Piles of scats for piles of DNA: deriving DNA of lizards from their faeces

Non-invasive genetic sampling using scats has a well established role in conservation biology, but has rarely been applied to reptiles. Using scats from captive and wild Egernia stokesii (Squamata, Scincidae) we evaluated two storage and six DNA-extraction methods and the reliability of subsequent genotype and sequence data. Accurate genotype and sequence data were obtained from frozen and dried captive lizard scat DNA extracted using a QIAamp® DNA Stool Mini Kit and a modified Gentra® Puregene® method, but success rates were reduced for wild lizard scats. Wild E. stokesii eat more plants than their captive counterparts, possibly resulting in scat DNA extracts containing plant compounds that inhibit PCR-amplifications. Notably, reliable genotypes and sequences were obtained from wild E. stokesii scat DNA extracted using a Qiagen DNeasy® Plant Mini Kit, a method designed to remove plant inhibitory compounds. Results highlight the opportunity for using scat-derived DNA in lizard studies, particularly for species that deposit scats in piles.

Prostaglandins: Their role in egg-laying of the cricket Teleogryllus commodus

Mating of the Teleogryllus commodus female causes increased oviposition mediated by PGE(2), which is synthesized in the female's spermatheca from the precursor, arachidonic acid, in the presence of a PG-synthesizing complex. The latter, together with sperm, is transferred from the male to the female via a spermatophore. Only nanogram quantities of PGE(2) injected into oviduct are necessary to simulate mating-induced egg release.

Isolation of cockroach Phe-Gly-Leu-amide allatostatins from the termite Reticulitermes flavipes and their effect on juvenile hormone synthesis

Immunoreactivity to cockroach Diploptera punctata allatostatin-7 (Dippu AST-7) has been demonstrated previously in axons innervating the corpora allata of the termite Reticulitermes flavipes. This peptide and Dippu AST-11 inhibited juvenile hormone (JH) synthesis by corpora allata (CA) of brachypterous neotenic reproductives (secondary reproductives) of termites. The present study shows that R. flavipes CA are also inhibited by Dippu AST-2, AST-5, AST-8, and AST-9 at approximately the same rank order of potency as demonstrated in D. punctata. Another allatostatin from Periplaneta americana (Peram AST-12) also inhibits JH synthesis by R. flavipes CA. Sensitivity to the allatostatins is higher in glands with low rates of JH synthesis than in those with relatively high JH synthetic rates as has been demonstrated in CA from male and female secondary reproductives as well as in those from non-egg-laying and egg-laying females. The identical inhibitory effects of R. flavipes brain extract on CA from both D. punctata and R. flavipes and the isolation and identification of five cockroach allatostatins (Dippu AST-1, AST-2, AST-5, AST-8, and Peram AST-12) from termite brain extract reflect the close relationship between cockroaches and termites.

The roles of Dippu-allatostatin in the modulation of hormone release in Locusta migratoria

Dippu-allatostatins (ASTs) have pleiotropic effects in Locusta migratoria. Dippu-ASTs act as releasing factors for adipokinetic hormone I (AKH I) from the corpus cardiacum (CC) and also alter juvenile hormone (JH) biosynthesis and release from the corpus allatum (CA). Dippu-AST-like immunoreactivity is found within lateral neurosecretory cells (LNCs) of the brain and axons within the paired nervi corporis cardiaci II (NCC II) to the CC and the CA, where there are extensive processes and nerve endings over both of these neuroendocrine organs. There was co-localization of Dippu-AST-like and proctolin-like immunoreactivity within these regions. Dippu-ASTs increase the release of AKH I in a dose-dependent manner, with thresholds below 10(-11)M (Dippu-AST 7) and between 10(-13) and 10(-12)M (Dippu-AST 2). Both proctolin and Dippu-AST 2 caused an increase in the cAMP content of the glandular lobe of the CC. Dippu-AST 2 also altered the release of JH from the locust CA, but this effect depended on the concentration of peptide and the basal release rates of the CA. These physiological effects for Dippu-ASTs in Locusta have not been shown previously.

Endocrine and reproductive differences and genetic divergence in two populations of the cockroach Diploptera punctata

The viviparous cockroach, Diploptera punctata, has been a valuable model organism for studies of the regulation of reproduction by juvenile hormone (JH) in insects. As a result of its truly viviparous mode of reproduction, precise regulation of JH biosynthesis and reproduction is required for production of offspring, providing a model system for the study of the relationship between JH production and oocyte growth and maturation. Most studies to date have focused on individuals isolated from a Hawaiian population of this species. A new population of this cockroach was found in Nakorn Pathom, Thailand, which demonstrated striking differences in cuticle pigmentation and mating behaviours, suggesting possible physiological differences between the two populations. To better characterize these differences, rates of JH release and oocyte growth were measured during the first gonadotrophic cycle. The Thai population was found to show significantly earlier increases in the rate of JH release, and oocyte development as compared with the Hawaiian population. Breeding experiments to determine the degree of interfertility between the two populations demonstrated greatly reduced fertility in crosses between the two populations. Additionally, levels of genetic divergence between the two populations estimated by sequencing a fragment of the mitochondrial 16S rRNA gene were surprisingly high. The significant differences in physiology and mating behaviours, combined with the reduced interfertility and high levels of sequence divergence, suggest that these two populations of D. punctata are quite distinct, and may even be in the process of speciation. Moreover, these studies have important implications for the study of JH function in the reproductive cycle of insects, as differences in timing of rates of JH biosynthesis may suggest a process of heterochrony in reproduction between the two populations.

A putative farnesoic acid O-methyltransferase (FAMeT) orthologue in Drosophila melanogaster (CG10527): relationship to juvenile hormone biosynthesis?

Juvenile hormones (JHs) are key regulators of both metamorphosis and adult reproductive processes. Farnesoic acid O-methyltransferase (FAMeT) is thought to be an important enzyme in the JH biosynthetic pathway, catalyzing methylation of farnesoic acid (FA) to methyl farnesoate (MF). Previous evidence in other insects suggested that FAMeT is rate limiting and regulated by a neuropeptide family, the allatostatins. A full-length cDNA encoding a 296 amino acid putative FAMeT has been isolated. A recombinant (r)FAMeT was cloned, expressed and a specific antiserum generated. rFAMeT was assayed for enzymatic activity using a radiochemical assay. In this assay, no activity was detected either with rFAMeT alone or when added to a corpus allatum CA extract. Immunohistochemical analysis was used to confirm the presence of FAMeT in the CA of Drosophila melanogaster ring gland. Analysis of MF, JHIII and JHB3 release in wild type and mutant stocks in the presence and absence of Drome AST (PISCF-type) suggest that Drosophila FAMeT has little if any effect on sesquiterpenoid biosynthesis. Drome AST appears to have a select effect on JH bisepoxide biosynthesis and not MF or JHIII. Additional analysis of MF, JHIII and JHB3 release in strains with a deficiency or decrease of FAMeT compared to wild type shows no significant decrease in MF, JHIII or JH bisepoxide synthesis. Deficiency strains that reduce the level of FAMeT showed reduced longevity relative to wildtype but this result may be due to other genetic influences.

