Identification of two allatostatins from the cricket, Gryllus bimaculatus de Geer (Ensifera, Gryllidae): additional members of a family of neuropeptides inhibiting juvenile hormone biosynthesis

Characterization of myoinhibitory peptide signaling system and its implication in larval metamorphosis and spawning behavior in Pacific abalone

Myoinhibitory peptides (MIPs) affect various physiological functions, including juvenile hormone signaling, muscle contraction, larval development, and reproduction in invertebrates. Although MIPs are ligands for MIP and/or sex peptide receptors (MIP/SPRs) in diverse arthropods and model organisms belonging to Lophotrochozoa, the MIP signaling system has not yet been fully investigated in mollusks. In this study, we identified the MIP signaling system in the Pacific abalone Haliotis discus hannai (Hdh). Similar to the invertebrate MIPs, a total of eight paracopies of MIPs (named Hdh-MIP1 to Hdh-MIP8), harboring a WX5-7Wamide motif, except for Hdh-MIP2, were found in the Hdh-MIP precursor. Furthermore, we characterized a functional Hdh-MIPR, which responded to the Hdh-MIPs, except for Hdh-MIP2, possibly linked with the PKC/Ca2+ and PKA/cAMP signaling pathways. Hdh-MIPs delayed larval metamorphosis but increased the spawning behavior. These results suggest that the Hdh-MIP signaling system provides insights into the unique function of MIP in invertebrates.

Comparative Transcriptomic Analysis Reveals Candidate Genes and Pathways Involved in Larval Settlement of the Barnacle Megabalanus volcano

Megabalanus barnacle is one of the model organisms for marine biofouling research. However, further elucidation of molecular mechanisms underlying larval settlement has been hindered due to the lack of genomic information thus far. In the present study, cDNA libraries were constructed for cyprids, the key stage for larval settlement, and adults of Megabalanus volcano. After high-throughput sequencing and de novo assembly, 42,620 unigenes were obtained with a N50 value of 1532 bp. These unigenes were annotated by blasting against the NCBI non-redundant (nr), Swiss-Prot, Cluster of Orthologous Groups (COG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. Finally, 19,522, 15,691, 14,459, and 10,914 unigenes were identified correspondingly. There were 22,158 differentially expressed genes (DEGs) identified between two stages. Compared with the cyprid stage, 8241 unigenes were down-regulated and 13,917 unigenes were up-regulated at the adult stage. The neuroactive ligand-receptor interaction pathway (ko04080) was significantly enriched by KEGG enrichment analysis of the DEGs, suggesting that it possibly involved in larval settlement. Potential functions of three conserved allatostatin neuropeptide-receptor pairs and two light-sensitive opsin proteins were further characterized, indicating that they might regulate attachment and metamorphosis at cyprid stage. These results provided a deeper insight into the molecular mechanisms underlying larval settlement of barnacles.

Transcriptomic identification of starfish neuropeptide precursors yields new insights into neuropeptide evolution

Neuropeptides are evolutionarily ancient mediators of neuronal signalling in nervous systems. With recent advances in genomics/transcriptomics, an increasingly wide range of species has become accessible for molecular analysis. The deuterostomian invertebrates are of particular interest in this regard because they occupy an ‘intermediate' position in animal phylogeny, bridging the gap between the well-studied model protostomian invertebrates (e.g. Drosophila melanogaster, Caenorhabditis elegans) and the vertebrates. Here we have identified 40 neuropeptide precursors in the starfish Asterias rubens, a deuterostomian invertebrate from the phylum Echinodermata. Importantly, these include kisspeptin-type and melanin-concentrating hormone-type precursors, which are the first to be discovered in a non-chordate species. Starfish tachykinin-type, somatostatin-type, pigment-dispersing factor-type and corticotropin-releasing hormone-type precursors are the first to be discovered in the echinoderm/ambulacrarian clade of the animal kingdom. Other precursors identified include vasopressin/oxytocin-type, gonadotropin-releasing hormone-type, thyrotropin-releasing hormone-type, calcitonin-type, cholecystokinin/gastrin-type, orexin-type, luqin-type, pedal peptide/orcokinin-type, glycoprotein hormone-type, bursicon-type, relaxin-type and insulin-like growth factor-type precursors. This is the most comprehensive identification of neuropeptide precursor proteins in an echinoderm to date, yielding new insights into the evolution of neuropeptide signalling systems. Furthermore, these data provide a basis for experimental analysis of neuropeptide function in the unique context of the decentralized, pentaradial echinoderm bauplan.

Newly identified allatostatin Bs and their receptor in the two-spotted cricket, Gryllus bimaculatus

A cDNA encoding allatostatin Bs (ASTBs) containing the W(X)6W motif was identified using a database generated by a next generation sequencer (NGS) in the two-spotted cricket, Gryllus bimaculatus. The contig sequence revealed the presence of five novel putative ASTBs (GbASTBs) in addition to GbASTBs previously identified in G. bimaculatus. MALDI-TOF MS analyses revealed the presence of these novel and previously identified GbASTBs with three missing GbASTBs. We also identified a cDNA encoding G. bimaculatus GbASTB receptor (GbASTBR) in the NGS data. Phylogenetic analysis demonstrated that this receptor was highly conserved with other insect ASTBRs, including the sex peptide receptor of Drosophila melanogaster. Calcium imaging analyses indicated that the GbASTBR heterologously expressed in HEK293 cells exhibited responses to all identified GbASTBs at a concentration range of 10(-10)-10(-5)M.

IDENTIFICATION OF THE FGL-AMIDE ALLATOSTATIN GENE OF THE PRIMITIVE TERMITE Mastotermes darwiniensis AND THE WOODROACH Cryptocercus darwini

Allatostatins with the C-terminal ending Tyr/Phe-Xaa-Phe-Gly-Leu/Ile-amide (FGLa/ASTs) are widespread neuropeptides with multiple functions. The gene encoding the FGLa/AST polypeptide precursor was first isolated from cockroaches and since then could be identified in many insects and crustaceans. With its strictly conserved regions in combination with variable regions the gene seems to be a good candidate for phylogenetic analyses between closely and distantly related species. Here, the structure of the FGLa/AST gene of the most primitive termite, the giant northern termite Mastotermes darwiniensis Froggatt, was identified. The FGLa/AST gene of the woodroach Cryptocercus darwini was also determined. Precursor sequences of both species possess the general organization of dictyopteran FGLa/AST precursors containing 14 putative FGLa/AST peptides. In M. darwiniensis, only 11 out of the 14 FGLa/AST-like peptides possess the C-terminal conserved region Y/FXFGL/I/V/M and four of the putative peptide structures are not followed by a Gly residue that would lead to nonamidated peptides. Phylogenetic analyses show the high degree of similarity of dictyopteran FGLa/AST sequences. The position of termites, nested within the Blattaria, confirms that termites have evolved from primitive cockroaches.

