Transcriptional expression of bursicon and novel bursicon-regulated genes in the house fly Musca domestica

Bursicon is a neuropeptide that regulates cuticle sclerotization (hardening and tanning) via a G protein-coupled receptor. It consists of two subunits, an alpha and a beta. In the present study, we investigated the transcriptional expression and in situ localization of bursicon alpha and beta in the central nerve system of the house fly Musca domestica. Most importantly, we identified two novel bursicon-regulated genes using recombinant bursicon (rbursicon) heterodimer in a neck-ligated house fly assay. RT-PCR analysis revealed that both bursicon alpha and beta subunits were present in the central nerve system of larval and pupal stages, reached the maximal level in pharate adults, and declined sharply after adult emergence, suggesting the release of the hormone upon adult emergence. In situ localization of bursicon transcripts showed that both bursicon alpha and beta transcripts were expressed in a set of neurosecretory cells (NSCs) in the thoracic-abdominal ganglia of M. domestica. Two Drosophila melanogaster homologous genes, designated CG7985hh and CG30287hh, were up-regulated by rbursicon in a time-dependent manner and verified by real-time PCR, implying their involvement in the cuticle tanning process.

Effects of bisphenol A on the development, growth, and sex ratio of the housefly Musca domestica

The effects of bisphenol A (BPA) on the life cycle of the housefly Musca domestica were examined. The sex ratio of the imago shifted in favor of males when eggs and larvae were exposed to BPA in culture media at concentrations of 1,000 microg kg(-1) for five generations and 100 microg kg(-1) for seven generations. Notably, at an initial concentration of 100 microg kg(-1), BPA levels in the growth medium decreased 61% at 4 h after egg inoculation, and no BPA was detected after 24 h. Pupal weight increased upon exposure to 100 microg kg(-1) BPA but decreased after exposure to 1,000 microg kg(-1), suggesting highly variable concentration-dependent toxicity. Both the survival ratio of eggs to the third instar larval stage and the ratio of pupae to larvae decreased, indicating that BPA affected both eggs and larvae. A delay in the timing of emergence typically was observed in insects exposed to >100 microg kg(-1) BPA. Compared to the control group, juvenile hormones II and III levels were elevated significantly in larvae between days 4 and 7 in medium spiked with 100 microg kg(-1) BPA. These results suggest that exposure to environmentally relevant concentrations of BPA during the early stages of the housefly life cycle can result in various disorders (pupal weight and sex ratio) that may be a consequence of endocrine disruption.

The nicotinic acetylcholine receptor subunits Mdalpha5 and Mdbeta3 on autosome 1 of Musca domestica are not involved in spinosad resistance

Spinosad is a relatively new insecticide that exerts its toxic action via nicotinic acetylcholine receptors (nAChRs). Spinosad resistance in house flies appears to be due to an altered target site. To evaluate the molecular basis of spinosad resistance, two nAChR subunit genes, Mdalpha5 and Mdbeta3 were cloned and characterized from an insecticide-susceptible (aabys) and spinosad resistant (rspin) strain of the house fly, Musca domestica. The Mdalpha5 and Mdbeta3 cDNAs encode proteins of 781 and 432 amino acid residues, respectively. Phylogenetic analysis with insect nAChR subunits suggested that Mdalpha5 and Mdbeta3 are most closely related to Dalpha5 and Dbeta3 of Drosophila melanogaster, respectively. Mdbeta3 is intronless, which is unique among all previously described nAChR genes. A-to-I RNA editing was found at 13 sites in Mdalpha5, eleven of which resulted in amino acid substitutions. No evidence for A-to-I RNA editing was found in Mdbeta3. Mdalpha5 expression, quantified by real time PCR, was 340- and 23-fold higher in the head and thorax than in the abdomen. Mdbeta3 expression was more uniform, being only 2.4-fold higher in the head and 1.4-fold lower in the thorax, compared to the abdomen. There was no difference in the expression of Mdalpha5 and Mdbeta3 between the aabys and rspin strains. Although Mdalpha5 and Mdbeta3 both map to the same chromosome as spinosad resistance, there were no unique features of either gene in rspin, relative to the aabys strain. This suggests neither Mdalpha5 nor Mdbeta3 is responsible for spinosad resistance in house flies.

