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May R Berenbaum - One of the best experts on this subject based on the ideXlab platform.
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ecologically appropriate xenobiotics induce cytochrome p450s in apis mellifera
PLOS ONE, 2012Co-Authors: Reed M Johnson, Mary A Schuler, Henry S Pollock, May R BerenbaumAbstract:Background Honey bees are exposed to phytochemicals through the nectar, pollen and propolis consumed to sustain the colony. They may also encounter mycotoxins produced by Aspergillus fungi infesting pollen in beebread. Moreover, bees are exposed to agricultural pesticides, particularly in-hive acaricides used against the parasite Varroa destructor. They cope with these and other xenobiotics primarily through enzymatic detoxificative processes, but the regulation of detoxificative enzymes in honey bees remains largely unexplored. Methodology/Principal Findings We used several approaches to ascertain effects of dietary toxins on bee susceptibility to synthetic and natural xenobiotics, including the acaricide tau-Fluvalinate, the agricultural pesticide imidacloprid, and the naturally occurring mycotoxin aflatoxin. We administered potential inducers of cytochrome P450 enzymes, the principal biochemical system for Phase 1 detoxification in insects, to investigate how detoxification is regulated. The drug phenobarbital induces P450s in many insects, yet feeding bees with phenobarbital had no effect on the toxicity of tau-Fluvalinate, a pesticide known to be detoxified by bee P450s. Similarly, no P450 induction, as measured by tau-Fluvalinate tolerance, occurred in bees fed xanthotoxin, salicylic acid, or indole-3-carbinol, all of which induce P450s in other insects. Only quercetin, a common pollen and honey constituent, reduced tau-Fluvalinate toxicity. In microarray comparisons no change in detoxificative gene expression was detected in phenobarbital-treated bees. However, northern blot analyses of guts of bees fed extracts of honey, pollen and propolis showed elevated expression of three CYP6AS P450 genes. Diet did not influence tau-Fluvalinate or imidacloprid toxicity in bioassays; however, aflatoxin toxicity was higher in bees consuming sucrose or high-fructose corn syrup than in bees consuming honey. Conclusions/Significance These results suggest that regulation of honey bee P450s is tuned to chemicals occurring naturally in the hive environment and that, in terms of toxicological capacity, a diet of sugar is not equivalent to a diet of honey.
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cyp9q mediated detoxification of acaricides in the honey bee apis mellifera
Proceedings of the National Academy of Sciences of the United States of America, 2011Co-Authors: Wenfu Mao, Mary A Schuler, May R BerenbaumAbstract:Although Apis mellifera, the western honey bee, has long encountered pesticides when foraging in agricultural fields, for two decades it has encountered pesticides in-hive in the form of acaricides to control Varroa destructor, a devastating parasitic mite. The pyrethroid tau-Fluvalinate and the organophosphate coumaphos have been used for Varroa control, with little knowledge of honey bee detoxification mechanisms. Cytochrome P450-mediated detoxification contributes to pyrethroid tolerance in many insects, but specific P450s responsible for pesticide detoxification in honey bees (indeed, in any hymenopteran pollinator) have not been defined. We expressed and assayed CYP3 clan midgut P450s and demonstrated that CYP9Q1, CYP9Q2, and CYP9Q3 metabolize tau-Fluvalinate to a form suitable for further cleavage by the carboxylesterases that also contribute to tau-Fluvalinate tolerance. These in vitro assays indicated that all of the three CYP9Q enzymes also detoxify coumaphos. Molecular models demonstrate that coumaphos and tau-Fluvalinate fit into the same catalytic pocket, providing a possible explanation for the synergism observed between these two compounds. Induction of CYP9Q2 and CYP9Q3 transcripts by honey extracts suggested that diet-derived phytochemicals may be natural substrates and heterologous expression of CYP9Q3 confirmed activity against quercetin, a flavonoid ubiquitous in honey. Up-regulation by honey constituents suggests that diet may influence the ability of honey bees to detoxify pesticides. Quantitative RT-PCR assays demonstrated that tau-Fluvalinate enhances CYP9Q3 transcripts, whereas the pyrethroid bifenthrin enhances CYP9Q1 and CYP9Q2 transcripts and represses CYP9Q3 transcripts. The independent regulation of these P450s can be useful for monitoring and differentiating between pesticide exposures in-hive and in agricultural fields.
