Expression pattern and function of alternative splice variants of glutamate-gated chloride channel in the housefly Musca domestica

Glutamate-gated chloride channels (GluCls) mediate fast inhibitory neurotransmission in invertebrate nervous systems. cDNAs encoding two alternative splice variants (MdGluClB and C) of the GluCl subunit were cloned from the housefly Musca domestica. The expression patterns of three variants, including the previously reported MdGluClA, differed among the body parts (head, thorax, abdomen, and leg) of the adult housefly and among developmental stages (embryo, larva, pupa, and adult). The MdGluClA and B transcripts were abundant in the central nervous system of the adult, whereas the MdGluClC transcript was expressed in the central nervous system and as the predominant variant in the peripheral tissues. The sensitivities to the agonist glutamate and the allosteric activator ivermectin B1a did not differ between channels containing MdGluCl variants when they were singly or co-expressed in Xenopus oocytes. By contrast, MdGluClA and B channels were more sensitive to the channel blockers fipronil and picrotoxinin than was MdGluClC channels. Heteromeric channels containing different subunit variants were more sensitive to picrotoxinin than were homomeric channels. Heteromeric channels were more sensitive to fipronil than were homomeric MdGluClC channels but not than homomeric MdGluClA and B channels. These results suggest that functionally indistinguishable but pharmacologically distinct GluCls are expressed in a spatially and temporally distinct manner in the housefly.

Cloning, expression, and purification of a new antibacterial substance gene from larvae of Musca domestica (Diptera: Muscidae)

Musca domestica L. (Diptera: Muscidae), the housefly, exhibits unique immune defenses and can produce antibacterial substances upon stimulation with bacteria. On the basis of the cDNA library constructed using the suppression subtractive hybridization method, a 1188-bp antibacterial substance gene, which we named AS566, was amplified by rapid amplification of cDNA ends from M. domestica larva stimulated with Salmonella pullorum (Enterobacteriaceae: Salmonella). In this study, the full-length AS566 gene was cloned and inserted into a His-tagged Escherichia coli (Enterobacteriaceae: Escherichia) prokaryotic expression system to enable production of the recombinant protein. The recombinant AS566 protein was purified in denatured form from inclusion bodies and renatured to obtain functionally active AS566 protein. The bacteriostatic activity of the recombinant purified AS566 protein was assessed using the Oxford plate assay system and the results indicated that AS566 had antibacterial activity against six bacteria, including an E. coli clinical isolate, S. pullorum, Streptococcus bovis (Streptococcaceae: Streptococcus), Streptococcus suis, and Staphylococcus aureus (Staphylococcaceae: Staphylococcus) in vitro. The antibacterial activity of AS566 toward Gram- bacteria was two times greater than that against Gram+ bacteria. The sequencing results and BLAST analysis showed that the antibacterial substance gene AS566 was not homologous to any other antibacterial substance genes in GenBank. The antibacterial mechanisms of the newly discovered AS566 protein warrant further study.

Differential distribution of glutamate- and GABA-gated chloride channels in the housefly Musca domestica

l-Glutamic acid (glutamate) mediates fast inhibitory neurotransmission by affecting glutamate-gated chloride channels (GluCls) in invertebrates. The molecular function and pharmacological properties of GluCls have been well studied, but not much is known about their physiological role and localization in the insect body. The distribution of GluCls in the housefly (Musca domestica L.) was thus compared with the distribution of γ-aminobutyric acid (GABA)-gated chloride channels (GABACls). Quantitative PCR and ligand-binding experiments indicate that the GluCl and GABACl transcripts and proteins are predominantly expressed in the adult head. Intense GluCl immunostaining was detected in the lamina, leg motor neurons, and legs of adult houseflies. The GABACl (Rdl) immunostaining was more widely distributed, and was found in the medulla, lobula, lobula plate, mushroom body, antennal lobe, and ellipsoid body. The present findings suggest that GluCls have physiological roles in different tissues than GABACls.