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.

Unravelling the Evolution of the Allatostatin-Type A, KISS and Galanin Peptide-Receptor Gene Families in Bilaterians: Insights from Anopheles Mosquitoes

Allatostatin type A receptors (AST-ARs) are a group of G-protein coupled receptors activated by members of the FGL-amide (AST-A) peptide family that inhibit food intake and development in arthropods. Despite their physiological importance the evolution of the AST-A system is poorly described and relatively few receptors have been isolated and functionally characterised in insects. The present study provides a comprehensive analysis of the origin and comparative evolution of the AST-A system. To determine how evolution and feeding modified the function of AST-AR the duplicate receptors in Anopheles mosquitoes, were characterised. Phylogeny and gene synteny suggested that invertebrate AST-A receptors and peptide genes shared a common evolutionary origin with KISS/GAL receptors and ligands. AST-ARs and KISSR emerged from a common gene ancestor after the divergence of GALRs in the bilaterian genome. In arthropods, the AST-A system evolved through lineage-specific events and the maintenance of two receptors in the flies and mosquitoes (Diptera) was the result of a gene duplication event. Speciation of Anopheles mosquitoes affected receptor gene organisation and characterisation of AST-AR duplicates (GPRALS1 and 2) revealed that in common with other insects, the mosquito receptors were activated by insect AST-A peptides and the iCa²⁺-signalling pathway was stimulated. GPRALS1 and 2 were expressed mainly in mosquito midgut and ovaries and transcript abundance of both receptors was modified by feeding. A blood meal strongly up-regulated expression of both GPRALS in the midgut (p < 0.05) compared to glucose fed females. Based on the results we hypothesise that the AST-A system in insects shared a common origin with the vertebrate KISS system and may also share a common function as an integrator of metabolism and reproduction. Highlights: AST-A and KISS/GAL receptors and ligands shared common ancestry prior to the protostome-deuterostome divergence. Phylogeny and gene synteny revealed that AST-AR and KISSR emerged after GALR gene divergence. AST-AR genes were present in the hemichordates but were lost from the chordates. In protostomes, AST-ARs persisted and evolved through lineage-specific events and duplicated in the arthropod radiation. Diptera acquired and maintained functionally divergent duplicate AST-AR genes.

Probing the active conformation of FGLamide allatostatin analogs with N-terminal modifications using NMR spectroscopy and molecular modeling

The FGLamide allatostatins (ASTs) can inhibit the production of juvenile hormone in vitro, and they therefore are regarded as possible insect growth regulator candidates for pest control. To understand the structural features of the ASTs that cause the differences in their activity the pentapeptide and four N-terminal modifications of AST analogs (H17, K9, K10 and K23) were selected to investigate their conformations. From NMR spectroscopy and molecular modeling, it is clear that K23 and K9 have a type IV β-turn and a γ turn in DMSO, respectively. The pentapeptide, H17 and K10 form a flexible conformation. Our study indicates that this flexible conformation could be an important and indispensable structural element for activity, whereas the turn structure may not be especially significant for biological activity.

Synthesis, biological activity, and conformational study of N-methylated allatostatin analogues inhibiting juvenile hormone biosynthesis

An allatostatin (AST) neuropeptide mimic (H17) is a potential insect growth regulator, which inhibits the production of juvenile hormone (JH) by the corpora allata. To determine the effect of conformation of novel AST analogues and their ability to inhibit JH biosynthesis, eight insect AST analogues were synthesized using H17 as the lead compound by N-methylation scanning, which is a common strategy for improving the biological properties of peptides. A bioassay using JH production by corpora allata of the cockroach Diploptera punctata indicated that single N-methylation mimics (analogues 1-4) showed more activity than double N-methylation mimics (analogues 5-8). Especially, analogues 1 and 4 showed roughly equivalent activity to that of H17, with IC50 values of 5.17 × 10(-8) and 6.44 × 10(-8) M, respectively. Molecular modeling based on nuclear magnetic resonance data showed that the conformation of analogues 1 and 4 seems to be flexible, whereas analogues 2 and 3 showed a type IV β-turn. This flexible linear conformation was hypothesized to be a new important and indispensable structural element beneficial to the activity of AST mimics.

Neuropeptidergic control of the hindgut in the black-legged tick Ixodes scapularis

The hindgut, as a part of the tick excretory system, plays an important physiological role in maintaining homoeostases and waste elimination. Immunoreactive projections from the synganglion to the hindgut were found using antibodies against four different neuropeptides: FGLamide related allatostatin, myoinhibitory peptide, SIFamide, and orcokinin. The presence of FGLamide related allatostatin, myoinhibitory peptide and SIFamide in both synganglia (source) and hindgut (target organ) extracts was confirmed by MALDI-TOF. Tissue-specific PCR revealed the expression of four putative FGLamide related allatostatin receptors and an SIFamide receptor in the hindgut. An antibody against Ixodes scapularis SIFamide receptor detected immunoreactive spots in epithelial cells as well as the visceral muscles surrounding the rectal sac, while staining with the antibody against myoinhibitory peptide receptor 1 revealed that the immunoreactivity was only associated with the visceral muscles. In hindgut motility assays, SIFamide activated hindgut motility in a dose-dependent manner. None of other three neuropeptides (FGLamide related allatostatin, myoinhibitory peptide and orcokinin) activated hindgut motility when tested alone. Myoinhibitory peptide antagonised the SIFamide-stimulated hindgut mobility when it was tested in combination with SIFamide.

Transcriptome and peptidome characterisation of the main neuropeptides and peptidic hormones of a euphausiid: the Ice Krill, Euphausia crystallorophias

Background

The Ice krill, Euphausia crystallorophias is one of the species at the base of the Southern Ocean food chain. Given their significant contribution to the biomass of the Southern Ocean, it is vitally important to gain a better understanding of their physiology and, in particular, anticipate their responses to climate change effects in the warming seas around Antarctica.

