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

Larval feeding status regulates the transcript levels of genes encoding PTTH and allatoregulatory peptides in silkworm Bombyx mori

In Bombyx mori, two dorsolateral neurosecretory cells (NSCs) in each of the two brain lobes have been identified as prothoracicotropic hormone (PTTH) producing cells. This neuropeptide in insects stimulates the prothoracic gland for the synthesis and release of ecdysone, responsible for the molting events. Allatotropin (AT) and allatostatin (AST) are allatoregulatory neuropeptides that regulate juvenile hormone biosynthesis. Here, by using RT-qPCR, we showed that in B. mori, nutritional stress modulates the mRNA expression of AT and AST-C (allatostain type C) in the central nervous system consisting of the brain lobes and all the associated ganglia. Using whole-mount in situ hybridization, we showed that the feeding status of Bombyx larvae also influences the expression of PTTH in the NSCs of the brain. Food deprivation significantly decreased the mRNA expression levels of PTTH in larvae at active or terminal growth period. Further, we showed that insulin modulates the expression level of PTTH. However, its action was dependent on the feeding status of the larvae. At feeding, the insulin decreased the PTTH expression level, while at food deprivation, the insulin increased the PTTH expression level. The data thus indicates that larval feeding status plays an important role in altering the mRNA expression levels of allatoregulatory peptide genes and PTTH.

C-Type allatostatin and its putative receptor from the mud crab serve an inhibitory role in ovarian development

C-Type allatostatins are a family of peptides that characterized by a conserved unblocked PISCF motif at the C-terminus. In insects, it is well known that C-type allatostatin has a potent inhibitory effect on juvenile hormone biosynthesis by the corpora allata. C-Type allatostatin has been widely identified from crustacean species but little is known about its roles. Therefore, this study investigated the tissue distribution patterns of C-type allatostatin and its putative receptor in the mud crab Scylla paramamosain, and further explored its potential effect on vitellogenesis. Firstly, cDNAs encoding C-type allatostatin (Sp-AST-C) precursor and its putative receptor (Sp-AST-CR) were isolated. Subsequently, RT-PCR revealed that Sp-AST-C was mainly expressed in the nervous tissue, middle gut and heart, whereas Sp-AST-CR had extensive expression in all tissues tested except the eyestalk ganglion and hepatopancreas. In addition, in situ hybridization in the cerebral ganglion showed that Sp-AST-C was localized in clusters 6 and 8 of the protocerebrum, clusters 9, 10 and 11 of the deutocerebrum, and clusters 14 and 15 of the tritocerebrum. Whole-mount immunofluorescence revealed a similar distribution pattern. Synthetic Sp-AST-C had no effect on the abundance of S. paramamosain vitellogenin (Sp-Vg) in the hepatopancreas and ovary in vitro but significantly reduced the expression of its receptor (Sp-VgR) in the ovary in a dose-dependent manner. Furthermore, Sp-VgR expression, vitellin content and oocyte diameter in the ovary were reduced 16 days after the first injection of Sp-AST-C. Finally, in situ hybridization showed that Sp-AST-CR transcript was specifically localized in the oocytes, which further indicated that the oocytes are the target cells for Sp-AST-C. In conclusion, our results suggested that the Sp-AST-C signaling system is involved in the regulation of ovarian development, possibly by directly inhibiting the uptake of yolk by oocytes and obstructing oocyte growth.

Neuropeptides as Regulators of Behavior in Insects

Neuropeptides are by far the largest and most diverse group of signaling molecules in multicellular organisms. They are ancient molecules important in regulating a multitude of processes. Their small proteinaceous character allowed them to evolve and radiate quickly into numerous different molecules. On average, hundreds of distinct neuropeptides are present in animals, sometimes with unique classes that do not occur in distantly related species. Acting as neurotransmitters, neuromodulators, hormones, or growth factors, they are extremely diverse and are involved in controlling growth, development, ecdysis, digestion, diuresis, and many more physiological processes. Neuropeptides are also crucial in regulating myriad behavioral actions associated with feeding, courtship, sleep, learning and memory, stress, addiction, and social interactions. In general, behavior ensures that an organism can survive in its environment and is defined as any action that can change an organism's relationship to its surroundings. Even though the mode of action of neuropeptides in insects has been vigorously studied, relatively little is known about most neuropeptides and only a few model insects have been investigated. Here, we provide an overview of the roles neuropeptides play in insect behavior. We conclude that multiple neuropeptides need to work in concert to coordinate certain behaviors. Additionally, most neuropeptides studied to date have more than a single function.

Developmental and sex-specific differences in expression of neuropeptides derived from allatotropin gene in the silkmoth Bombyx mori

Allatotropin (AT) and related neuropeptides are widespread bioactive molecules that regulate development, food intake and muscle contractions in insects and other invertebrates. In moths, alternative splicing of the at gene generates three mRNA precursors encoding AT with different combinations of three structurally similar AT-like peptides (ATLI-III). We used in situ hybridization and immunohistochemistry to map the differential expression of these transcripts during the postembryonic development of Bombyx mori. Transcript encoding AT alone was expressed in numerous neurons of the central nervous system and frontal ganglion, whereas transcripts encoding AT with ATLs were produced by smaller specific subgroups of neurons in larval stages. Metamorphosis was associated with considerable developmental changes and sex-specific differences in the expression of all transcripts. The most notable was the appearance of AT/ATL transcripts (1) in the brain lateral neurosecretory cells producing prothoracicotropic hormone; (2) in the male-specific cluster of about 20 neurons in the posterior region of the terminal abdominal ganglion; (3) in the female-specific medial neurons in the abdominal ganglia AG2-7. Immunohistochemical staining showed that these neurons produced a mixture of various neuropeptides and innervated diverse peripheral organs. Our data suggest that AT/ATL neuropeptides are involved in multiple stage- and sex-specific functions during the development of B. mori.

Functional characterization of ASTC (allatostatin C) and ASTCC (allatostatin double C) in Clostera anastomosis (Lepidoptera: Notodontidae)

ASTC (allatostatin C) and ASTCC (allatostatin double C) are two neuropeptide genes that encode allatostatin C-like peptides. Whether these peptides inhibit or have other effects on juvenile hormone (JH) synthesis in the corpora allata remains in question. The juvenile hormone acid O-methyltransferase (JHAMT), a key gene in the JH biosynthesis pathway, was selected to study the effects of ASTC and ASTCC on juvenile hormones. In this study, we first characterized the expression patterns and correlations between ASTC and ASTCC in Clostera anastomosis under natural conditions, and then the functions of these two genes were investigated by RNAi. The results showed the expression of JHAMT was strongly positive correlated with ASTC and ASTCC in the heads of larvae after ASTC and ASTCC were knocked down simultaneously, while negative correlations were found in the heads of female adults. These results suggest that both ASTC and ASTCC may stimulate JH biosynthesis in larvae while inhibit in female adults of C. anastomosis. And after either ASTC or ASTCC was knocked down alone, the correlation between the two genes were positive, indicating ASTC and ASTCC may function dependently in female heads. In addition, simultaneous suppression of ASTC and ASTCC increased the mortalities of larvae and pupae.