Venom of the ectoparasitoid, Nasonia vitripennis, influences gene expression in Musca domestica hemocytes

Insect hosts have evolved potent innate immunity against invasion by parasitoid wasps. Host/parasitoids live in co-evolutionary relationships. Nasonia vitripennis females inject venom into their dipteran hosts just prior to laying eggs on the host's outer integument. The parasitoid larvae are ectoparasitoids because they feed on their hosts within the puparium, but do not enter the host body. We investigated the influence of N. vitripennis venom on the gene expression profile of hemocytes of their hosts, pupae of the housefly, Musca domestica. We prepared venom by isolating venom glands and treated experimental host pupae with venom. We used suppression subtractive hybridization (SSH) to determine the influence of venom on hemocyte gene expression. At 1 h post treatment, we recorded decreases in transcript levels of 133 EST clones derived from forward a subtractive library of host hemocytes and upregulation in transcript levels of 111 EST clones from the reverse library. These genes are related to immune and stress response, cytoskeleton, cell cycle and apoptosis, metabolism, transport, and transcription/translation regulation. We verified the reliability of our data with reverse transcription quantitative real-time PCR analysis of randomly selected genes, and with assays of enzyme activities. These analyses showed that the expression level of all selected genes were downregulated after venom treatment. Outcomes of our experiments support the hypothesis that N. vitripennis venom influences the gene expression in host hemocytes. We conclude that the actions of venom on host gene expression influence host biology in ways that benefit the development and emergence of the next generation of parasitoids.

The phenolic monoterpenoid carvacrol inhibits the binding of nicotine to the housefly nicotinic acetylcholine receptor

BACKGROUND

The phenolic monoterpenoid carvacrol, which is found in many plant essential oils (thyme, oregano and Alaska yellow cedar), is highly active against pest arthropods, but its mechanisms of action are not fully understood. Here, carvacrol is shown to bind in a membrane preparation containing insect nicotinic acetylcholine receptors (nAChRs). [(14) C]-Nicotine binding assays with Musca domestica (housefly) nAChRs were used in this study to demonstrate carvacrol's binding to nAChRs, thereby acting as a modulator of the receptors.

RESULTS

Carvacrol showed a concentration-dependent inhibition of [(14) C]-nicotine binding in a membrane preparation of housefly heads containing nAChRs, with IC50 = 1.4 μM, in a non-competitive pattern. Binding studies with neonicotinoid insecticides revealed that imidacloprid and thiamethoxam did not inhibit the binding of [(14) C]-nicotine, while dinotefuran, from the guanidine subclass of neonicotinoids, inhibited nicotine binding like carvacrol.

CONCLUSIONS

Carvacrol binds to housefly nAChRs at a binding site distinct from nicotine and acetylcholine, and the nAChRs are a possible target of carvacrol for its insecticidal activity.

Expression of lysozyme in the life history of the house fly (Musca domestica l.)

From egg to adult, all life history stages of house flies associate with septic environments teeming with bacteria. House fly lysozyme was first identified in the larval midgut, where it is used for digestion of microbe-rich meals because of its broad-spectrum activity against gram-positive and gram-negative bacteria as well as fungi. This study aimed to determine the temporal expression of lysozyme in the life history of house flies (from egg through adults) on both the mRNA and protein level, and to determine the tissue-specific expression of lysozyme in adult flies induced by feeding Staphylococcus aureus. From 30-min postoviposition through adulthood, all life history stages of the house fly express lysozyme on the mRNA level. In adult flies, lysozyme is expressed both locally in the alimentary canal and systemically in the fat body. Interestingly, we found that during the normal life history of flies, lysozyme protein was only detected in larval stages and older adults, likely because of ingestion of immune-stimulating levels of bacteria, not experienced during egg, pupa, and teneral adult stages. Constitutive expression on the mRNA level implies that this effector is a primary defense molecule in all stages of the house fly life history, and that a mechanism for posttranscriptional control of mature lysozyme enzyme expression may be present. Lysozyme active enzyme primarily serves both a digestive and defensive function in larval and adult flies, and may be a key player in the ability of Musca domestica L. to thrive in microbe-rich environments.