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Role of detoxification in Varroa destructor (Acari: Varroidae) tolerance of the miticide tau-Fluvalinate.
International Journal of Acarology, 2010Co-Authors: Reed M Johnson, Zachary Y. Huang, May R BerenbaumAbstract:ABSTRACT The varroa mite (Varroa destructor Anderson and Trueman) is a devastating pest of honey bees (Apis mellifera L.). Beekeepers have relied on the pyrethroid pesticide tau-Fluvalinate as a principal agent of varroa mite control. While this miticide was quite effective at controlling varroa mites through the 1990s, its efficacy has waned as resistance to tau-Fluvalinate has appeared in many populations of mites. Resistance in some populations of varroa mites has been associated with elevated detoxification of tau-Fluvalinate. Honey bees tolerate miticidal tau-Fluvalinate applications principally through rapid detoxification mediated by cytochrome-P450 mono-oxygenases, with the other detoxification enzyme families, the carboxylesterases and glutathione-S-transferases, playing much smaller roles in miticide tolerance. The goal of this study was to test the capability of the glutathione-S-transferase enzyme inhibitors diethyl maleate and curcumin, which should interfere minimally with honey bee detoxifi...
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mediation of pyrethroid insecticide toxicity to honey bees hymenoptera apidae by cytochrome p450 monooxygenases
Journal of Economic Entomology, 2006Co-Authors: Reed M Johnson, May R BerenbaumAbstract:Honey bees, Apis mellifera L., often thought to be extremely susceptible to insecticides in general, exhibit considerable variation in tolerance to pyrethroid insecticides. Although some pyrethroids, such as cyfluthrin and lambda-cyhalothrin, are highly toxic to honey bees, the toxicity of tau-Fluvalinate is low enough to warrant its use to control parasitic mites inside honey bee colonies. Metabolic insecticide resistance in other insects is mediated by three major groups of detoxifying enzymes: the cytochrome P450 monooxygenases (P450s), the carboxylesterases (COEs), and the glutathione S-transferases (GSTs). To test the role of metabolic detoxification in mediating the relatively low toxicity of tau-Fluvalinate compared with more toxic pyrethroid insecticides, we examined the effects of piperonyl butoxide (PBO), S,S,S-tributylphosphorotrithioate (DEF), and diethyl maleate (DEM) on the toxicity of these pyrethroids. The toxicity of the three pyrethroids to bees was greatly synergized by the P450 inhibitor PBO and synergized at low levels by the carboxylesterase inhibitor DEF. Little synergism was observed with DEM. These results suggest that metabolic detoxification, especially that mediated by P450s, contributes significantly to honey bee tolerance of pyrethroid insecticides. The potent synergism between tau-Fluvalinate and PBO suggests that P450s are especially important in the detoxification of this pyrethroid and explains the ability of honey bees to tolerate its presence.
Jan Hubert - One of the best experts on this subject based on the ideXlab platform.
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tau Fluvalinate and other pesticide residues in honey bees before overwintering
Pest Management Science, 2019Co-Authors: Tomas Erban, Marta Vaclavikova, Daniela Tomesova, Tatana Halesova, Jan HubertAbstract:BACKGROUND Pesticides have often been linked to honey bee colony losses, which occur mainly over winter. In this study, we investigated residues in nine colonies at a model agricultural research site during the period before wintering. Moreover, we applied the acaricide tau-Fluvalinate to the colonies via a strip formulation. The pesticide content was determined by UHPLC-QqQ-MS/MS in bees from brood comb initially collected in mid-September immediately prior to the start of tau-Fluvalinate treatment and 30 later at the time of tau-Fluvalinate strip removal. RESULTS In addition to commonly analyzed pesticides, we detected two plant growth regulators, chlormequat and metazachlor, in the bee colonies. Whereas thiacloprid, chlormequat and acetamiprid decreased after 30 days and contributed considerably to differences between sample time points, other pesticides appeared to be rather stable. Interestingly, we identified diazinon, which has been banned in the European Union since 2007. The residues of methiocarb sulfoxide and imidacloprid-urea in the absence of their parent compounds indicate historical environmental contamination that can be identified by the detection of residues in a bee colony. tau-Fluvalinate was detected only after the 30-day treatment at an average (± SD) concentration of 1.29 ± 1.93 ng/bee, ranging from 0.06 to 7.13 ng/bee. CONCLUSION The multidimensional behavior of pesticides in a bee colony was indicated. Although the research area is used for agriculture, the measured pesticide level was relatively low. The recorded concentrations of tau-Fluvalinate should not be dangerous to bees, as the values were ∼ 200-5000-fold lower than the reported median lethal dose (LD50 ) values. © 2019 Society of Chemical Industry.
