Juvenile Hormone Synthesis Research Articles

The synthesis and degradation of juvenile hormone in Drosophila are under common control.

The synthesis and degradation of juvenile hormone in Drosophila are under common control.

Hormonal control of egg dumping and guarding in the lace bug, Gargaphia solani (Hemiptera: Tingidae)

This study examines the effect of juvenile hormone (JH) or a similarly acting juvenoid on the expression of maternal egg guarding and its life history alternative, egg dumping, in the lace bug, Gargaphia solani Heidemann. JH manipulations were indirect: methoprene, a synthetic JH analog, and precocene II, an allatocidal phytochemical commonly used to reduce JH synthesis, were applied exogenously to test the hypothesis that high JH titers promote egg production and egg dumping behavior, while low titers terminate egg production and initiate maternal care. As predicted, egg dumpers treated with precocene II ignored dumping opportunities and became egg guarders. Similarly, egg guarders that were treated with methoprene became gravid within 2 days and abandoned their eggs to become egg dumpers. These manipulations suggest that hormones can trigger the expression of both egg dumping and egg guarding in G. solani even when environmental conditions are inappropriate.

Juvenile hormone regulation of longevity in the migratory monarch butterfly.

Monarch butterflies (Danaus plexippus) of eastern North America are well known for their long-range migration to overwintering roosts in south-central Mexico. An essential feature of this migration involves the exceptional longevity of the migrant adults; individuals persist from August/September to March while their summer counterparts are likely to live less than two months as adults. Migrant adults persist during a state of reproductive diapause in which both male and female reproductive development is arrested as a consequence of suppressed synthesis of juvenile hormone. Here, we describe survival in monarch butterflies as a function of the migrant syndrome. We show that migrant adults are longer lived than summer adults when each are maintained under standard laboratory conditions, that the longevity of migrant adults is curtailed by treatment with juvenile hormone and that the longevity of summer adults is increased by 100% when juvenile hormone synthesis is prevented by surgical removal of its source, the corpora allatum. Thus, monarch butterfly persistence through a long winter season is ensured in part by reduced ageing that is under endocrine regulation, as well as by the unique environmental properties of their winter roost sites. Phenotypic plasticity for ageing is an integral component of the monarch butterflies' migration-diapause syndrome.

Ionotropic glutamate receptors mediate juvenile hormone synthesis in the cockroach, Diploptera punctata

By monitoring changes in the cytosolic [Ca 2+] i and rates of juvenile hormone (JH) synthesis in response to l-glutamate agonists and antagonists, we identified and characterized glutamate receptor subtypes in corpus allatum (CA) cells of the cockroach, Diploptera punctata. During the first ovarian cycle, corpora allata exhibited a cycle of changes in sensitivity to l-glutamate correlated to cyclic changes in rates of JH synthesis. When exposed to 60 μM l-glutamate in vitro, the active corpora allata of day-4 mated females produced 60% more JH, while inactive corpora allata at other ages showed 10–20% stimulatory response. Pharmacological characterization using various l-glutamate receptor agonists and antagonists indicated that several ionotropic subtypes of l-glutamate receptors were present in the CA. The CA showed an increase in rates of JH synthesis in response to NMDA, kainate, and quisqualate, but not to AMPA in both L-15 medium and minimum incubation medium. In contrast, applications of the metabotropic receptor-specific agonist trans-ACPD failed to elicit a change in the cytosolic [Ca 2+] i and JH production. An elevation of cytosolic calcium concentration, followed by 20–30% rise in JH production, was observed when active CA cells were exposed to 10–40 μM kainate. Kainate had no stimulatory effect on JH synthesis in calcium-free medium. The kainate-induced JH synthesis was blocked by 20 μM CNQX but was not affected by 20 μM NBQX. Kainate-stimulated JH production was not suppressed by MK-801 (a specific blocker of NMDA-receptor channel), nor was NMDA-stimulated JH production affected by CNQX (a specific antagonist of kainate receptor). These data suggest that active CA cells are stimulated to synthesize more JH by a glutamate-induced calcium rise via NMDA-, kainate- and/or quisqualate-sensitive subtypes of ionotropic l-glutamate receptors. The metabotropic-subtype and ionotropic AMPA-subtype l-glutamate receptors are unlikely to be present on active CA cells.