Genetic control of courtship behavior in the housefly: evidence for a conserved bifurcation of the sex-determining pathway

In Drosophila melanogaster, genes of the sex-determination hierarchy orchestrate the development and differentiation of sex-specific tissues, establishing sex-specific physiology and neural circuitry. One of these sex-determination genes, fruitless (fru), plays a key role in the formation of neural circuits underlying Drosophila male courtship behavior. Conservation of fru gene structure and sex-specific expression has been found in several insect orders, though it is still to be determined whether a male courtship role for the gene is employed in these species due to the lack of mutants and homologous experimental evidence. We have isolated the fru ortholog (Md-fru) from the common housefly, Musca domestica, and show the gene's conserved genomic structure. We demonstrate that male-specific Md-fru transcripts arise by conserved mechanisms of sex-specific splicing. Here we show that Md-fru, is similarly involved in controlling male courtship behavior. A male courtship behavioral function for Md-fru was revealed by the behavioral and neuroanatomical analyses of a hypomorphic allele, Md-tra(man) , which specifically disrupted the expression of Md-fru in males, leading to severely impaired male courtship behavior. In line with a role in nervous system development, we found that expression of Md-fru was confined to neural tissues in the brain, most prominently in optic neuropil and in peripheral sensory organs. We propose that, like in Drosophila, overt sexual differentiation of the housefly depends on a sex-determining pathway that bifurcates downstream of the Md-tra gene to coordinate dimorphic development of non-neuronal tissues mediated by Md-dsx with that of neuronal tissues largely mediated by Md-fru.

A full-scale house fly (Diptera: Muscidae) larvae bioconversion system for value-added swine manure reduction

Manure produced from confined animal farms can threaten public and environmental health if not managed properly. Herein, a full-scale commercial bioconversion operation in DeQing County, China for value-added swine manure reduction using house fly, Musca domestica L., larvae is reported. The greenhouse-assisted larvae bioreactor had a maximum daily treatment capacity of 35 m(3) fresh raw manure per day. The bioconversion process produced a fresh larvae yield of 95-120 kg m(3) fresh raw manure. This process provided an alternative animal foodstuff (having 56.9 and 23.8% protein and total fat as dry matter, respectively), as well as captured nutrients for agricultural re-utilization. Bioconversion reduced odour emission (characterized by 3-methylindole) and the Escherichia coli (E. coli) index by 94.5 and 92.0%, respectively, and reductions in total weight, moisture and total Kjeldahl nitrogen in solids were over 67.2, 80.0 and 76.0%, respectively. Yearly profit under this trial period ranged from US$33.4-46.1 per m(3). It is concluded that swine manure larvae bioconversion technology with subsequent production of value-added bio-products can be a promising avenue when considering a programme to reduce waste products in an intensive animal production system.

[Effect of light regime on biochemical parameters of development of stress-reactions of Musca domestica L. lines with different lifspan]

The paper presents results obtained at recording under conditions of stresses of different character of activities of enzymes (tyrosinase, DOPA-oxidase, acetylcholinesterase) and level of the catecholamine content in tissues of head and fat body of imago and larvae of housefly from lines with different lifespan. A suggestion is put forward about different mechanisms mediating photoperiodic regulation of metabolism in individuals with different intensity of metabolism.

Stress-induced HSP70 from Musca domestica plays a functionally significant role in the immune system

As important molecular chaperones, members of the 70kDa heat shock protein (HSP70) family play essential roles in stress tolerance and innate immunity in organisms. The full-length complementary DNA (cDNA) of a novel inducible HSP70, named as MdHSP70, was isolated from Musca domestica. The cDNA clone consisted of 2411 bp with a 1956 bp open reading frame which encodes 651 amino acids. Using real-time quantitative polymerase chain reaction (qPCR), we investigated the transcriptional profile of the gene under heat shock, cadmium stress and in response to bacteria. Increased expression of MdHSP70 was observed in response to both heat shock and Cd stress. The expression of MdHSP70 was significantly induced by Escherichia coli or Staphylococcus aureus stimulation. Larvae were fed bacteria expressing dsRNA targeting the MdHSP70 gene. Our results showed high mortality in larvae treated with dsRNA of MdHSP70 at heat shock, Cd stress and bacterial invasion, suggesting that MdHSP70 is potentially involved in the stress and immune responses of the house fly and perhaps contributes to protection against cellular injury.

