Book Review: Insect Physiology and Biochemistry. Second Edition. CRC Press, Boca Raton.

Insect physiology is a specialized discipline within the larger framework of animal physiology. Almost every graduate program in Entomology has a requirement for an insect physiology course and an up to date textbook is required. Students using insects as model organisms should also be interested in this textbook. The textbook primarily describes physiology but there is quite a bit of biochemistry, which adds to the text as a resource. Physiology and biochemistry should be taught together; in order to understand physiology the biochemistry behind the physiology must also be understood. This 2nd edition textbook does a nice job of presenting information to students

The PRXamide Neuropeptide Signalling System: Conserved in Animals

The PRXamide family of neuropeptides is based on the core amino acids at the C-terminal end that are required for activity and on sequence homology of their cell-surface G protein-coupled receptors. The PRXamide family of neuropeptides includes the pyrokinins, pheromone biosynthesis-activating neuropeptides, diapause hormone, CAPA/periviscerokinins (aka cardioacceleratory peptide 2b), and ecdysis-triggering hormone found throughout the Insecta. The vertebrate homologues include neuromedin U because it has a PRNamide C-terminal sequence. The vertebrate G protein-coupled receptors that are homologous to the insect receptors also include receptors for ghrelin, motilin, and thyrotropin-releasing hormone in addition to the neuromedin U receptor. This review will not only summarize the recent literature on this neuropeptide family but also include recent information about the prevalence of the neuropeptides across the Insecta based primarily on genomic and transcriptomic sequence information. Information is also included about the PRXamide ligands and their receptors in other protostome and deuterostome lineages. The conservation of ligands and receptors among all animals will be presented along with ideas on the coevolution of ligands and receptors. The first four pages of this chapter are available

Site-directed mutagenesis and PBAN activation of the Helicoverpa zea PBAN-receptor

Pheromone biosynthesis-activating neuropeptide (PBAN) and pyrokinins belong to a family of insect peptide hormones that have a common FXPRLamide C-terminal ending. The G-protein-coupled receptors (GPCRs) for this peptide family were first identified from a moth and Drosophila with sequence similarity to neuromedin U receptors from vertebrates. We have characterized the PBAN-receptor (PBAN-R or PR) active binding domains using chimeric GPCRs and proposed that extracellular loop 3 is critical for ligand selection. Here, we characterized the 3rd extracellular domain of PBAN-R through site-directed point mutations. Results are discussed in context of the structural features required for receptor activation using receptor activation experiments and in silico computational modeling. This research will help in characterizing these receptors towards a goal of finding agonists and/or antagonists for PBAN/pyrokinin receptors

Interplay Between Oxytetracycline and the Homozygote kdr (L1014F) Resistance Genotype on Fecundity in Anopheles gambiae (Diptera: Culicidae) Mosquitoes

The insecticide resistance in Anopheles gambiae mosquitoes has remained the major threat for vector control programs but the fitness effects conferred by these mechanisms are poorly understood. To fill this knowledge gap, the present study aimed at testing the hypothesis that antibiotic oxytetracycline could have an interaction with insecticide resistance genotypes and consequently inhibit the fecundity in An. gambiae. Four strains of An. gambiae: Kisumu (susceptible), KisKdr (kdr (L1014F) resistant), AcerKis (ace-1 (G119S) resistant) and AcerKdrKis (both kdr (L1014F) and ace-1 (G119S) resistant) were used in this study. The different strains were allowed to bloodfeed on a rabbit previously treated with antibiotic oxytetracycline at a concentration of 39·10–5 M. Three days later, ovarian follicles were dissected from individual mosquito ovaries into physiological saline solution (0.9% NaCl) under a stereomicroscope and the eggs were counted. Fecundity was substantially lower in oxytetracycline-exposed KisKdr females when compared to that of the untreated individuals and oxytetracycline-exposed Kisumu females. The exposed AcerKis females displayed an increased fecundity compared to their nontreated counterparts whereas they had reduced fecundity compared to that of oxytetracycline-exposed Kisumu females. There was no substantial difference between the fecundity in the treated and untreated AcerKdrKis females. The oxytetracycline-exposed AcerKdrKis mosquitoes had an increased fecundity compared to that of the exposed Kisumu females. Our data indicate an indirect effect of oxytetracycline in reducing fecundity of An. gambiae mosquitoes carrying kdrR (L1014F) genotype. These findings could be useful for designing new integrated approaches for malaria vector control in endemic countries

Identification and characterization of the pyrokinin/pheromone biosynthesis activating neuropeptide family of G protein-coupled receptors from Ostrinia nubilalis