Allatotropin inhibits juvenile hormone biosynthesis by the corpora allata of adult Bombyx mori

Juvenile hormone (JH) synthesis by the corpora allata (CA) does not occur during the pupal stage in both male and female Bombyx mori but begins shortly before adult ecdysis and thereafter only in females. JH biosynthesis in female adults was prevented by allatotropin (AT) through the corpora cardiaca (CC) and the tightly attached oesophagus before adult ecdysis, but after ecdysis, removal of the CC had little effect and only the oesophagus was necessary for AT to prevent JH synthesis. AT could not prevent JH synthesis by the CA alone in either stage. Short neuropeptide F (sNPF) acted directly on the CA, preventing JH biosynthesis without preventing the JH biosynthetic enzymes before adult ecdysis, but had little effect after ecdysis, indicating that the action of AT was not via sNPF. The inhibition of JH synthesis by AT was indirect. Both AT and a factor(s) from the AT-stimulated oesophagus through the CC were necessary for the inhibitory action, which was due to the prevention of some of the JH biosynthetic enzymes. These results clearly show that AT prevents JH synthesis in adult CA in B. mori, although AT stimulates JH biosynthesis by the CA in several insect species.

Neuropeptides affecting the transfer of juvenile hormones from males to females during mating in Spodoptera frugiperda

In the polyandric moth, Spodopterafrugiperda, juvenile hormone (JH) is transferred from the male accessory reproductive glands (AG) to the female bursa copulatrix (BC) during copulation (see Hassanien et al., 2014). Here we used the RNA interference technique to study the role of allatoregulating neuropeptides in controlling the synthesis and transfer of JH during mating. Knockdown of S. frugiperda allatostatin C (Spofr-AS type C) in freshly emerged males leads to an accumulation of JH in the AG beyond that in the control and mating results in a higher transport of JH I and JH II into the female BC. Knockdown of S. frugiperda allatotropin 2 (Spofr-AT2) significantly reduces the amount of JH in the AG as well as its transfer into the female BC during copulation. Knockdown of S. frugiperda allatostatin A (Spofr-AS type A) and S. frugiperda allatotropin (Spofr-AT; Hassanien et al., 2014) only slightly affects the accumulation of JH in the AG and its transfer from the male to the female. We conclude that Spofr-AS type C and Spofr-AT2 act as true allatostatin and true allatotropin, respectively, on the synthesis of JH I and JH II in the male AG. Moreover, both peptides seem to control the synthesis of JH III in the corpora allata of adult males and its release into the hemolymph.

Neuropeptides in insect mushroom bodies

Owing to their experimental amenability, insect nervous systems continue to be in the foreground of investigations into information processing in - ostensibly - simple neuronal networks. Among the cerebral neuropil regions that hold a particular fascination for neurobiologists are the paired mushroom bodies, which, despite their function in other behavioral contexts, are most renowned for their role in learning and memory. The quest to understand the processes that underlie these capacities has been furthered by research focusing on unraveling neuroanatomical connections of the mushroom bodies and identifying key players that characterize the molecular machinery of mushroom body neurons. However, on a cellular level, communication between intrinsic and extrinsic mushroom body neurons still remains elusive. The present account aims to provide an overview on the repertoire of neuropeptides expressed in and utilized by mushroom body neurons. Existing data for a number of insect representatives is compiled and some open gaps in the record are filled by presenting additional original data.

Families of allatoregulator sequences: a 2011 perspective1This review is part of a virtual symposium on recent advances in understanding a variety of complex regulatory processes in insect physiology and endocrinology, including development, metabolism, cold hardiness, food intake and digestion, and diuresis, through the use of omics technologies in the postgenomic era

Three different peptide families have been named “allatostatins” (ASTs), based on their initial purifications which were based on their ability to inhibit juvenile hormone (JH) biosynthesis. These include (i) a family of peptides that have a consensus C-terminal sequence Y/FXFGL-NH2; (ii) a family of peptides with a conserved C-terminal sequence W(X)6W-NH2; and(iii) a family of peptides with C-terminal sequence PISCF, some of which are C-terminally-amidated. Each allatostatin family has functions distinct and apart from the inhibition of JH biosynthesis. A peptide family known as the “allatotropins” serve to stimulate JH biosynthesis. This family of peptides also has been proven to exert multiple effects dependent on the species in question. Genome and peptidome projects are uncovering new members of these families and it is clear that these structures are not just confined to Insecta but are found in a range of invertebrates. The receptors for these neuropeptides have been identified and tested experimentally for specific ligand binding. The Y/FXFGLa-ASTs exert their action through galanin-like receptors, W(X)6Wa-ASTs through a sex peptide-binding receptor, and PISCF-ASTs through somatostatin-like receptors. These receptors are conserved through evolutionary time and are being identified in numerous invertebrates by way of genome projects.

Identification of cDNAs encoding allatotropin and allatotropin-like peptides from the silkworm, Bombyx mori

The cDNAs encoding allatotropin (AT) and allatotropin-like peptides (ATLPs) were isolated from the silkworm, Bombyx mori. Similar to those of the tobacco hornworm, Manduca sexta, four peptides (AT, ATLP1, ATLP2, and ATLP3) are present in three different variants generated by alternative splicing. RT-PCR analyses showed that these splice variants are expressed in the central nervous system with differing expression patterns in each ganglion. Immunohistochemistry using an anti-AT antibody confirmed that AT-expressing cells were located in these central nervous ganglia as well as in two large anterior cells of the frontal ganglia. Injection of synthetic AT and ATLP-1 into B. mori larvae increased the latency to feed, indicating that AT and ATLP might function in the regulation of feeding behavior in B. mori.

Exogenous and endogenous protease inhibitors in the gut of the fall armyworm larvae, Spodoptera frugiperda

A dose-dependent inhibition of endogenous trypsin and aminopeptidase occurs in the lumen of Spodoptera frugiperda after feeding L6 larvae exogenous inhibitors soybean trypsin inhibitor (SBTI), tosyl-L-lysine chloromethyl ketone-HCl (TLCK), or bestatin, respectively, for 3 days. TLCK inhibits trypsin in tissue extracts and in secretions more strongly than SBTI. The aminopeptidase released into the lumen (containing the peritrophic membrane) is strongly inhibited by bestatin, but the membrane-bound enzyme is not. A bound enzyme may be more resistant to an inhibitor than unbound. A cross-class elevation of aminopeptidase activity occurs in response to ingested trypsin inhibitor, but there was no cross-class effect of aminopeptidase inhibitor (bestatin) on trypsin activity. An endogenous trypsin and aminopeptidase inhibitor is present in the lumen and ventricular cells. The strength of the endogenous trypsin inhibition seems to be in the same range as that resulting from ingestion of the exogenous inhibitor SBTI. In some insect species, considerable trypsin secretion occurs in unfed as well as in fed animals, and endogenous protease inhibitors might function to protect the ventricular epithelium by inactivation of trypsin when less food is available.