Swine manure vermicomposting via housefly larvae (Musca domestica): the dynamics of biochemical and microbial features

Improper handling of animal manure generated from concentrated swine operations greatly deteriorates water ecosystems. In this study, a full-scale vermireactor using housefly larvae (Musca domestica) was designed to investigate the effectiveness and efficiency of swine manure reduction, and to explore the associated biochemical-biological mechanisms. The one-week larvae vermireactor resulted in a total weight reduction rate of 106±17 kg/(m(3) d) and moisture reduction of 80.2%. Microbial activities in manure decreased by 45% after vermicomposting, while the activities of cellulose, proteases, and phosphatases in the vermicompost were significantly 69 times, 48%, and 82% lower than those in raw manure, respectively. The vermicompost was exclusively dominated by Entomoplasma somnilux, Proteobacterium, and Clostridiaceae bacterium where the microbial diversity was decreased from 2.57 in raw manure to 1.77. Correlation coefficients statistic showed that organic C might be a key indicator of the biochemical features and microbial functions of the larvae vermireactor.

Quantitative structure-activity relationships of monoterpenoid binding activities to the housefly GABA receptor

BACKGROUND

Monoterpenoids are a large group of plant secondary metabolites. Many of these naturally occurring compounds have shown good insecticidal potency on pest insects. Previous studies in this laboratory have indicated that some monoterpenoids have positive modulatory effects on insect GABA receptors. In this study, the key properties of monoterpenoids involved in monoterpenoid binding activity at the housefly GABA receptor were determined by developing quantitative structure-activity relationship (QSAR) models, and the relationship between the toxicities of these monoterpenoids and their GABA receptor binding activities was evaluated.

RESULTS

Two QSAR models were determined for nine monoterpenoids showing significant effects on [³H]-TBOB binding and for nine p-menthane analogs with at least one oxygen atom attached to the ring. The Mulliken charges on certain carbon atoms, the log P value and the total energy showed significant relationships with binding activities to the housefly GABA receptor in these two QSAR models.

CONCLUSIONS

From the QSAR models, some chemical and structural parameters, including the electronic properties, hydrophobicity and stability of monoterpenoid molecules, were suggested to be strongly involved in binding activities to the housefly GABA receptor. These findings will help to understand the mode of action of these natural insecticides, and provide guidance to predict more monoterpenoid insecticides.

Biodegradation of pig manure by the housefly, Musca domestica: a viable ecological strategy for pig manure management

The technology for biodegradation of pig manure by using houseflies in a pilot plant capable of processing 500–700 kg of pig manure per week is described. A single adult cage loaded with 25,000 pupae produced 177.7±32.0 ml of eggs in a 15-day egg-collection period. With an inoculation ratio of 0.4–1.0 ml eggs/kg of manure, the amount of eggs produced by a single cage can suffice for the biodegradation of 178–444 kg of manure. Larval development varied among four different types of pig manure (centrifuged slurry, fresh manure, manure with sawdust, manure without sawdust). Larval survival ranged from 46.9±2.1%, in manure without sawdust, to 76.8±11.9% in centrifuged slurry. Larval development took 6–11 days, depending on the manure type. Processing of 1 kg of wet manure produced 43.9–74.3 g of housefly pupae and the weight of the residue after biodegradation decreased to 0.18–0.65 kg, with marked differences among manure types. Recommendations for the operation of industrial-scale biodegradation facilities are presented and discussed.

Spinosad resistance in female Musca domestica L. from a field-derived population

BACKGROUND

Bait-formulated spinosad is currently being introduced for housefly (Musca domestica L.) control around the world. Spinosad resistance was evaluated in a multiresistant field population and strains derived from this by selection with insecticides. Constitutive and spinosad-induced expression levels of three cytochrome P450 genes, CYP6A1, CYP6D1 and CYP6D3, previously reported to be involved in insecticide resistance, were examined.