Effects of locomotor stimulation and protein synthesis inhibition on circadian rhythms in size changes of L1 and L2 interneurons in the fly's visual system

Axons of monopolar cell interneurons L1 and L2 in the first optic lobe (lamina) of the fly Musca domestica undergo cyclical changes in diameter. These axons swell during the day and shrink during the night. In addition, the axons' size depends on light conditions since they are largest in continuous light (LL), somewhat smaller under day/night (LD) conditions, and smallest under constant darkness (DD). In this study we found that sizes of both cells can further increase in free flying flies under LD conditions, while the visual stimulation alone does not have significant effect on the cross-sectional area of L1 and L2 axons. The stimulation of free flying had no effect on L1 and L2 sizes if it was performed at the beginning of subjective day in LL or DD. Our results indicate that a maximal increase in size of L1 and L2 is observed when stimulation of free flying is synchronized with a fly' daily peak of activity. We also found that protein synthesis is needed to increase size of monopolar cell axons during the day when they normally swell.

High-level expression of the recombinant hybrid peptide cecropinA(1-8)-magainin2(1-12) with an ubiquitin fusion partner in Escherichia coli

The hybrid antibacterial peptide CA-MA [cecropinA(1-8)-magainin2(1-12)] with potent antimicrobial properties but no hemolytic activity is a potential alternative antibiotic. To explore a new approach for high-level expression of the hybrid peptide CA-MA in Escherichia coli, the sequence of ubiquitin (UBI) from housefly was inserted into the plasmid pQE30 to construct the vector pQEUBI. The cDNA fragment encoding CA-MA with preferred codons of E. coli was obtained by recursive PCR (rPCR) and cloned into the vector pQEUBI to express the fusion protein (His)(6)-UBI-CA-MA. The fusion protein was expressed in soluble form under the optimized conditions at high level (more than 36% of the total proteins). With (His)(6)-tag, the fusion protein was easily purified by Ni-NTA chromatography and 36 mg of fusion protein was purified from 1L of culture medium. The fusion protein was efficiently cleaved by ubiquitin C-terminal hydrolase (UCH), yielding recombinant CA-MA with high antimicrobial activity. After removing the contaminants by Ni-NTA chromatography, recombinant CA-MA was purified to homogeneity by reversed-phase HPLC and 6.8mg of pure active CA-MA was obtained from 1L culture medium. Analysis of recombinant CA-MA by MALDI-TOF-MS showed that the molecular weight of the purified recombinant CA-MA was 2559Da, which perfectly matches the mass (2559Da) calculated from the amino acid sequence. Analysis of CA-MA by circular dichroism (CD) revealed that the secondary structures of CA-MA in water solution were 17.4% alpha-helix and 82.6% random coil but no beta-sheet. Our results demonstrated that functional CA-MA can be produced in sufficient quantities using the ubiquitin fusion technique. This is the first report on the heterologous expression of a hybrid antibacterial peptide fused to ubiquitin in E. coli.

Insect muscarinic acetylcholine receptor: pharmacological and toxicological profiles of antagonists and agonists

The insect muscarinic acetylcholine receptor (mAChR) is evaluated as a potential target for insecticide action. The mammalian M2/M4-selective antagonist radioligand [3H]AF-DX 384 (a pirenzepine analogue) binds to Drosophila mAChR at a single high-affinity site identical to that for the nonselective antagonist [3H]quinuclidinyl benzilate (QNB) and with a pharmacological profile distinct from that of all mammalian mAChR subtypes. Three nonselective antagonists (QNB, scopolamine, and atropine) show the highest affinity (Ki=0.5-2.4 nM) at the Drosophila target, and AF-DX 384 and M3-selective 4-DAMP (dimethyl-4-(diphenylacetoxy)piperidinium iodide) rank next in potency (Ki=5-18 nM). Eleven muscarinic antagonists generally exhibit higher affinity than eight agonists. On injection into houseflies, the antagonists 4-DAMP and (S)-(+)-dimethindene produce suppressed movement, the agonist (methyloxadiazolyl)quinuclidine causes knockdown and tremors, and all of them inhibit [3H]QNB binding ex vivo, indicating possible mAChR-mediated intoxication. The insect mAChR warrants continuing study in lead generation to discover novel insecticides.