Negligible Senescence during Reproductive Dormancy inDrosophila melanogaster

Some endemic Drosophila overwinter in a state of adult reproductive diapause where egg maturation is arrested in previtellogenic stages. When maintained at cool temperatures, adult Drosophila melanogaster enter reproductive dormancy, that is, diapause or diapause-like quiescence. The ability to survive for extended periods is a typical feature of diapause syndromes. In adults this somatic persistence may involve reduced or slowed senescence. Here we assess whether reproductively dormant D. melanogaster age at slow rates. Adults were exposed to dormancy-inducing conditions for 3, 6, or 9 wk. After this period, demographic parameters were measured under normal conditions and compared to the demography of newly eclosed cohorts. The age-specific mortality rates of postdormancy adults were essentially identical to the mortality rates of newly eclosed, young flies. Postdormancy reproduction, in contrast, declined with the duration of the treatment; somatic survival during dormancy may tradeoff with later reproduction. Adults in reproductive dormancy were highly resistant to heat and to oxidative stress. Suppressed synthesis of juvenile hormone is known to regulate reproductive diapause of many insects. Treatment of dormant D. melanogaster with a juvenile hormone analog restored vitellogenesis, suppressed stress resistance, and increased demographic senescence. We conclude that D. melanogaster age at slow rates as part of their reproductive dormancy syndrome; the data do not agree with an alternative hypothesis based on heat-dependent "rate of living." We suggest that low temperature reduces neuroendocrine function, which in turn slows senescence as a function of altered stress response, nutrient reallocation, and metabolism.

In vivo effects of Manduca sexta allatostatin and allatotropin on larvae of the tomato moth, Lacanobia oleracea

Abstract. Injection of Manduca sexta allatotropin (Manse‐AT) into fifth or sixth stadium larval Lacanobia oleracea had no significant effect on larval growth, development or food consumption, compared to control injected insects. In contrast, injection of M. sexta allatostatin (Manse‐AS) into fifth stadium larvae resulted in a retardation of growth, reduction in feeding and increased mortality, compared to control injected insects, but had no effect on non‐feeding (day 7) sixth instar larvae. Results suggest that Manse‐AS is not acting on the corpora allata (CA) to inhibit Juvenile Hormone (JH) synthesis to produce the observed effects, but most likely by its myoinhibiting action on the foregut. Inhibition of foregut peristalsis by Manse‐AS in vivo appears to suppress feeding, resulting in increased mortality. Foregut peristalsis may be inhibited by the intact peptide or a deletion peptide produced by cleavage of Manse‐AS by haemolymph enzymes, because Manse‐AS (5‐15) also inhibits muscle contractions in the foregut in vitro.

Negligible Senescence during Reproductive Dormancy in Drosophila melanogaster

Some endemic Drosophila overwinter in a state of adult reproductive diapause where egg maturation is arrested in previtellogenic stages. When maintained at cool temperatures, adult Drosophila melanogaster enter reproductive dormancy, that is, diapause or diapause‐like quiescence. The ability to survive for extended periods is a typical feature of diapause syndromes. In adults this somatic persistence may involve reduced or slowed senescence. Here we assess whether reproductively dormant D. melanogaster age at slow rates. Adults were exposed to dormancy‐inducing conditions for 3, 6, or 9 wk. After this period, demographic parameters were measured under normal conditions and compared to the demography of newly eclosed cohorts. The age‐specific mortality rates of postdormancy adults were essentially identical to the mortality rates of newly eclosed, young flies. Postdormancy reproduction, in contrast, declined with the duration of the treatment; somatic survival during dormancy may tradeoff with later reproduction. Adults in reproductive dormancy were highly resistant to heat and to oxidative stress. Suppressed synthesis of juvenile hormone is known to regulate reproductive diapause of many insects. Treatment of dormant D. melanogaster with a juvenile hormone analog restored vitellogenesis, suppressed stress resistance, and increased demographic senescence. We conclude that D. melanogaster age at slow rates as part of their reproductive dormancy syndrome; the data do not agree with an alternative hypothesis based on heat‐dependent “rate of living.” We suggest that low temperature reduces neuroendocrine function, which in turn slows senescence as a function of altered stress response, nutrient reallocation, and metabolism.