Methodology/Principal Findings

Illumina sequencing was used to produce a transcriptome of the ice krill. Analysis of the assembled contigs via two different methods, produced 36 new pre-pro-peptides, coding for 61 neuropeptides or peptide hormones belonging to the following families: Allatostatins (A, B et C), Bursicon (α and β), Crustacean Hyperglycemic Hormones (CHH and MIH/VIHs), Crustacean Cardioactive Peptide (CCAP), Corazonin, Diuretic Hormones (DH), the Eclosion Hormone (EH), Neuroparsin, Neuropeptide F (NPF), small Neuropeptide F (sNPF), Pigment Dispersing Hormone (PDH), Red Pigment Concentrating Hormone (RPCH) and finally Tachykinin. LC/MS/MS proteomics was also carried out on eyestalk extracts, which are the major site of neuropeptide synthesis in decapod crustaceans. Results confirmed the presence of six neuropeptides and six precursor-related peptides previously identified in the transcriptome analyses.

Conclusions

This study represents the first comprehensive analysis of neuropeptide hormones in a Eucarida non-decapod Malacostraca, several of which are described for the first time in a non-decapod crustacean. Additionally, there is a potential expansion of PDH and Neuropeptide F family members, which may reflect certain life history traits such as circadian rhythms associated with diurnal migrations and also the confirmation via mass spectrometry of several novel pre-pro-peptides, of unknown function. Knowledge of these essential hormones provides a vital framework for understanding the physiological response of this key Southern Ocean species to climate change and provides a valuable resource for studies into the molecular phylogeny of these organisms and the evolution of neuropeptide hormones.

Receptors for the neuropeptides, myoinhibitory peptide and SIFamide, in control of the salivary glands of the blacklegged tick Ixodes scapularis

Tick salivary glands are important organs that enable the hematophagous feeding of the tick. We previously described the innervation of the salivary gland acini types II and III by a pair of protocerebral salivary gland neurons that produce both myoinhibitory peptide (MIP) and SIFamide (Šimo et al., 2009b). In this study we identified authentic receptors expressed in the salivary glands for these neuropeptides. Homology-based searches for these receptors in the Ixodes scapularis genome sequence were followed by gene cloning and functional expression of the receptors. Both receptors were activated by low nanomolar concentrations of their respective ligands. The temporal expression patterns of the two ligands and their respective receptors suggest that the SIFamide signaling system pre-exists in unfed salivary glands, while the MIP system is activated upon initiation of feeding. Immunoreactivity for the SIFamide receptor in the salivary gland was detected in acini types II and III, surrounding the acinar valve and extending to the basal region of the acinar lumen. The location of the SIFamide receptor in the salivary glands suggests three potential target cell types and their probable functions: myoepithelial cell that may function in the contraction of the acini and/or the control of the valve; large, basally located dopaminergic granular cells for regulation of paracrine dopamine; and neck cells that may be involved in the control of the acinar duct and its valve.

Organization of the olfactory system of nymphalidae butterflies

Olfaction is in many species the most important sense, essential for food search, mate finding, and predator avoidance. Butterflies have been considered a microsmatic group of insects that mainly rely on vision due to their diurnal lifestyle. However, an emerging number of studies indicate that butterflies indeed use the sense of smell for locating food and oviposition sites. To unravel the neural substrates for olfaction, we performed an anatomical study of 2 related butterfly species that differ in food and host plant preference. We found many of the anatomical structures and pathways, as well as distribution of neuroactive substances, to resemble that of their nocturnal relatives among the Lepidoptera. The 2 species differed in the number of one type of olfactory sensilla, thus indicating a difference in sensitivity to certain compounds. Otherwise no differences could be observed. Our findings suggest that the olfactory system in Lepidoptera is well conserved despite the long evolutionary time since butterflies and moths diverged from a common ancestor.

Transcriptomic analysis of neuropeptides and peptide hormones in the barnacle Balanus amphitrite: evidence of roles in larval settlement

The barnacle Balanus amphitrite is a globally distributed marine crustacean and has been used as a model species for intertidal ecology and biofouling studies. Its life cycle consists of seven planktonic larval stages followed by a sessile juvenile/adult stage. The transitional processes between larval stages and juveniles are crucial for barnacle development and recruitment. Although some studies have been conducted on the neuroanatomy and neuroactive substances of the barnacle, a comprehensive understanding of neuropeptides and peptide hormones remains lacking. To better characterize barnacle neuropeptidome and its potential roles in larval settlement, an in silico identification of putative transcripts encoding neuropeptides/peptide hormones was performed, based on transcriptome of the barnacle B. amphitrite that has been recently sequenced. Potential cleavage sites andstructure of mature peptides were predicted through homology search of known arthropod peptides. In total, 16 neuropeptide families/subfamilies were predicted from the barnacle transcriptome, and 14 of them were confirmed as genuine neuropeptides by Rapid Amplification of cDNA Ends. Analysis of peptide precursor structures and mature sequences showed that some neuropeptides of B. amphitrite are novel isoforms and shared similar characteristics with their homologs from insects. The expression profiling of predicted neuropeptide genes revealed that pigment dispersing hormone, SIFamide, calcitonin, and B-type allatostatin had the highest expression level in cypris stage, while tachykinin-related peptide was down regulated in both cyprids and juveniles. Furthermore, an inhibitor of proprotein convertase related to peptide maturation effectively delayed larval metamorphosis. Combination of real-time PCR results and bioassay indicated that certain neuropeptides may play an important role in cypris settlement. Overall, new insight into neuropeptides/peptide hormones characterized in this study shall provide a platform for unraveling peptidergic control of barnacle larval behavior and settlement process.

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.

The FGLamide-allatostatins influence foraging behavior in Drosophila melanogaster

Allatostatins (ASTs) are multifunctional neuropeptides that generally act in an inhibitory fashion. ASTs were identified as inhibitors of juvenile hormone biosynthesis. Juvenile hormone regulates insect metamorphosis, reproduction, food intake, growth, and development. Drosophila melanogaster RNAi lines of PheGlyLeu-amide-ASTs (FGLa/ASTs) and their cognate receptor, Dar-1, were used to characterize roles these neuropeptides and their respective receptor may play in behavior and physiology. Dar-1 and FGLa/AST RNAi lines showed a significant reduction in larval foraging in the presence of food. The larval foraging defect is not observed in the absence of food. These RNAi lines have decreased for transcript levels which encodes cGMP- dependent protein kinase. A reduction in the for transcript is known to be associated with a naturally occuring allelic variation that creates a sitter phenotype in contrast to the rover phenotype which is caused by a for allele associated with increased for activity. The sitting phenotype of FGLa/AST and Dar-1 RNAi lines is similar to the phenotype of a deletion mutant of an AST/galanin-like receptor (NPR-9) in Caenorhabditis elegans. Associated with the foraging defect in C. elegans npr-9 mutants is accumulation of intestinal lipid. Lipid accumulation was not a phenotype associated with the FGLa/AST and Dar-1 RNAi lines.