RESULTS

In 2004 a baseline for spinosad toxicity of Danish houseflies where all field populations were considered to be susceptible was established. In the present study, females of a multiresistant field population 791a were, however, 27-fold spinosad resistant at LC(50), whereas 791a male houseflies were susceptible. Strain 791a was selected with spinosad, thiamethoxam, fipronil and imidacloprid, resulting in four strains with individual characteristics. Selection of 791a with spinosad did not alter spinosad resistance in either males or females, but counterselected against resistance to the insecticides thiamethoxam and imidacloprid targeting nicotinic acetylcholine receptors. A synergist study with piperonyl butoxide, as well as gene expression studies of CYP6A1, CYP6D1 and CYP6D3, indicated a partial involvement of cytochrome P450 genes in spinosad resistance.

CONCLUSION

This study reports female-linked spinosad resistance in Danish houseflies. Negative cross-resistance was observed between spinosad and neonicotinoids in one multiresistant housefly strain. Spinosad resistance involved alterations of cytochrome P450 gene expression.

Condensed tannins inhibit house fly (Diptera: Muscidae) development in livestock manure

Reducing chemical use for suppressing internal and external parasites of livestock is essential for protecting environmental health. Although plant condensed tannins are known to suppress gastro-intestinal parasites in small ruminants, no research on the effects of tannins on external arthropod populations such as the house fly, Musca domestica L., have been conducted. We examined the impact of plant material containing condensed tannins on house fly development. Prairie acacia (Acacia angustissima (Mill.), Kuntze variety hirta (Nutt.) B.L. Rob.) herbage, panicled tick-clover (Desmodium paniculatum (L.) DC.) herbage, and quebracho (Shinopsis balansae Engl.) extracts were introduced at rates of 1, 3 or 5% condensed tannins/kg beef cattle, dairy cattle, and goat manure, respectively. In a second experiment, we also introduce purified catechin at 1 or 3% of dairy manure dry matter and measured its impact on house fly development. For the house flies used in these experiments, the following was recorded: percent fly emergence (PFE), average daily gain (ADG), and average fly weight (AFW). No effects (P>0.05) in house fly development were measured in the caprine manure. Prairie acacia (20.9% condensed tannins) had no effect on house flies developing in either bovine manures. Tick clover (4.9% condensed tannins) had a negative effect on all three quantifiable variables of house fly development in the bovine manures, whereas quebracho extract (64.0% condensed tannins) at the 3 and 5% rate reduced fly emergence in beef manure and average daily gain in dairy manure. The application of purified catechin at 3%, but not 1%, reduced fly PFE, ADG, and AFW.

Identification and characterization of the cysteine protease inhibitor gene MdCPI from Musca domestica

Cysteine proteinase inhibitors (CPIs) are involved in many vital cellular processes such as signalling pathways, apoptosis, immune response and development; however, no CPIs have yet been reported from the housefly Musca domestica. Here we report the isolation and characterization of a housefly CPI gene designated MdCPI. The gene contains an open reading frame of 357 bp encoding a protein of 118 amino acid residues with a putative signal peptide of 17 amino acid residues. Protein alignment demonstrated a high homology to that of Sarcophaga crassipalpis (identity = 51%). Phylogenetic analysis suggested that all CPIs from dipterans, including the housefly, belong to the I25A family and may be descended from a single common ancestor. The gene was expressed in and purified from Escherichia coli. Biochemical studies showed that MdCPI exerts an inhibiting function on papain, which is a classical assay to confirm CPIs. Real-time quantitative PCR and immunolocalization analysis revealed that MdCPI is specifically expressed in haemocytes and fat bodies. It is highly down-regulated in larvae and markedly up-regulated in the pupal stage, suggesting that it may be related to development.