Release of neurosecretory granules within the corpus allatum in relation to the regulation of juvenile hormone synthesis in Diploptera punctata

The release of neurosecretory granules within the corpora allata (CA) of the viviparous cockroach Diploptera punctata has been compared in glands with intact nerves from the brain (Brain–CA) and those detached from the brain. Measurements of juvenile hormone (JH) synthesis in vitro, comparing these two conditions of the CA at several stages of vitellogenesis in adult females, showed lower production of hormone in Brain–CA complexes than in CA alone. Glands treated with tannic acid to trap exocytotic granules before fixation for electron microscopical examination showed, in sample sections, 10 times more exocytotic profiles in the glands with intact nerves to the brain than in the isolated glands. Sections treated with antibody against allatostatin I (Dip 7), a member of the neuropeptide family that inhibits JH synthesis by CA in vitro, showed neurosecretory granules in allatostatin immunoreactive nerves to be 75±4% of the granules in the sample of sections of CA. Because the total quantity of allatostatin in CA was found by ELISA not to vary significantly with changes in JH synthesis, it is concluded that the lower rates of JH synthesis by glands with intact nerves to the brain are most likely due to the release of small amounts of allatostatin within the CA.

Interaction between Manduca sexta allatotropin and Manduca sexta allatostatin in the fall armyworm Spodoptera frugiperda

A peptide that strongly stimulates juvenile hormone (JH) biosynthesis in vitro by the corpora allata (CA) was purified from methanolic brain extracts of adult Spodoptera frugiperda. Using HPLC separation followed by Edman degradation and mass spectrometry, the peptide was identified as Manduca sexta allatotropin (Mas-AT). Treating the CA from adult S. frugiperda with synthetic Mas-AT (at 10 −6 M) caused an up to sevenfold increase in JH biosynthesis. The stimulation of JH synthesis was dose-dependent and reversible. Synthetic M. sexta allatostatin (Mas-AS) (10 −6 M) did not affect the spontaneous rate of JH secretion from CA of adult S. frugiperda, nor did any of the allatostatins of the Phe–Gly–Leu–amide peptide family tested. However, when CA had been activated by Mas-AT (10 −6 M), addition of synthetic Mas-AS (10 −6 M) reduced JH synthesis by about 70%. This allatostatic effect of Mas-AS on allatotropin-activated glands was also reversible. When CA were incubated in the presence of both Mas-AT (10 −6 M) and various concentrations of Mas-AS (from 10 −8 to 10 −5 M), the stimulation of JH-biosynthesis observed was inhibited in a dose-dependent manner. The experiments demonstrate a novel mechanism of allatostatin action. In S. frugiperda JH synthesis was inhibited only in those glands which had previously been activated by an allatotropin.

A review of the role of neurosecretion in the control of juvenile hormone synthesis: a tribute to Berta Scharrer

In the 1950s, Berta Scharrer predicted that neurosecretions from the brain regulated corpus allatum activity based upon the observation of the change in localization of neurosecretory material in the brain and change in gland activity after severance of nerves between the brain and corpus allatum. Isolation and characterization of neuropeptide regulators of juvenile hormone production by the corpora allata in the late 1980s has confirmed this prediction. Both a stimulatory allatotropin and an inhibitory allatostatin have been isolated from moth brains. Two families of allatostatins, both quite different from each other and that of moths, have been isolated from cockroaches and crickets. The wide distribution of these peptides in the nervous system, in nerves to visceral muscle, in endocrine cells of the midgut and in blood cells, indicate multifunctions in the insects in which they are allatoregulatory. Some of these other functions have been demonstrated in these insects and in insects in which these neuropeptides occur but do not act as corpus allatum regulators. For the latter group, the neuropeptide regulators of the corpora allata have yet to be isolated. The families of neurosecretory regulators will continue to grow.