Control of the release of digestive enzymes in the larvae of the fall armyworm, Spodoptera frugiperda

There is a basal level of enzyme activity for trypsin, aminopeptidase, amylase, and lipase in the gut of unfed larval (L6) Spodoptera frugiperda. Trypsin activity does not decrease with non-feeding, possibly because of the low protein levels in plants along with high amino acid requirements for growth and storage (for later reproduction in adults). Therefore, trypsin must always be present so that only a minimal protein loss via egestion occurs. Larvae, however, adjust amylase activity to carbohydrate ingestion, and indeed amylase activity is five-fold higher in fed larvae compared to unfed larvae. Gut lipase activity is low, typical of insects with a high carbohydrate diet. A flat-sheet preparation of the ventriculus was used to measure the release of enzymes in response to specific nutrients and known brain/gut hormones in S. frugiperda. Sugars greatly increase (>300%) amylase release, but starch has no effect. Proteins and amino acids have little or no effect on trypsin or aminopeptidase release. The control of enzyme release in response to food is likely mediated through neurohormones. Indeed, an allatostatin (Spofr-AS A5) inhibits amylase and trypsin, and allatotropin (Manse- AT) stimulates amylase and trypsin release. Spofr-AS A5 also inhibits ileum myoactivity and Manse-AT stimulates myoactivity. The epithelial secretion rate of amylase and trypsin was about 20% of the amount of enzyme present in the ventricular lumen, which, considering the efficient counter-current recycling of enzymes, suggests that the secretion rate is adequate to replace egested enzymes.

Allatotropin-related peptide in cockroaches: identification via mass spectrometric analysis of single identified neurons

The first insect allatotropin-related peptide (ATRP) was isolated from head extracts of the adult sphinx moth Manduca sexta [Kataoka H, Toschi A, Li JP, Carney RL, Schooley DA, Kramer SJ. Identification of an allatotropin from adult Manduca sexta. Science 1989;243:1481-3.]. Meanwhile ATRPs are known from different holometabolous insects but only a single ATRP could be identified from hemimetabolous insects [Paemen L, Tips A, Schoofs L, Proost P, Van Damme J, De Loof A. Lom-AG-myotropin: a novel myotropic peptide from the male accessory glands of Locusta migratoria. Peptides 1991;12:7-10.]. This means that the extensive analysis of neuropeptides from Leucophaea maderae and Periplaneta americana, which led to the discovery of many novel insect neuropeptides, did not result in the detection of any ATRP. In this study, we used another approach to find a cockroach ATRP by first identifying Manse-AT immunoreactive neurons in the terminal ganglion that can be stained by retrograde labeling and are suitable for dissection and subsequent mass spectrometric analysis. The peptidomic analysis of these putative ATRP neurons paved the way for the identification of the first cockroach ATRP. MALDI-TOF/TOF tandem mass spectrometry revealed a sequence identity with Locmi-AG-MT-1 which classifies this ATRP as a highly conserved neuropeptide. A mass spectrometric screening of the nervous system allowed the detection of ATRP-ion signals in different parts of the CNS of P. americana as well as L. maderae. The data obtained in this study will be incorporated in a map of peptidergic neurons from the CNS of the American cockroach, P. americana.

RNA interference with the allatoregulating neuropeptide genes from the fall armyworm Spodoptera frugiperda and its effects on the JH titer in the hemolymph

The juvenile hormone (JH) titer was measured by liquid chromatography-mass spectrometry (LC-MS) with electrospray ionization (ESI). Three JH homologs, the JH I-III were detected in various amounts in larvae, prepupae and virgin adult females of Spodoptera frugiperda. In penultimate larvae, the JH II and III titers were relatively high, but decreased continuously during the 3 days of that stage, whereas JH I was detectable at low amounts only on the first 2 days. At the beginning of the last larval stage almost no JH could be detected but thereafter, a consistent low amount of JH III was present until the prepupal stage. In adult virgins, the JH titer peaked on the 2nd and 6th day after the imaginal molt. The measured hormone titers well agree with general lepidopteran physiology, because in larvae the JH titer should be high to prevent premature metamorphosis, but decrease in last instar larvae before pupation, whereas in adults JH returns to control various aspects of reproduction. JH biosynthesis is thought to be the main factor influencing the JH titer in the hemolymph and there is evidence that neuropeptides either act stimulatory (allatotropins) or inhibitory (allatostatins) on this process. After silencing of either the allatostatin AS-C-type (Spofr/Manse-AS) or the allatotropin AT 2 (Spofr-AT 2) gene the transcript level was reduced in brain and gut of last instar larvae as well as of adult S. frugiperda. This suppression led to an increased JH titer in larvae, suggesting an allatostatic activity of both the peptides in this stage. As a result of the elevated hormone titer, the last larval stage was prolonged. In prepupae, the JH titer was decreased, but the animals pupated and molted normally. In adult female virgin moths the effect on the JH titer was inversely dependent on the age of the moths and varied among the JH homologs, indicating that the peptides act either allatostatic or allatotropic. For both peptides, gene silencing clearly reduced the oviposition rates of adult females.

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.

Juvenile hormonal activity of mono- and polyenehomobenzenes in Drosophila virilis, Spodoptera frugiperda and Araschnia levana

A series of mono- and polyenehomobenzenes was synthesised by a highly regioselective palladium-catalysed allylic alkylation of substituted and unsubstituted benzylic Grignard reagents employing catalytic amounts of catalyst and tested for juvenile hormone activity on the fruit fly Drosophila virilis Sturtevant (Diptera: Drosophilidae), on an important agricultural pest species, the fall armyworm Spodoptera frugiperda JE Smith (Lepidoptera: Noctuidae), and on the map butterfly Araschnia levana L. (Lepidoptera: Nymphalidae). In D. virilis only polyenehomobenzenes with a geranyl chain and a methyl, methoxy or isopropyl group at the para position of the aromatic ring displayed significant juvenile hormonal activity at low doses. A monoenehomobenzene and polyenehomobenzenes with longer allylic chains or without a substituted aromatic ring were not active. In S. frugiperda and in A. levana, a mono-, a di- and a tetraene displayed juvenile hormonal activity. In the lepidopteran species, a trend for the necessity of a substitution at position 4 of the phenyl group for high juvenile hormonal activity was also found.

Interactions between allatostatins and allatotropin on spontaneous contractions of the foregut of larval Lacanobia oleracea

The interactions between the activity of three neuropeptides, Manduca sexta allatostatin (Manse-AS), M. sexta allatotropin (Manse-AT) and cydiastatin 4, on the spontaneous foregut contractions of the tomato moth, Lacanobia oleracea, were investigated. Bioassays revealed that application of Manse-AS to the foregut at high concentrations (10(-7)M) stopped contractions completely, and this inhibition could not be reversed by Manse-AT. Conversely, Manse-AS could inhibit a Manse-AT stimulated tissue. In contrast, Manse-AT reversed the inhibition of foregut peristalsis by cydiastatin 4 (10(-7)M), and cydiastatin 4 counteracted the stimulation by Manse-AT. These results imply that the Manse-AS inhibitory effect is dominant over the stimulatory action of Manse-AT. However, when two peptides with opposing actions were added together, the overall effect on foregut peristalsis was determined by the relative concentrations of each peptide, suggesting that in these experiments, no peptide was dominant over the other. When Manse-AS and cydiastatin 4 were applied to foregut tissues simultaneously the overall effect was not significantly different to the individual peptides, i.e. there was no additive effect. This suggests that the individual activities of Manse-AS and cydiastatin 4 are suppressed by an undetermined mechanism in the presence of the other peptide. These results question the need for two structurally different allatostatins that have the same physiological effect on foregut peristalsis in L. oleracea larvae.