Comparative genomic analysis of allatostatin-encoding (Ast) genes in Drosophila species and prediction of regulatory elements by phylogenetic footprinting

The role of the YXFGLa family of allatostatin (AST) peptides in dipterans is not well-established. The recent completion of sequencing of genomes for multiple Drosophila species provides an opportunity to study the evolutionary variation of the allatostatins and to examine regulatory elements that control gene expression. We performed comparative analyses of Ast genes from seven Drosophila species (Drosophila melanogaster, Drosophila simulans, Drosophila ananassae, Drosophila yakuba, Drosophila pseudoobscura, Drosophila mojavensis, and Drosophila grimshawi) and used phylogenetic footprinting methods to identify conserved noncoding motifs, which are candidates for regulatory regions. The peptides encoded by the Ast precursor are nearly identical across species with the exception of AST-1, in which the leading residue may be either methionine or valine. Phylogenetic footprinting predicts as few as 3, to as many as 17 potential regulatory sites depending on the parameters used during analysis. These include a Hunchback motif approximately 1.2 kb upstream of the open reading frame (ORF), overlapping motifs for two Broad-complex isoforms in the first intron, and a CF2-II motif located in the 3'-UTR. Understanding the regulatory elements involved in Ast expression may provide insight into the function of this neuropeptide family.

Evolutionary selective trends of insect/mosquito antimicrobial defensin peptides containing cysteine-stabilized alpha/beta motifs

Insect defensins containing cysteine-stabilized alpha/beta motifs (Cs-alpha/beta defensin) are cationic, inducible antibacterial peptides involved in humoral defence against pathogens. To examine trends in molecular evolution of these antimicrobial peptides, sequences similar to the well-characterized Cs-alpha/beta defensin peptide of Anopheles gambiae, using six cysteine residues as landmarks, were retrieved from genomic and protein databases. These sequences were derived from different orders of insects. Genes of insect Cs-alpha/beta defensin appear to constitute a multigene family in which the copy number varies between insect species. Phylogenetic analysis of these sequences revealed two main lineages, one group comprising mainly lepidopteran insects and a second, comprising Hemiptera, Coleoptera, Diptera and Hymenoptera insects. Moreover, the topology of the phylogram indicated dipteran Cs-alpha/beta defensins are diverse, suggesting diversity in immune mechanisms in this order of insects. Overall evolutionary analysis indicated marked diversification and expansion of mature defensin isoforms within the species of mosquitoes relative to non-mosquito defensins, implying the presence of finely tuned immune responses to counter pathogens. The observed higher synonymous substitution rate relative to the nonsynonymous rate in almost all the regions of Cs-alpha/beta defensin of mosquitoes suggests that these peptides are predominately under purifying selection. The maximum-likelihood models of codon substitution indicated selective pressure at different amino acid sites in mosquito mature Cs-alpha/beta defensins is differ and are undergoing adaptive evolution in comparison to non-mosquito Cs-alpha/beta defensins, for which such selection was inconspicuous; this suggests the acquisition of selective advantage of the Cs-alpha/beta defensins in the former group. Finally, this study represents the most detailed report on the evolutionary strategies of Cs-alpha/beta defensins of mosquitoes in particular and insects in general, and indicates that insect Cs-alpha/beta defensins have evolved by duplication followed by divergence, to produce a diverse set of paralogues.

Phe-Gly-Leu-amide allatostatin in the termite Reticulitermes flavipes: content in brain and corpus allatum and effect on juvenile hormone synthesis

In the subterranean termite Reticulitermes flavipes, allatostatins (ASTs) with the C-terminus Phe-Gly Leu-amide were localized by immunocytochemistry with antibody against a cockroach AST, Dippu AST-7. AST-immunoreactivity occurred in the corpus cardiacum and corpus allatum and in the lateral and medial neurosecretory cells of the brain that innervate these organs as well as in many other nerve cells of the brain. This was observed in workers, nymphs, soldiers and secondary reproductives. A radioimmunoassay, using anti-Dippu AST-11, demonstrated about 40 fmole equivalents of AST in brains of soldiers and secondary reproductives. The product of the corpora allata in this species was determined to be juvenile hormone III. Its synthesis by corpora allata of secondary reproductives, determined by in vitro radiochemical assay, was inhibited in a dose-dependent fashion by two cockroach allatostatins, Dippu AST-7 and Dippu AST-11. Thus, as in cockroaches and crickets, allatostatin-containing nerves innervate the corpora allata of this termite species and their production of juvenile hormone is inhibited by these neuropeptides.

A study of signal transduction for the two diuretic peptides of Diploptera punctata

We investigated second messengers involved in the action of the CRF-related peptide Dippu-DH46 and the calcitonin-like peptide Dippu-DH31 in Diploptera punctata. Dippu-DH46 causes a dose-dependent increase in intracellular cAMP levels, its diuretic activity is mimicked by cAMP agonists, but is attenuated by Rp-cAMPS. Dippu-DH46 acts synergistically with kinins and thapsigargin; both mobilize intracellular Ca2+. Dippu-DH46 also acts synergistically with cAMP agonists, and its effect is inhibited by a PKC inhibitor, suggesting it also activates intracellular Ca2+. Dippu-DH31 has no effect on cAMP levels and its activity is not blocked by cAMP agonists. Neither peptide stimulated cGMP levels in a dose-dependent manner, nor does cGMP have any effect on fluid secretion.

Comparative immunohistochemistry and cellular distribution of farnesoic acid O-methyltransferase in the shrimp and the crayfish

Farnesoic acid O-methyltransferase (FAMeT) catalyzes the conversion of farnesoic acid (FA) to methylfarnesoate (MF) by the mandibular organ (MO) of crustaceans. Here we report the cellular localization of FAMeT and radiochemical assay of endogenous FAMeT activity in shrimp (Metapenaeus ensis) and crayfish (Procambarus clarkii) tissues. As in the eyestalk (ES), FAMeT is concentrated in specific neurosecretory cells of the ventral nerve cord (VNC) whereas only weak FAMeT immunoreactivity was observed in the MO. FAMeT was also detected in the ventral nerve cord, heart (HET), eyestalk, and muscle of the juvenile shrimp. Although the VNC shows the greatest FAMeT immunoreactivity, the heart extract exhibited the highest FAMeT enzymatic activity. These results suggest that FAMeT in the VNC may be inactive or inactivated at the stages of development tested. Contrary to the previous reports in other crustaceans, MO extract in shrimp shows only low FAMeT activity. The eyestalk, epidermis, ovary and testis show appreciable FAMeT activity. The presence of FAMeT in neurosecretory cells of VNC and eyestalk of shrimp and crayfish implies a possible interaction of FAMeT with the eyestalk CHH-family of neuropeptides. The widespread activity of FAMeT suggests that it has a wide spectrum of action in many tissues that contribute to the function and regulation of MF synthesis in shrimp and crayfish.