Terpenoid ω-hydroxylase (CYP4C7) messenger RNA levels in the corpora allata: a marker for ovarian control of juvenile hormone synthesis in Diploptera punctata

Ribonuclease protection assays were used to measure changes in allatal transcript levels of the CYP4C7 gene which encodes a cytochrome P450 terpenoid ω-hydroxylase thought to play a role in the metabolism of JH and its precursors. Denervation of the corpora allata does not affect the pattern of expression of the CYP4C7 gene. Transplantation experiments show that CYP4C7 mRNA levels are dependent on a humoral factor characteristic of the reproductive state of the insect. Messenger RNA levels rise substantially in mated or denervated females, or in mated or virgin females treated with hydroprene, when the follicle length is over 1.5 mm. Vitellogenic ovaries however exert a negative influence on CYP4C7 expression, as ovariectomy in mated females causes a premature rise in CYP4C7 mRNA levels. The half-life of the CYP4C7 transcript is approx. 2 h when the corpora allata are incubated in vitro. Under these conditions, coincubation with a post-vitellogenic ovary maintains high CYP4C7 transcript levels in the glands. Excess juvenile hormone or analog applied at the end of vitellogenesis blocks ovulation or causes abortion of embryos deposited in the brood sac. We conclude that expression of the CYP4C7 gene is tightly controlled by the ovary, and it coincides with the ovarian signal to turn off juvenile hormone synthesis. The role of the CYP4C7 enzyme may be to ensure the clearance of allatal juvenile hormone and its precursors at the end of the gonotrophic cycle.

Effects of chilling stress on allatal growth and juvenile hormone synthesis in the cockroach, Diploptera punctata

During the ovarian cycle of the cockroach, Diploptera punctata, a mitotic wave occurs in the corpora allata before an increase in gland volume and juvenile hormone (JH) synthesis. Previous studies have demonstrated that the brain inhibits mitosis and JH synthesis in corpus allatum (CA) cells until adult females have mated. Herein, we report that chilling stress effectively suppresses mating induced proliferation of CA cells. In mated females, chilling on melting ice for 0.5–3 hours caused a strong, dose-dependent decrease in mitotic activity. In insects chilled for 3 hours, although the mitotic wave in the CA was practically abolished, CA volume and JH synthesis finally reached peak levels typical of unchilled insects, despite a 2-day delay. Consequently, oocyte maturation and oviposition were also delayed by 2 days, yet in both chilled and unchilled insects, peak values of basal oocyte length were the same. By allowing virgin females to mate on different days after chilling, we found that the chilling effect could be retained in the insect body for at least 2 days. During this period, signals from mating could not effectively remove inhibition of CA cell proliferation. Unilaterally disconnecting the CA from the brain revealed that chilling stress mediated CA cell proliferation via the brain, and did not directly affect the CA.

Role of feeding in the reproductive ‘group effect’ in females of the German cockroach Blattella germanica (L.)

We have found that whether a female German cockroach, Blattella germanica (L.), is kept alone or in the presence of another female has a major impact on how fast it reproduces and how much it eats. By the sixth day of adulthood, females paired since adult eclosion had substantially larger oöcytes than did females isolated during the same time, and females paired with intact females, or with ones rendered incapable of feeding, consumed more rat chow in the first six days of adulthood than did isolated females. The stimulatory effect of pairing on reproduction was, however, partially independent of feeding because the oöcytes of solitary and paired females differed in size on day 6 even when they were given, and had consumed, the same amount of food. This result was confirmed with analysis of covariance using the total food intake of a female as the covariate in the analysis. A female's social condition probably influenced the development of its oöcytes by affecting the quantity of juvenile hormone synthesized by its corpora allata. The corpora allata of paired females produced more hormone than did those of isolated ones, even when all females had consumed an equivalent amount of food. Moreover, females treated with a juvenile hormone analog, fenoxycarb, reproduced more quickly than identically reared and fed control females, showing that juvenile hormone could influence reproduction independently of feeding. We conclude that both group rearing and food intake accelerate oöcyte development by diminishing the brain's inhibition on the synthesis of juvenile hormone.

Triple co-localisation of two types of allatostatin and an allatotropin in the frontal ganglion of the lepidopteran Lacanobia oleracea (Noctuidae): innervation and action on the foregut

