown but they may help to modulate the activity of the corpora allata.     

Changes in follicle cell morphology,ovarian protein synthesis and ovarian DNA synthesis during oöcyte maturation in Leucophaea maderae: Role of juvenile hormone

Changes in follicle cell morphology were correlated with changes in rates of protein synthesis and DNA synthesis by the ovary during ovarian maturation in Leucophaea maderae. During the vitellogenic period of oöcyte development, which lasts approx, 15 days, morphological changes in the follicle cells are accompanied by moderate rates of ovarian protein synthesis and rapid rates of ovarian DNA synthesis. At approx. 15 days after mating, the shape of the follicle cells changes from cuboidal to squamous, ovarian DNA synthesis is arrested, and ovarian protein synthesis increases slightly. During the final period of oöcyte development, which lasts approx, two days, the interfollicular channels between the follicle cells have disappeared and the squamous follicle cells, which contain an extensive rough endoplasmic reticulum, deposit a chorion around the mature oöcyte. These morphological changes are accompanied by a radical increase in ovarian protein synthesis, while ovarian DNA synthesis remains arrested. Immediately before ovulation, ovarian protein synthesis starts to decline, reaching a minimal level 24 hr post-ovulation.Ovarian maturation is dependent on the presence of juvenile hormone (JH) only during the vitellogenic stage of oöcyte development. Decapitation of insects at any point during the first 10 days after mating arrests the synthesis of DNA and retards the synthesis of protein by the ovary, resulting in degeneration of the oöcyte. Subsequent injection of JH restores both events to normal levels within 72 hr. Decapitation on or after the tenth day following mating does not alter normal oöcyte development, chorion deposition, ovulation or egg case formation.Primary induction of protein synthesis in ovaries from virgin females can be achieved by either an in vivo or in vitro exposure of the tissue to JH, thus confirming a site of action for JH to be ovarian tissue. Electrophoretic analysis of the soluble proteins from JH-exposed ovaries in vivo reveals that JH stimulates general protein synthesis, rather than the synthesis of a specific major protein such as vitellogenin.     

A specific photoaffinity label for hemolymph and ovarian juvenile hormone-binding proteins in Leucophaea maderae

A tritium-labeled diazocarbonyl juvenile hormone (JH) analog, (10-[10,11-3H]epoxyfarnesyl diazoacetate, [3H]EFDA), covalently bound to proteins in both hemolymph and ovarian extracts when reaction mixtures were irradiated with UV light. The addition of various concentrations of unlabeled JH III selectively inhibited [3H]EFDA photoattachment to proteins. Using the Scatchard method of analysis, [3H]EFDA bound specifically and with relatively high affinity (KD = 1.5 X 10(-6) M) to a macromolecule in each extract, although nonspecific binding to other molecules was also present (20-50%). To determine if [3H]EFDA bound at the JH III-binding site on the binding proteins, radioactive [3H]JH III or [3H]EFDA was complexed with proteins in the presence of various concentrations of either unlabeled JH III or JH I under equilibrium conditions. The results demonstrated that the natural hormone, JH III, displaced both bound labeled ligands 4.1 +/- 0.5 times better than the homolog JH I. Thus, the photoaffinity label [3H]EFDA bound at the same site on the protein as [3H] JH III. Fluorescent autoradiography of [3H]EFDA-labeled proteins separated by sodium dodecyl sulfate electrophoresis revealed that several proteins in both hemolymph and ovarian extracts bound [3H]EFDA. To determine the specificity of binding, extracts were irradiated with UV light in the presence of unlabeled JH III and [3H]EFDA. The results demonstrated that JH III prevented photoattachment of [3H]EFDA to a major protein in each extract. The molecular weight of these proteins was estimated at approximately 200,000 for both the hemolymph protein and the ovarian protein.     