A C-terminal aldehyde analog of the insect kinins inhibits diuresis in the housefly

The insect kinins are present in a wide variety of insects and function as potent diuretic peptides in flies. A C-terminal aldehyde insect kinin analog, Fmoc-RFFPWG-H (R-LK-CHO), demonstrates stimulation of Malpighian tubule fluid secretion in crickets, but shows inhibition of both in vitro and in vivo diuresis in the housefly. R-LK-CHO reduced the total amount of urine voided over 3 h from flies injected with 1 microL of distilled water by almost 50%. The analog not only inhibits stimulation of housefly fluid secretion by the native kinin Musdo-K, but also by thapsigargin, a SERCA inhibitor, and by ionomycin, a calcium ionophore. The activity of R-LK-CHO is selective, however, as related C-terminal aldehyde analogs do not demonstrate an inhibitory response on housefly fluid secretion. The selective inhibitory activity of R-LK-CHO on housefly tubules represents an important lead in the development of environmentally friendly insect management agents based on the insect kinins.

Sodium channel gene expression associated with pyrethroid resistant house flies and German cockroaches

The voltage-gated sodium channels of the insect nervous system are the primary target of DDT and pyrethroid insecticides. The loss of target site sensitivity to insecticides resulting from a substitution of leucine to phenylalanine, termed the L-to-F kdr mutation, in the sodium channel of the insect nervous system is known to be important in insecticide resistance. Yet, little is known about the molecular basis underlying the genotype and kdr-mediated resistance phenotype relationship. Here we report a systematic study of resistance-associated kdr allelic expression within and among resistant and susceptible house fly and German cockroach populations. We compared genomic DNA and RNA sequences within the same individuals from different insect strains, finding no correlation for the kdr allele at the genomic DNA level with levels of susceptibility or resistance to insecticide. However, there was a strong correlation between kdr allele expression and the levels of insecticide resistance. This correlation is probably regulated through RNA variation and RNA editing. These results suggest a role for posttranscriptional regulation in the connection of the sodium channel genotype and its mutation-mediated resistance phenotype.

Expression and characterization of a housefly cecropin gene in the methylotrophic yeast, Pichia pastoris

A 371 bp full-length cDNA (GenBank Accession No. DQ232774) was obtained from housefly Musca domestica by using degenerate primers and subsequent amplification by 5'- and 3'-RACE. The cecropin gene, Mdcec and Mdcec/6His, was cloned into expression pPICZalpha-A vector and was expressed in the methylotrophic yeast, Pichia pastoris. The recombinant Mdcec was purified using cationic exchange chromatography and 1.2mg pure active Mdcec was obtained from 100ml culture broth supernatant. To facilitate purification of Mdcec, the C-terminal 6His-tagged Mdcec was also expressed in P. pastoris. The recombinant Mdcec/6His was purified to homogeneity by a nickel chelating sepharose column and 2.0mg pure active Mdcec/6His was obtained from 100ml culture broth supernatant. Anti-microbial assays demonstrated that Mdcec had broad spectrum of antimicrobial property against fungi, as well as Gram-positive and Gram-negative bacteria. Mdcec/6His showed a similar activity to Mdcec against bacteria, but a slight higher activity against fungi. These results indicate that the 6His-tag can enhance the cationic nature and stability of Mdcec. This is the first report on the heterologous expression of a cecropin and cecropin with a 6His tag in P. pastoris. Our results suggest that the P. pastoris expression system can be used to produce large quantities of fully functional M. domestica cecropin for both research and industrial purpose.