The role of allatostatins in juvenile hormone synthesis in insects and crustaceans

Allatostatins are pleiotropic neuropeptides for which one function in insects is the inhibition of juvenile hormone synthesis. Juvenile hormone, an important regulator of development and reproduction in insects, is produced by the corpora allata. Mandibular organs, the crustacean homologs of insect corpora allata, produce precursors of juvenile hormone with putatively similar functions. Three types of allatostatins in insects have been isolated: FGLamides, W(X)(6)Wamides, and PISCFs. All act rapidly and reversibly; however, although these types occur in all groups of insects studied, they act as inhibitors of juvenile hormone production in only some groups. Only the FGLamide-type peptides have been isolated in crustaceans, in which they may function to stimulate production of hormone by the mandibular glands, as occurs in early cockroach embryos. Much remains to be learned in order to understand the role of allatostatins in the modulation of hormone production.

Functional analysis of the allatostatin-A type gene in the cricket Gryllus bimaculatus and the armyworm Spodoptera frugiperda

Double-stranded RNA (dsRNA) gene interference is an efficient method to silence gene expression in a sequence specific manner. Here we show, that dsRNA targeting the allatostatin (AS)-A type (FGL/I/V-amide) gene of Gryllus bimaculatus (Ensifera, Gryllidae) and Spodoptera frugiperda (Lepidoptera, Noctuidae) injected into freshly moulted larvae or adult crickets and moths produced a rapid and long-lasting reduction in the mRNA levels in various tissues. The effect lasted up to 7 days. Following dsRNA injection, the juvenile hormone (JH) titers in the hemolymph were clearly raised in both species. AS-dsRNA injection induced a reduced body weight in larval and adult crickets and the imaginal moult was incomplete. Silencing allatostatin type-A expression also reduced the egg and testes development in crickets, and the oviposition rate was drastically diminished in both species.

Allatotropin-like peptide in Heliothis virescens: tissue localization and quantification

The mating-induced increase in juvenile hormone (JH) biosynthesis in Heliothis virescens females may be stimulated by production and/or release of stimulatory neuropeptides such as allatotropins (AT). Although there is evidence that H. virescens allatotropin may be structurally related to Manduca sexta allatotropin (Manse-AT), little is known of its occurrence and distribution in H. virescens. An enzyme-linked immunosorbent assay (ELISA) using a monoclonal antibody against Manse-AT was used to quantify concentrations of Manse-AT immunoreactivity in tissue extracts of H. virescens. In mated females, the highest concentrations of Manse-AT-like material occurred in the brain. The ventral nervous system and the accessory glands also contained considerable amounts of Manse-AT-like material, whereas concentrations were very low in ovaries, fat body, and flight muscle. The Manse-AT antibody was used for whole-mount immunocytochemistry to localize Manse-AT-immunoreactivity in the central nervous system. Several groups of Manse-AT-immunoreactive cells were discovered in the brain, subesophageal ganglion, and thoracic and abdominal ganglia of H. virescens females and males. Strong immunoreactivity was detected in axons going through the corpora cardiaca and branching out over the surface of the corpora allata. The presence of Manse-AT-like material in various locations in the central nervous system suggests that these peptides may have other as yet unknown functions. At the posterior margin of the terminal ganglion of males, a group of large immunoreactive cells was observed that was not present in females. Other than that, there were no obvious differences between virgin and mated females or males. The lack of differences in AT distribution in mated and virgin females suggests that mating-induced differences in female JH biosynthesis rates may be caused by changes in cellular response to AT at the level of the CA, rather than by changes in the amounts of AT acting on the CA.

Structural organization and expression analysis of the cDNA encoding allatotropin in the cotton bollworm, Helicoverpa armigera

The cDNA encoding allatotropin (AT), which stimulates juvenile hormone (JH) biosynthesis by the adult corpora allata (CA) of Lepidoptera, was cloned from Helicoverpa armigera (Har). Har-AT cDNA encodes a 135-amino acid polypeptide precursor containing a 13-amino acid AT sequence identical to Manduca sexta AT (Mas-AT). Three other H. armigera AT cDNAs encoding 172, 213, and 246 amino acids were also cloned. The four isoforms were produced by alternative splicing and termed Har-AT1, -AT2, -AT3, and -AT4, respectively. The basic organization of the Har-AT1 polypeptide precursor is similar to that of known ATs from other Lepidoptera with 80-97% identity at amino acid level. From the processing of the polypeptide precursor, three AT-like peptides named Har-ATL-I, -II, and -III were predicted. However, functions of the three AT-like peptides remain to be further elucidated. The evidence of Northern blots showed that a 0.7-kb Har-AT1 transcript is present in the brain and 0.7-kb Har-AT1 and 1.0-kb Har-AT4 transcripts are present in the abdominal ganglion (AG). Using quantitative RT-PCR, Har-AT mRNAs were detectable at much lower levels in other neural tissues, such as suboesophageal ganglion (SG) and thoracic ganglion (TG), but not in non-neural tissue, such as the epidermis, midgut, and fat body. We investigated the spatial and temporal expression of Har-AT gene in the central nervous system, and showed that expression patterns of four isoforms are distinct from each other. The results from immunocytochemistry showed that Har-AT transcript is located in the central nervous system, mainly in the brain and terminal abdominal ganglion (TAG). Thus, the AT gene products, besides affecting JH biosynthesis, might have broad influence on many biological processes in H. armigera.

Effects of Manduca allatotropin and localization of Manduca allatotropin-immunoreactive cells in earwigs

Manduca sexta allatotropin (Manse-AT) was first isolated on the basis of its ability to stimulate production of juvenile hormone in that insect. We examined whether this neuropeptide affects corpus allatum activity and visceral muscle contraction in adult females of the earwig, Euborellia annulipes. We also assessed the presence of allatotropin-like material in tissues using immunocytochemistry. Manse-AT at 1 nM to 10 muM stimulated juvenile hormone production in vitro by glands of low activity from 2-day virgin females. In glands of high activity from 12-day mated females, 1 and 100 nM allatotropin were effective, but 10 muM was not. Similarly, hindguts of 2-day and 12-day females significantly increased in motility in vitro in response to Manse-AT. A monoclonal antibody to Manse-AT was used to demonstrate allatotropin-like material throughout the nervous system of 2-day, virgin females. Immunoreactivity was most pronounced within varicosities of the corpora cardiaca and perisympathetic organs. No immunofluorescence was observed in gut tissue. Lastly, we showed that extract of retrocerebral complexes also enhanced in vitro hindgut motility from 2-day virgin females, in a dose-dependent manner. These results indicate material similar to M. sexta allatotropin in female earwigs and that such peptides may modulate juvenile hormone biosynthesis and visceral muscle contractions. Sensitivity to the peptides may change with physiological stage.