The triple co-localisation of peptidergic material immunoreactive to antisera raised against allatostatins of the Y/FXFGL-NH2 type, Manduca sexta allatostatin (Mas-AS), and allatotropin has been demonstrated in a single pair of anterodorsal neurones in the frontal ganglion of the tomato moth, Lacanobia oleracea (Noctuidae). Another pair of posterior neurones contain only Y/FXFGL-NH2-type allatostatin immunoreactivity. The neurites of all four cells trifurcate, and axons project to the brain in the frontal connectives and to the foregut in the recurrent nerve. Axons from the anterior neurones, within the recurrent nerve, have prominent lateral branches supplying muscles of the crop, and axons from both anterior and posterior cells show profuse branching and terminal arborisations in the region of the stomodeal valve. The brain contributes Y/FXFGL-NH2-immunoreactive material, but not allatotropin or Mas-AS, to the recurrent nerve via NCC 1+2 and NCC 3. All three peptides have a reversible effect on the spontaneous (peristaltic) contractions of the foregut (crop) in vitro. Thus, both types of allatostatin are inhibitory at 10(-12) to 10(-7) M, whereas allatotropin is strongly myostimulatory at 10(-14) M. This is the first demonstration of the gut myoinhibitory effects of Mas-AS and, taken together with the effects of Y/FXFGL-NH2-type allatostatins and allatotropin, reveals a different functional aspect to that normally attributed to these three peptides, i.e. control of juvenile hormone synthesis by the corpus allatum.

Effects of ovariectomy and mating on the activity of the corpora allata in adult female Blattella germanica (L.) (Dictyoptera: Blattellidae)

Summary In adult female cockroaches, the ovary greatly affects the synthesis of Juvenile Hormone (JH) by the corpora allata, and in females of some cockroach species, removal of the ovaries results in a permanent depression of JH synthesis. We report that the corpora allata in ovariectomised, adult virgins of the German cockroach, Blattella germanica (L.), increase and then decrease in activity, as they do in intact females. Moreover, the distal tubules in the left colleterial glands of ovariectomised females accumulate abundant protein, the production of which is regulated by JH. In both ovariectomised and sham-operated females, the activity of the corpora allata more than tripled between days 1 and 4 of adulthood, during which the oocytes of sham-operated females grew considerably in length. The corpora allata of sham-operated females produced even more JH on day 7, but very little on day 10, by which time all females had oviposited. The glands of ovariectomised females, by constrast, produced a similar amount of JH on day 7 as on day 4, but much less on day 10. Beginning on day 13, the activity of the corpora allata increased again in ovariectomised females, an increase that did not occur until day 22 in sham-operated females. Mating of ovariectomised females on day 6 resulted in a significant increase in the activity of the corpora allata by day 10. We conclude that both the ovary and mating stimulate the synthesis of JH early in the reproductive cycle, but that neither is needed for the occurrence of a complete cycle of JH synthesis.

NADPH diaphorase and nitric oxide synthase in the corpus cardiacum–corpus allatum of the cockroach Diploptera punctata

Juvenile hormone synthesis by corpora allata is regulated partly by allatostatin containing nerves from the brain that innervate the corpora cardiaca and the corpora allata. To investigate whether NO also participates in the regulation of juvenile hormone synthesis, antibody against NO synthase and the histochemical test for NADPH diaphorase activity, a marker for NO synthase, were applied to the corpora cardiaca-corpora allata of Diploptera punctata. Strong NADPH diaphorase activity occurred in corpus allatum cells but not in nerve fibers in the corpora allata or corpora cardiaca. In contrast, NO immunoreactivity occurred in nerves in the corpora cardiaca but not within the corpora allata. NO and allatostatin were not colocalized. NO synthase and NADPH diaphorase activity were localized in similar areas of the subesophageal ganglion and cells in the pars intercerebralis of the brain. Positive correlation of the quantity of NADPH diaphorase activity with juvenile hormone synthesis during the gonadotrophic cycle and lack of such correlation in subesophageal ganglia suggest that NADPH diaphorase activity reflects the necessity of NADPH in the pathway of juvenile hormone synthesis. These data suggest that NO is unlikely to play a significant role in the regulation of the corpora allata.

Variation in JH synthesis rate in mature honeybees and its possible role in reprogramming of hypopharyngeal gland function.

Juvenile hormone (JH) synthesis was higher in followers than in dancers, which suggests that higher JH levels in followers might be an internal motivational stimulus to induce them to leave me hive to search for food. The positive correlation of in vitro JH synthesis rate and α-glucosidase activity in the hypopharyngeal gland suggests that JH is involved in the reprogramming of the hypopharyngeal gland from producing larval food (immature adults) to production of α-glucosidase in mature adults.