More than two decades of research on insect neuropeptide GPCRs: an overview

This review focuses on the state of the art on neuropeptide receptors in insects. Most of these receptors are G protein-coupled receptors (GPCRs) and are involved in the regulation of virtually all physiological processes during an insect's life. More than 20 years ago a milestone in invertebrate endocrinology was achieved with the characterization of the first insect neuropeptide receptor, i.e., the Drosophila tachykinin-like receptor. However, it took until the release of the Drosophila genome in 2000 that research on neuropeptide receptors boosted. In the last decade a plethora of genomic information of other insect species also became available, leading to a better insight in the functions and evolution of the neuropeptide signaling systems and their intracellular pathways. It became clear that some of these systems are conserved among all insect species, indicating that they fulfill crucial roles in their physiological processes. Meanwhile, other signaling systems seem to be lost in several insect orders or species, suggesting that their actions were superfluous in those insects, or that other neuropeptides have taken over their functions. It is striking that the deorphanization of neuropeptide GPCRs gets much attention, but the subsequent unraveling of the intracellular pathways they elicit, or their physiological functions are often hardly examined. Especially in insects besides Drosophila this information is scarce if not absent. And although great progress made in characterizing neuropeptide signaling systems, even in Drosophila several predicted neuropeptide receptors remain orphan, awaiting for their endogenous ligand to be determined. The present review gives a précis of the insect neuropeptide receptor research of the last two decades. But it has to be emphasized that the work done so far is only the tip of the iceberg and our comprehensive understanding of these important signaling systems will still increase substantially in the coming years.

The pro-apoptotic action of the peptide hormone, Neb-colloostatin, on insect haemocytes

The gonadoinhibitory peptide hormone, Neb-colloostatin, was first isolated from ovaries of the flesh fly Neobellieria bullata. This 19-mer peptide is thought to be a cleaved product of a collagen-like precursor molecule that is formed during remodelling of the extracellular matrix. In this study, we report that upon injection of pico- and nanomolar doses, this peptide exerts a pro-apoptotic action on haemocytes of Tenebrio molitor adults, as visualized by changes in morphology and viability. The F-actin cytoskeleton was found aggregating into distinctive patches. This may be responsible for the observed inhibition of adhesion of haemocytes and for the stimulation of filopodia formation. However, Neb-colloostatin injection did not induce the formation of authophagic vacuoles. Our results suggest that physiological concentrations of Neb-colloostatin may play an important role in controlling the quantity and activity of haemocytes in insect haemolymph. They also suggest that in periods that Neb-colloostatin is released, this peptide may cause a weakening of the insects' immune system. This is the first report that exposure to a peptide hormone causes apoptosis in insect haemocytes.

Toward a consensus nomenclature for insect neuropeptides and peptide hormones

The nomenclature currently in use for insect neuropeptide and peptide hormone families is reviewed and suggestions are made as to how it can be rationalized. Based upon this review, a number of conventions are advanced as a guide to a more rationale nomenclature. The scheme that is put forward builds upon the binomial nomenclature scheme proposed by Raina and Gäde in 1988, when just over 20 insect neuropeptides had been identified. Known neuropeptides and peptide hormones are assigned to 32 structurally distinct families, frequently with overlapping functions. The names given to these families are those that are currently in use, and describe a biological function, homology to known invertebrate/vertebrate peptides, or a conserved structural motif. Interspecific isoforms are identified using a five-letter code to indicate genus and species names, and intraspecific isoforms are identified by Roman or Arabic numerals, with the latter used to signify the order in which sequences are encoded on a prepropeptide. The proposed scheme is sufficiently flexible to allow the incorporation of novel peptides, and could be extended to other arthropods and non-arthropod invertebrates.

Influence of codon usage bias on FGLamide-allatostatin mRNA secondary structure

The FGLamide allatostatins (ASTs) are invertebrate neuropeptides which inhibit juvenile hormone biosynthesis in Dictyoptera and related orders. They also show myomodulatory activity. FGLamide AST nucleotide frequencies and codon bias were investigated with respect to possible effects on mRNA secondary structure. 367 putative FGLamide ASTs and their potential endoproteolytic cleavage sites were identified from 40 species of crustaceans, chelicerates and insects. Among these, 55% comprised only 11 amino acids. An FGLamide AST consensus was identified to be (X)(1→16)Y(S/A/N/G)FGLGKR, with a strong bias for the codons UUU encoding for Phe and AAA for Lys, which can form strong Watson-Crick pairing in all peptides analyzed. The physical distance between these codons favor a loop structure from Ser/Ala-Phe to Lys-Arg. Other loop and hairpin loops were also inferred from the codon frequencies in the N-terminal motif, and the first amino acids from the C-terminal motif, or the dibasic potential endoproteolytic cleavage site. Our results indicate that nucleotide frequencies and codon usage bias in FGLamide ASTs tend to favor mRNA folds in the codon sequence in the C-terminal active peptide core and at the dibasic potential endoproteolytic cleavage site.

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

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

Two novel neuropeptides in innervation of the salivary glands of the black-legged tick, Ixodes scapularis: myoinhibitory peptide and SIFamide

The peptidergic signaling system is an ancient cell-cell communication mechanism that is involved in numerous behavioral and physiological events in multicellular organisms. We identified two novel neuropeptides in the neuronal projections innervating the salivary glands of the black-legged tick, Ixodes scapularis (Say, 1821). Myoinhibitory peptide (MIP) and SIFamide immunoreactivities were colocalized in the protocerebral cells and their projections terminating on specific cells of salivary gland acini (types II and III). Immunoreactive substances were identified by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) analysis: a 1,321.6-Da peptide with the sequence typical for MIP (ASDWNRLSGMWamide) and a 1,395.7-Da SIFamide (AYRKPPFNGSIFamide), which are highly conserved among arthropods. Genes encoding these peptides were identified in the available Ixodes genome and expressed sequence tag (EST) database. In addition, the cDNA encoding the MIP prepropeptide was isolated by rapid amplification of cDNA ends (RACE). In this report, we describe the anatomical structure of specific central neurons innervating salivary gland acini and identify different neuropeptides and their precursors expressed by these neurons. Our data provide evidence for neural control of salivary gland by MIP and SIFamide from the synganglion, thus leading a basis for functional studies of these two distinct classes of neuropeptides.