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spatio temporal dynamics of varroa destructor resistance to tau Fluvalinate in czechia associated with l925v sodium channel point mutation
Pest Management Science, 2019Co-Authors: Jitka Stará, Martin Kamler, Marta Nesvorna, Stano Pekar, Ivo Doskocil, Jan HubertAbstract:BACKGROUND Extensive application of pyrethroids to control Varroa destructor, an invasive mite devastating bee colonies, has resulted in a global spread of resistant mite populations. In this study, we analyzed the spatio-temporal dynamics of resistant V. destructor populations in Czechia, stemming from the L925V mutation. Mites were collected during 2011-2018 directly or from winter beeswax debris, and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and densitometry was used to detect the L925V mutation. RESULTS Pooled samples of 10 mites were classified, based on their PCR-RFLP patterns, as tau-Fluvalinate-sensitive (56%), resistant (9%), or mixed (35%), with the latter including sensitive and resistant homo- and heterozygotes. We identified two zones with higher frequencies of resistance, one in southern Moravia and the other in Bohemia. The mutant populations were evenly distributed throughout the monitored districts, with a few temporal and spatial local fluctuations. The greatest increase in resistance was observed in 2016, following massive losses of bee colonies in the winter of 2015. This event appeared to be closely associated with fluctuations in resistant mite populations and their dispersion. CONCLUSION Two outbreaks of resistance were detected in Czechia; however, the amount of applied tau-Fluvalinate was not correlated with the frequency of resistance in mites. There was no remarkable increase in mite resistance in 2011-2018, although the use of tau-Fluvalinate increased 40-fold between 2011 and 2015. PCR-RFLP analysis, performed on mites present in beeswax debris, is a suitable method for monitoring the L925V mutation in V. destructor. © 2018 Society of Chemical Industry.
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detection of tau Fluvalinate resistance in the mite varroa destructor based on the comparison of vial test and pcr rflp of kdr mutation in sodium channel gene
Experimental and Applied Acarology, 2019Co-Authors: Jitka Stará, Martin Kamler, Tomas Erban, Marta Nesvorna, Stano Pekar, Hana Vinsova, Jan Kopecky, Ivo Doskocil, Jan HubertAbstract:Varroa destructor is the major cause of honey bee (Apis mellifera) colony losses. Mite control is limited to several miticides. The overuse of tau-Fluvalinate has resulted in resistance via a knockdown resistance (kdr) mutation in the sodium channel gene NaVChs (L925V/I/M). In this study, we used the discriminating concentration of tau-Fluvalinate (0.25 µg/mL) to detect the resistance of mites in a bioassay. Further, we verified the presence of the kdr mutation in mites from the bioassay via PCR amplification of a fragment of the voltage-gated sodium channel gene (NaVCh), restriction fragment length polymorphisms (RFLPs), and densitometry analyses in pools of surviving or dead mites. Resistance values corresponding to the densitometry of the resistant allele were related to mite survival. In the vial test, the survival of the control group was significantly higher (70.4%) than that of the tau-Fluvalinate-treated group (34.3%). Mite survival in the vial test was significantly correlated with the mean proportion of resistance values. Individuals that died after tau-Fluvalinate application exhibited an average resistance value of 0.0783, whereas individuals that survived exhibited an average resistance of 0.400. The concentration of tau-Fluvalinate in the vials was checked using high performance liquid chromatography under different temperatures and exposure times, and indicates that the stability of tau-Fluvalinate stored in the refrigerator (4 ± 1 °C) is at least 14 days. PCR–RFLP of the NaVCh gene fragment verified that the vial test is a suitable, rapid, and cost-effective method for the identification of tau-Fluvalinate resistance based on kdr mutation in V. destructor in apiaries.
