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.     

The role of allatostatic and allatotropic neuropeptides in the regulation of juvenile hormone biosynthesis in Lacanobia oleracea (Lepidoptera: Noctuidae)

In the sphinghid moth Manduca sexta, two allatoactive neuropeptides appear to be responsible for regulating juvenile hormone (JH) production by the corpora allata (CA). These peptides (M. sexta allatostatin, Mas-AS, and M. sexta allatotropin, Mas-AT) respectively inhibit and stimulate in vitro JH biosynthesis by CA in this insect. However, although Mas-AS inhibits CA in both larval and adult insects, Mas-AT is active only in adult M. sexta. The situation in other lepidopteran species is less clear-cut and, although both peptides have been detected (usually by immunologic and/or molecular techniques) in several other moths (including noctuids), their function as regulators of JH production remains uncertain. In the tomato moth Lacanobia oleracea (Lepidoptera: Noctuidae), we have previously demonstrated the occurrence of Mas-AS and/or Mas-AT in extracts of CA, brain and other organs, and have shown that both peptides are present in larval and adult forms. However, in L. oleracea, although Mas-AS inhibits larval and adult CA in vitro, it does so only at relatively high concentrations, and to a maximum of only approximately 70%. By contrast, Mas-AT (which is also present in larval and adult L. oleracea) stimulates larval and adult CA, but is substantially more potent ( approximately 100 fold) than the allatostatin. In this paper we present the results of paired, concurrent measurements (using ELISA) of levels of Mas-AS and Mas-AT in brains, CA and hemolymph (plasma and hemocytes) of L. oleracea at times when there are marked changes in JH titers. We also present data on the in vitro rates of JH biosynthesis by isolated CA, and on hemolymph JH esterase activity measured at the same critical developmental times, and discuss all of these data in relation to the putative allatoregulatory roles of the M. sexta allatotropic and allatostatic neuropeptides in L. oleracea.     

Juvenile hormone biosynthesis by corpora allata of larval tomato moth, Lacanobia oleracea, and regulation by Manduca sexta allatostatin and allatotropin

Juvenile hormone (JH) biosynthesis and the effects of synthetic Manduca sexta allatostatin (Mas-AS) and M. sexta allatotropin (Mas-AT) were investigated in isolated corpora allata (CA) of Vth stadium larvae of the tomato moth, Lacanobia oleracea. Reversed-phase high-performance liquid chromatography (RP-HPLC) of JH extracted from CA shows that larvae produce predominantly JH II and its corresponding acid. It appears that the acid homologue is a result of JH esterase activity in the CA (and other tissues) rather than the lack of JH acid methyltransferase. Mean rates of synthesis (100-200fmol/pr/h) were inhibited ca. 70% by Mas-AS and stimulated in a dose-dependent manner up to three times by Mas-AT. However, Mas-AS had no significant effect on Mas-AT-stimulated rates of JH biosynthesis. Using RP-HPLC and an enzyme-linked immunosorbent assay (ELISA) to Mas-AT, a peak of Mas-AT-like immunoreactivity was detected in larval L. oleracea brain homogenates. Co-elution of this immunoreactive peak with synthetic Mas-AT suggests that this neuropeptide is also present in L. oleracea.     

Neuropeptide co-localisation in the lepidopteran frontal ganglion studied by electron-microscopic gold-labelling immunocytochemistry

An immunogold-labelling electron-microscopic study of the frontal ganglion of two noctuids, Lacanobia oleracea and Helicoverpa armigera, has been carried out with antisera directed against three neuropeptides; allatostatins of the Y/FXFGL-NH₂ type, Manduca sexta allatostatin (Mas-AS) and M. sexta allatotropin. The ganglion of both noctuids has two pairs of large peptidergic neurones with many clusters of electron-dense granules, one pair being situated anteriorly and the other posteriorly. By means of a double-labelling (flip-flop) technique, with different sizes of gold particles, all possible paired combinations of the three different types of peptide have been visualised within granules of the anterior neurones, leading to the conclusion that the three peptides are co-packaged and co-stored in these cells. Within the posterior neurones of L. oleracea, gold labelling of granules is only linked to the Y/FXFGL-NH₂ allatostatin antisera and, in contrast to the anterior cells of this species in which double gold labelling results in a sparse accumulation of gold particles for any one peptide type, single labelling gives a more intense, uniform pattern of gold particles. In contrast to L. oleracea, the gold-labelling pattern seen in the posterior neurones of H. armigera reflects the co-localisation of allatostatins of the Y/FXFGL-NH₂ type with Mas-AS in this species. Allatotropin is absent in the posterior neurones of both species.Grant funding was from the Wellcome Trust: grant no. 068105 (A.T.)     