Modelling insecticide-binding sites in the voltage-gated sodium channel

A homology model of the housefly voltage-gated sodium channel was developed to predict the location of binding sites for the insecticides fenvalerate, a synthetic pyrethroid, and DDT an early generation organochlorine. The model successfully addresses the state-dependent affinity of pyrethroid insecticides, their mechanism of action and the role of mutations in the channel that are known to confer insecticide resistance. The sodium channel was modelled in an open conformation with the insecticide-binding site located in a hydrophobic cavity delimited by the domain II S4-S5 linker and the IIS5 and IIIS6 helices. The binding cavity is predicted to be accessible to the lipid bilayer and therefore to lipid-soluble insecticides. The binding of insecticides and the consequent formation of binding contacts across different channel elements could stabilize the channel when in an open state, which is consistent with the prolonged sodium tail currents induced by pyrethroids and DDT. In the closed state, the predicted alternative positioning of the domain II S4-S5 linker would result in disruption of pyrethroid-binding contacts, consistent with the observation that pyrethroids have their highest affinity for the open channel. The model also predicts a key role for the IIS5 and IIIS6 helices in insecticide binding. Some of the residues on the helices that form the putative binding contacts are not conserved between arthropod and non-arthropod species, which is consistent with their contribution to insecticide species selectivity. Additional binding contacts on the II S4-S5 linker can explain the higher potency of pyrethroid insecticides compared with DDT.

Role of the transcriptional repressor mdGfi-1 in CYP6D1v1-mediated insecticide resistance in the house fly, Musca domestica

Gfi-1 is a C(2)H(2)-type zinc finger protein that is a transcriptional repressor in vertebrates and has been implicated in control of CYP6D1 expression in house flies (Musca domestica). A 15 bp insert, which disrupts a putative mdGfi-1 binding site in the CYP6D1v1 promoter has been implicated as a cause of increased expression of CYP6D1, and thus insecticide resistance. Using electrophoretic mobility shift assays we demonstrate that the CYP6D1 promoter from susceptible strains binds mdGfi-1. The 15 bp insert that interrupts the mdGfi-1-binding site in insecticide-resistant strains reduces the amount of mdGfi-1 binding by 9- to 20-fold, consistent with the role of mdGfi-1 in resistance. Partial sequences of mdGfi-1 (spanning the first intron) from individual houseflies from 11 different strains revealed the presence of 23 alleles. There was no consistent difference in the mdGfi-1 alleles between susceptible and CYP6D1-mediated insecticide-resistant strains, indicating that mdGfi-1 alleles were not likely involved in resistance. Polymorphisms were used to map mdGfi-1 to autosome 1. Quantitative real time PCR (qRT-PCR) revealed Gfi-1 expression was higher in the thorax compared to the head and abdomen, and varied between life stages and between strains. However, similar levels of mdGfi-1 were detected in susceptible and resistant adults suggesting that altered levels of mdGfi-1 were not likely a cause of insecticide resistance. The significance of these results to understanding insecticide resistance is discussed.

Preliminary studies on the zinc-induced metallothionein protein with antibacterial activity in housefly larvae, Musca domestica

Three isoforms of metallothionein protein induced with Zinc were isolated and purified from housefly larvae, Musca domestica, by gel filtration on Sephadex G-75, G-25 and anion exchange on DEAE-52 chromatography. Among them, one was found to possess antibacterial activity, and was further characterized by SDS-polyacrylamide gel electrophoresis, sulphydryl group determination, enzyme hydrolysis, and spectra property. Our results showed that the novel protein has the characteristics of heat-stable, low-molecular weight (6 kDa), rich-cysteine (approximately 12 cysteine residues in one molecule), metal affinity, and antibacterial activity. This paper was the first to report that metallothionein had antibacterial activity. We expect that this characteristic would give some help to investigate definite physiological functions of metallothionein.