Immunostaining for allatotropin and allatostatin-A and -C in the mosquitoes Aedes aegypti and Anopheles albimanus

Confocal laser-scanning microscopy was used to carry out a comparative study of the immunostaining for three families of neuropeptides, viz., allatostatin-A (AS-A), allatostatin-C (AS-C) and allatotropin (AT), in adult female mosquitoes of Aedes aegypti and Anopheles albimanus. The specific patterns of immunostaining for each of the three peptides were similar in both species. The antisera raised against AT, AS-A, and AS-C revealed intense immunoreactivity in the cells of each protocerebral lobe of the brain and stained cells in each of the ventral ganglia and neuronal projections innervating various thoracic and abdominal tissues. Only the AS-A antiserum labeled immunoreactive endocrine cells in the midgut. The distribution of the peptides supports the concept that they play multiple regulatory roles in both species.

Immunocytochemical localization of an allatotropin in developmental stages of Heliothis virescens and Apis mellifera

Juvenile hormone biosynthesis by the corpora allata is regulated by stimulatory neuropeptides called allatotropins and inhibitory neuropeptides called allatostatins. This study localized Manduca sexta allatotropin-like material in developmental stages of the noctuid moth Heliothis virescens and the honeybee Apis mellifera. Immunocytochemical methods using both fluorescence-tagged antibodies and enzyme-coupled antibodies were used to stain the central nervous tissue of both species. H. virescens contains M. sexta allatotropin (Manse-AT)-like material consistently throughout larval development. The distribution patterns of Manse-AT immunoreactive cell bodies in the CNS persisted from one larval instar to the next. It will be discussed how larval Manse-AT distribution patterns differed from those in adults. The total number of AT-containing cells in brain and subesophageal ganglion gradually increased during larval development, whereas in the thoracic and abdominal ganglia, the number of AT-containing neurons remained constant. In the honeybee A. mellifera, Manse-AT immunoreactive cells were only found in a few brains from late last instar larvae (prepupae). Manse-AT-like material was present in a group of 6-8 cells in the pars intercerebralis. However, we did not find any Manse-AT-like material in brains of early last instar larvae, whose corpora allata (CA) are more sensitive to in vitro stimulation by Manse-AT than prepupal CA.

Manduca sexta allatotropin and the in vitro biosynthesis of juvenile hormone by moth corpora allata: a comparison of Pseudaletia unipuncta females from two natural populations and two selected lines

We compared the effects of Manduca sexta allatotropin (Manse-AT) on the rate of in vitro juvenile hormone (JH) biosynthesis by the corpora allata (CA) of different-aged virgin females from migrant (Quebec) and non-migrant (Azores) populations of the armyworm, Pseudaletia unipuncta, as well as from early- and late-calling lines selected from the Quebec population. There was a significant age x strain interaction, with the observed rates of JH biosynthesis in early adult life closely reflecting strain-specific differences in the age at onset of calling. In considering data for all ages combined, treatment of CA with Manse-AT resulted in a significant increase in the rate of JH biosynthesis for all but the Late strain, although significant differences for this strain were detected at certain ages. The CA of females from the Azores strain showed the strongest stimulation, with those of 0- and 1-day-old individuals displaying a singularly high degree of sensitivity. Selection for early- and late-calling lines resulted in significant differences in the temporal patterns of JH biosynthesis but did not markedly affect the sensitivity of the CA to Manse-AT. These findings are discussed within the context of the age-related differences observed in the rates of in vitro JH biosynthesis and JH haemolymph titers previously reported in comparisons of the Quebec and Azorean strains of the true armyworm.

Allatotropin regulation of juvenile hormone synthesis by the corpora allata from the lubber grasshopper, Romalea microptera

The in vitro synthesis of juvenile hormone (JH) by corpora allata (CA) from the lubber grasshopper (Romalea microptera) was stimulated by low concentrations of brain extract and this effect was reduced at higher concentrations, suggesting the presence of allatotropin (AT) and allatostatin (AST) factors in the brain. The AT activity of brain extracts caused a rapid and reversible stimulation and appeared to be a peptide(s). Reversed phase (C18) HPLC analysis of brain extracts disclosed two peaks of AT activity but no significant AST activity. Manse-AT, Schgr-NPF, and Locmi-FLRF had no effect on JH synthesis by lubber CA, indicating that the Rommi-AT factors are distinct from these peptides. High concentrations of Dippu-AST-7 and Grybi-AST-1 inhibited JH synthesis, implying that AST factors might be present in lubber grasshoppers. CA response to AT activity of brain extracts varied during the oviposition cycle ( approximately 35 days), with the maximum response occurring on days 16-18. AT activity of brain extracts also varied during the cycle, being highest on day 25. Our data suggest that the lubber CA is largely regulated by AT activity, and that JH synthesis reflects both CA response to AT activity and the level of AT activity in the brain.

Mas-allatotropin/Lom-AG-myotropin I immunostaining in the brain of the locust, Schistocerca gregaria

Mas-allatotropin (Mas-AT) and Lom-accessory gland-myotropin I (Lom-AG-MTI) are two members of a conserved family of insect neuropeptides, collectively termed allatotropins, which have diverse functions, ranging from stimulation of juvenile hormone secretion to myotropic effects on heart and hindgut. In addition, allatotropins appear to be abundant within the nervous system, suggesting neuroactive roles. To identify neurons in the insect brain suitable for a neurophysiological analysis of the roles of allatotropins, we used antisera against Mas-AT and Lom-AG-MTI to map allatotropin-immunoreactive neurons in the brain of a suitable insect, the locust Schistocerca gregaria. Both antisera revealed basically identical staining patterns throughout the locust brain with more than 12,500 immunostained interneurons per brain hemisphere. Neurosecretory cells were not labeled, and the retrocerebral complex was devoid of immunostaining. Prominent immunoreactive cell types include about 9,600 lamina monopolar neurons, medulla to lobula interneurons, local neurons of the antennal lobe, a giant interneuron of the mushroom body, projection neurons of the glomerular lobe to the mushroom body, and three systems of tangential neurons of the central complex. Several groups of neurons showed colocalization of Mas-AT- and gamma-aminobutyric acid immunostaining. Mass spectrometric analysis identified a peptide with a molecular mass identical to Lom-AG-MTI in all major parts of the locust brain but not in the retrocerebral complex. This study strongly suggests that Lom-AG-MTI is highly abundant in the locust brain, and is likely to play a neuroactive role in many brain circuits including all stages of sensory processing, learning and memory, and higher levels of motor control.