昆虫神经肽allatostatin与allatotropin的研究新近展

昆虫神经肽ａｌｌａｔｏｓｔａｔｉｎ与ａｌｌａｔｏｔｒｏｐｉｎ的研究新近展关雪辰（中国科学院动物研究所北京１０００８０）昆虫神经激素是肽类激素,它控制昆虫许多关键的生理过程,例如生长、变态、生殖和行为等。保幼激素（ＪＨ）对昆虫的卵子发生成熟起着重要的调...     

昆虫神经肽allatostati与allatotropin的研究新近展

Recently, two families of insect neuropeptides, the allatostatin, andallatotropin, have been identified. All allatostatins and allatotropins identified so farare neurosecretory polypeptides. A 13-amino acid allatotropin has been identifiedfrom adult Manduca sexta. A group of five structurally related allatostatins has beenidentified from Diploptara punctata. They either inhibit (allatostatin) or stimulate(allatotropin) the production of JH by CA. In this paper recent advances in researchon insect neuropeptides AS and AT and their biological significance are reported.     

Allatotropic and allatostatic activities in extracts of brain and the effects of Manduca sexta allatotropin and Manduca sexta allatostatin on juvenile hormone synthesis in vitro by corpora allata from the Eri silkworm, Samia cynthia ricini

Both allatotropic and allatostatic activities were found in crude extracts of brain from adult and larval Eri silkworm, Samia cynthia ricini, but it seems that allatotropic activity dominates in each stage. There was a high level of allatotropic activity in the crude extract of brain from newly emerged female adults, but allatostatic activity appeared in the bioassay when excessive amounts of crude extracts of brain were added. Crude extracts of brain from premoulting fourth‐instar larvae and from newly ecdysed fifth‐instar larvae exhibited allatotropic activities, whereas extracts of brain from the second and third day of the fifth‐instar larvae inhibited juvenile hormone (JH) release slightly. Allatotropic activity from the brains of adults and larvae stimulated both adult and larval corpora allata (CA) to synthesize JH. Manduca sexta allatotropin (AT) (Mas‐AT) and M. sexta allatostatin (AST) (Mas‐AST) also stimulated and inhibited both adult and larval S. cynthia ricini CA to synthesize JH, respectively. Higher concentrations of Mas‐AT (10^?4 or 10^?3 M) showed an inhibitory effect on adult CA. CA from newly emerged female adults were the most sensitive to inhibition by Mas‐AST, whereas CA from female pharate adults at about 6 h before adult emergence were the most sensitive to stimulation by Mas‐AT and S. cynthia ricini brain allatotropic activity. An extract of brain and Mas‐AT induced some of the non‐active female pharate adult CA at 12 h before emergence to synthesize a small amount of JH.     

Responsiveness of the adult cricket (Gryllus bimaculatus andAcheta domesticus) retrocerebral complex to allatostatin-1 from a cockroach,Diploptera punctata

Brain-retrocerebral complexes of female crickets,Gryllus bimaculatus andAcheta domesticus, treated with antibody to allatostatin-1 from a cockroach,Diploptera punctata, show extensive immunoreactivity. The results suggest that allatostatins or allatostatin-like molecules are produced in neurosecretory cells of the brain and are delivered to the corpora allata through nervous connections and/or via haemolymph. Radiochemical measurements of juvenile hormone III biosynthesis by isolated corpora cardiaca-corpora allata complexes from adultG. bimaculatus have been used to demonstrate an in vitro sensitivity of these glands to allatostatin-1 fromD. punctata. Allatostatin-1 is a relatively potent inhibitor of juvenile hormone III biosynthesis in corpora allata of both young adult females and males. In glands taken from 3-day virgin females, 50% inhibition of hormone biosynthesis is reached at ca. 3 nmol·l^-1 allatostatin-1. The inhibitory action of allatostatin-1 is rapid, dose-dependent and reversible. Addition of 200 mol·l^-1 farnesol to the incubation medium prevents inhibition of juvenile hormone III biosynthesis by allatostatin-1. Juvenile hormone III biosynthesis by isolated corpora allata of 3-day female house crickets,A. domesticus, is also susceptible to inhibition by 1 mol·l^-1 allatostatin-1.Abbreviations ASB2 Diploptera punctata allatostatin-5 - CA corpora allata - CC corpora cardiaca - Dip A-1 Diploptera punctata allatostatin-1 - HEPES 4-(2-hydroxyethyl)piperazine-1-ethanesulphonic acid - JH juvenile hormone(s) - Mas-AS Manduca sexta allatostatin - MF methyl farnesoate - NCA nervus corporis allati - NCC nervus corporis cardiaci - SEM standard error of mean - TRIS Tris(hydroxymethyl)aminomethane     

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.     