Localization and physiological effects of RFamides in the corpora allata of the cockroach Diploptera punctata in relation to allatostatins

The distribution of FMRFamide immunoreactivity in the brain-retrocerebral complex of adult female Diploptera punctata was examined. Immunoreactivity was observed in the brain and corpus allatum as well as in the corpus cardiacum. Immunoreactivity co-localized with allatostatin immunoreactivity within several lateral neurosecretory cells of the brain and in their endings within the corpus allatum. By in vitro radiochemical assay of juvenile hormone release, the effect of two native D. punctata RFamides, an FLRFamide (Leucomyosuppressin) and an FIRFamide were examined. The latter, for which the sequence (SKPANFIRFamide) is reported here, stimulated juvenile hormone release but acted only on corpora allata from females at the end of vitellogenesis (day 6). The interaction of these two RFamides and three D. punctata allatostatins, Dippu-AST 2, 5, and 7 were similarly examined. Only Dippu-AST 2 stimulated release of RFamides from the corpora allata and only on day 6 whereas both RFamides were able to attenuate the inhibitory activity of Dippu-AST 2.

Methyl farnesoate and juvenile hormone production in embryos of Diploptera punctata in relation to innervation of corpora allata and their sensitivity to allatostatin

Corpora allata (CA) of embryos of Diploptera punctata have been previously shown to produce JH III. We have re-examined sesquiterpenoid biosynthesis throughout embryonic development and have found that early embryos produce both methyl farnesoate (MF) and JH III; as development proceeds, less MF and more JH is produced. The cockroach allatostatin peptide Dippu-allatostatin (AST) 7 inhibits sesquiterpenoid production by CA of mid to late embryos whereas it exerts a dose-dependent stimulatory effect in early embryos. This stimulatory effect is particularly apparent on MF biosynthesis. CA become innervated by allatostatin-containing nerves in early embryos (35% development). Shortly thereafter, the allatostatin-containing innervation of the CA appears complete.

Characterization of an additional molt inhibiting hormone-like neuropeptide from the shrimp Metapenaeus ensis

We have identified a second form of the type-II neuropeptide encoding a molt inhibiting hormone-like (MeeMIH-B) neuropeptide. MeeMIH-B showed only a 70% amino acid identity to the MIH-A (formerly MIH) isolated from the same species, suggesting a possible different function of the deduced neuropeptide. Like other neuropeptide members of the CHH family, the MIH-B gene consists of three exons separated by two introns. The levels of MIH-B mRNA transcript in the eyestalk decrease in the initial phase of gonad maturation and increase towards the end of maturation. The drop in MIH-B level suggests an inhibitory role for this neuropeptide in the initiation of vitellogenesis. MIH-B transcripts can also be detected in the brain, thoracic ganglion and ventral nerve cord. Together with the CHH-B peptide that we have previously described, this is the second peptide of the CHH family that can also be identified in the ventral nerve cord and in the XOSG complex. A recombinant MIH-B was produced and a polyclonal antibody against rMIH-B was subsequently generated. Specific anti-rMIH-B antiserum recognized the presence of MIH-B in the sinus gland, X-organs, as well as a giant neuron of the ventral nerve cord. Injection of rMIH-B delayed the molting cycle of the maturing female. Taken together, the results of this study suggest that a drop in MIH-B level may be required for the delay in the molting of the maturing females.

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.

Expression of allatostatin in the oviducts of the cockroach Diploptera punctata

The cockroach allatostatins (Y/FXFGL/Ia ASTs) are a ubiquitous family of peptides in the invertebrates. They affect numerous physiological processes including the inhibition of juvenile hormone III (JH) biosynthesis, inhibition of muscle contraction, inhibition of ovarian ecdysteroid biosynthesis and inhibition of vitellogenin (Vg) release from the fat body. We have developed and optimized a sensitive and specific quantitative competitive reverse transcriptase polymerase chain reaction (QC-RT-PCR) method to quantify Diploptera punctata AST (Dippu-AST) expression. Using this technique we show that tissues of both lateral and common oviducts and the ovary express message for Dippu-AST. Moreover, the pattern of expression observed in the oviducts and ovary is strikingly similar with significant changes occurring during the reproductive cycle. Specifically, expression of AST is drastically reduced during the time of maximal vitellogenin (Vg) uptake, with higher levels measured prior to and following vitellogenesis. Furthermore, using immunocytochemistry, we have shown Dippu-AST-like-immunoreactivity in the terminal abdominal ganglion, as well as in ventral nerve 7, some branches of which innervate the common and lateral oviducts with other branches innervating the bursa copulatrix and brood sac of mated female D. punctata. The pattern of Dippu-AST expression and immunocytochemical staining suggests that ASTs function, in part, to regulate the cycle of vitellogenesis in mated female D. punctata.

Function and cellular localization of farnesoic acid O-methyltransferase (FAMeT) in the shrimp, Metapenaeus ensis

The isoprenoid methyl farnesoate (MF) has been implicated in the regulation of crustacean development and reproduction in conjunction with eyestalk molt inhibiting hormones and ecdysteroids. Farnesoic acid O-methyltransferase (FAMeT) catalyzes the methylation of farnesoic acid (FA) to produce MF in the terminal step of MF synthesis. We have previously cloned and characterized the shrimp FAMeT. In the present study, recombinant FAMeT (rFAMeT) was produced for bioassay and antiserum generation. FAMeT is widely distributed in shrimp tissues with the highest concentration observed in the ventral nerve cord. Interestingly, an additional larger protein in the eyestalk also showed immunoreactivity to anti-FAMeT serum. FAMeT was localized in the neurosecretory cells of the X-organ-sinus gland complex of the eyestalk. As shown by RT-PCR, FAMeT mRNA is constitutively expressed throughout the molt cycle in the eyestalk and the ventral nerve cord. To show that our cloned gene product had FAMeT activity, we demonstrated that expressed rFAMeT gene product catalyzed the conversion of FA to MF in a radiochemical assay. The ubiquitous distribution of FAMeT suggests that this enzyme is involved in physiological processes in addition to gametogenesis, oocyte maturation and development and metamorphosis of the shrimp. We hypothesize that FAMeT directly or indirectly (through MF) modulates the reproduction and growth of crustaceans by interacting with the eyestalk neuropeptides as a consequence of its presence in the neurosecretory cells of the X-organ-sinus gland.