Neuropeptide signaling sequences identified by pyrosequencing of the American dog tick synganglion transcriptome during blood feeding and reproduction

Ticks are important vectors of numerous pathogens that impact human and animal health. The tick central nervous system represents an understudied area in tick biology and no tick synganglion-specific transcriptome has been described to date. Here we characterize whole or partial cDNA sequences of fourteen putative neuropeptides (allatostatin, insulin-like peptide, ion-transport peptide, sulfakinin, bursicon alpha/beta, eclosion hormone, glycoprotein hormone alpha/beta, corazonin, four orcokinins) and five neuropeptide receptors (gonadotropin receptor, leucokinin-like receptor, sulfakinin receptor, calcitonin receptor, pyrokinin receptor) translated from cDNA synthesized from the synganglion of unfed, partially fed and replete female American dog ticks, Dermacentor variabilis. Their homology to the same neuropeptides in other taxa is discussed. Many of these neuropeptides such as an allatostatin, insulin-like peptide, eclosion hormone, bursicon alpha and beta and glycoprotein hormone alpha and beta have not been previously described in the Chelicerata. An insulin-receptor substrate protein was also found indicating that an insulin signaling network is present in ticks. A putative type-2 proprotein processing convertase was also sequenced that may be involved in cleavage at monobasic and dibasic endoproteolytic cleavage sites in prohormones. The possible physiological role of the proteins discovered in adult tick blood feeding and reproduction will be discussed.

Mass spectrometric characterization and physiological actions of novel crustacean C-type allatostatins

The crustacean stomatogastric ganglion (STG) is modulated by numerous neuropeptides that are released locally in the neuropil or that reach the STG as neurohormones. Using 1,5-diaminonaphthalene (DAN) as a reductive screening matrix for matrix-assisted laser desorption/ionization (MALDI) mass spectrometric profiling of disulfide bond-containing C-type allatostatin peptides followed by electrospray ionization quadrupole time-of-flight (ESI-Q-TOF) tandem mass spectrometric (MS/MS) analysis, we identified and sequenced a novel C-type allatostatin peptide (CbAST-C1), pQIRYHQCYFNPISCF-COOH, present in the pericardial organs of the crab, Cancer borealis. Another C-type allatostatin (CbAST-C2), SYWKQCAFNAVSCFamide, was discovered using the expressed sequence tag (EST) database search strategy in both C. borealis and the lobster, Homarus americanus, and further confirmed with de novo sequencing using ESI-Q-TOF tandem MS. Electrophysiological experiments demonstrated that both CbAST-C1 and CbAST-C2 inhibited the frequency of the pyloric rhythm of the STG, in a state-dependent manner. At 10(-6)M, both peptides were only modestly effective when initial frequencies of the pyloric rhythm were >0.8Hz, but almost completely suppressed the pyloric rhythm when applied to preparations with starting frequencies <0.7Hz. Surprisingly, these state-dependent actions are similar to those of the structurally unrelated allatostatin A and allatostatin B families of peptides.

Role of allatostatin-like factors from the brain of Tenebrio molitor females

The effect of brain extract from females of freshly emerged Tenebrio molitor on ovary, oocyte development, total protein content of hemolymph, and ovary was studied in 4-day-old adult mealworm females. Injections of extracts of 2-brain equivalents into intact (unligatured) Tenebrio females did not affect ovarian and oocyte development. Injections of ligated females, however, with 2-brain equivalents on day 1 and 2 after adult emergence strongly inhibited ovarian growth and oocyte development. At day 4, ligated and injected females did not develop their ovaries and pre-vitellogenic oocytes were not found. The changes in ovarian development correlated with an increase in the concentration of soluble proteins in the hemolymph as compared with the saline-injected controls. Additionally, a strong reduction of total protein content in ovarian tissue was observed. Reverse phase HPLC separation of a methanolic brain extract of T. molitor females showed that fraction 5 has a similar retention time to synthetic cockroach allatostatin. Fraction 5 was eluted at 12.88 min, which was closest to the internal standard Dippu-AST I, which eluted at 12.77 min. An ELISA of fraction 5 from the methanolic brain extract using antibodies against allatostatins Grybi-AST A1 and Grybi-AST B1 from cricket Gryllus bimaculatus showed that fraction 5 cross-reacted with Grybi-AST A1 antibodies. The cross-reactivity was similar to the synthetic allatostatin from D. punctata, which was used as a positive control. These observations demonstrate a possible role for allatostatin-like brain factor(s) in regulating the reproductive cycle of Tenebrio molitor.

FGLamide Allatostatin genes in Arthropoda: introns early or late?

FGLamide allatostatins are invertebrate neuropeptides which inhibit juvenile hormone biosynthesis in Dictyoptera and related orders and also show myomodulatory activity. The FGLamide allatostatin (AST) gene structure in Dictyoptera is intronless within the ORF, whereas in 9 species of Diptera, the FGLamide AST ORF has one intron. To investigate the evolutionary history of AST intron structure, (intron early versus intron late hypothesis), all available Arthropoda FGLamide AST gene sequences were examined from genome databases with reference to intron presence and position/phase. Three types of FGLamide AST ORF organization were found: intronless in I. scapularis and P. humanus corporis; one intron in D. pulex, A. pisum, A. mellifera and five Drosophila sp.; two introns in N. vitripennis, B. mori strains, A. aegypti, A. gambiae and C. quinquefasciatus. The literature suggests that for the majority of genes examined, most introns exist between codons (phase 0) which may reflect an ancient function of introns to separate protein modules. 60% of the FGLamide AST ORFs introns were between the first and second base within a codon (phase 1), 28% were between the second and third nucleotides within a codon (phase two) and 12% were phase 0. As would be required for correct intron splicing consensus sequence, 84% of introns were in codons starting with guanine. The positioning of introns was a maximum of 9 codons from a dibasic cleavage site. Our results suggest that the introns in the analyzed species support the intron late model.