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Comparison of tau-Fluvalinate, acrinathrin, and amitraz effects on susceptible and resistant populations of Varroa destructor in a vial test
Experimental and Applied Acarology, 2016Co-Authors: Martin Kamler, Jitka Stará, Tomas Erban, Marta Nesvorna, Jan HubertAbstract:The parasitic mite Varroa destructor is a major pest of the western honeybee, Apis mellifera . The development of acaricide resistance in Varroa populations is a global issue. Discriminating concentrations of acaricides are widely used to detect pest resistance. Two methods, using either glass vials or paraffin capsules, are used to screen for Varroa resistance to various acaricides. We found the glass vial method to be useless for testing Varroa resistance to acaridices, so we developed a polypropylene vial bioassay. This method was tested on tau-Fluvalinate-, acrinathrin-, and amitraz-resistant mite populations from three apiaries in Czechia. Acetone was used as a control and technical grade acaricide compounds diluted in acetone were applied to the polypropylene vials. The solutions were spread on the vial surface by rolling the vial, and were then evaporated. Freshly collected Varroa females were placed in the vials and the mortality of the exposed mites was measured after 24 h. The Varroa populations differed in mortality between the apiaries and the tested compounds. Mites from the Kyvalka site were resistant to acrinathrin, tau-Fluvalinate, and amitraz, while mites from the Postrizin site were susceptible to all three acaricides. In Prelovice apiary, the mites were susceptible to acrinathrin and amitraz, but not to tau-Fluvalinate. The calculated discriminating concentrations for tau-Fluvalinate, acrinathrin, and amitraz were 0.66, 0.26 and 0.19 µg/mL, respectively. These results indicate that polyproplyne vial tests can be used to determine discriminating concentrations for the early detection of acaricide resistant Varroa . Finally, multiple-resistance in Kyvalka may indicate metabolic resistance.
Zachary Y. Huang - One of the best experts on this subject based on the ideXlab platform.
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Role of detoxification in Varroa destructor (Acari: Varroidae) tolerance of the miticide tau-Fluvalinate.
International Journal of Acarology, 2010Co-Authors: Reed M Johnson, Zachary Y. Huang, May R BerenbaumAbstract:ABSTRACT The varroa mite (Varroa destructor Anderson and Trueman) is a devastating pest of honey bees (Apis mellifera L.). Beekeepers have relied on the pyrethroid pesticide tau-Fluvalinate as a principal agent of varroa mite control. While this miticide was quite effective at controlling varroa mites through the 1990s, its efficacy has waned as resistance to tau-Fluvalinate has appeared in many populations of mites. Resistance in some populations of varroa mites has been associated with elevated detoxification of tau-Fluvalinate. Honey bees tolerate miticidal tau-Fluvalinate applications principally through rapid detoxification mediated by cytochrome-P450 mono-oxygenases, with the other detoxification enzyme families, the carboxylesterases and glutathione-S-transferases, playing much smaller roles in miticide tolerance. The goal of this study was to test the capability of the glutathione-S-transferase enzyme inhibitors diethyl maleate and curcumin, which should interfere minimally with honey bee detoxifi...
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effect of a Fluvalinate resistance associated sodium channel mutation from varroa mites on cockroach sodium channel sensitivity to Fluvalinate a pyrethroid insecticide
Insect Biochemistry and Molecular Biology, 2006Co-Authors: Zhiqi Liu, Zachary Y. Huang, Jianguo Tan, Ke DongAbstract:Fluvalinate is a pyrethroid insecticide that is widely used in the control of the varroa mite (Varroa destructor), an ecto-parasite of the honeybee. Previously we identified four Fluvalinate-resistance-associated mutations in the sodium channel gene of the varroa mite. One of the mutations caused a leucine (L) to proline (P) change at 1770 in the linker connecting domains III and IV of the sodium channel. Interestingly, at the position corresponding to the L to P mutation, all known insect (including honeybee) sodium channel proteins already naturally contain a P residue (e.g., P1577 in the cockroach sodium channel BgNa(v)). To determine whether insect sodium channels are less sensitive to Fluvalinate than arachnid sodium channels, we replaced P1577 with an L in a BgNa(v) variant (BgNa(v)1-1) and examined the sensitivity of the recombinant channel to Fluvalinate. The P1577L substitution did not alter the gating properties of the BgNa(v)1-1 channel expressed in Xenopus oocytes. However, the BgNa(v)1-1(P1577L) channel was five-fold more sensitive to Fluvalinate compared with the BgNa(v)1-1 channel. These results not only implicate the L to P mutation in Fluvalinate resistance in varroa mites, but also suggest a possible contribution of L1770 to the higher sensitivity of varroa mites to Fluvalinate than their insect hosts.