Characterization and baculovirus-directed expression of a myosuppressin encoding cDNA from the true armyworm, Pseudaletia unipuncta

Insect myosuppressins are a highly conserved sub-family of peptides which are primarily characterized by the ability to suppress contraction of visceral muscles in a variety of insect species. We have isolated a cDNA from the true armyworm, Pseudaletia unipuncta, that encodes a prohormone containing a peptide identical to ManducaFLRFamide. We have shown that this myosuppressin gene appears to be expressed in late larval and adult insects. In Manduca sexta, a number of extended-FLRFamide peptides have previously been purified including ManducaFLRFamide, F7D (DPSFLRFamide), F7G (GNSFLRFamide) and two larger peptides F24 and F39 that contain the shorter ManducaFLRFamide sequence at their C-terminus. Comparison with the true armyworm prepropeptide characterized here identifies F24 and F39 as partially processed products from the same precursor. Expression in the true armyworm was shown by in situ hybridization to occur in over 150 cells throughout the adult brain and nerve cord, and also to occur in both open and closed endocrine type cells of the gut. Overexpression of the P. unipuncta FLRFamide cDNA from a baculovirus vector in cabbage looper caterpillars was used to assess the potential for myosuppressin expression as a means of enhancing virus efficacy. Viral expression of the armyworm prohormone cDNA resulted in raised levels of RFamide-like products in the hemolymph of infected insects, but the products were found to be chemically distinguishable from authentic mature peptide and probably represent partially processed hormone.

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.

Biosynthetic pathway of insect juvenile hormone III in cell suspension cultures of the sedge Cyperus iria

In most insect species, juvenile hormones regulate critical physiological processes such as metamorphosis and reproduction. In insects, these sesquiterpenoids are synthesized by retrocerebral endocrine organs, the corpora allata, via the classical mevalonate (MVA) pathway. One of these compounds, juvenile hormone III (JH III), has also been identified in the sedge Cyperus iria. In higher plants, biosynthesis of the sesquiterpenoid backbone may proceed through two distinct pathways: the MVA pathway or the 2C-methyl erythritol 4-phosphate pathway or through a combination of both pathways. Cell suspension cultures of C. iria were used to elucidate the biosynthetic pathway of JH III in the plant. Enzyme inhibition and labeling studies conclusively demonstrated that the biosynthesis of the sesquiterpenoid backbone of JH III proceeds via the MVA pathway. Inhibitor and precursor feeding studies also suggest that later steps of JH III biosynthesis in C. iria are similar to the insect pathway and that the final enzymatic reaction in JH III biosynthesis is catalyzed by a cytochrome P(450) monooxygenase.

Biosynthetic pathway of insect juvenile hormone III in cell suspension cultures of the sedge Cyperus iria

In most insect species, juvenile hormones regulate critical physiological processes such as metamorphosis and reproduction. In insects, these sesquiterpenoids are synthesized by retrocerebral endocrine organs, the corpora allata, via the classical mevalonate (MVA) pathway. One of these compounds, juvenile hormone III (JH III), has also been identified in the sedge Cyperus iria. In higher plants, biosynthesis of the sesquiterpenoid backbone may proceed through two distinct pathways: the MVA pathway or the 2C-methyl erythritol 4-phosphate pathway or through a combination of both pathways. Cell suspension cultures of C. iria were used to elucidate the biosynthetic pathway of JH III in the plant. Enzyme inhibition and labeling studies conclusively demonstrated that the biosynthesis of the sesquiterpenoid backbone of JH III proceeds via the MVA pathway. Inhibitor and precursor feeding studies also suggest that later steps of JH III biosynthesis in C. iria are similar to the insect pathway and that the final enzymatic reaction in JH III biosynthesis is catalyzed by a cytochrome P(450) monooxygenase.

The Drosophila melanogaster homologue of an insect calcitonin-like diuretic peptide stimulates V-ATPase activity in fruit fly Malpighian tubules

The Drosophila melanogaster homologue of an insect calcitonin-like diuretic hormone was identified in a BLAST search of the Drosophila genome database. The predicted 31-residue amidated peptide (D. melanogaster DH(31); Drome-DH(31)) was synthesised and tested for activity on fruit fly Malpighian tubules. It increases tubule secretion by approximately 35 % of the response obtained with a myokinin from the housefly Musca domestica (muscakinin; Musdo-K) and has an EC(50) of 4.3 nmol l(−)(1). The diuretic activities of Drome-DH(31) and Musdo-K were additive when tested at threshold and supra-maximal concentrations, which suggests that they target different transport processes. In support of this, Drome-DH(31) increased the rate of secretion by tubules held in bathing fluid with a reduced Cl(−) concentration, whereas Musdo-K did so only in the presence of Drome-DH(31). Stimulation with Drome-DH(31) increased the lumen-positive transepithelial potential in the main secretory segment of the tubule. This was attributed to activation of an apical electrogenic proton-translocating V-ATPase in principal cells, since it was associated with hyperpolarisation of the apical membrane potential and acidification of secreted urine by 0.25 pH units. Exogenous 8-bromo-cyclic AMP and cyclic GMP increased tubule secretion to the same extent as Drome-DH(31) and, when tested together with the diuretic peptide, their activities were not additive. Stimulation with Drome-DH(31) resulted in a dose-dependent increase in cyclic AMP production by tubules incubated in saline containing 0.5 mmol l(−)(1) 3-isobutyl-1-methylxanthine, whereas cyclic GMP production was unchanged. Taken together, the data are consistent with Drome-DH(31) activating an apical membrane V-ATPase via cyclic AMP. Since the K(+) concentration of the secreted urine was unchanged, it is likely that Drome-DH(31) has an equal effect on K(+) and Na(+) entry across the basolateral membrane.

Flights of fancy: possible roles of allatostatin and allatotropin in migration and reproductive success of Pseudaletia unipuncta

Many invertebrate neuropeptides have recently been identified and there is evidence that the same compound may serve different roles in different species and/or multiple functions within a given species. However, until the relevant receptors or 'knock out' animals, lacking the neuropeptide of interest, become available it will be difficult to clarify the precise inter- and intraspecific functions of these neuropeptides. In the present paper, we argue that until these tools are available a more meaningful understanding of the roles of neuropeptides could be obtained by carrying out experiments within an ecological context. Furthermore, this approach would allow us to generate hypotheses that could be rigorously tested when more sophisticated techniques are developed. We discuss these ideas using our interdisciplinary research on the reproductive biology of the true armyworm, Pseudaletia unipuncta, as a case study.

Molecular characterization of a cDNA from the true armyworm Pseudaletia unipuncta encoding Manduca sexta allatotropin peptide(1)

Allatotropin (AT) is an insect neuropeptide isolated from the tobacco hornworm, Manduca sexta, stimulates juvenile hormone (JH) biosynthesis by the corpora allata. A cDNA isolated from the true armyworm, Pseudaletia unipuncta, encodes a 135 amino acid AT precursor peptide which contains the AT peptide, with processing sites necessary for its endoproteolytic cleavage and amidation, plus two additional peptides of unknown function. The encoded AT peptide is identical to that isolated from M. sexta and Agrius convolvuli. Southern blot analysis indicated that AT is a single copy gene per haploid genome and is present in two allelic forms. A single transcript of approximately 1.5 kilobases was detected by northern blot analysis. The expression of the AT gene was analyzed during development from sixth instar larvae to five day-old moths. Initial expression was observed in late pupae and this expression was maintained throughout the adult stages in both sexes. In one day-old moths, expression was at its lowest level of the stages that express AT mRNA but levels increased in day 3 and day 5 adults. This pattern of AT expression in adult P. unipuncta moths mirrors that of JH biosynthesis and supports the notion that AT may act in the adult stages. Immunohistochemistry and in situ hybridization revealed that AT expression was localized to numerous structures of the nervous system, suggesting that AT may have functions distinct from regulation of JH biosynthesis.