Comparative peptidomics of Caenorhabditis elegans versus C. briggsae by LC-MALDI-TOF MS

Neuropeptides are important signaling molecules that function in cell-cell communication as neurotransmitters or hormones to orchestrate a wide variety of physiological conditions and behaviors. These endogenous peptides can be monitored by high throughput peptidomics technologies from virtually any tissue or organism. The neuropeptide complement of the soil nematode Caenorhabditis elegans has been characterized by on-line two-dimensional liquid chromatography and quadrupole time-of-flight tandem mass spectrometry (2D-nanoLC Q-TOF MS/MS). Here, we use an alternative peptidomics approach combining liquid chromatography (LC) with matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry to map the peptide content of C. elegans and another Caenorhabditis species, Caenorhabditis briggsae. This study allows a better annotation of neuropeptide-encoding genes from the C. briggsae genome and provides a promising basis for further evolutionary comparisons.

Reconstruction of ancestral FGLamide-type insect allatostatins: a novel approach to the study of allatostatin function and evolution

Allatostatins (ASTs) are a class of regulatory neuropeptides, with diverse functions, found in an array of invertebrate phyla. ASTs have complex gene structure, in which individual ASTs are cleaved from a precursor peptide. Little is known about the molecular evolution of AST structure and function, even in extensively studied groups such as cockroaches. This paper presents the application of a novel technique for the analysis of this system, that of ancestral reconstruction, whereby ancestral amino acid sequences are resurrected in the laboratory. We inferred the ancestral sequences of a well-characterized peptide, AST 7, for the insect ancestor, as well as several cockroach ancestors. Peptides were assayed for in vitro inhibition of JH production in Diploptera punctata and Periplaneta americana. Our results surprisingly, indicate a decrease in potency of the ancestral cockroach AST7 peptide in comparison with more ancient ones such as the ancestral insect peptide, as well as more recently evolved cockroach peptides. We propose that this unexpected decrease in peptide potency at the cockroach ancestor may be related to the concurrent increase in peptide copy number in the lineages leading to cockroaches. This model is consistent with current physiological data, and may be linked to the increased role of ASTs in the regulation of reproductive processes in the cockroaches.

Quantification of allatostatin receptor mRNA levels in the cockroach, Diploptera punctata, using real-time PCR

The cockroach allatostatin receptor (Dippu-AstR) is a 425 amino acid G-protein coupled receptor that is related to the mammalian galanin receptor. Using relative standard curve real-time PCR analysis, changes in Dippu-AstR mRNA expression levels were examined in tissues of adult mated and virgin female Diploptera punctata. Tissues were chosen that were either known targets of allatostatin (Dippu-AST) action or sites of Dippu-AST localization. Tissues examined included brain, corpora allata (CA), gut, ovaries, testes and abdominal ganglia. Dippu-AstR was expressed in all tissues examined for 7 days after adult emergence. Juvenile hormone (JH) biosynthesis is known to peak on day 5 post-emergence in mated females. In mated females, Dippu-AstR mRNA was at the highest levels on day 6 post-emergence in brain and CA and day 2 post-emergence in midgut. Dippu-AstR expression was found to correlate with the decline in JH biosynthesis noted on day 5 post-emergence and early inhibition of feeding. Dippu-AstR mRNA expression in virgin female midgut and CA was dramatically elevated on days 6 and 7, respectively. Expression of Dippu-AstR mRNA was found to be similar in the abdominal ganglia of mated or virgin females. Ovarian Dippu-AstR expression declined to low levels by day 4. Testes exhibited maximal Dippu-AstR mRNA expression on days 4 and 7 of adult life. A role for Dippu-AST in testes of Diploptera is unknown.

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.

Effects of the NMDA receptor antagonist MK-801 on female reproduction and juvenile hormone biosynthesis in the cricket Gryllus bimaculatus and the butterfly Bicyclus anynana

Apart from regulating insect development, juvenile hormones (JHs) play an important role in insect reproduction, where they initiate vitellogenin synthesis and regulate the uptake of yolk by the ovary. JH synthesis is a tightly regulated process controlled by neurons and peptidergic neurosecretory cells. One of the known stimulatory regulators of JH biosynthesis is glutamate, and its N-methyl-d-aspartate (NMDA) receptor has been recently found in the cockroach Diploptera punctata. In this study we demonstrate a strong reduction in reproductive output in the tropical butterfly Bicyclus anynana and the Mediterranean field cricket Gryllus bimaculatus caused by the NMDA receptor antagonist MK-801. Such inhibiting effects on reproduction could be overruled by the application of JH mimics. In G. bimaculatus, MK-801 inhibits in vitro JH biosynthesis in the corpora allata and reduces in vivo JH haemolymph titres in a dose-dependent manner. These results suggest that JH biosynthesis in the corpora allata is at least in part controlled by an NMDA receptor with Ca2+ as a second level messenger. Based on our findings we consider NMDA receptor antagonists as important tools for manipulating juvenile hormone biosynthesis and therefore for gaining a better understanding of the mechanistic basis of reproduction.

Oogenesis-flight syndrome in crickets: age-dependent egg production, flight performance, and biochemical composition of the flight muscles in adult female Gryllus bimaculatus

Age-dependent changes in flight performance, biochemical composition of flight muscles, and fresh mass of the flight muscles and ovaries were analysed in adult female two-spotted crickets, Gryllus bimaculatus. After the final moult the flight muscle mass increased significantly to a maximum at days 2 and 3. On day 2 the highest flight activity was also observed. Between days 2 and 3 the ovary weight started to rapidly increase due to vitellogenic egg growth, which continued at a high rate until day 10. With the onset of ovarial growth, flight performance decreased and the flight muscles started to histolyse. A high correlation between flight muscle mass and the content of protein, lipid, glycogen, and free carbohydrate in the flight muscle indicated that energy-rich substrates from the degrading flight muscles were used to fuel oogenesis, although flight muscle histolysis can provide only a small fraction of the substrates needed for egg production. In general, there was a clear trade-off between egg production and flight ability. Surprisingly, however, some females possessed well-developed ovaries but displayed no signs of flight muscle histolysis. This observation was corroborated by flight experiments which revealed that, although most flying females had small ovaries, some of them carried an appreciable amount of mature eggs, and thus, somehow managed to evade the oogenesis-flight syndrome.