Insects have two closely related G protein-coupled receptors belonging to the pyrokinin/pheromone biosynthesis activating neuropeptide (pyrokinin/PBAN) family, one with the ligand PBAN or pyrokinin-2 and another with diapause hormone or pyrokinin-1 as a ligand. A related receptor is activated by products of the capa gene, periviscerokinins. Here we characterized the PBAN receptor and the diapause hormone receptor from the European corn borer, Ostrinia nubilalis. We also identified a partial sequence for the periviscerokinin receptor. Quantitative PCR of mRNA for all three receptors indicated differential expression in various life stages and tissues. All three splice variants of the PBAN receptor were identified with all variants found in pheromone gland tissue. Immunohistochemistry of V5 tags of expressed receptors indicated that all three variants and the diapause hormone receptor were expressed at similar levels in Spodoptera frugiperda 9 (Sf9) cells. However, the A- and B-variants were not active in our functional assay, which confirms studies from other moths. Functional expression of the C-variant indicated that it is has a 44 nM half effective concentration for activation by PBAN. The diapause hormone receptor was activated by diapause hormone with a 150 nM half effective concentration.This article is from Insect Molecular Biology 22 (2013): 331, doi:10.1111/imb.12025. Posted with permission.</p

Sex pheromone biosynthetic pathway for disparlure in the gypsy moth, Lymantria dispar

6 pages, 7 figures.-- PMID: 12533665 [PubMed].-- PMCID: PMC298683.-- Printed version published Feb 4, 2003.-- Full text version available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC298683/?tool=pubmedThe pheromone biosynthetic pathway for production of the sex pheromone disparlure, 2-methyl-7R,8S-epoxy-octadecane, was determined for the gypsy moth. Each step in the pathway was followed by using deuterium-labeled compounds that could be identified by using GC/MS. This approach provides unequivocal determination of specific reactions in the pathway. It was shown that the alkene precursor, 2-methyl-Z7-octadecene, is most likely made in oenocyte cells associated with abdominal epidermal cells. The pathway begins with valine contributing carbons for chain initiation, including the methyl-branched carbon, followed by chain elongation to 19 carbons. The double bond is introduced with an unusual Δ12 desaturase that utilizes a methyl-branched substrate. The resulting 18-methyl-Z12-nonadecenoate is decarboxylated to the hydrocarbon, 2-methyl-Z7-octadecene. The alkene is then transported to the pheromone gland through the hemolymph, most probably by lipophorin. At the pheromone gland, the alkene is unloaded and transformed into the epoxide disparlure for release into the environment. A chiral HPLC column was used to demonstrate that the (R,S)-stereoisomer of the epoxide, (+)-disparlure is found in pheromone glands.This work was supported by grants from the U.S. Department of Agriculture–National Research Initiative (2001-35302-10882) and the U.S.–Spain Joint Commission on Scientific and Technological Cooperation, and by Hatch Act and State of Iowa funds.Peer reviewe

Neonicotinoids Can Cause Arrested Pupal Ecdysis in Lepidoptera

Recently, we reported a novel mode of action in monarch butterfly (Danaus plexippus) larvae exposed to neonicotinoid insecticides: arrest in pupal ecdysis following successful larval ecdysis. In this paper, we explore arrested pupal ecdysis in greater detail and propose adverse outcome pathways to explain how neonicotinoids cause this effect. Using imidacloprid as a model compound, we determined that final-instar monarchs, corn earworms (Helicoverpa zea), and wax moths (Galleria mellonella) showed high susceptibility to arrested pupal ecdysis while painted ladies (Vanessa cardui) and red admirals (Vanessa atalanta) showed low susceptibility. Fall armyworms (Spodoptera frugiperda) and European corn borers (Ostrinia nubilalis) were recalcitrant. All larvae with arrested ecdysis developed pupal cuticle, but with incomplete shedding of larval cuticle and unexpanded pupal appendages; corn earworm larvae successfully developed into adults with unexpanded appendages. Delayed initiation of pupal ecdysis was also observed with treated larvae. Imidacloprid exposure was required at least 26 h prior to pupal ecdysis to disrupt the molt. These observations suggest neonicotinoids may disrupt the function of crustacean cardioactive peptide (CCAP) neurons, either by directly acting on their nicotinic acetylcholine receptors or by acting on receptors of inhibitory neurons that regulate CCAP activity

Control of sex pheromone biosynthesis in the moth Mamestra brassicae by the pheromone biosynthesis activating neuropeptide

The physiological route for the action of the pheromone biosynthesis activating neuropeptide (PBAN) was determined in Mamestra brassicae (L.) (Lepidoptera:Noctuidae). Removal of the ventral nerve cord including the terminal abdominal ganglia did not affect PBAN stimulation of pheromone production and the biogenic amine octopamine did not stimulate pheromone production in isolated abdomens. PBAN-like activity was found in the hemolymph of intact females in scotophase and not in the hemolymph of decapitated females or females in photophase. Our results suggest that PBAN follows a humoral route to its site of action rather than a neural one after being released from the brain. The hormonal control of the pheromone biosynthetic pathway was investigated using labeled precursors. Our results suggest that PBAN regulates an early step in the pheromone biosynthetic pathway, contrary to a previous report that it stimulates the Δ11-desaturase