orcokinin and proctolin

The genome of the spider mite was prospected for the presence of genes coding neuropeptides, neurohormones and their putative G-protein coupled receptors. Fifty one candidate genes were found to encode neuropeptides or neurohormones. These include all known insect neuropeptides and neurohormones, with the exception of sulfakinin, corazonin, neuroparsin and PTTH. True orthologs of adipokinetic hormone (AKH) were neither found, but there are three genes encoding peptides similar in structure to both AKH and the AKH-corazonin-related peptide. We were also unable to identify the precursors for pigment dispersing factor (PDF) or the recently discovered trissin. However, the spider mite probably does have such genes, as we found their putative receptors. A novel arthropod neuropeptide gene was identified that shows similarity to previously described molluscan neuropeptide genes and was called EFLamide. A total of 65 putative neuropeptide GPCR genes were also identified, of these 58 belong to the A-family and 7 to the B-family. Phylogenetic analysis showed that 50 of them are closely related to insect GPCRs, which allowed the identification of their putative ligand in 39 cases with varying degrees of certainty. Other spider mite GPCRs however have no identifiable orthologs in the genomes of the four holometabolous insect species best analyzed. Whereas some of the latter have orthologs in hemimetabolous insect species, crustaceans or ticks, for others such arthropod homologs are currently unknown.

Topics: Amino Acid Sequence; Animals; Arthropod Proteins; Insect Hormones; Insulins; Invertebrate Hormones; Molecular Sequence Data; Nerve Tissue Proteins; Neuropeptides; Neurotransmitter Agents; Oligopeptides; Receptors, G-Protein-Coupled; Tetranychidae

The Aphidoidea is an insect superfamily comprising most of the known aphid species. While small in size, these animals are of considerable economic importance as many members of this taxon are serious agricultural pests, inflicting physical damage upon crop plants and serving as vectors in the transmission of viral plant diseases. In terms of identifying the paracrines/hormones used to modulate behavior, particularly peptides, members of the Aphidoidea have largely been ignored, as it is not tractable to isolate the large pools of tissue needed for standard biochemical investigations. Here, a bioinformatics approach to peptide discovery has been used to overcome this limitation of scale. Specifically, in silico searches of publicly accessible aphidoidean ESTs were conducted to identify transcripts encoding putative peptides precursors, with the mature peptides contained within them deduced using peptide processing software and homology to known arthropod sequences. In total, 39 ESTs encoding putative peptides precursors were identified from four aphid species: Acyrthosiphon pisum (14 ESTs), Aphis gossypii (four ESTs), Myzus persicae (20 ESTs) and Toxoptera citricida (one EST). These precursors included ones predicted to encode isoforms of B-type allatostatin, crustacean cardioactive peptide, FMRFamide-related peptide (both myosuppressin and short neuropeptide F subfamilies), insect kinin, orcokinin, proctolin, pyrokinin/periviscerokinin/pheromone biosynthesis activating neuropeptide, SIFamide and tachykinin-related peptide. In total, 83 peptides were characterized from the identified precursors, most novel, including two B-type allatostatins possessing the variant -WX(7)Wamide motif, two N-terminally extended proctolin isoforms and an N-terminally truncated and substituted SIFamide. Collectively, these results expand greatly the number of known/predicted aphid peptide paracrines/hormones, and provide a strong foundation for future molecular and physiological investigations of peptidergic control in this insect group.

Topics: Amino Acid Sequence; Animals; Aphids; Computational Biology; Expressed Sequence Tags; FMRFamide; Insect Hormones; Molecular Sequence Data; Neuropeptides; Oligopeptides; Peptide Hormones; Sequence Homology, Amino Acid; Tachykinins

The Ixodoidea (ticks) are important vectors in the transmission of many human diseases; for example, the blacklegged tick Ixodes scapularis is the major vector in the transmission of Lyme disease, the most frequently reported vector-borne illness in the United States. The development of expressed sequence tags (ESTs) for ixodoidean cDNA libraries, and their public deposition, has generated a rich resource for protein discovery in members of this taxon, thereby providing an opportunity for better understanding the physiology and behavior of these disease vectors. Here, in silico searches of publicly accessible ESTs were conducted to identify transcripts encoding putative ixodoidean neuropeptide precursors, with the mature peptides contained within them predicted using online peptide processing programs and homology to known arthropod sequences. In total, 37 putative neuropeptide-encoding ESTs were identified from three ixodoidean species: I. scapularis (29 ESTs), Rhipicephalus microplus (seven ESTs) and Amblyomma americanum (one EST). Among those identified from I. scapularis were ones predicted to encode isoforms of corazonin, crustacean hyperglycemic hormone/ion transport peptide, diuretic hormone (both calcitonin- and corticotropin-releasing factor-like), FMRFamide-related peptide (both short neuropeptide F and sulfakinin subfamilies) orcokinin, proctolin, pyrokinin/periviscerokinin/pheromone biosynthesis activating neuropeptide, SIFamide, and tachykinin-related peptide. Collectively, 80 distinct ixodoidean neuropeptides were characterized from the identified precursors. These results not only expand greatly the number of known/predicted ixodoidean neuropeptides, but also provide a strong foundation for future molecular and physiological investigations of peptidergic control in this important group of disease-transmitting arthropods.

Topics: Amino Acid Sequence; Animals; Base Sequence; Databases, Genetic; Databases, Nucleic Acid; Expressed Sequence Tags; Gene Library; Insect Proteins; Molecular Sequence Data; Neuropeptides; Oligopeptides; Sequence Alignment; Ticks

The pericardial organs (POs) are a pair of neurosecretory organs that surround the crustacean heart and release neuromodulators into the hemolymph. In adult crustaceans, the POs are known to contain a wide array of peptide and amine modulators. However, little is known about the modulatory content of POs early in development. We characterize the morphology and modulatory content of pericardial organs in the embryonic lobster, Homarus americanus. The POs are well developed by midway through embryonic (E50) life and contain a wide array of neuromodulatory substances. Immunoreactivities to orcokinin, extended FLRFamide peptides, tyrosine hydroxylase, proctolin, allatostatin, serotonin, Cancer borealis tachykinin-related peptide, cholecystokinin, and crustacean cardioactive peptide are present in the POs by approximately midway through embryonic life. There are two classes of projection patterns to the POs. Immunoreactivities to orcokinin, extended FLRFamide peptides, and tyrosine hydroxylase project solely from the subesophageal ganglion (SEG), whereas the remaining modulators project from the SEG as well as from the thoracic ganglia. Double-labeling experiments with a subset of modulators did not reveal any colocalized peptides in the POs. These results suggest that the POs could be a major source of neuromodulators early in development.

Topics: Animals; Heart; Nephropidae; Nervous System; Neural Pathways; Neuropeptides; Neurosecretory Systems; Neurotransmitter Agents; Oligopeptides; Serotonin; Tyrosine 3-Monooxygenase