Structure,haemolymph titre,and regulatory effects of juvenile homone during ovarian maturation in Leucophaea maderae

Juvenile hormone (JH) synthesized and secreted in vitro by the corpora allata of mated adult Leucophaea maderae females was determined to be JH III (methyl-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate).The haemolymph titre of JH was determined during maturation of the terminal oöcytes in the first reproductive cycle of L. maderae. In virgin females, JH is not detectable in the haemolymph during the first eight days following adult emergence; however, by 10 days after emergence, trace quantities of JH are apparent. Mating stimuli induce a dramatic increase in the concentration of haemolymph JH, with a peak occurring approximately 12 days after mating; thereafter, the JH concentration declines until it has reached an undetectable level 19 days after mating, at the time of chorion deposition.During ovarian maturation, changes in the rates of synthesis of vitellogenin by the fat body and DNA by the ovary correlate closely with the haemolymph titre of JH. However, no such correlation exists between the JH titre and the extensive ovarian protein synthesis that occurs in L. maderae coincident with chorion formation.The effects of JH I and JH III on both vitellogenin synthesis and ovarain DNA synthesis are statistically similar.     

Ecdysteroid regulation of ovarian growth and oocyte maturation in the red flour beetle,Tribolium castaneum

Previous studies from our laboratory showed the involvement of juvenile hormone (JH) and ecdysteroid signaling in the regulation of female reproduction in the red flour beetle, Tribolium castaneum. JH regulates vitellogenin (Vg) synthesis in the fat body but the role of ecdysteroid signaling is not known. Here, we report on ecdysteroid regulation of ovarian growth and oocyte maturation. Microarray analysis of RNA isolated from ovaries showed the up-regulation of several genes coding for proteins involved in ecdysteroid signaling on the 4th day after female adult eclosion. The functional analyses of genes coding for proteins involved in ecdysteroid and JH signaling pathways by RNA interference (RNAi) revealed that ecdysteroids but not JH regulate ovarian growth and primary oocyte maturation. Ultrastructural studies showed the temporal sequences of key events in oogenesis including the development of primary oocytes, the differentiation and development of follicle epithelial cells, and the formation of intercellular spaces to facilitate uptake of Vg protein. RNAi studies showed that ecdysone receptor (EcR) and ultraspiracle (USP) are required for the ovarian growth, primary oocyte maturation and the growth and migration of the follicle cells. These studies suggest important roles for ecdysteroids in the regulation of oocyte maturation in the beetle ovaries.     

Reproductive maturation in the pitcher-plant mosquito, Wyeomyia smithii

ABSTRACT. Females of Wyeomyia smithii (Coquillett) mate immediately following adult eclosion. Those from Massachusetts emerge with their ovaries at a more advanced stage of development than those from Florida. Decapitation of teneral females prevented the completion of ovarian maturation among individuals from Florida but not from Massachusetts. Application of a JH analogue to Florida pupae induced precocious ovarian development and compensated for decapitation of adults. Juvenile hormone analogue (Altosid) treatment after decapitation at emergence did not stimulate egg development in Florida females beyond the previtellogenic stage (Stage II). Precocious ovarian maturation apparently results from the action in pupae of JH which mediates an early release of a gonotropic factor from the head.     

Juvenile hormone titers,juvenile hormone biosynthesis,ovarian development and social environment in Bombus terrestris

The effects of the social environment and age on juvenile hormone (JH) and reproduction were investigated by measuring ovarian development, hemolymph levels of JH III, and rates of JH biosynthesis from the same individual bumble bees (Bombus terrestris). Differences in social environment were associated with differences in rates of JH biosynthesis, JH titer and ovarian development. Young queenless workers had a higher rate of JH biosynthesis, JH titer and ovarian development than queenright (QR) workers of similar age. Dominant workers in QR colonies had a higher rate of JH biosynthesis, JH titer and ovarian development than low ranked workers of similar size. There was a positive correlation between JH titer and ovarian development, but no correlation between rate of JH biosynthesis and ovarian development or between JH biosynthesis and JH titer. Both JH titer and rate of JH biosynthesis increased with age from emergence to 3 days of age, but 6-day-old workers, egg-laying workers, and actively reproducing queens had high JH titers and highly developed ovaries but low rates of JH biosynthesis. These results show that reproduction in B. terrestris is strongly affected by the social environment and the influence of the environment on reproduction is mediated by JH. Our data also indicate that the rate of JH biosynthesis measured in vitro is not a reliable indicator of JH titer or ovarian development in B. terrestris; possible reasons are discussed.     