[Alternative splicing of pre-mRNA encoding the Musca domestica latrophilin-like protein(LLP): primary structures of four spliced forms of mRNA and their protein products]

An internal DNA fragment (approximately 2000 bp) homologous to the conserved regions of genes encoding latrophilin-like proteins (LLPs) was obtained by the PCR technique using degenerate primers to these gene regions. The gene-specific primers were synthesized based on the results of sequencing of the isolated fragment, and all overlapping cDNA fragments of the llp gene encoding the Musca domestica LLP were obtained by the rapid amplification of cDNA 5'- and 3'-ends (5'- and 3'-RACE). Four alternatively spliced mRNAs were found while sequencing the obtained cDNA fragments. Two long mRNAs (approximately 6000 nt) differ in the structures of both the sites encoding signal peptides and 5'-terminal untranslated regions. They encode large proteins (approximately 1800 aa), whose domain organization is similar to that of mammalian latrophilins. Each deduced protein contains a domain with seven transmembrane regions followed by an extended cytoplasmic C-terminal domain. Two other mRNA forms are derived from these long mRNAs; they encode proteins severly truncated at their C-termini (approximately 900 aa). They are composed of only three transmembrane regions and a short unique cytoplasmic C-terminal domain (23 aa). The limitations and drawbacks of the existing 3'-RACE techniques found during study of the long alternatively spliced cDNAs are analyzed, and ways for overcoming these difficulties are proposed.

[Study on the interaction mechanism of antibacterial peptide MDL-1 in Musca domestica L and E. coli DNA by fluorescence spectra]

In this paper, the interaction of the antibacterial peptide MDL-1 of Musca domestica L and E. coli DNA was investigated by fluorescence spectra. The interaction mode was studied by using ethidium bromide (EB) as an extrinsic fluorescence probe. The result of fluorescence spectra and Scatchard plot indicate that the binding constant and the number of binding sites between DNA and EB decrease with increasing concentration of MDL-1. The change in binding constant and binding sites showed that the conformation of DNA transformed. When the EB molecule just fitted into the interval, the fluorescence intensity was maximum. When MDL-1 was present in the system, the EB molecules was excluded from DNA, then the fluorescence intensity decreased. The result showed that the style was eletrostatic binding, groove binding and intercalation in the interaction of MDL-1 and double helix DNA. The binding constant of MDL-1 complex with DNA was determined. Meanwhile, it helped to explain the molecule mechanism of antibacterial peptides from the interaction style and structure characteristic of antibacterial peptide and bacterial DNA.

Kinetic characteristics of native gamma-glutamylcysteine ligase in the aging housefly, Musca domestica L

The catalytic activity of gamma-glutamylcysteine ligase (gamma-GCL; EC 6.3.2.2) was compared between relatively young (4-day-old) and old (19-day-old) houseflies (Musca domestica) in order to understand the mechanism of putative deterioration of glutathione homeostasis during the aging process. Hanes-Woolf analyses ([S]/v vs [S]) indicated that gamma-GCL had significantly higher affinities for its substrates in the young than in the old flies. The K(m) values in the young and old flies were, respectively, for glutamate 0.6 and 5.5 mM; for cysteine 0.3 and 4.6 mM; and for ATP 1.2 and 2.9 mM. Furthermore, young but not old flies exhibited substrate-dependent inhibition of gamma-GCL activity at >5 mM cysteine indicating a loss of metabolic regulation during aging. The age-associated differences in the affinity of native gamma-GCL towards its substrates suggest that de novo synthesis of glutathione would be relatively less efficient in the old houseflies.

Elemental changes in the brain, muscle, and gut cells of the housefly,Musca domestica, exposed to heavy metals

The toxic effects of heavy metals on organisms are well established. However, their specific action at the cellular level in different tissues is mostly unknown. We have used the housefly, Musca domestica, as a model organism to study the toxicity of four heavy metals: copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb). These have been fed to larvae at low and high, semi-lethal concentrations, and their accumulation in the head, thorax, and abdomen was subsequently measured in adult flies. In addition, their impact on the cellular concentration of several elements important for cell metabolism-sodium (Na+), magnesium (Mg++), phosphorous (P), sulphur (S), chloride (Cl-) and potassium (K+)-were measured in neural cells, muscle fibers, and midgut epithelial cells. Our study showed that the heavy metals accumulate mainly in the abdomen, in which the concentrations of two of the xenobiotic metals, Cd and Pb, were 213 and 23 times more concentrated, respectively, than in controls. All the heavy metals affected the cellular concentration of light elements in all cell types, but the changes observed were dependent on tissue type and were specific for each heavy metal, and its concentration.