Low expression of nicotinic acetylcholine receptor subunit Mdα2 in neonicotinoid-resistant strains of Musca domestica L

BACKGROUND

Neonicotinoid action as well as resistance involves interaction with nicotinic acetylcholine receptors (nAChRs). In the housefly, neonicotinoid resistance also involves cytochrome P450, as indicated by bioassay with synergist as well as altered expression. In bioassay, synergism was only partial and indicated possible target-site resistance. The nAChR α2 subunit is important in neonicotinoid toxicity to insects, and gene expression of the Mdα2 subunit was investigated in field populations and laboratory strains of neonicotinoid-resistant and insecticide-susceptible houseflies, Musca domestica L. The genomic sequence covering exon III-VII of Mdα2 was analysed for mutations.

RESULTS

Gene expression profiling of Mdα2 revealed notable differences between neonicotinoid-resistant and insecticide-susceptible houseflies. On average, the neonicotinoid-resistant field population 766b and the imidacloprid selected strain 791imi had 60% lower copy numbers of Mdα2 compared with the susceptible reference strain. Sequencing of exon III-VII of the Mdα2, encoding acetylcholine binding-site regions and three out of four transmembrane domains, did not reveal any mutations explaining the increased neonicotinoid tolerance in the strains examined.

CONCLUSION

Previous discoveries and the results of this study suggest that the neonicotinoid resistance mechanism in Danish houseflies involves both cytochrome P450 monooxygenase-mediated detoxification and reduced expression of the nAChR subunit α2.

[Heterologous expression of attacin gene from Musca domestica in Pichia pastoris]

OBJECTIVE

To construct recombinant expression plasmid with an antibacterial peptide (attacin) mature peptide gene from Musca domestica and express an antibacterial peptide attacin in Pichia pastoris.

METHODS

The coding region of attacin mature peptide was cloned into the expression vector pPIC9K. The recombinant plasmid was linearized by digestion with Sac I and transformed into P. pastoris GS115 by electroporation. The insert clones containing multiple copies were selected with geneticin, pha, enotype and PCR. The expression of P. pastoris GS115/pPIC9K-attacin were induced with methanol. The supernatant of the expressed protein was analyzed by SDS-PAGE and Western blotting. The anti-bacterial activity of expression product was analyzed by agarose diffusion assay.

RESULTS

The expression plasmid was constructed and transformed into P. pastoris GS115. SDS-PAGE and Western blotting analysis indicated that the recombinant containing recombinant plasmid pPIC9K-attacin expressed a Mr 22000 protein. The expression product inhibited the growth of E. coli K12D31.

CONCLUSION

The attacin gene from Musca domestica has been expressed in P. pastoris.

Synthesis and structure-activity relationship analysis of bicyclophosphorothionate blockers with selectivity for housefly gamma-aminobutyric acid receptor channels

BACKGROUND

Bicyclophosphorothionates (2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-sulfides) are blockers (or non-competitive antagonists) of gamma-aminobutyric acid (GABA) receptor channels. Twenty-two bicyclophosphorothionates with different 3- and 4-substituents were synthesised, and [(3)H]4'-ethynyl-4-n-propylbicycloorthobenzoate (EBOB) binding assays were performed to evaluate their affinities for housefly and rat GABA receptors.

RESULTS

Introduction of an isopropyl group at the 3-position enhanced the affinity of bicyclophosphorothionates for housefly GABA receptors and reduced the affinity towards rat GABA receptors. The 4-isopentyl-3-isopropylbicyclophosphorothionate showed the highest affinity for housefly GABA receptors (IC(50) = 103 nM) among the analogues tested, while the 4-cyclohexylbicyclophosphorothionate showed the highest affinity for rat GABA receptors (IC(50) = 125 nM). Among the bicyclophosphorothionates synthesised to date, the former analogue exhibited the highest selectivity for housefly GABA receptors, with an IC(50)(rat)/IC(50)(fly) ratio of approximately 97. Three-dimensional GABA receptor models successfully explained the structure-activity relationships of the bicyclophosphorothionates.

CONCLUSION

The results indicate that minor structural modifications of blockers can change their selectivity for insect versus mammalian GABA receptors. The substituent at the 3-position of the bicyclophosphorothionates dictates selectivity for housefly versus rat GABA receptors. This information should prove useful for the design of safer insecticides and parasiticides.