Significance of haemolymph juvenile hormone titer changes in timing of migration and reproduction in adult Oncopeltus fasciatus

Previous studies had shown that both migratory flight and ovarian maturation in Oncopeltus fasciatus were stimulated by juvenile hormone (JH), yet the two behaviors were mutually exclusive. To understand the relationship of this hormone to these behaviors, haemolymph juvenile hormone titers were determined in both sexes of Oncopeltus throughout the adult stage by the Manduca pigmentation bioassay. Animals reared under long day conditions (17L:7D, 24°C) showed an immediate rise in haemolymph titers of JH after adult emergence whereas those reared in a short day photoperiod (12L:12D, 24°C) had a more gradual increase in hormone titers. Migratory flight behavior occurred during periods of intermediate hormone titers while oviposition did not begin until JH titers had reached their peak. It was concluded that lower JH titers normally stimulate flight in the prereproductive adult whereas higher titers are required for complete ovarian development. The corpus allatum in Oncopeltus thus coordinates migration and reproduction in response to the environmental cues of photoperiod, temperature, and food quality.     

Ecdysterone antagonism,mimicry, and synergism of juvenile hormone action on the Monarch butterfly reproductive tract

Previous research on Monarch butterflies has shown that juvenile hormone (JH) stimulates the development of the ovary and certain reproductive glands of both sexes. Ecdysterone injections into intact Monarchs demonstrate that low doses of this hormone inhibit ovarian development, and higher doses stimulate the male and female reproductive glands. In addition, experiments using neckligatured adults show that ecdysterone stimulates the reproductive glands of both sexes, in the apparent absence of JH, with the most pronounced effect being observed on the female colleterial gland. Other studies with neck-ligatured animals demonstrate that ecdysterone also synergizes with JH on the female gland and all three male glands. The feasibility of using Monarch reproductive glands for studies on the mode of action and interaction of JH and ecdysterone, and the possibility of a rôle of ecdysterone in the normal regulation of Monarch oögenesis, are discussed.     

Growth of the male accessory gland in adult locusts: Roles of juvenile hormone,JH esterase,and JH binding proteins

The participation of juvenile hormone (JH) in the regulation of growth and protein synthesis in the accessory reproductive gland of male Locusta migratoria has been investigated. After elimination of endogenous JH with ethoxyprecocene, the accessory gland failed to grow, but growth was restored by a single application of the JH analog, pyriproxyfen. Pyriproxyfen appeared to stimulate total protein synthesis by 3 h, with a significant effect by 12 h, in contrast to 24 h observed in fat body. The dose curve for stimulation of protein synthesis 12 h after applying pyriproxyfen gave an ED₅₀ of 0.1 μg; the dose curve for gland growth at 72 h was biphasic, with steps at about 0.01 μg and 10 μg, suggesting two phases in JH action. SDS-PAGE analysis showed several components that were stimulated by pyriproxyfen, the effect being strongest in an 11 kDa band. A 5 kDa component was enhanced in the soluble and reduced in the particulate fraction after precocene treatment. The accessory gland contained JH esterase activity at levels about 100 times those in fat body or hemolymph, and was higher in precocene treated locusts. Binding activity for [³H]10R -JH III was high in cytosolic and nuclear fractions, and was identified immunologically as due to the previously described hemolymph JH binding protein. The results indicate that the mode of action of JH in the accessory gland may differ from that in the fat body. The presence of intracellular JH binding protein suggests a direct action of JH within the gland, that may be modulated by JH esterase. © 1995 Wiley-Liss, Inc.     