Cross-resistance potential of fipronil in Musca domestica

The toxicity of fipronil to insecticide-susceptible houseflies and the cross-resistance potential of fipronil were determined for six insecticide-resistant laboratory housefly strains by topical application and feeding bioassay. The insecticide-resistant strains represented different levels and patterns of resistance to pyrethroids, organophosphates, carbamates and organochlorines. Five strains were almost susceptible to fipronil in feeding bioassay with resistance factors at LC50 between 0.36 and 3.0. Four of these strains were almost susceptible to topically applied fipronil (resistance factors at LD50 were 0.55, 0.83, 3.3 and 2.5, respectively), whereas one strain was 13-fold resistant to topically applied fipronil. A highly gamma-HCH-resistant strain, 17e, was 430-fold resistant to fipronil in topical application bioassay and 23-fold resistant in feeding bioassay at LD50/LC50. We also tested the toxicity of fipronil in a feeding bioassay and gamma-HCH in topical application bioassay on thirteen housefly field populations. Eleven of the field populations had resistance factors for fipronil ranging from 0.98 to 2.4 at LC50, whereas two populations were 4.0- and 4.6-fold resistant to fipronil. The resistance level to gamma-HCH at LD50 in the field populations ranged from 1.8- to 8.1-fold. The two strains showing fipronil resistance were 3.4- and 8.1-fold resistant to gamma-HCH. Fipronil and gamma-HCH toxicities were positively correlated in the field populations. Biochemical assays of esterase, glutathione S-transferase and cytochrome P450 monooxygenase indicated that the low fipronil resistance observed in laboratory and field strains could be caused by elevated detoxification or be due to a target-site resistance mechanism with cross-resistance to gamma-HCH.

Continuous recording of excretory water loss from Musca domestica using a flow-through humidity meter: hormonal control of diuresis

Water loss from adult male houseflies was continuously recorded using a flow-through humidity meter, which enabled losses to be apportioned between the sum of cuticular and respiratory transpiration, salivation and excretion. Transpiration accounted for >95% of water lost from sham-injected flies, compared with excretion (3.0%) and salivation (2.4%). In contrast, excretion accounted for 40% of water lost from flies injected with > or =3 microl of saline, whereas salivary losses were unchanged. Saline injections (1-5 microl) expanded the abdomen in the dorsal-ventral plane, and this expansion was positively correlated with the magnitude of the ensuing diuresis, suggesting the signal for diuretic hormone release originates from stretch receptors in abdominal tergal-sternal muscles. The effects of decapitation, severing the ventral nerve cord within the neck or ligaturing the neck, showed the head was needed to initiate and maintain diuresis, but was neither the source of diuretic hormone nor did it control the discharge of urine from the anus. These findings indicate the head is part of the neural-endocrine pathway between abdominal stretch receptors and sites for diuretic hormone release from the thoracic-abdominal ganglion mass. Evidence is presented for Musdo-K having a hormonal role in the control of diuresis, although other neuropeptides may also be implicated.

Mitochondria: are they the seat of senescence?

The frequently quoted figure for the fractional univalent reduction of oxygen to superoxide in mitochondria is certainly too high by at least one order of magnitude. This is so because the higher number (2%) was derived from mitochondria whose cytochrome c oxidase was blocked with cyanide. Nevertheless, even the more correct number (0.1%) means that the production of O(2)(-) and H(2)O(2) in mitochondria is large and apt to result in damage to macromolecules in spite of such defensive enzymes as superoxide dismutases and glutathione peroxidase. The data available for nematodes and flies provide a compelling case for the view that the accumulation of oxidative damage to specific mitochondrial proteins leads to the progressive dysfunction that we see as senescence. The data available from work with mammals are much weaker and do not yet allow a strong position to be taken.