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association of novel mutations in a sodium channel gene with Fluvalinate resistance in the mite varroa destructor
Journal of Apicultural Research, 2002Co-Authors: Ruiwu Wang, Patti J Elzen, Ke Dong, Jeff Pettis, Zachary Y. HuangAbstract:SUMMARYVarroa (Varroa destructor) has recently become resistant to Apistan, a pyrethroid pesticide with tau-Fluvalinate as its active ingredient. In many insect pests, resistance to pyrethroid insecticides is due to reduced target-site (sodium channel) sensitivity to pyrethroids in the nervous system, a phenomenon called knockdown resistance (kdr). A number of studies showed that kdr and kdr-type resistance is a result of point mutations in the para family of sodium channel genes. To investigate the molecular mechanism of resistance to Fluvalinate in varroa, we have cloned and sequenced a large cDNA fragment corresponding to segment 3 of domain II (IIS3) to segment 6 of domain IV (IVS6) of a para-homologous sodium channel gene (VmNa) from susceptible and resistant mite populations. The deduced amino acid sequence from this cDNA shares 71%, 60%, and 50% identity with the corresponding region of the para-homologous protein of the Southern cattle tick, Boophilus microplus, Drosophila melanogaster Para, and r...
Reed M Johnson - One of the best experts on this subject based on the ideXlab platform.
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Acaricide, Fungicide and Drug Interactions in Honey Bees (Apis mellifera)
2016Co-Authors: Reed M JohnsonAbstract:Background: Chemical analysis shows that honey bees (Apis mellifera) and hive products contain many pesticides derived from various sources. The most abundant pesticides are acaricides applied by beekeepers to control Varroa destructor. Beekeepers also apply antimicrobial drugs to control bacterial and microsporidial diseases. Fungicides may enter the hive when applied to nearby flowering crops. Acaricides, antimicrobial drugs and fungicides are not highly toxic to bees alone, but in combination there is potential for heightened toxicity due to interactive effects. Methodology/Principal Findings: Laboratory bioassays based on mortality rates in adult worker bees demonstrated interactive effects among acaricides, as well as between acaricides and antimicrobial drugs and between acaricides and fungicides. Toxicity of the acaricide tau-Fluvalinate increased in combination with other acaricides and most other compounds tested (15 of 17) while amitraz toxicity was mostly unchanged (1 of 15). The sterol biosynthesis inhibiting (SBI) fungicide prochloraz elevated the toxicity of the acaricides tau-Fluvalinate, coumaphos and fenpyroximate, likely through inhibition of detoxicative cytochrome P450 monooxygenase activity. Four other SBI fungicides increased the toxicity of tau-Fluvalinate in a dose-dependent manner, although possible evidence of P450 induction was observed at the lowest fungicide doses. Non-transitive interactions between some acaricides were observed. Sublethal amitraz pre-treatment increased the toxicity of the three P450-detoxified acaricides, but amitraz toxicity was not changed by sublethal treatmen
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using video tracking to assess sublethal effects of pesticides on honey bees apis mellifera l
Environmental Toxicology and Chemistry, 2012Co-Authors: Bethany S Teeters, Reed M Johnson, Marion D Ellis, Blair D SiegfriedAbstract:Concern about the role of pesticides in honey bee decline has highlighted the need to examine the effects of sublethal exposure on bee behaviors. The video-tracking system EthoVisionXT (Noldus Information Technologies) was used to measure the effects of sublethal exposure to tau-Fluvalinate and imidacloprid on honey bee locomotion, interactions, and time spent near a food source over a 24-h observation period. Bees were either treated topically with 0.3, 1.5, and 3 µg tau-Fluvalinate or exposed to 0.05, 0.5, 5.0, 50, and 500 ppb imidacloprid in a sugar agar cube. Tau-Fluvalinate caused a significant reduction in distance moved at all dose levels (p < 0.05), as did 50 and 500 ppb imidacloprid (p < 0.001). Bees exposed to 50 and 500 ppb spent significantly more time near the food source than control bees (p < 0.05). Interaction time decreased as time in the food zone increased for both chemicals. This study documents that video-tracking of bee behavior can enhance current protocols for measuring the effects of pesticides on honey bees at sublethal levels. It may provide a means of identifying problematic compounds for further testing.