Haemolymph vitellogenin,juvenile hormone,and oöcyte growth in the adult cockroach Nauphoeta cinerea during first pre-oviposition period

In the cockroach Nauphoeta cinerea the incorporation of a protein of low solubility into the oöcytes begins at day 5 of its adult life. An immunologically identical protein appears in the haemolymph two days earlier. The concentration of this protein, i.e. ‘vitellogenin’ in the haemolymph increases up to the onset of yolk incorporation into the oöcytes. During ovarian development no correlation could be detected between vitellogenin titre and several other parameters (ovary dry weight, length of the basal oöcytes, haemolymph protein concentration, body weight and age when ovulation occurred). In young females vitellogenin titre depends on the age, i.e. the volume of the corpora allata and hence on the presence and the titre of JH. During the period of egg maturation the total haemolymph protein concentration generally tends to drop while materials not precipitable by trichloracetic acid circulate at higher concentration after ecdysis and before ovulation.Early decapitation prevents vitellogenin synthesis and oöcyte growth, but when JH is applied to decapitated females, the normal vitellogenin titre is re-established, ovarian development, however, cannot be fully resumed. A dose-response curve shows that serial application of the hormone is much more effective than single large doses. Farnesylmethylester, a JH mimic, is about a hundred times less active, but more persistent than JH. Copulation seems to enhance the synthesis and release of endogenous JH, while food and water uptake are necessary to guarantee and optimal ovarian development. JH and high vitellogenin titre never restore ovarian development in females deprived of food and/or water or in those decapitated shortly after ecdysis.     

JUVENILE HORMONE BINDING PROTEIN IN THE OVARIES OF HOUSEFLY MUSCA DOMESTICA VACINA

Abstract  By using charcocal binding assay, the juvenile hormone binding protein (JHBP) was determined in the ovaries of houseflies. This ovarian JHBP possesses high affinity with juvenile hormone III (JH III) and has a K_d of 2.1 III 10^--⁸ M. The binding of ³H-juvenile hormone III (³H-JH III) to this protein was inhibited by unlablled JH III, but not by juvenile hormone analog ZR 512 or ZR 515. The level of this ovarian JHBP reached the highest in houseflies 48 h after emergence, and was 6. 5-fold and 15. 5-fold higher than that in housefIies 60 h and 72 h after emergence, respectively. No binding activity was detected in the ovaries of houseflies 24 h or 36 h after emergence. The absence of JHBP in the ovaries of houseflies 36 h after emergence could be reversed by applying JH III to newly emerged houseflies. The data suggest that the fluctuation of the JHBP concentration might associate with the action of juvenile hormone (JH) on housefly vitellogenesis.     

Juvenile hormone regulation of structural changes and DNA synthesis in the follicular epithelium of Leucophaea maderae

Juvenile hormone (JH I) stimulates specific morphological and biochemical changes in the follicular epithelium surrounding the terminal oöcytes in Leucophaea maderae. These include extracellular and intracellular structural changes, increased rates of follicle cell DNA synthesis, and elevated follicle cell DNA concentrations.Using females decapitated 24 hr after ecdysis, we have shown that JH I injections stimulate the following structural changes in the follicular epithelium: the appearance of channels between adjacent follicle cells and of spaces between the follicular epithelium and the maturing oöcyte; an increase in follicle cell size; the development of an extensive rough endoplasmic reticulum system; and an enlarged nucleus within each follicle cell. No increase in the number of follicle cells surrounding the developing terminal follicles is found in 7-day JH I-treated females, although the terminal follicles are almost twice as long as those in untreated females.In addition, we have demonstrated that JH stimulates the following biochemical events in the ovary: a 3.5 fold increase in thymidine incorporation into follicle cell DNA, with no subsequent transfer of such DNA to the developing oöcyte, and a 1.4 fold increase in ovarian DNA in 7-day JH-treated females. These data indicated that JH stimulates follicle cell DNA synthesis. The absence of any corresponding division of follicle cells suggests that JH I may induce polyploidy in follicle cells.Extended exposure of decapitated females to JH I does not result in complete ovarian maturation. Although fat bodies in the treated insects continue to display an increasing rate of vitellogenin synthesis, DNA synthesis in the terminal follicles declines rapidly after day 9, and the terminal follicles ultimately degenerate.     