Characterization of a novel peptide with allatotropic activity in the fall armyworm Spodoptera frugiperda

A cDNA that encodes 53 amino acids, including one copy of the RVRGNPISCF-OH peptide, was cloned from Spodoptera frugiperda. This peptide strongly stimulates the synthesis and release of juvenile hormone (JH) in vitro by the corpora allata (CA) of S. frugiperda and was code-named Spofr-AT 2. Northern blotting and reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed that the preprohormone is expressed as one transcript in the brain, midgut (Mg) and ovary (Ov) in a tissue- and developmental-specific manner. Whole-mount in situ hybridization confirmed the gene expression in the suboesophageal ganglion (SOG) and in the ovary of adult females. Treating the CA with the synthetic peptide caused an up to tenfold increase in the release of JH. The stimulation was dose-dependent with an apparent EC(50) of ca. 10(-7) M. CA that were activated with Spofr-AT 2 could be inhibited by the addition of synthetic allatostatin type-C from Manduca sexta (Manse-AS). This is the first report on the presence and function of two different peptides with allatotropic activity in an insect species.

Expression and localization of the Spodoptera frugiperda allatotropin (Spofr-AT) and allatostatin (Spofr-AS) genes

Manduca sexta allatotropin and allatostatin were the first corpora allata (CA) regulating neuropeptides identified from Lepidoptera. Recently, we cloned the allatotropin (Spofr-AT) and the allatostatin (Spofr-AS) genes from the fall armyworm Spodoptera frugiperda. Using one-step RT-PCR for semi-quantification of the gene expression, we now demonstrate that three mRNA isoforms of the Spofr-AT gene and the Spofr-AS gene are expressed in brain, digestive tract, and reproductive organs of larvae, pupae, and adults in a time- and tissue-specific manner. Expression rates in the brain and in various parts of the digestive tract prove the dual role of the peptides as brain/gut (neuro)peptides. The functional meaning of ovarian and testes expression of the genes is not yet clear, although myoregulatory properties of the peptides are probable. The tissue-specific localization of the prohormone expression, as demonstrated by whole mount in situ hybridization, confirms the overall distribution of the prohormones as shown by RT-PCR and supports the pleiotropic functions of the peptides.

Regulation of juvenile hormone biosynthesis in Heliothis virescens by Manduca sexta allatotropin

In Heliothis virescens, reproduction is strictly dependent on juvenile hormone (JH). In females, mating induces a sharp increase in JH titers, which stimulates increased vitellogenin biosynthesis and higher rates of egg production. JH biosynthesis is presumably stimulated by production and/or release of stimulatory neuropeptides such as allatotropins. There is evidence that allatotropin of H. virescens may be structurally related to Manduca sexta allatotropin (Manse-AT). In a radiochemical in vitro assay, synthetic Manse-AT stimulated JH biosynthesis by corpora allata (CA) of virgin H. virescens females in a dose-dependent manner, but had no effect on CA activity in H. virescens males. In females, the CA showed a transient increase in sensitivity to Manse-AT shortly after mating. Several structurally related peptides stimulated CA activity to a similar extent as Manse-AT. Corpora allata activity was stimulated by a Ca2+ ionophore, A23187. A membrane-permeable Ca2+ chelator, BAPTA/AM, antagonized the stimulatory effects of Manse-AT, suggesting that Manse-AT may enhance CA activity by increasing intracellular Ca2+ concentration.

Juvenile hormone synthesis, metabolism, and resulting haemolymph titre in Heliothis virescens larvae parasitized by Toxoneuron nigriceps

Last instar larvae of the tobacco budworm, Heliothis virescens F., fail to pupate and have little 20-hydroxyecdysone when parasitized by Toxoneuron nigriceps (Viereck). In this paper, we extend these observations to juvenile hormone (JH) to determine if parasitism by this wasp affects other endocrine systems. To this end, we compared the production of JH by corpora cardiaca-corpora allata complexes (CC-CA), the metabolism of JH by haemolymph enzymes, and the haemolymph titre of JH in parasitized and non-parasitized control larvae of H. virescens during the last larval instar. CC-CA from parasitized and control larvae had similar peaks of JH synthesis on day 1 of the fifth instar, with JH II accounting for more than 90% of total JH in both groups. On subsequent days, JH synthesis dropped to undetectable levels more quickly in non-parasitized controls than in parasitized larvae. JH metabolism by haemolymph of parasitized and control animals increased from low levels on day 1 of the fifth instar to high levels on days 2 and 3 of the instar. JH metabolism was significantly higher in control larvae than in parasitized larvae. After day 3, JH metabolism decreased in both groups, but was significantly higher in parasitized larvae. The major metabolite of JH in both groups was JH acid, though traces of JH diol and JH acid diol were also detected. The haemolymph titre of JH in both groups peaked on day 1 of the fifth instar and, similar to the synthesis of JH by CC-CA, decreased more rapidly in control larvae. As a result, non-parasitized animals had significantly lower JH titres on day 2. The higher JH titres observed in parasitized larvae during the early fifth instar may contribute to their developmental arrest. The possible role of these JH alterations in the host developmental and metabolic redirection is discussed and a more comprehensive physiological model accounting for host-parasitoid interactions is proposed.

Identification of neuropeptides from brains of larval Manduca sexta and Lacanobia oleracea using MALDI-TOF mass spectrometry and post-source decay

The occurrence of neuropeptides in the brain of larvae of the tobacco hawkmoth, Manduca sexta, and tomato moth, Lacanobia oleracea, was investigated using matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry (MS) and post-source decay (PSD). Methanolic extracts of 100 brains separated by reversed-phase high performance liquid chromatography yielded numerous ion peaks, some of which were common to both species. In M. sexta six [M+H](+) ions were in agreement with peptides previously structurally characterised from M. sexta (FLRF-amides I, II and III, M. sexta allatostatin, CAP(2b) and myoinhibitory peptide VI), whereas a further five corresponded to other known lepidopteran peptides (cydiastatins 3 and 4, helicostatins 1 and 6 and helicokinin II). Of these the identities of FLRF-amide I, cydiastatins 3 and 4 and CAP(2b) were confirmed by PSD analysis. Fourteen [M+H](+) ions corresponding to known lepidopteran peptides (FLRF-amide I, cydiastatins 2, 3 and 4, helicostatins 1, 5, 6, 7 and 9, CCAP, CAP(2b), M. sexta allatostatin and myoinhibitory peptide VI) were measured in L. oleracea brain extracts. From this insect, cydiastatins 3 and 4, helicostatin 5 and FLRF-amide I were identified by PSD. These peptides had not previously been structurally characterised from L. oleracea.

Insect allatotropins belong to a family of structurally-related myoactive peptides present in several invertebrate phyla

Originally named for its ability to stimulate juvenile hormone production by lepidopteran corpora allata, allatotropin has emerged as a neuropeptide with multiple neural, endocrine and myoactive roles. This paper describes the experimental evidence for allatotropin action, its localization in several species of insects, and its multiple effects on a variety of different tissues that lead to increased hemolymph circulation and gut motility. The overall physiological effects may also include species-specific effects such as the regulation of nutrient absorption, modulation of the circadian cycle and migratory preparedness. In addition, we present evidence suggesting that allatotropins are members of a family of myoactive peptides found in several invertebrate phyla. Finally, we speculate that the myoactive properties of allatotropins are basal and it is likely that the stimulatory action of allatotropins on juvenile hormone synthesis evolved secondarily.