Terminal steps in JH biosynthesis in the honey bee (Apis mellifera L. ): developmental changes in sensitivity to JH precursor and allatotropin

Juvenile hormone (JH) is considered the prime endogenous signal for the induction of queen development in honey bees (Apis mellifera L.). At the beginning of the last (5th) larval stadium, worker corpora allata synthesize less JH than queen corpora allata as a consequence of a limited production of JH precursors and a caste- and stage-specific block of the terminal step in JH biosynthesis. As previously shown, the Manduca sexta allatotropin stimulates JH biosynthesis in honey bee corpora allata in a dose-dependent and reversible manner, but can not overcome the stage-specific block in the terminal step of JH biosynthesis that is typical for worker early 5th instars. In experiments with M. sexta allatotropin and with the JH precursor farnesoic acid, we found characteristic stage-specific differences in their effects on JH biosynthesis. From the end of the spinning stage on, corpora allata could be stimulated by farnesoic acid to a much higher extent than in earlier developmental stages, suggesting a sudden increase in epoxidase activity. Manduca sexta allatotropin, however, stimulated corpora allata activity until the end of the spinning stage, at which time the corpora allata become suddenly insensitive. These data suggest that in worker larvae, important changes in the regulation of the terminal enzymatic steps in JH biosynthesis occur at the transition from the spinning stage to the prepupal stage. However, the analysis of in vitro activities of the involved enzymes, O-methyltransferase and methyl farnesoate epoxidase, remained inconclusive.

Injection of Dip-allatostatin or Dip-allatostatin pseudopeptides into mated female Diploptera punctata inhibits endogenous rates of JH biosynthesis and basal oocyte growth

Studies on the catabolism of allatostatins (ASTs) provided the rationale for the design of a series of Dip-allatostatin-derived pseudopeptide mimetic analogues. In vitro, the Dip-ASTs and pseudopeptides show varying degrees of resistance to catabolism and all show significant inhibition of juvenile hormone (JH) biosynthesis. This study was undertaken to determine whether potent Dip-ASTs and/or their pseudopeptide mimetic counterparts caused 'allatostatic' effects in vivo following injection into mated female Diploptera punctata. Animals injected with aqueous solvent or Dip-AST 7(1-7) N-terminal fragment, which excludes the active core region of the ASTs, were used as controls. An in vitro radiochemical assay revealed that injection of Dip-AST 5, 7 or pseudopeptide analogues 397-2 or AST(b)&phi;2 significantly inhibited the biosynthesis of JH (P<0.05). The results also indicate that basal oocyte growth was significantly inhibited by injection of these same compounds, with the exception of Dip-AST 7 (P<0.05). Analogues 396-1 and 419 did not significantly inhibit rates of JH biosynthesis but did significantly inhibit the growth of basal oocytes. Analyses of feeding, excretion and food absorption/utilization patterns of these same animals suggested that these compounds are not toxic to the insect; rather they directly inhibit the biosynthesis of JH by the corpora allata, and reduce the rate of growth of basal oocytes. Disruption of critical reproductive and/or developmental processes by pseudopeptide analogues of the ASTs could provide novel and selective strategies for future insect pest management.

Partial characterization of a putative allatostatin receptor in the midgut of the cockroach Diploptera punctata

Dippu-allatostatins (Dippu-ASTs) are a family of peptides originally isolated from the cockroach Diploptera punctata which appear to be pleiotropic in function. All members of the family are able to inhibit the biosynthesis of juvenile hormone by corpora allata in vitro. In addition, ASTs are able to modulate the contraction of visceral muscles and may play a role in the regulation of digestive enzyme secretion by the midgut. We have identified a putative AST receptor in the cockroach midgut using a radioligand-binding assay. (125)I-Dippu-AST 7 binding to midgut membranes was specific, saturable, and reversible. The midgut appears to contain a single class of binding sites for Dippu-AST 7, with K(d) of 20.9 +/- 3.6 nM and B(max) of 1.8 +/- 0.15 pmol. mg(-1) membrane protein. The relative affinity of the 13 members of the Dippu-AST family was determined using a single-point competitive binding assay. Dippu-AST 7 and 2 appear to have higher affinity for the midgut AST receptor than Dippu-AST 5, 9, 10, or 11. Other Dippu-ASTs were unable to compete with (125)I-Dippu-AST 7 for binding, even at high concentration.

Cockroach diuretic hormones: characterization of a calcitonin-like peptide in insects

Insect diuretic hormones are crucial for control of water balance. We isolated from the cockroach Diploptera punctata two diuretic hormones (DH), Dippu-DH(31) and Dippu-DH(46), which increase cAMP production and fluid secretion in Malpighian tubules of several insect species. Dippu-DH(31) and -DH(46) contain 31 and 46 amino acids, respectively. Dippu-DH(46) belongs to the corticotropin-releasing factor (CRF)-like insect DH family, whereas Dippu-DH(31) has little sequence similarity to the CRF-like DH, but is similar to the calcitonin family. Dippu-DH(46) and -DH(31) have synergistic effects in D. punctata but have only additive effects in Locusta migratoria. Dippu-DH(31) represents a distinct type of insect DH with actions that differ from those of previously identified insect peptides with diuretic activity.

The regulation of juvenile hormone production in arthropods. Functional and evolutionary perspectives

Although sesquiterpenoids are probably the ancestral regulators of reproduction and secondarily of metamorphosis in arthropods, our discussion suggests that the neuropeptides that regulate the biosynthesis of these compounds have arisen on several distinct occasions. These peptides probably occurred originally as regulators of other physiological processes and were subsequently co-opted for the regulation of sesquiterpenoid biosynthesis, perhaps first in adult forms and thereafter in larval forms. The evolution of peptides to assume additional physiological functions probably occurred as a result of gene duplication, both at the peptide level and at the receptor level. There are likely to be numerous regulators of sesquiterpenoid biosynthesis in both Insecta and Crustacea, and investigations to date have only begun to reveal the host of peptide families involved in the regulation of juvenile hormone-related biosynthesis across the arthropods.

Allatostatins: a growing family of neuropeptides with structural and functional diversity

The high degree of conservation of the core sequence of the "cockroach-types" of AST and their widespread distribution suggest that they should be considered a ubiquitous family of peptides within the invertebrates, regulating a range of important physiological processes. These functional processes, by either neural or humoral routes of action, include the inhibition of endocrine function, interneuronal functions, neuromodulatory roles, myotropic and myoendocrine roles, and direct action on biosynthetic pathways. The myomodulatory function appears to be conserved through evolutionary time, whereas the JH inhibitory activity appears to be confined to specific orders. This suggests that the myomodulatory role was the more ancestral of these two particular functions. Certainly, further purification and gene cloning as a means to precursor identification and functional analysis will be a prerequisite to understanding the diverse functions of this peptide family.