Knockdown of the juvenile hormone receptor gene inhibits soldier-specific morphogenesis in the damp-wood termite Zootermopsis nevadensis (Isoptera: Archotermopsidae)

The Methoprene-tolerant (Met) protein has been established as a juvenile hormone (JH) receptor. Knockdown of the Met gene caused precocious metamorphosis and suppression of ovarian development. However, the function of Met in caste development of social insects is unclear. In termites, JH acts as a central factor for caste development, especially for soldier differentiation, which involves two molts from workers via a presoldier stage. Increased JH titer in workers is needed for the presoldier molt, and the high JH titer is maintained throughout the presoldier period. Although presoldiers have the fundamental morphological features of soldiers, the nature of the cuticle is completely different from that of soldiers. We expected that JH signals via Met are involved in soldier-specific morphogenesis of the head and mandibles during soldier differentiation, especially in the presoldier period, in natural conditions. To test this hypothesis, we focused on soldier differentiation in an incipient colony of the damp-wood termite Zootermopsis nevadensis. Met homolog (ZnMet) expression in heads increased just after the presoldier molt. This high expression was reduced by ZnMet double stranded (dsRNA) injection before the presoldier molt. Although this treatment did not cause any morphological changes in presoldiers, it caused strong effects on soldiers, their mandibles being significantly shorter and head capsules smaller than those of control soldiers. Injection of ZnMet dsRNA throughout the presoldier stage did not affect the formation of soldier morphology, including cuticle formation. These results suggested that the rapid increase in ZnMet expression and subsequent activation of JH signaling just after the presoldier molt are needed for the formation of soldier-specific weapons. Therefore, besides its established role in insect metamorphosis, the JH receptor signaling also underlies soldier development in termites.     

Vitellogenin synthesis,processing and hormonal regulation in the tick,Ornithodoros parkeri (Acari:Argasidae)

This study was undertaken to determine the processing of vitellogenin (Vg) and the role of juvenile hormone (JH) in the regulation of vitellogenesis in the tick Ornithodoros parkeri. Ticks usually require a blood meal to induce vitellogenesis. However, we have shown that a pyrethroid, cypermethrin (CyM), can stimulate Vg synthesis in unfed Ornithodoros moubata females. Vg concentration and synthesis were analyzed by SDS-PAGE spotting-scanning and fluorography using [³⁵S]-methionine. Although unfed females show high titers of Vg in the hemolymph, this is not due to new synthesis. Vg synthesis stimulated by engorgement increases beginning on day 2 after engorgement and reaches a maximum level on day 8. Vg is synthesized in the fat body, secreted into the hemolymph and then processed and incorporated into the ovaries as vitellin. JH I, II and III, methoprene (JHA), and CyM were topically applied to unfed females and Vg synthesis analyzed on day 5 by fluorography. JH and JHA did not stimulate Vg synthesis. CyM stimulated Vg synthesis but not ovarian development. These preliminary results indicate that JH does not function in the regulation of vitellogenin synthesis in this species.     