Characterization of age and cuticular hydrocarbon variation in mating pairs of house fly, Musca domestica, collected in the field

House flies, Musca domestica L., were collected in copula over two summers from six dairies located in three climatically distinct regions in the U.S.A. southern California, Minnesota and Georgia. Ages of males and females from a total of 511 mating pairs were estimated using pterin analysis. Cuticular hydrocarbon profiles and gonotrophic ages of females also were evaluated. Mean age of mating males ranged from 54 to 102 degree-days (DD) (4-10 days based on field air temperatures), depending on the farm. Very young males (< 10-20 DD) and old males (> 200 DD) were rare in mating pairs. Mean female age at mating ranged from 20 to 46 DD (2.5-4 days). All mating females had eggs in the early stages of vitellogenesis and 99.2% were nulliparous. However, some older and parous females were collected, demonstrating that re-mating can occur in the field. Head width measurements of mating pairs suggested that assortative mating by size did not occur. The cuticular hydrocarbon profiles of females were determined, with emphasis on (Z)-9-tricosene (muscalure). Overall, only 55% of mating females had detectable amounts (> 4 etag per fly) of (Z)-9-tricosene. Of the females that had detectable (Z)-9-tricosene, variation in amount per female was high in all fly populations, and thus was not statistically related to the size or age of the mating female. The proportion of mating females with detectable levels of (Z)-9-tricosene varied by geographic region. Seventy-one, 63, and 27% of females from southern California, Minnesota and Georgia had detectable amounts of (Z)-9-tricosene. Principal components analysis of the eight most abundant hydrocarbons from mating females, by state, revealed state-level distinctiveness of hydrocarbons in house fly populations, which may reflect genetic variation associated with environmental stresses in those geographical zones.

Extended FMRFamides in dipteran insects: conservative expression in the neuroendocrine system is accompanied by rapid sequence evolution

Extended FMRFamides are found throughout the central nervous system (CNS) of insects and exhibit diverse physiological effects on different target organs, such as muscles, intestine, and the nervous system. The genes encoding for extended FMRFamides are known from a number of flies, including Drosophila species, and the pest insects Lucilia cuprina, Calliphora vomitoria, and Musca domestica. No data, however, exist about the expression of the numerous paralogs of the latter three species, and studies on Drosophila melanogaster resulted in controversial findings. We could unambiguously verify, that all predictable products of the extended FMRFamide precursor are expressed in neurohemal tissues of the thoracic neuromers of these flies and can easily be identified and also sequenced by using single specimens. In addition to the confirmation of extended FMRFamides in species with known precursor sequences, the current knowledge about homologous peptides of Sarcophaga (=Neobellieria) bullata could be extended by de novo sequencing using tandem mass spectrometry. The most intriguing finding in this study was the detection of an internal gene duplication, followed by an amino acid substitution, in an insecticide-resistant strain of L. cuprina. To our knowledge, this is the first detection of such an intraspecific event and confirms the low conservation of the extended FMRFamide gene sequences. In insects, no other neuropeptide family is known that shows such sequence variability between related species.

Identification of a novel bursicon-regulated transcriptional regulator, md13379, in the house fly Musca domestica

Bursicon is a neuropeptide that regulates cuticle sclerotization (hardening and tanning) and wing expansion in insects via a G-protein coupled receptor. The hormone consists of alpha and beta subunits. In the present study, we cloned bursicon alpha and beta genes in the house fly Musca domestica using 3' and 5' RACE and expressed the recombinant bursicon (rbursicon) heterodimer in mammalian 293 cells and insect Highfive(TM) cells. The rbursicon displayed a strong bursicon activity in the neck-ligated house fly assay. Using rbursicon, we identified and cloned a novel bursicon-regulated gene in M. domestica encoding a transcriptional regulator homologous to ataxin-7-like3 in human, CG13379 in Drosophila and sgf11 in yeast Saccharomyces cerevisiae. We named the gene md13379. Both ataxin-7-like3 and sgf11 are a novel subunit of the SAGA (Spt-Ada-Gcn5-Acetyltransferase) complex that is involved in regulation of gene transcription. Real-time PCR analysis of temporal response profile revealed that the level of md13379 transcript was up-regulated by 6.6 fold 1 h after rbursicon injection, which correlates well with the cuticle sclerotization process observed in the rbursicon-injected flies. The composite data suggest that md13379 plays a role in regulating the expression of bursicon-regulated genes involved in the cuticle sclerotization process. Arch. Insect Biochem. Physiol. 2008. (c) 2008 Wiley-Liss, Inc.