Glutamate-induced rise in cytosolic calcium concentration stimulates in vitro rates of juvenile hormone biosynthesis in corpus allatum of Diploptera punctata

We show that in a cockroach, Diploptera punctata, endocrine function of the corpus allatum may be modulated by l-glutamate, a major fast excitatory neurotransmitter in the central nervous system of vertebrates and invertebrates. The widely accepted concept that synthesis of juvenile hormone (JH) depends upon intracellular calcium concentration, is extended by the finding that 60 and 100 μM l-glutamate induces both an increase in calcium concentration in the cytosol of corpus allatum cells, and stimulates JH synthesis in vitro. We show that l-glutamate stimulates JH synthesis by inducing calcium influx since in calcium-free medium the stimulatory effect is not observed. Furthermore, the non-specific glutamate-receptor antagonist, 100 μM kynurenate, and 1.8 mM magnesium, inhibit the stimulatory effect of l-glutamate on JH synthesis in vitro. These results suggest that functional ionotropic glutamate receptors are present on the surface of the cells in corpus allatum, and that rates of JH are at least in part regulated via these receptors.

Protocerebral neurons inhibiting proliferation of corpus allatum cells in the cockroach,Diploptera punctata

A mitotic wave before an increase in juvenile hormone (JH) synthesis was observed in the corpora allata during each ovarian cycle in the cockroach Diploptera punctata and was shown subsequently to be inhibited by the brain until adult females mated. Each corpus allatum (CA) was innervated by groups of neurons in the contralateral pars intercerebralis (PI) and the ipsilateral pars lateralis (PL). In this article, a third set of neurons is identified that innervates the CA located extralaterally in the contralateral PL. The topography of the brain neurons innervating the CA was reconstructed from confocal optical sections after vital staining with two fluorescent carbocyanine dyes, 1,1'-dihexadecyl-3, 3,3',3'-tetramethylindocarbocyanine perchlorate [DiIC(16) (3)] and 3, 3'-dioctadecyloxacarbocyanine perchlorate [DiOC(18) (3)]. This provided information necessary to disconnect specific pathways within the brain of virgin females and to determine the effect on mitosis in the corpora allata and on the growth of oocytes. Disconnection of the CA from the PI neurons was followed by a prolonged period of moderate mitotic activity in the glands. Disconnection of the CA from PI and contralateral PL neurons was followed by a rapid wave of high mitotic activity in the CA similar to that observed after mating. The ipsilateral PL neurons did not appear to influence CA cell proliferation, because mitotic activity in glands was similar whether or not glands were connected to these neurons. Disconnection of the contralateral PI and/or ipsilateral PL neurons, but not the contralateral PL neurons, from the CA resulted in oocyte growth indicative of increased JH synthesis. The authors conclude that, whereas contralateral PI neurons inhibit both CA cell proliferation and JH synthesis, ipsilateral PL neurons affect only JH synthesis, and contralateral PL neurons modulate cell proliferation slightly only.

Reverse physiology in drosophila: identification of a novel allatostatin-like neuropeptide and its cognate receptor structurally related to the mammalian somatostatin/galanin/opioid receptor family.

By using degenerate oligonucleotide primers deduced from the conserved regions of the mammalian somatostatin receptors, a novel G-protein-coupled receptor from Drosophila melanogaster has been isolated exhibiting structural similarities to mammalian somatostatin/galanin/opioid receptors. To identify the bioactive ligand, a 'reverse physiology' strategy was used whereby orphan Drosophila receptor-expressing frog oocytes were screened against potential ligands. Agonistic activity was electrophysiologically recorded as inward potassium currents mediated through co-expressed G-protein-gated inwardly rectifying potassium channels (GIRK). Using this approach a novel peptide was purified from Drosophila head extracts. Mass spectrometry revealed an octapeptide of 925 Da with a sequence Ser-Arg-Pro-Tyr-Ser-Phe-Gly-Leu-NH(2) reminiscent of insect allatostatin peptides known to control diverse functions such as juvenile hormone synthesis during metamorphosis or visceral muscle contractions. Picomolar concentrations of the synthesized octapeptide activated the cognate receptor response mediated through GIRK1, indicating that we have isolated the 394-amino-acid Drosophila allatostatin receptor which is coupled to the Gi/Go class of G proteins.