Mosquito larvicidal activities of farnesol and farnesyl acetate via regulation of juvenile hormone receptor complex formation in Aedes mosquito

Due to their target specificity and low-toxicity, insect growth regulators (IGRs) are regarded as promising alternatives to chemical insecticides. In this study, farnesol and farnesyl acetate exhibited juvenile hormone (JH)-based IGR activities. While farnesyl acetate showed JH agonist (JHA) activity in concentration-dependent manner, farnesol was identified as JH antagonist (JHAN) by interfering pyriproxyfen-mediated binding JH receptor complex. Both compounds showed mosquito larvicidal activities and caused retardation of ovarian growth of female Aedes albopictus by modulating the formation of JH receptor complex, expression of JH-inducible genes, and thereby disrupting JH-based endocrine regulations. These results suggested that farnesol and farnesyl acetate could be applicable for investigating underlying mechanisms of JH-regulated insect physiologies as well as developing novel eco-friendly insecticides.     

Cell size control by ovarian factors regulates juvenile hormone synthesis in corpora allata of the cockroach, Diploptera punctata

The corpora allata synthesize and release juvenile hormone (JH) that in turn regulates insect growth, metamorphosis and reproduction. In the corpus allatum (CA) of the female adult cockroach Diploptera punctata, cyclic rise and decline in JH synthesis rates occur concurrently with cyclic growth and atrophy during an ovarian cycle. Here, we report that protein content decreases, whereas Golgi population, lysosomal content and autophagic activities increase with decrease in CA cell size. Also, the concentration of cyclic GMP (cGMP) is low in large cells and high in small cells. Results of treating CA with ovarian tissue suggest that a putative peptidergic growth regulator released from mature ovaries acts directly on active CA cells and induces the elevation of intracellular cGMP content. Consequently, elevated cGMP may inhibit protein synthesis or trigger massive and synchronous autophagic activities, resulting in cell atrophy and reduction of protein content. As a result of the depletion of cellular machinery, CA glands exhibit long-term depression in JH synthesis.     

外源保幼激素对异色瓢虫卵巢发育及生殖相关基因转录水平的影响

【目的】本研究旨在明确外源保幼激素(juvenile hormone, JH)对异色瓢虫Harmonia axyridis成虫卵巢发育以及生殖信号通路中关键基因转录水平的影响。【方法】以萝卜蚜Lipaphis erysimi饲喂的异色瓢虫雌成虫为空白对照组,以点滴同体积丙酮的雌成虫为溶剂对照组,对人工饲料饲喂的羽化后第2天的雌成虫点滴不同剂量(80, 120和160 ng/头)JHⅢ1, 3, 5, 7和9 d后,解剖成虫卵巢,拍照并测量卵巢长度及其第一卵室的长度和宽度。利用qPCR分析在最适JHⅢ剂量(120 ng/头)处理后1, 5和9 d的异色瓢虫雌成虫生殖信号通路中关键基因JH受体methoprene-tolerant (Met)基因、krüppel homolog 1 (Kr-h1)基因、卵黄原蛋白(vitellogenin, Vg)基因(Vg1和Vg2)和卵黄原蛋白受体(vitellogenin receptor, VgR)基因表达水平。【结果】与溶剂对照组相比,点滴80和120 ng/头剂量JHⅢ可促进异色瓢虫成虫卵巢发育,其中120 ng/头剂量JHⅢ处理羽化后第2天雌...     

Erratum

Allatotropin (AT) is a 13 amino acid neuropeptide isolated from the tobacco hornworm, Manduca sexta, which stimulates the biosynthesis of juvenile hormone (JH) in adult females of this insect. In this paper we report that AT stimulates inositol phosphate formation in both female and male corpora allata (CA) of adult Manduca sexta. Furthermore, thapsigargin, a potent Ca²⁺-ATPase inhibitor, staurosporine, a potent inhibitor of protein kinases A and C, and 2,5-di-(tert-butyl)-1,4-hydroquinone (DBHQ), a potent inhibitor of liver microsomal ATP-dependent Ca²⁺ sequestration, all stimulate JH biosynthesis without changing the basal level of inositol phosphates. These data suggest that AT activates an inositol 1,4,5-trisphosphate (IP₃) pathway. Furthermore, increases in the free intracellular Ca²⁺ concentration in the CA stimulate JH biosynthesis. © 1992 Wiley-Liss, Inc.