Allatoregulatory peptides in Lepidoptera, structures, distribution and functions

Allatoregulatory peptides either inhibit (allatostatins) or stimulate (allatotropins) juvenile hormone (JH) synthesis by the corpora allata (CA) of insects. However, these peptides are pleitropic, the regulation of JH biosynthesis is not their only function. There are currently three allatostatin families (A-, B-, and C-type allatostatins) that inhibit JH biosynthesis, and two structurally unrelated allatotropins. The C-type allatostatin, characterised by its blocked N-terminus and a disulphide bridge between its two cysteine residues, was originally isolated from Manduca sexta. This peptide exists only in a single from in Lepidoptera and is the only peptide that has been shown to inhibit JH synthesis by the CA in vitro in this group of insects. The C-type allatostatin also inhibits spontaneous contractions of the foregut. The A-type allatostatins, which exist in multiple forms in a single insect, have also been characterised from Lepidoptera. This family of peptides does not appear to have any regulatory effect on JH biosynthesis, but does inhibit foregut muscle contractions. Two structurally unrelated allatotropins stimulate JH biosynthesis in Lepidoptera. The first was identified in M. sexta (Manse-AT) and occurs in other moths. The second (Spofr AT2) has only been identified in Spodoptera frugiperda. Manduca sexta allatotropin also stimulates heart muscle contractions and gut peristalsis, and inhibits ion transport across the midgut of larval M. sexta. The C-terminal (amide) pentapeptide of Manse-AT is important for JH biosynthesis activity. The most active conformation of Manse-AS requires the disulphide bridge, although the aromatic residues also have a significant effect on biological activity. Both A- and C-type allatostatins and Manse-AT are localised in neurosecretory cells of the brain and are present in the corpora cardiaca, CA and ventral nerve cord, although variations in localisation exist in different moths and at different stages of development. The presence of Manse-AS and Manse-AT in the CA correlates with the biological activity of these peptides on JH biosynthesis. There is currently no explanation for the presence of A-type allatostatins in the CA. The three peptide types are also co-localised in neurosecretory cells of the frontal ganglion, and are present in the recurrent nerve that supplies the muscles of the gut, particularly the crop and stomodeal valve, in agreement with their role in the regulation of gut peristalsis. There is also evidence that they are expressed in the midgut and reproductive tissues.     

Allatotropic activity in the brain of female Phormia regina (Diptera: Calliphoridae)

In Phormia regina, the rate of juvenile hormone (JH) synthesis rises rapidly after the ingestion of an adequate protein meal. In a previous publication we have localized the neurons containing Manduca sexta allatotropin (Mas-AT)-like substances in the brain of P. regina and demonstrated the allatotropic effect of synthetic Mas-AT in sugar-fed flies in vitro. In this current study, we examined the possible role of the brain of P. regina after the fly received a protein meal. In vitro studies showed that the brain releases, at 8 h after a protein meal, a factor(s) with a strong allatotropic effect. This factor(s) stimulates the corpus allatum (CA) to produce 6.9 times more juvenile hormones (JHs) than the control CA. Time course studies showed that the release of this allatotropic factor(s) is temporally controlled. Only the brains collected from flies at 6 and 8 h after the onset of a liver meal release allatotropic factor(s). Injection of anti-Mas-AT antiserum partially suppressed the fly follicle development in vivo. Presence of anti-Mas-AT antiserum decreased the allatotropic effect of the brain released allatotropic factor(s) in vitro. In addition to a Mas-AT-like substance, it is possible that the brains of liver-fed P. regina females may synthesize other allatotropic factors that are chemically unrelated or partially related to Mas-AT, which cannot be recognized/neutralized by our anti-Mas-AT antiserum.     

Stimulation of juvenile hormone biosynthesis by analogues of a Manduca sexta allatotropin: in vitro studies.