Stimulation of JH biosynthesis by the corpora allata of adult female Aedes aegypti in vitro: effect of farnesoic acid and Aedes allatotropin

Previous studies have demonstrated that the synthesis of juvenile hormone (JH) by the isolated corpora allata (CA) complex in vitro as well as the JH titer in the yellow fever mosquito Aedes aegypti are elevated before feeding and low after a blood meal. In the present study, we used an in vitro radiochemical assay to analyze the effect of farnesoic acid (FA) and Aedes allatotropin (Aedes-AT) on the biosynthesis of JH and methyl farnesoate (MF) by the isolated CA complex of A. aegypti adult female. CA complex from day-0 females (0-1 h after emergence) exhibited a low basal juvenile hormone III (JH III) biosynthetic activity and did not respond to either allatotropic or FA stimulation. However, incubation of CA complexes from newly emerged females with Aedes-AT plus FA resulted in very high production of JH III. This is the first report suggesting that allatotropin makes corpora allata in newly emerged females capable for JH biosynthesis. When we studied CA complexes dissected from females 1 day after emergence, the stimulatory action of Aedes-AT was strong and dose-dependent, with maximum stimulation in the range of 10(-8)-10(-9) mol l(-1), suggesting that Aedes-AT is indeed a true allatotropin (a molecule with allatotropic activity) in A. aegypti. The addition to the culture medium of 40 micro mol l(-1) FA, a JH precursor, resulted in a 9-fold increase in JH III biosynthesis in 2-, 4- and 6-day-old sugar-fed females. The two major labeled products synthesized by the stimulated CA complex were identified as JH III and MF by RP-HPLC and GC-MS. Treatment of CA complexes with FA, but not Aedes-AT, resulted in an increase in MF. Application of both Aedes-AT and FA to the CA complexes of 2-, 4- and 6-day-old females resulted in the same effects as FA alone. These data suggest that in sugar-fed females, FA and Aedes-AT exert different effects on the terminal steps in JH biosynthesis.

Vanessa cardui adipokinetic hormone (Vanca-AKH) in butterflies and a moth

Small neuropeptides of the adipokinetic hormone/red pigment-concentrating hormone (AKH/RPCH) family regulate energy metabolism in insects. Within lepidopterans, the nonapeptide Manduca sexta AKH (Manse-AKH) represents a widely occurring AKH, whereas the decapeptide Helze-HrTH (at first isolated from Heliothis zea) seems to be restricted to moths. Here we show that Vanca-AKH, a non-amidated undecapeptide which we recently found in the painted lady butterfly, Vanessa cardui, is also present in the retrocerebral complex of several other butterflies (Danaus plexippus, Precis coenia, Aglais urticae) and a moth (Spodoptera frugiperda). This study also demonstrates the power of modern nano-electrospray-quadrupole TOF tandem mass spectrometry in the sequence confirmation of peptides from minute amounts of small neuropeptides.

Molecular characterisation of cDNAs from the fall armyworm Spodoptera frugiperda encoding Manduca sexta allatotropin and allatostatin preprohormone peptides

Allatotropin (AT) is a 13-residue amidated neuropeptide, first isolated from pharate adult heads of the tobacco hornworm, Manduca sexta (Manse-AT), which strongly stimulates the biosynthesis of juvenile hormones (JH) in the corpora allata (CA) of adult moths. In Spodoptera frugiperda, a cDNA that encodes 134 amino acids, including an AT peptide, has been cloned. The S. frugiperda allatotropin mature peptide (Spofr-AT) [GFKNVEMMTARGFa] is identical to that isolated from M. sexta. The basic organization of the Spofr-AT precursor is similar to that of Agrius convolvuli, M. sexta, Pseudaletia unipuncta, and Bombyx mori with 83-93% amino acid sequence identity. The Spofr-AT gene is expressed in at least three mRNA isoforms with 134, 171 and 200 amino acids, differing from each other by alternative splicing. All allatostatins (AS) have an inhibitory action on the JH biosynthesis in the CA. A cDNA that encodes 125 amino acid residues including one copy of the Manse-AS peptide has been cloned from S. frugiperda (Spofr-AS; QVRFRQCYFNPISCF). The basic organization of the Spofr-AS precursor is similar to that of P. unipuncta with 85% amino acid sequence identity. Using one step RT-PCR for semi-quantification of the gene expression, we showed that the three mRNAs of the Spofr-AT gene and the Spofr-AS gene are expressed in brains of last instar larvae, prepupae, pupae, and adults of both sexes of S. frugiperda with variable intensity.

Myotropic effect of helicokinins, tachykinin-related peptides and Manduca sexta allatotropin on the gut of Heliothis virescens (Lepidoptera: Noctuidae)

Different insect neuropeptides (helicokinins, tachykinin-related and allatoregulating peptides) were investigated with regard to their myostimulatory effects using whole-gut preparations isolated from fifth instar Heliothis virescens larvae. The experiments demonstrated that representatives of all three peptide families are able to induce and amplify gut contractions in this species in a dose-dependent manner. Structure-activity studies (alanine scan, D-amino acid scan and truncated analogues) with the helicokinin Hez-K1 supported the finding, that the core sequence for biological activity of kinins is the amidated C-terminal pentapeptide (FSPWG-amide). Similar investigations with insect tachykinin isolated from Leucophaea madera (Lem-TRP1) revealed that the minimum sequence evoking a physiological gut response in H. virescens is the amidated hexapeptide (GFLGVR-amide), which represents the conserved amino acid sequence for Leucophaea TRPs in general. The peptide concentration causing a half-maximal gut contraction (EC(50)) for Lem-TRP1 was about 26 nM. Although the potency of Lem-TRP1 was 9-fold lower compared with Hez-KI (EC(50): 3 nM), the maximal tension of the gut obtained with Lem-TRP1 was 1.7-fold higher compared with Hez-KI. The EC(50) of Manduca sexta allatotropin (Mas-AT; 79 nM) was of lowest potency among all three peptides tested. In a pharmacological study, co-incubation experiments with Lem-TRP1, Hez-KI or Mas-AT and compounds interfering with signal transduction pathways were employed to investigate the mode of action of the myotropic effects of these peptides. Cadmium and the protein kinase C (PKC) inhibitor tamoxifen attenuated the contractile effects of all three peptides tested. The data suggest that in the gut muscle of H. virescens the myotropic peptides bind to G-protein-coupled receptors that cause contraction by promoting the entry of extracellular calcium mediated by a PKC involved pathway.

Biological activity of Manduca sexta allatotropin-like peptides, predicted products of tissue-specific and developmentally regulated alternatively spliced mRNAs

The insect neuropeptide, allatotropin (Manse-AT), exerts multiple functions including the stimulation of juvenile hormone (JH) biosynthesis in adults and the inhibition of active ion transport across the midgut epithelium of feeding larvae. The Manse-AT gene is expressed in multiple regions of the nervous system as three mRNAs that differ by alternative splicing. The specific mRNA isoform present differs in a tissue- and developmental-specific manner thus providing a mechanism for the regulated production of peptides specific to each isoform. These peptides are predicted to include three allatotropin-like (Manse-ATL) peptides that exhibit limited structural identity to Manse-AT and overlapping biological activities.