Inter-phyla studies on neuropeptides: the potential for broad-spectrum anthelmintic and/or endectocide discovery

Flatworm, nematode and arthropod parasites have proven their ability to develop resistance to currently available chemotherapeutics. The heavy reliance on chemotherapy and the ability of target species to develop resistance has prompted the search for novel drug targets. In view of its importance to parasite/pest survival, the neuromusculature of parasitic helminths and pest arthropod species remains an attractive target for the discovery of novel endectocide targets. Exploitation of the neuropeptidergic system in helminths and arthropods has been hampered by a limited understanding of the functional roles of individual peptides and the structure of endogenous targets, such as receptors. Basic research into these systems has the potential to facilitate target characterization and its offshoots (screen development and drug identification). Of particular interest to parasitologists is the fact that selected neuropeptide families are common to metazoan pest species (nematodes, platyhelminths and arthropods) and fulfil specific roles in the modulation of muscle function in each of the three phyla. This article reviews the inter-phyla activity of two peptide families, the FMRFamide-like peptides and allatostatins, on motor function in helminths and arthropods and discusses the potential of neuropeptide signalling as a target system that could uncover novel endectocidal agents.

Neuropeptidergic signaling in the nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans joins the menagerie of behavioral model systems next to the fruit fly Drosophila melanogaster, the marine snail Aplysia californica and the mouse. In contrast to Aplysia, which contains 20,000 neurons having cell bodies of hundreds of microns in diameter, C. elegans harbors only 302 tiny neurons from which the cell lineage is completely described, as is the case for all the other somatic cells. As such, this nervous system appears at first sight incommensurable with those of higher organisms, although genome-wide comparison of predicted C. elegans genes with their counterparts in vertebrates revealed many parallels. Together with its short lifespan and ease of cultivation, suitability for high-throughput genetic screenings and genome-wide RNA interference approaches, access to an advanced genetic toolkit and cell-ablation techniques, it seems that this tiny transparent organism of only 1mm in length has nothing to hide. Recently, highly exciting developments have occurred within the field of neuropeptidergic signaling in C. elegans, not only because of the availability of a sequenced genome since 1998, but especially because of state of the art post genomic technologies, that allow for molecular characterization of the signaling molecules. Here, we will focus on endogenous, bioactive (neuro)peptides and mainly discuss biosynthesis, peptide sequence information, localization and G-protein coupled receptors of the three major peptide families in C. elegans.

Mass spectrometric characterization and physiological actions of VPNDWAHFRGSWamide, a novel B type allatostatin in the crab, Cancer borealis

The neural networks in the crustacean stomatogastric ganglion are modulated by neuroactive substances released locally into the neuropil of the stomatogastric ganglion and by circulating hormones released by neuroendocrine structures including the pericardial organs. Using nanoscale liquid chromatography coupled to electrospray ionization quadrupole-time-of-flight mass spectrometry, we have identified and sequenced a novel B type allatostatin (CbAST-B1), VPNDWAHFRGSWamide, present in the pericardial organs of the crabs, Cancer borealis, and Cancer productus. We describe the physiological actions of CbAST-B1 on the pyloric rhythm of the stomatogastric ganglion of the crab, Cancer borealis. CbAST-B1 reduces the pyloric network frequency in a dose-dependent manner. The effect of bath-applied CbAST-B1 depends on the preceding physiological state of the preparation. Surprisingly, despite marked amino-acid sequence dissimilarity between the novel CbAST-B1 and the A type allatostatin family of peptides (AST-A), the physiological effects of CbAST-B1 are similar to those of AST-A.

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.

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.

Naturally occurring antisense RNA of allatostatin gene in the prawn, Macrobrachium rosenbergii

Allatostatins are important regulatory neuropeptides which are widely distributed in invertebrates and execute their functions through either neural or humoral routes. However, the regulatory mechanism of the gene expression is unclear. In this paper, we report a naturally occurring antisense transcript, named as asMacro-AST A, of the crustacean FGLamide allatostatin gene (Macro-AST A) from the prawn, Macrobrachium rosenbergii. The asMacro-AST A contains an 843-bp sequence fully complementary to the 3' end of the Macro-AST A. To our knowledge, this is the first report of a natural antisense transcript in crustacean and the first endogenous antisense transcript of all identified allatostatin genes. Northern blotting analysis demonstrated that the gene was expressed in the thoracic ganglia where the sense gene was also expressed. Furthermore, we have detected a RNA-RNA duplex between the sense-antisense complementary region by using RNase protection analysis and RT-PCR. These results suggest that the antisense gene may play a role in the regulation of Macro-AST A gene expression.

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.

Molecular cloning and characterization of FGLamide allatostatin gene from the prawn, Macrobrachium rosenbergii

Allatostatins are important regulatory neuropeptides that inhibit juvenile hormone (JH) biosynthesis by the corpora allata (CA) in insects. However, to date, the structure and expression of the gene encoding allatostatins have not been reported in any species other than insects. In this study, we used a combination of a semi-nested polymerase chain reaction (PCR) and screening of a central nervous system cDNA library of Macrobrachium rosenbergii to isolate and sequence a cDNA clone (2885 bp) encoding a 701 amino acid FGLamide allatostatin precursor polypeptide. This is the first reported allatostatin gene in crustacean. The deduced precursor was conceptually split into at least 35 FGLamide allatostatins at dibasic cleavage sites (Lys and Lys/Arg), far more than reported for any other known FGLamide allatostatin precursors from insects (13-14 allatostatins). Reverse transcription-polymerase chain reaction (RT-PCR) analysis demonstrated that the gene was expressed in the brain, gut, thoracic and abdominal ganglia, but not in the heart, muscle, ovary, gill, or hepatopancreas. Furthermore, developmentally-dependent expression of the gene was observed in the brain and thoracic ganglia of the prawn by using semi-quantitative RT-PCR analysis.

Allatostatin-like immunoreactivity in the abdomen of the locust Schistocerca gregaria

A polyclonal antibody against allatostatin 1 (AST-1) of cockroach Diploptera punctata was used to investigate the distribution of AST-like immunoreactivity within the abdomen of the locust, Schistocerca gregaria. In the abdominal ganglia, AST-like immunoreactivity was found in both cell bodies and neuropile. In ganglia 6 and 7, staining was found in serial homologous cell bodies in anterior dorsolateral and dorsomedial, and posterior ventrolateral and ventromedial locations. In the terminal ganglion, the numerous immunoreactive somata were smaller in size than those in the unfused ganglia. The combination of backfill experiments with immunocytochemistry showed that, in abdominal ganglion 7, one neuron of the ventromedian cell body cluster and two of the ventrolateral cluster innervated the oviduct, which itself was covered with a dense mesh of AST-immunoreactive varicosities. Combining electron microscopy with immunohistochemistry revealed AST-like immunoreactivity in dense-core vesicles located in neurohaemal-like terminals lacking structures normally found in synapses. A mesh of AST-immunoreactive varicosities was also found on the muscles of the spermatheca and the spermathecal duct. In addition, a mesh of strongly stained varicosities was present in the distal perisympathetic organs (neurohaemal organs in the abdomen) and on the lateral heart nerves (a putative neurohaemal release zone). These data indicate that AST is an important neuroactive substance that is probably involved in multiple tasks in the control of the locust abdomen.