Two analogues of a Manduca sexta allatotropin (Mas-AT) were synthesized. They correspond to the active fragment, amino acids 5-13, of the natural Mas-AT with substitution of norleucine for methionine. ATANA has the structure Val-Glu-Nle-Nle-Thr-Ala-Arg-Gly-Phe-NH2, ATAA is acetylated at the N-terminus. Allatotropic potency was evaluated by measuring the in vitro rates of juvenile hormone (JH) biosynthesis in corpora allata (CA) of M. Sexta. At a concentration of 20 nM, ATANA and ATAA increased JH production in day 0, day 1, and day 3 adult female CA by a factor of 3-8. Larval CA were not affected. These results correspond to activities reported for the natural Mas-At. ATANA did not stimulate pharate adult female CA to produce JH. Stimulation of female CA with ATANA was reversed when the CA were transferred to fresh medium while stimulation with ATAA under the same condition persisted. Exogenous farnesoate was converted to JH-III at a rate exceeding the highest ATANA-stimulated rate. ATANA in addition to farnesoate did not increase JH-III production, but increased JH-II production in addition to the already high production rate for JH-III. It is inferred that Mas-AT stimulates a rate-limiting enzyme in the biosynthesis of farnesoate and its homologues but does not affect epoxidation and methylation.     

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.     

Effects of allatotropin and allatostatin on in vitro production of juvenile hormones by the corpora allata of virgin females of the moths of Heliothis virescens and Manduca sexta

Retrocerebral complexes (RCs) were isolated from adult females of the moths Heliothis virescens and Manduca sexta. Different homologs of juvenile hormone (JH) produced by the isolated RCs were identified and amounts measured by capillary gas chromatography-chemical ionization (isobutane)-mass spectroscopy. Only JH I, II and III were identified. Incubation of RCs from both species in media containing acetate, but no propionate, induced production of approximately equal amounts of JH II and JH III, but the amount of JH I present was very low in all samples. Incubation of RCs with synthetic Manduca sexta allatotropin stimulated significant increases in production of all three homologs but increases in JH I and JH II were greater than those for JH III. The effect of allatotropin was mimicked by addition of propionate to the medium, which indicated that allatotropin increased supply of acetyl- and propionyl-CoA precursors. Incubation of tissue from H. virescens females during the first 24 h after eclosion with synthetic Manduca sexta allatostatin did not reduce production of JH. However, incubation of tissue from 3-day-old females with allatostatin significantly reduced production of JH. Similarly, incubation of tissue from H. virescens females during the first 24 h after eclosion with both allatotropin and allatostatin did not increase JH over the amount present in extracts from tissue incubated without the neuropeptides, indicating that allatostatin negated the action of allatotropin. Incubation of tissue from H. virescens females with allatostatin plus farnesol or JH III acid resulted in significant production of JH III, but neither JH I nor JH II was detected. These findings indicated that allatostatin acts prior to formation of the sesquiterpene alcohol precursors of JH.     

Neuropepride Regulators of Insect Corpora Allata

SYNOPSIS. Neuropeptides of the insect brain that regulate juvenilehormone synthesis by the corpora allata include allatotropins,stimulatory modulators, and allatostatins, inhibitory modulators.A radiochemical assay for juvenile hormone synthesis by corporaallata in vitro was utilized in the high pressure liquid chromatographicisolation of brain neuropeptides leading to the determinationof their primary structure. Identified are an allatotropin andan allatostatin from a Lepidopteran, Manduca sexta, and a familyof five allatostatins from a Dictyopteran, Diploptera punctata.These neuropeptides are all unique, effective at low concentration(10^–10 to 10^–8 M), act quickly (within hrs) andappear to be effective only within the same order of insectsas that from which the peptides were isolated. The physiologicalstate of the corpora allata conditions the effectiveness ofthe allatostatins of D. punctata. These neuropeptide regulatorsof corpora allatal function may have multiple regulatory roles.This is indicated for D. punctata allatostatin I by specificreceptors in brain and fat body as well as in corpora allatalmembrane preparations, and also by immunocytochemical localizationof allatostatin I in medial nerve cells that terminate withinthe brain as well as in the lateral neurosecretory cells thatterminate on corpus allatum cells.     

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB₃ and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB₃ biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C_16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.     