Effects of an allatostatin and a myosuppressin on midgut carbohydrate enzyme activity in the cockroach Diploptera punctata

Neuropeptides of the cockroach allatostatin (AST) family are known for their ability to inhibit the production of juvenile hormone by the corpora allata of cockroaches. Since their discovery, they have also been shown to modulate myotropic activity in a range of insect species as well as to act as neurotransmitters in Crustaceans and possibly in insects. The midgut of cockroaches contains numerous endocrine cells, some of which produce AST whereas others produce the FMRFamide-related peptide, leucomyosuppressin (LMS). We have determined if ASTs and LMS are also able to influence carbohydrate-metabolizing enzyme activity in the midgut of the cockroach, Diploptera punctata. Dippu-AST 7 stimulates activity of both invertase and alpha-amylase in a dose-dependent fashion in the lumen contents of ligatured midguts in vitro, but not in midgut tissue, whereas the AST analog AST(b)phi2, a cyclopropyl-ala, hydrocinnamic acid analog of Dippu-AST 6, has no effect. Leucomyosuppressin also stimulates enzyme activity in lumen contents only, although the EC50 is considerably greater than for Dippu-AST. Dippu-AST is also able to inhibit proctolin-induced contractions of midgut muscle, and this action had already been described for LMS [18]. Thus, in this organ, AST and LMS have at least two distinct physiological effects.

Production of insect juvenile hormone III and its precursors in cell suspension cultures of the sedge, Cyperus iria L

 Juvenile hormones (JHs) are sesquiterpenoids that regulate metamorphosis and reproduction in most insect species. There has been one report of an insect JH in plants: JH III, methyl-10R,11-epoxy-3,7,11-trimethyl 2E, 6E-dodecadienoate, has been identified in two sedge species, Cyperus iria L. and C. aromaticus (Ridley) Mattf and Kük. This is the first report of callus and cell suspension cultures derived from C. iria. Farnesol and methyl farnesoate, two biosynthetic intermediates of JH III in insects, as well as JH III have been identified in suspension culture cell extracts by gas chromatography-mass spectroscopy. These cultures thus provide a useful in vitro model to investigate the biosynthesis of JH III in the sedge, C. iria.

The molecular evolution of the allatostatin precursor in cockroaches

Allatostatins (ASTs) of the Tyr/Phe-Xaa-Phe-Gly Leu/Ile-NH2 family are a group of insect neuropeptides that inhibit juvenile hormone biosynthesis by the corpora allata. We have obtained genomic DNA sequences that specify the preproallatostatin precursor for the cockroaches, Blatta orientalis, Blattella germanica, Blaberus (cranufer and Supella longipalpa. The sequences obtained are similar to those of Diploptera punctata and Periplaneta americana reported previously. The precursors of all these cockroach species are similar in size, and the organization of the ASTs that they contain (there are 13 or 14, depending on the species) have been conserved. With the sequences of these precursors, and using the homologous sequence in the orthopteran Schistocera gregari as an outgroup, a phylogenetic analysis using parsimony was carried out. The dendrograms obtained from these analyses. using the amino acid as well as the nucleotide sequences, are comparable with current models for cockroach phylogeny. Parsimony analysis was also used to study the genealogy of the different ASTs within the same precursor. Results suggest that the AST sequences were generated through a process of internal gene duplication which occurred before these species diverged from each other in evolutionary time.

Hemolymph and tissue-bound peptidase-resistant analogs of the insect allatostatins

While neuropeptides of the allatostatin family inhibit in vitro production of juvenile hormone, which modulates aspects of development and reproduction in the cockroach, Diploptera punctata, they are susceptible to inactivation by peptidases in the hemolymph, gut, and bound to internal tissues. Patterns of peptidase cleavage were investigated in two allatostatin analogs in which sterically bulky components were incorporated into the active core region to block peptidase attack. The results were used to design and synthesize the first pseudopeptide analog of an insect neuropeptide resistant to degradation by both hemolymph and tissue-bound peptidases. This pseudotetrapeptide allatostatin mimetic analog represents a valuable tool to neuroendocrinologists studying mechanisms by which the natural peptides operate and the physiological consequences of challenging an insect with an allatostatin that is not readily degraded via peptidase enzymes. Disruption of critical physiological processes modulated by neuropeptides such as the allatostatins via peptidase-resistant mimetic analogs could form the basis for novel pest insect management strategies in the future.

Synthesis, biological activity, and conformational studies of insect allatostatin neuropeptide analogues incorporating turn-promoting moieties

Allatostatins are 6-18 amino acid peptides synthezed by insects to control production of juvenile hormones, which in turn regulate functions including metamorphosis and egg production. Four insect allatostatin neuropeptide analogues incorporating turn-promoting pseudopeptide moieties in the region responsible for biological activity were prepared by solid phase peptide synthetic methods. Bioassay indicated that activities approached those of the natural neuropeptides, and molecular models based on NMR data showed similar conformations and the presence of a beta-turn in the active core region for the four analogues. Differences in activity are believed to be due to differences in bulk and relative position of atoms in the unnatural portion of the analogues, and their differing degrees of conformational freedom. The studies support the feasibility of development of neuropeptide-based insect control agents resistant to peptidase deactivation.

In situ hybridization analysis of leucomyosuppressin mRNA expression in the cockroach, Diploptera punctata

In the cockroach Diploptera punctata, sequencing of the cDNA for the insect myoinhibitory neuropeptide, leucomyosuppressin (LMS), has demonstrated that LMS is the only Phe-Met-Arg-Phe-amide (NH2) (FMRFamide)-related peptide to be encoded by this gene (Donly et al. [1996] Insect Biochem. Mol. Biol. 26:627-637). However, in the present study, high performance liquid chromatography analysis of brain extracts showed six discrete FMRFamide-like immunoreactive fractions, one of which co-eluted with LMS. This study compared the distribution of FMRFamide-related peptides visualized by immunohistochemistry with LMS mRNA expression demonstrated by in situ hybridization in D. punctata. Immunohistochemistry with a polyclonal antiserum generated against FMRFamide, but which recognizes extended RFamide peptides, demonstrated numerous RFamide-like immunoreactive cells and processes in both nervous and nonnervous tissues. RFamide-like immunoreactivity was found in cells and processes of the brain and optic lobes, the stomatogastric nervous system, including the frontal and ingluvial ganglia, and the suboesophageal ganglion. Immunoreactivity was also present in all ganglia of the ventral nerve cord and in the alimentary canal. Within the alimentary canal, positively stained processes were found in the crop, midgut, and hindgut, and immunoreactive endocrinelike cells were located in the midgut. In situ hybridization with a digoxigenin-labeled RNA probe spanning the entire LMS coding region showed cell bodies containing LMS mRNA in all ganglia studied, other than the ingluvial ganglion. Expression was most abundant in the brain and optic lobes and in the frontal and suboesophageal ganglia. LMS mRNA was also apparent, although less intensely, in all other ganglia of the ventral nerve cord. Within the alimentary canal, LMS mRNA-positive cells were only visible in the anterior portion of the midgut, in the endocrinelike cells. The appearance of LMS mRNA in the central nervous system, stomatogastric nervous system, and midgut suggests that LMS may play a central role in Diploptera and may be associated with feeding and digestion.