Genotoxic evaluation of the biocomponents of the cricket, Gryllus bimaculatus, using three mutagenicity tests

The mutagenic potential of the extracted components of Gryllus bimaculatus, a species of cricket, was evaluated using short-term genotoxicity tests including the Ames, chromosome aberration, and micronuclei tests. In a Salmonella typhimurium assay, G. bimaculatus extract did not produce any mutagenic response in the absence or presence of S9 mix with TA98, TA100, TA1535, and TA1537. Chromosome aberration testing showed that G. bimaculatus had no significant effect on Chinese hamster ovary (CHO) cells. In the mouse micronucleus test, no significant alteration in occurrence of micronucleated polychromatic erythrocytes was observed in ICR male mice intraperitoneally administered with G. bimaculatus extract at doses of 15, 150, or 1500 mg/kg. These results indicate that G. bimaculatus extract exerts no mutagenic effect in these in vitro and in vivo systems.

Development of A-type allatostatin immunoreactivity in antennal lobe neurons of the sphinx moth Manduca sexta

The antennal lobe (AL) of the sphinx moth Manduca sexta is a well-established model system for studying mechanisms of neuronal development. To understand whether neuropeptides are suited to playing a role during AL development, we have studied the cellular localization and temporal expression pattern of neuropeptides of the A-type allatostatin family. Based on morphology and developmental appearance, we distinguished four types of AST-A-immunoreactive cell types. The majority of the cells were local interneurons of the AL (type Ia) which acquired AST-A immunostaining in a complex pattern consisting of three rising (RI-RIII) and two declining phases (DI, DII). Type Ib neurons consisted of two local neurons with large cell bodies not appearing before 7/8 days after pupal ecdysis (P7/P8). Types II and III neurons accounted for single centrifugal neurons, with type II neurons present in the larva and disappearing in the early pupa. The type III neuron did not appear before P7/P8. RI and RII coincided with the rises of the ecdysteroid hemolymph titer. Artificially shifting the pupal 20-hydroxyecdysone (20E) peak to an earlier developmental time point resulted in the precocious appearance of AST-A immunostaining in types Ia, Ib, and III neurons. This result supports the hypothesis that the pupal rise in 20E plays a role in AST-A expression during AL development. Because of their early appearance in newly forming glomeruli, AST-A-immunoreactive fibers could be involved in glomerulus formation. Diffuse AST-A labeling during early AL development is discussed as a possible signal providing information for ingrowing olfactory receptor neurons.

Peptidomic analysis of the larval Drosophila melanogaster central nervous system by two-dimensional capillary liquid chromatography quadrupole time-of-flight mass spectrometry

Peptides are the largest class of signalling molecules found in animals. Nevertheless, in most proteomic studies peptides are overlooked since they literally fall through the mazes of the net. In analogy with proteomics technology, where all proteins expressed in a cell or tissue are analyzed, the peptidomic approach aims at the simultaneous visualization and identification of the whole peptidome of a cell or tissue, i.e. all expressed peptides with their post-translational modifications. In this paper we describe the analysis of the larval fruit fly central nervous system using two-dimensional capillary liquid chromatography/quadrupole time-of-flight tandem mass spectrometry (LC/Q-TOF-MS/MS. Using the central nervous systems of only 50 larval Drosophila as starting material, we identified 38 peptides in a single analysis, 20 of which were not detected in a previous study that reported on the one-dimensional capillary LC/MS/MS analysis of the same tissue. Among the 38 sequenced peptides, some originate from precursors, such as the tachykinin and the IFamide precursor that were entirely missed in the first study. This clearly demonstrates that the two-dimensional capillary LC approach enhances the coverage of the peptidomic analysis.

Cloning and tissue-specific localization of cricket-type allatostatins from Gryllus bimaculatus

Cricket- or B-type allatostatins [W(X(6))W-amides] inhibit the biosynthesis of juvenile hormones in vitro in crickets. Peptides of this family are present also in other insects where they may bare different functions. Here we report the identification of a partial sequence of the B-type preproallatostatin from Gryllus bimaculatus. By PCR screening of a random primer cDNA library and by RACE, a 535bp 3'cDNA sequence was obtained which encodes a putative translation product of 85 amino acids, containing three copies of Grybi-AST B1 and one copy each of Grybi-AST B2, Grybi-AST B3, and Grybi-AST B6. The last represents a novel member of this peptide family. By means of one-step RT-PCR, RNA dot blot, and RT in situ PCR analyses the mRNA expression of the gene in the central nervous system and the digestive tract of female adult crickets was demonstrated. The results confirm that the B-type allatostatins of G. bimaculatus are brain-gut 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.

The distribution and effects of Dippu-allatostatin-like peptides in the blood-feeding bug, Rhodnius prolixus

Using a polyclonal antiserum to Dippu-allatostatin 7 (Dippu-AST 7; formerly AST 1) of the cockroach Diploptera punctata, we have demonstrated the presence of AST-like immunoreactivity (ALI) in cells and processes throughout the nervous system, gut, and peripheral tissues of unfed fifth instar and adult Rhodnius prolixus. ALI in apparent neurosecretory cells of the brain, suboesophageal ganglion, and mesothoracic ganglionic mass, as well as in midgut endocrine cells, suggests that Rhodnius allatostatins may act as neurohormones/hormones. The presence of ALI in possible interneurons and areas of neuropile throughout the CNS also suggests roles as neuromodulators and/or neurotransmitters. Dippu-AST 7 inhibits spontaneous and leucokinin 1 (LK 1)-induced contractions of the Rhodnius hindgut in a dose-dependent manner. The low concentrations capable of inhibiting both spontaneous (10(-12)M) and LK 1-induced contractions (10(-10) to 10(-9)M) suggest that ASTs may be acting as neurohormones/hormones on the hindgut. We have also shown that Dippu-AST 7 influences the muscle activity of the Rhodnius dorsal vessel at concentrations as low as 10(-11)M.