P450 reductase and cytochrome b5 interactions with cytochrome P450: effects on house fly CYP6A1 catalysis

The interactions of protein components of the xenobiotic-metabolizing cytochrome P450 system, CYP6A1, P450 reductase, and cytochrome b5 from the house fly (Musca domestica) have been characterized. CYP6A1 activity is determined by the concentration of the CYP6A1-P450 reductase complex, regardless of which protein is present in excess. Both holo- and apo-b5 stimulated CYP6A1 heptachlor epoxidase and steroid hydroxylase activities and influenced the regioselectivity of testosterone hydroxylation. The conversion of CYP6A1 to its P420 form was decreased by the addition of apo-b5. The effects of cytochrome b5 may involve allosteric modification of the P450 enzyme that modify the conformation of the active site. The overall stoichiometry of the P450 reaction was substrate-dependent. High uncoupling of CYP6A1 was observed with generation of hydrogen peroxide, in excess over the concomitant testosterone hydroxylation or heptachlor epoxidation. Inclusion of cytochrome b5 in the reconstituted system improved efficiency of oxygen consumption and electron utilization from NADPH, or coupling of the P450 reaction. Depending on the reconstitution conditions, coupling efficiency varied from 8 to 25% for heptachlor epoxidation, and from 11 to 70% for testosterone hydroxylation. Because CYP6A1 is a P450 involved in insecticide resistance, this suggests that xenobiotic metabolism by constitutively overexpressed P450s may be linked to significant oxidative stress in the cell that may carry a fitness cost.

Purification and characterization of a thermal stable antimicrobial protein from housefly larvae, Musca domestica, induced by ultrasonic wave

This work describes the induction, purification and partial biochemical characterizations of an antimicrobial protein from the housefly larvae induced by ultrasonic wave. It has been purified to apparent homogeneity by ammonium sulfate precipitation followed by Sephadex G-75, Bio-gel P6 gel filtration, and CM-Sepharose Fast Flow cation exchange chromatography. The protein is a cationic protein with an apparent molecular weight of 16315 Da determined by no-denaturing electrophoresis and SDS-PAGE, respectively. Biochemical profile assays show that this protein has good thermal stability, and repeatedly frozen and defrosted durability. The optimum pH for antimicrobial activity is around pH5. The antimicrobial range of the protein includes Gram-positive, Gram-negative bacteria and some fungi. Results of the membrane permeability assays suggest that the probable mode of action of this protein is membrane-disrupting mechanism.

Role of a serine residue (S278) in the pore-facing region of the housefly L-glutamate-gated chloride channel in determining sensitivity to noncompetitive antagonists

Gamma-hexachlorocyclohexane (gamma-HCH), fipronil and picrotoxinin are noncompetitive antagonists (NCAs) of L-glutamate-gated chloride channels (GluCls), yet their potencies are weaker than those on gamma-aminobutyric acid receptors (GABARs). The A302S mutation of Drosophila RDL (resistant to dieldrin) GABAR confers NCA resistance, and housefly GluCls (MdGluCls) possess S278 as the residue corresponding to the A302. Thus, the effects of S278A mutation on the NCA actions on MdGluCls were investigated. The S278A mutation resulted in enhanced blocking by NCAs of the MdGluCl response to 30 microM L-glutamate. However, such actions of gamma-HCH and picrotoxinin, but not of fipronil, on the S278A mutant were reduced with 200 microM L-glutamate. Further increases in the L-glutamate concentration led to potentiation by NCAs of the mutant response to L-glutamate.