Structure-activity studies with endogenous allatostatins from Periplaneta americana: expressed receptor compared with functional bioassay

The A-allatostatins (F/YXFGLamides) are insect neuropeptides with inhibitory actions on juvenile hormone (JH) synthesis, muscular contraction and vitellogenesis. They exist in multiple forms within each species. In the cockroach, Periplaneta americana, only one receptor for A-allatostatin has been identified thus far. Here, we have characterised the receptor response to all 15 of the endogenous A-allatostatins encoded by the P. americana allatostatin prohormone gene, together with some analogues, using an indirect heterologous system involving co-expression of the receptor and a potassium channel subunit in Xenopus laevis oocytes and electrophysiological measurements. We have also determined the relative potency of the same peptides to inhibit JH synthesis in corpora allata. Our data reveal that the heterologously expressed receptor responds to all of the endogenous allatostatins and, although differences in potency are recorded, this cannot readily be related to particular differences in the primary structure of the peptides. Similarly, all allatostatins act on the corpora allata to inhibit the synthesis of JH, again with varying potency not readily related to peptide structure. Interestingly, some of the peptides did not perform consistently across the two assays. We show that the receptor is widely expressed in adult P. americana tissues (head, retrocerebral glands, fat body, ovary, male accessory gland, gut, leg muscle, Malpighian tubule and nerve cord) as well as in early larval instars. The spatial expression supports the known pleiotropic activity of allatostatins and role as a paracrine effector. This is the first report of such a detailed characterisation of an invertebrate receptor for allatostatin.     

Neuropeptide regulators of the juvenile hormone biosynthesis (in vitro) in the beetle,Tenebrio molitor (Coleoptera,Tenebrionidae)

The genome of Tribolium castaneum encodes two allatostatin [AS type B; W(X)₆Wamide and AS type C; PISCF‐OH] and one allatotropin (AT) precursor, but no AS type A (FGLamide) (Tribolium Genome Sequencing Consortium, 2008: Nature 452:949–955). Here we studied the activity (in vitro) of peptides derived from these precursors on the synthesis/release of juvenile hormone (JH) III. The corpora cardiaca‐corpora allata (CC‐CA) complexes of adult females of another tenebrionid beetle, the mealworm Tenebrio molitor, were used. Incubating the gland complexes in a medium containing Trica‐AS B3 peptide, we showed that the peptide has allatostatic function in T. molitor. The activity of the type C AS depended on the age of the test animals and their intrinsic rate of JH III biosynthesis. The Trica‐AS C peptide inhibited the JH release from CA of 3‐day‐old females with a high intrinsic rate of JH synthesis, but activated JH release from the CA of 7‐day‐old females with a lower intrinsic rate of JH production. The allatotropin peptide (Trica‐AT) also activated the JH release from the CA of 7‐day‐old females in a dose‐dependent and reversible manner. Unexpectedly, a type A AS derived from the precursor of the American cockroach Periplaneta americana (Peram‐AS A2b) inhibited the JH release from the CA of younger and older females in the concentration range of 10^?8 to 10^?4 M, and the effects were fully reversible in the absence of peptide. These data suggest a complex role of allatoactive neuropeptides in the regulation of JH III biosynthesis in beetles. © 2010 Wiley Periodicals, Inc.     

Morph-specific diurnal variation in allatostatin immunostaining in the corpora allata of Gryllus firmus: Implications for the regulation of a morph-specific circadian rhythm for JH biosynthetic rate

Previous studies have documented a circadian cycle in juvenile hormone (JH) biosynthesis in the long-winged, flight-capable morph, but not in the short-winged flightless morph of the cricket Gryllus firmus. One rapid and reversible inhibitor of in vitro JH biosynthesis by the corpora allata (CA) in crickets is the neuropeptide Phe-Gly-Leu/Ile-amide type of allatostatins (ASTs). To investigate the possible role of allatostatin regulation of the morph-specific circadian cycle of JH production, the quantity of this type of AST in the nerves within the CA was determined by the density of anti-AST-immunostaining in confocal images using the Image J program. The density of immunostaining was inversely related to the rate of JH biosynthesis: Immunostaining in the CA was high and did not differ between morphs early in the photophase when the in vitro rate of JH biosynthesis is low and equivalent in the morphs. However, during the end of the photophase, when the rate of JH biosynthesis rises dramatically in the flight-capable morph, but not in the flightless morph, immunostaining was significantly lower in the flight-capable compared to the flightless morph. These results indicate that morph-specific differences in delivery of AST to the CA and its probable release likely regulate the morph-specific circadian pattern of JH biosynthesis. Also, the negative correlation between AST density and JH production provides evidence for predicting the periods of altered release of these rapid-acting paracine regulators of JH biosynthesis.