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ecologically appropriate xenobiotics induce cytochrome p450s in apis mellifera
PLOS ONE, 2012Co-Authors: Reed M Johnson, Mary A Schuler, Henry S Pollock, May R BerenbaumAbstract:Background Honey bees are exposed to phytochemicals through the nectar, pollen and propolis consumed to sustain the colony. They may also encounter mycotoxins produced by Aspergillus fungi infesting pollen in beebread. Moreover, bees are exposed to agricultural pesticides, particularly in-hive acaricides used against the parasite Varroa destructor. They cope with these and other xenobiotics primarily through enzymatic detoxificative processes, but the regulation of detoxificative enzymes in honey bees remains largely unexplored. Methodology/Principal Findings We used several approaches to ascertain effects of dietary toxins on bee susceptibility to synthetic and natural xenobiotics, including the acaricide tau-Fluvalinate, the agricultural pesticide imidacloprid, and the naturally occurring mycotoxin aflatoxin. We administered potential inducers of cytochrome P450 enzymes, the principal biochemical system for Phase 1 detoxification in insects, to investigate how detoxification is regulated. The drug phenobarbital induces P450s in many insects, yet feeding bees with phenobarbital had no effect on the toxicity of tau-Fluvalinate, a pesticide known to be detoxified by bee P450s. Similarly, no P450 induction, as measured by tau-Fluvalinate tolerance, occurred in bees fed xanthotoxin, salicylic acid, or indole-3-carbinol, all of which induce P450s in other insects. Only quercetin, a common pollen and honey constituent, reduced tau-Fluvalinate toxicity. In microarray comparisons no change in detoxificative gene expression was detected in phenobarbital-treated bees. However, northern blot analyses of guts of bees fed extracts of honey, pollen and propolis showed elevated expression of three CYP6AS P450 genes. Diet did not influence tau-Fluvalinate or imidacloprid toxicity in bioassays; however, aflatoxin toxicity was higher in bees consuming sucrose or high-fructose corn syrup than in bees consuming honey. Conclusions/Significance These results suggest that regulation of honey bee P450s is tuned to chemicals occurring naturally in the hive environment and that, in terms of toxicological capacity, a diet of sugar is not equivalent to a diet of honey.
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Role of detoxification in Varroa destructor (Acari: Varroidae) tolerance of the miticide tau-Fluvalinate.
International Journal of Acarology, 2010Co-Authors: Reed M Johnson, Zachary Y. Huang, May R BerenbaumAbstract:ABSTRACT The varroa mite (Varroa destructor Anderson and Trueman) is a devastating pest of honey bees (Apis mellifera L.). Beekeepers have relied on the pyrethroid pesticide tau-Fluvalinate as a principal agent of varroa mite control. While this miticide was quite effective at controlling varroa mites through the 1990s, its efficacy has waned as resistance to tau-Fluvalinate has appeared in many populations of mites. Resistance in some populations of varroa mites has been associated with elevated detoxification of tau-Fluvalinate. Honey bees tolerate miticidal tau-Fluvalinate applications principally through rapid detoxification mediated by cytochrome-P450 mono-oxygenases, with the other detoxification enzyme families, the carboxylesterases and glutathione-S-transferases, playing much smaller roles in miticide tolerance. The goal of this study was to test the capability of the glutathione-S-transferase enzyme inhibitors diethyl maleate and curcumin, which should interfere minimally with honey bee detoxifi...