Primary characterization and basal promoter activity of two hexamerin genes of Musca domestica

Hexamerins are high molecular-weight proteins found in the hemolymph of insects and have been proposed to function as storage proteins. In previous studies, two Musca domestica hexamerins, designated Hex-L and Hex-F were characterized. Hex-L is synthesized exclusively by the larval fat bodies, is secreted into the hemolymph and likely provides a source of amino acids and energy during metamorphosis. Hex-F synthesis is induced by a proteinaceous meal and occurs only in the adult insect fat bodies. Hex-F also is secreted into the hemolymph and it has been suggested that in females it may be an amino acid reservoir to be used during the final stages of egg formation. Genomic clones containing full-length copies of the genes MdHexL1 and MdHexF1, encoding subunits of the larval and the adult female hexamerin, respectively, were isolated. Complete nucleotide sequences, including the 5'-end untranscribed regions, were determined and analyzed for each of the genes. Comparisons of the conceptual translation products of the cloned genes indicated that MdHexL1 and MdHexF1 are related to the larval serum proteins (LSP) 1 and 2 of Calliphora vicina and Drosophila melanogaster. DNA fragments containing the putative promoters of the two hexamerin genes were compared and cloned into a plasmid vector so as to drive the expression of the GFP reporter gene. The constructs were assayed in vitro in transfected S2 Drosophila melanogaster cells demonstrating that the cloned M. domestica DNA fragments exhibit promoter activity.

[Study on the potential use of baculoviruses to eradicate insects in pest control]

The biological activity of baculovirus AcMNPV and its recombinant SPX were determined on cockroaches Blattella germanica, pharaoh's ants Monomorium pharaonis and flies Musca domestica--species very difficult to eradicate. Baculovirus AcMNPV is one of the best known viruses of wide host range. Its recombinant SPX contained the gene for natural toxin. It is known that this toxin paralyses nervous system of insects by blocking sodium channels. The studies on the influences of baculoviruses showed in the case of cockroaches Blattella germanica L. the disturbances of development. The result of using high concentration baculoviruses SPX 2 x 10(7) pfu/ml for a long time of exposition 8 weeks it was.

Sex determination in Drosophila melanogaster and Musca domestica converges at the level of the terminal regulator doublesex

Sex-determining cascades are supposed to have evolved in a retrograde manner from bottom to top. Wilkins' 1995 hypothesis finds support from our comparative studies in Drosophila melanogaster and Musca domestica, two dipteran species that separated some 120 million years ago. The sex-determining cascades in these flies differ at the level of the primary sex-determining signal and their targets, Sxl in Drosophila and F in Musca. Here we present evidence that they converge at the level of the terminal regulator, doublesex ( dsx), which conveys the selected sexual fate to the differentiation genes. The dsx homologue in Musca, Md-dsx, encodes male-specific (MdDSX(M)) and female-specific (MdDSX(F)) protein variants which correspond in structure to those in Drosophila. Sex-specific regulation of Md-dsx is controlled by the switch gene F via a splicing mechanism that is similar but in some relevant aspects different from that in Drosophila. MdDSX(F) expression can activate the vitellogenin genes in Drosophila and Musca males, and MdDSX(M) expression in Drosophila females can cause male-like pigmentation of posterior tergites, suggesting that these Musca dsx variants are conserved not only in structure but also in function. Furthermore, downregulation of Md-dsx activity in Musca by injecting dsRNA into embryos leads to intersexual differentiation of the gonads. These results strongly support a role of Md-dsx as the final regulatory gene in the sex-determining hierarchy of the housefly.

Efficacy of insect parasitoid Dirhinus himalayanus (Hymenoptera: Chalcididae) & insect growth regulator, triflumuron against house fly, Musca domestica (Diptera: Muscidae)

BACKGROUND & OBJECTIVES

In fly management programme chemicals are extensively used. Combined use of insect growth regulator (IGR) and parasitoids would yield a better reduction in fly density, as exposure of fly larvae to sub lethal dose of IGR enhances pupal duration and thereby increases the exposure time for parasitism. The objective of the present study was to explore the additive effect of both Dirhinus himalayanus, an insect parasitoid and triflumuron, an IGR in controlling house fly, Musca domestica.