Inactivation of Dip-allatostatin 5 by membrane preparations from the cockroach Diploptera punctata

Incubation of Dip-AST 5 (Asp-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH2) with membrane preparations of midgut, hindgut, brain, or corpora allata (CA) results in its inactivation in terms of the inhibition of juvenile hormone biosynthesis. Dip-AST 5 is initially cleaved at Gly7-Leu8 to yield the N-terminal heptapeptide (Asp-Arg-Leu-Tyr-Ser-Phe-Gly). At supraphysiological concentration, the half-life of Dip-AST 5 varied from 24 min by membrane preparations of brain to approximately 53 min following incubation with midgut membrane preparations. At more physiological concentrations (nanomolar), Dip-AST 5 was still initially cleaved to yield the inactive N-terminal heptapeptide with a half-life ranging from 23 min with brain membrane preparations to 85 min with membrane preparations of midgut. The fact that Dip-AST 5 is rapidly degraded to an inactive product by membrane preparations or whole tissues (CA) indicates that Dip-AST 5 has a different metabolic fate in tissue preparations than in diluted hemolymph (Garside et al., 1997). These findings demonstrate that the degradation of allatostatins by tissue preparations of D. punctata may play an important role in the termination of their ability to inhibit juvenile hormone biosynthesis by the CA and/or to modulate muscle activity in the hindgut.

Degradation of Dip-allatostatins by hemolymph from the cockroach, Diploptera punctata

Incubation of Dip-AST 7 (APSGAQRLYGFGLa) or Dip-AST 9 (GDGRLYAFGLa) (5 microM) with hemolymph for 30 min results in cleavage by a putative endopeptidase, yielding the C-terminal hexapeptide. This metabolic product is subsequently cleaved by an amastatin-sensitive aminopeptidase to yield the the C-terminal pentapeptide, as treatment with the competitive aminoexopeptidase inhibitor, amastatin, results in a significant accumulation of the C-terminal hexapeptide. Interestingly, Dip-AST 5 (DRLYSFGLa) (6 microM), which in common with Dip-AST 7 and 9 possesses Arg-Leu-Tyr, is not rapidly cleaved. However, [3H-Tyr]Dip-AST 5 at physiological concentrations (4 nM), appears to be cleaved by the same enzymes that cleave Dip-AST 7 and 9, albeit at a reduced rate. Incubation of other members of the Dip-allatostatin family with hemolymph also results in cleavage of the peptides, suggesting that there are a variety of endo- and/or exopeptidases present in the hemolymph of D. punctata.

Molecular characterization of the inhibitory myotropic peptide leucomyosuppressin

The myoinhibitory peptide leucomyosuppressin (LMS) (pQDVDHVFLRFamide) has been identified and characterized at the molecular level in the cockroach Diploptera punctata through analysis of the organization of both brain cDNA and genomic DNA. Processing of the precursor predicted from DNA sequence would release a single LMS peptide. The organization of the precursor appears to be conserved in other insects and may reflect a functional organization for this subfamily of extended FLRFamides. The expression of the LMS gene appears in numerous cells of the pars-intercerebralis of the cockroach protocerebellum as well as in numerous endocrine cells of the midgut.

Isolation and characterization of schistostatin-2(11-18) from the desert locust, Schistocerca gregaria: a truncated analog of schistostatin-2

An octapeptide was isolated from 7000 brains of the desert locust. Schistocerca gregaria by screening of HPLC fractions using a RIA for Dip-AST-2 (allatostatin-2 from the cockroach). Maldi-TOF-MS revealed a mass of 921.4 Da. The primary structure of the peptide is LPVYNFGL-NH2. It is identical to the C-terminal portion of schistostatin-2 from Schistocerca gregaria. Therefore, it was designated Scg-AST-2(11-18). The chromatographic properties of the synthetic peptide are identical to these of the native peptide. The peptide is a truncated product of Scg-AST-2, suggesting that an endopeptidase which cleaves between Arg and Leu is present in the brain complex of S. gregaria. Although, Scg-AST-2(11-18) contains the same C-terminus as Dip-AST-2, it has no inhibitory activity on the corpora allata (CA) of 2-day-old virgin females of D. punctata. This suggests that Scg-AST2 (11-18) may be the result of a proteolytic inactivation mechanism and/or that it may be involved in stage-dependent down regulation of allatostatic activity. To our knowledge, Scg-AST-2 is the first isolated peptide which has the active core of the allatostatin peptide family but nevertheless shows no activity in this bioassay.

Isolation and characterization of eight myoinhibiting peptides from the desert locust, Schistocerca gregaria: new members of the cockroach allatostatin family

Eight myoinhibiting peptides were purified by high performance liquid chromatography from a methanolic extract of 7000 brains of the desert locust, Schistocerca gregaria. Complete sequences were obtained via a novel, combined approach employing: (1) chemical microsequencing and (2) post-source decay analysis on a reflectron time-of-flight mass spectrometer using matrix-assisted laser desorption/ionisation. Each of the peptides shows C-terminal amino acid sequence similarity to cockroach and cricket allatostatins and to blowfly callatostatins. Therefore, these novel peptides were designated Schistocerca gregaria allatostatins (Scg-ASTs) or schistostatins and their primary structures were determined to be: Ala-Tyr-Thr-Tyr-Val-Ser-Glu-Tyr-Lys-Arg-Leu-Pro-Val-Tyr-Asn-Phe-Gly-Leu- NH2 (Scg-AST-2), Ala-Thr-Gly-Ala-Ala-Ser-Leu-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-3), Gly-Pro-Arg-Thr-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-4), Gly-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-5), Ala-Arg-Pro-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-6), Ala-Gly-Pro-Ala-Pro-Ser-Arg-Leu-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-7), Glu-Gly-Arg-Met-Tyr-Ser-Phe-Gly-Leu-NH2 (Scg-AST-8), and Ala-Pro-Ala-Glu-His-Arg-Phe-Ser-Phe-Gly-Leu-NH2 (Scg-AST-10). Synthetic Scg-AST peptides inhibit the peristaltic movements of the oviduct of S. gregaria. Although all eight peptides show potent inhibitory effects on juvenile hormone (JH) biosynthesis by corpora allata (CA) of the cockroach Diploptera punctata, no allatostatic effects were observed on CA of the desert locust (S. gregaria).