Degradation of Manduca sexta allatostatin and allatotropin by proteases associated with the foregut of Lacanobia oleracea larvae

The degradation of synthetic Manduca sexta allatostatin (Manse-AS) and allatotropin (Manse-AT), by enzymes of the foregut of larvae of the tomato moth, Lacanobia oleracea was investigated using reversed-phase high performance liquid chromatography (RP-HPLC) together with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and Edman sequencing. Metabolism of 1nmol Manse-AS by foregut extract (1microg protein) was rapid, t(1/2) approximately 5min, with two major products produced. Mass spectrometry of HPLC fractions identified cleavage products Manse-AS-(4-15) and Manse-AS-(6-15), which indicates enzymatic cleavage at the C-terminal side of arginine residues (R(3) and R(5)). This degradation of Manse-AS could be inhibited by up to 80% by the serine protease inhibitor aprotinin, but not PMSF, pepstatin, E64, EDTA, or 1,10-phenanthroline.M. sexta allatotropin was also rapidly degraded when incubated with foregut extract, t(1/2) approximately 8min, producing two metabolic products, one of which was identified as Manse-AT-(1-11), showing enzymatic cleavage at the C-terminal side of arginine (R(11)). The second product was identified as Manse-AT-(1-8). Hydrolysis of Manse-AT could only be partially inhibited by high doses of aprotinin (30%).

Enhanced haemolymph circulation by insect ventral nerve cord: hormonal control byPseudaletia unipunctaallatotropin and serotonin

The ventral diaphragm (VD) in many insects is a muscular membrane that essentially partitions a perineural sinus from the rest of the abdomen. In the true armyworm moth Pseudaletia unipuncta (Lepidoptera: Noctuidae) we describe how the VD is characterized by a series of aliform muscles inserted into a tissue matrix that is fused to the dorsal surface of the ventral nerve cord (VNC) itself. Because of this arrangement, the abdominal VNC can attain high rates of lateral oscillation, and is capable of directing haemolymph flow. We have previously demonstrated Manduca sexta allatotropin(Manse-AT)-like immunoreactivity throughout the central nervous system (CNS)in P. unipuncta, and that both Manse-AT and serotonin (5-HT) are dose-dependent stimulators of the dorsal vessel. Here we describe both Manse-AT- and 5-HT-like immunoreactivity associated with the VD. Furthermore,both Manse-AT and 5-HT are dose-dependent stimulators of the rates of VNC oscillation, and together are capable of maintaining highly elevated rates of VNC oscillation for extended periods of time. These data indicate that both the dorsal vessel and the VD/VNC are similarly modulated by both Manse-AT and 5-HT, and that VNC oscillations play a more active role in overall haemolymph circulation than previously recognized.

Juvenile hormone biosynthesis in the fall armyworm, Spodoptera frugiperda (Lepidoptera, Noctuidae)

The in vitro production of juvenile hormones (JH) was investigated by using corpora allata (CA) of larvae and corpora cardiaca-corpora allata (CC-CA) complexes of adult females of the fall armyworm Spodoptera frugiperda. In female moths, JH release was high compared to that in 5th and 6th instar larvae. Concentrations of 0.11-0.12 mM methionine, 180-200 mM Na(+), 5.8-8.3 mM K(+), 10-50 mM Ca(2+) and a pH range of 5.7-6.3 yielded optimal incorporation of L-[methyl-(3)H] methionine in vitro by CC-CA complexes. The highest hourly incorporation occurred during a 9-h incubation period following a 1.5-h lag-phase. JH release from CC-CA complexes of adult females was shown to be age-dependent with a peak value on day 2 (approx. 4 pmol h(-1) CA(-1)). By a combination of reversed phase (RP)- and normal phase (NP)-high performance liquid chromatography (HPLC), two major labelled products released by the complex were separated. One compound co-migrated with chemically synthesized JH II diol, the second compound with JH III diol. Only traces of JH II and III could be detected in some samples. Gland extracts also contained both the major radiolabelled products. Double labelling experiments using [3H]methionine and [14C]acetate confirmed their de novo synthesis in CC-CA complexes of female moths. The nature of chemically synthesized reference JH III diol was proved by LC-MS (ESI mass spectrometry) and 1H-NMR (nuclear magnetic resonance spectroscopy).

Cardioacceleratory effects of Manduca sexta allatotropin in the true armyworm moth, Pseudaletia unipuncta

Manduca sexta allatotropin (Manse-AT), a peptide originally isolated on the basis of its ability to stimulate juvenile hormone (JH) biosynthesis in the tobacco hornworm, is a potent in vitro stimulator of the corpora allata (CA) in Pseudaletia unipuncta (Lepidoptera: Noctuidae). At 10(-6)M, Manse-AT stimulated in vitro rates of JH biosynthesis by CA of day 0 and 6 adult females 15- and 10-fold respectively. Both Manse-AT and serotonin were also shown to be dose-dependent stimulators of heart rate in day 0, 3 and 6 adult males and females. Furthermore, analysis suggests that there are differences in both resting and Manse-AT-stimulated heart rates depending on age and rearing conditions.

Metabolism of Manduca sexta allatostatin by hemolymph of larvae of the tomato moth, Lacanobia oleracea

The degradation of synthetic Manduca sexta allatostatin (Manse-AS) by hemolymph from larvae of the tomato moth, Lacanobia oleracea was investigated using reversed phase-high performance liquid chromatography (RP-HPLC), and matrix assisted laser desorption ionisation-time of flight mass spectrometry. Metabolism of 1 nmole Manse-AS in diluted hemolymph was rapid, t(1/2) = 3.5 min, with a number of products produced. Mass spectrometry of HPLC fractions identified cleavage products, which indicated a sequential degradation of Manse-AS from the N-terminal to Manse-AS (7-15). The most abundant products identified were Manse-AS (5-15), (6-15), and (7-15). These metabolites were synthesized and assayed for biological activity on juvenile hormone (JH) biosynthesis in vitro. All three of the above deletion peptides showed allatostatin activity, but were not as potent as Manse-AS (1-15).

Structure elucidation and biological activity of an unusual adipokinetic hormone from corpora cardiaca of the butterfly, Vanessa cardui

A structurally unusual member of the adipokinetic hormone/red pigment-concentrating hormone peptide family was isolated from corpora cardiaca of the painted lady butterfly, Vanessa cardui. Its primary structure was assigned by Edman degradation and nano-electrospray-time-of-flight mass spectrometry as pQLTFTSSWGGK (Vac-AKH). Vac-AKH represents the first 11mer and the first nonamidated peptide in this family. The peptide shows significant adipokinetic activity in adult specimens of V. cardui. Injection of 10 pmol of synthetic Vac-AKH into 4-day-old decapitated males resulted in an approximately 150% increase of hemolymph lipids after 90 min. Half maximal adipokinetic activity was achieved with about 0. 1 pmol of Vac-AKH. During a 2-h incubation of corpora cardiaca/corpora allata complexes in medium containing 50 mM KCl, significant amounts of Vac-AKH were released from the glands.

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.