METHODS

In the field trial the study sites were allocated based on two-way ANOVA performed on one year pre-treatment survey. Parasitoid release and IGR treatment were initiated when the growth rate (lambda) of M. domestica was in an increasing trend. Parasitoids were released at a rate of 6 number/m2 for three months (February-April 2000), whereas IGR was applied at a dose of 10 mg/m2 at fortnightly interval from February to December 2000. Control efficacy was assessed using Mulla's formula.

RESULTS

Reduction in puparia density was 59.29, 48.67 and 69.08 per cent respectively in areas, where parasitoids, ICR and combination of both IGR and parasitoids were used. Corresponding figures for adult population were 55.69, 49.71 and 77.14 per cent respectively. The per cent reduction in puparia and adult density was significantly (P<0.05) higher in the experimental areas than in the check. When the per cent reduction in adult and puparia density among different experimental areas was compared, it was observed that the reduction in fly density was significantly higher in the areas, where the combination of both parasitoid-IGR (P=0.00102) and IGR (P=0.03175) were used, while in areas where parasitoid (P=0.06191) were released the reduction in fly density was not significant. Similarly, there was a significant reduction in puparia density in areas where both parasitoid-IGR combination (P=0.0001) or IGR (P=0.002) were used, whereas in parasitoid (P=0.0612) released areas it was not significant.

INTERPRETATION & CONCLUSION

The results show that the combined use of parasitoid and IGR is effective in reducing puparia and fly density. Therefore, for sustenance of an effective fly control programme, both parasitoid and IGR may be used.

Insecticidal activity and nicotinic acetylcholine receptor binding of dinotefuran and its analogues in the housefly, Musca domestica

The insecticidal activity of dinotefuran and 23 related compounds against the housefly, Musca domestica (L) was measured by injection with metabolic inhibitors. Dinotefuran was less active than imidacloprid and clothianidin by a factor of 10 in molar concentrations. Their binding activities to the fly-head membrane preparation were measured by using [125I]alpha-bungarotoxin ([125I]alpha-BGTX) and [3H]imidacloprid ([3H]IMI) as radioligands. The activity of some selected compounds measured with [3H]IMI was 10(4)-fold higher than that measured with [125I]alpha-BGTX. With [3H]IMI as a radioligand, dinotefuran was 13-fold less active than imidacloprid. The inhibitory effect of dinotefuran on the binding of [3H]IMI to the membrane preparation was in a competitive manner. Quantitative analysis of the insecticidal activity of the test compounds with the binding activity measured with [3H]IMI showed that the higher the binding activity, the higher was the insecticidal activity.

Reducing waste contamination from animal-processing plants by anaerobic thermophilic fermentation and by flesh fly digestion

There is currently no market in Israel for the large amounts of waste from fish- and poultry-processing plants. Therefore, this waste is incinerated, as part of the measures to prevent the spread of pathogens. Anaerobic methanogenic thermophilic fermentation (AMTF) of wastes from the cattle-slaughtering industry was examined previously, as an effective system to treat pathogenic bacteria, and in this article, we discuss a combined method of digestion by thermophilic anaerobic bacteria and by flesh flies, as a means of waste treatment. The AMTF process was applied to the wastes on a laboratory scale, and digestion by rearing of flesh fly (Phaenicia sericata) and housefly (Musca domestica) larvae on the untreated raw material was done on a small scale and showed remarkable weight conversion to larvae. The yield from degradation of poultry waste by flesh fly was 22.47% (SD = 3.89) and that from fish waste degradation was 35.34% (SD = 12.42), which is significantly higher than that from rearing houseflies on a regular rearing medium. Bacterial contents before and after thermophilic anaerobic digestion, as well as the changes in the chemical composition of the components during the rearing of larvae, were also examined.