Molecular cloning of the precursor cDNA for schistostatins, locust allatostatin-like peptides with myoinhibiting properties

The cDNA encoding the precursor polypeptide for schistostatins, allatostatin-like peptides which have been shown to inhibit peristaltic movements of the lateral oviducts of Schistocerca gregaria, has been cloned and sequenced. Translation of this sequence reveals the presence of a pre-proschistostatin consisting of 283 amino acids. It contains ten different peptide sequences which are flanked by dibasic cleavage sites and C-terminal amidation signals. Eight of these peptides were identical to the schistostatins (or Scg-ASTs) that were previously purified from Schistocerca gregaria brain extracts. Two novel peptide sequences were discovered. One of these is the first AST-like peptide which has a C-terminal valine residue. Two peptides contain within their sequence an internal dibasic site which suggests a possible role for alternative processing and/or degradation. The schistostatin precursor differs from cockroach pre-proallatostatins in size, in sequence and in organization. It contains a lower number of peptides (10 versus 13 or 14) which are interrupted only once by an acidic spacer region (versus four in Diploptera punctata and Periplaneta americana). Northern analysis showed the presence of a 2.4 kb mRNA band in the locust central nervous system and midgut. This indicates that schistostatins, like other ASTs, are a good example of insect brain/gut peptides.

Molecular characterization of a cDNA from Pseudaletia unipuncta encoding the Manduca sexta allatostatin peptide (Mas-AST)

A 15-residue neuropeptide, Manduca sexta allatostatin (Mas-AST), strongly inhibits juvenile hormone (JH) biosynthesis in vitro by corpora allata (CA) from Manduca fifth-stadium larvae and adult females as well as Helicoverpa zea adult females (Kramer et al., 1991 Proc. Natl. Acad. Sci (USA) 88, 9458-9462). In contrast, this study found that 1.0 microM Mas-AST has no JH biosynthesis inhibitory activity in Pseudaletia unipuncta sixth instar larvae or newly-emerged (day 0) adults but inhibited CA of 5-day-old adult females by 60%. From a P. unipuncta brain cDNA library, was isolated a cDNA that encodes a 125 amino acid polypeptide containing the Mas-AST sequence. Within the precursor, Mas-AST is situated at the carboxy terminus and is flanked by different dibasic proteolytic cleavage signals. The Pseudaletia gene specifying the Mas-AST peptide is present as a single copy per haploid genome. Expression of this gene was low in Pseudaletia sixth instar larvae, prepupae and early pupae but was relatively high in late pupae, and day 1 and 3 adults of both sexes. In day 5 adults, the relative transcript level appears to be maintained in females but declines in males. This pattern of Mas-AST expression does not correlate well with the profile of JH biosynthesis in Pseudaletia, which increases during the first 5 days of adult life, suggesting additional or alternative functions for this peptide.

Characterization of the gene for leucomyosuppressin and its expression in the brain of the cockroach Diploptera punctata

Using HPLC separation, radioimmunoassay, and subsequent bioassay, we have detected the presence of an active peptide, which co-elutes with the insect myoinhibitory peptide leuco-myosuppressin, in the brain of the cockroach Diploptera punctata. We have isolated a cDNA encoding the precursor for this peptide from cDNA libraries representing D. punctata brain RNA. The cDNA sequence contains an open reading frame that upon translation would result in a prepropolypeptide of 96 amino acids. Proteolytic cleavage of the predicted precursor could result in several peptides, including a 10 amino acid C-terminal peptide that would, upon modification of the NH2 and COOH-terminal amino acids, be identical to the insect FLRFamide, leucomyosuppressin. No other RFamide products are predicted to be processed from the precursor. Southern blot analysis indicates that the gene is present in the D. punctata genome in a single copy. Northern blot analysis shows that the gene is predominantly expressed as a 3.8 kb mRNA in cockroach brain. Study of the expression of the leucomyosuppressin gene in D. punctata brain, using in situ hybridization, indicates that expression occurs primarily in the pars intercerebralis of the protocerebrum, a region showing abundant FMRFamide-like immunoreactive neurosecretory cells. Immunohistochemistry and HPLC coupled to radioimmunoassay indicates that leucomyosuppressin represents a significant proportion of FMRFamide-related peptide production in the brain. However, HPLC analysis also indicates the presence of significant levels of other related peptides, demonstrating the presence of more than one FMRFamide-related gene in this insect.

Comparison of the allatostatin neuropeptide precursors in the distantly related cockroaches Periplaneta americana and Diploptera punctata

Allatostatins are a family of insect neuropeptides that inhibit juvenile hormone biosynthesis by the corpora allata. We have characterized cDNA and genomic DNA sequences that specify a preproallatostatin precursor in the oviparous cockroach Periplaneta americana. Comparison of this precursor with that previously described [Donly, B. C., Ding, Q., Tobe, S. S. & Bendena, W. G. (1993) Proc. Natl Acad. Sci. USA 90, 8807-8811] for the viviparous cockroach Diploptera punctata revealed several common features. First, the precursors are remarkably similar in size and the organization of the peptides within the precursor is conserved. The separation of the peptides into groups by acidic domains within the precursor has been maintained. The P. americana precursor contains 14 allatostatin-like peptides that contain the core C-terminal sequence (Tyr/Phe)-Xaa-Phe-Gly-(Leu/Ile)-NH2, as compared to the D. punctata precursor, which contains 13. Five of the peptides are perfectly conserved between the two species. The remainder, with one exception, contain amino acid substitutions in the N-terminal address portion of the peptide. Several features of expression are also similar between these two species. In both, a single copy gene specifies a large allatostatin transcript of 5.0 kb in P. americana and 9.2 kb in D. punctata. In P. americana, allatostatin transcripts appear to be produced by numerous cells in different regions of the brain.

Identification and partial characterization of receptors for allatostatins in brain and corpora allata of the cockroach Diploptera punctata using a binding assay and photoaffinity labeling

We have developed both an in vitro binding assay and a photoaffinity labeling assay to demonstrate and partially characterize putative receptors for allatostatins in brain and in corpora allata of Diploptera punctata. Isolated brain membranes were photoaffinity labeled with 125I-RYBPA (photoaffinity analogue of dip-allatostatin 5). Following labeling with 125I-RYBPA, SDS-PAGE and autoradiography revealed the presence of a putative receptor (37 kDa) for dip-allatostatin 5 and dip-allatostatin 7. Specific labeling was demonstrated by dose-dependent competition with either dip-allatostatin 5 or dip-allatostatin 7. The in vitro binding assay indicated that the receptor for dip-allatostatin 5 had a Kd of (9.0 +/- 0.9).10(-10) M and Bmax of 2.2 +/- 0.3 pmol/mg membrane protein. For dip-allatostatin 7, two Kd values of (1.5 +/- 0.1).10(-9) M and (3.8 +/- 0.3).10(-9) M were obtained, with Bmax values of 7.2 +/- 0.7 pmol/mg membrane protein and 11.4 +/- 1.0 pmol/mg membrane protein respectively. This indicates that there were probably two putative receptor sites for dip-allatostatin 7 although only one band was observable following photoaffinity labeling. Binding was saturable, specific and reversible. Using the in vitro binding assay, the Kd of the putative receptor in CA for dip-allatostatin 7 was shown to be (7.2 +/- 0.9).10(-10) M.