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mediation of pyrethroid insecticide toxicity to honey bees hymenoptera apidae by cytochrome p450 monooxygenases
Journal of Economic Entomology, 2006Co-Authors: Reed M Johnson, May R BerenbaumAbstract:Honey bees, Apis mellifera L., often thought to be extremely susceptible to insecticides in general, exhibit considerable variation in tolerance to pyrethroid insecticides. Although some pyrethroids, such as cyfluthrin and lambda-cyhalothrin, are highly toxic to honey bees, the toxicity of tau-Fluvalinate is low enough to warrant its use to control parasitic mites inside honey bee colonies. Metabolic insecticide resistance in other insects is mediated by three major groups of detoxifying enzymes: the cytochrome P450 monooxygenases (P450s), the carboxylesterases (COEs), and the glutathione S-transferases (GSTs). To test the role of metabolic detoxification in mediating the relatively low toxicity of tau-Fluvalinate compared with more toxic pyrethroid insecticides, we examined the effects of piperonyl butoxide (PBO), S,S,S-tributylphosphorotrithioate (DEF), and diethyl maleate (DEM) on the toxicity of these pyrethroids. The toxicity of the three pyrethroids to bees was greatly synergized by the P450 inhibitor PBO and synergized at low levels by the carboxylesterase inhibitor DEF. Little synergism was observed with DEM. These results suggest that metabolic detoxification, especially that mediated by P450s, contributes significantly to honey bee tolerance of pyrethroid insecticides. The potent synergism between tau-Fluvalinate and PBO suggests that P450s are especially important in the detoxification of this pyrethroid and explains the ability of honey bees to tolerate its presence.
Martin S Williamson - One of the best experts on this subject based on the ideXlab platform.
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novel mutations in the voltage gated sodium channel of pyrethroid resistant varroa destructor populations from the southeastern usa
PLOS ONE, 2016Co-Authors: James D Ellis, Joel Gonzalezcabrera, Sonia Rodriguezvargas, T Emyr G Davies, L M Field, Daniel R Schmehl, Klemens Krieger, Martin S WilliamsonAbstract:The parasitic mite Varroa destructor has a significant worldwide impact on bee colony health. In the absence of control measures, parasitized colonies invariably collapse within 3 years. The synthetic pyrethroids tau-Fluvalinate and flumethrin have proven very effective at managing this mite within apiaries, but intensive control programs based mainly on one active ingredient have led to many reports of pyrethroid resistance. In Europe, a modification of leucine to valine at position 925 (L925V) of the V. destructor voltage-gated sodium channel was correlated with resistance, the mutation being found at high frequency exclusively in hives with a recent history of pyrethroid treatment. Here, we identify two novel mutations, L925M and L925I, in tau-Fluvalinate resistant V. destructor collected at seven sites across Florida and Georgia in the Southeastern region of the USA. Using a multiplexed TaqMan® allelic discrimination assay, these mutations were found to be present in 98% of the mites surviving tau-Fluvalinate treatment. The mutations were also found in 45% of the non-treated mites, suggesting a high potential for resistance evolution if selection pressure is applied. The results from a more extensive monitoring programme, using the Taqman® assay described here, would clearly help beekeepers with their decision making as to when to include or exclude pyrethroid control products and thereby facilitate more effective mite management programmes.
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molecular and functional characterization of cyp6bq23 a cytochrome p450 conferring resistance to pyrethroids in european populations of pollen beetle meligethes aeneus
Insect Biochemistry and Molecular Biology, 2014Co-Authors: Martin S Williamson, Christoph T Zimmer, Chris Bass, Martin Kaussmann, Katharina Wolfel, Oliver Gutbrod, Ralf NauenAbstract:The pollen beetle (Meligethes aeneus F.) is widespread throughout much of Europe where it is a major coleopteran pest of oilseed rape (Brassica napus). The reliance on synthetic insecticides for control, particularly the pyrethroid class, has led to the development of populations with high levels of resistance. Resistance to pyrethroids is now widespread throughout Europe and is thought to be mediated by enhanced detoxification by cytochrome P450ś and/or mutation of the pyrethroid target-site, the voltage-gated sodium channel. However, in the case of cytochrome P450 mediated detoxification, the specific enzyme(s) involved has (have) not yet been identified. In this study a degenerate PCR approach was used to identify ten partial P450 gene sequences from pollen beetle. Quantitative PCR was then used to examine the level of expression of these genes in a range of pollen beetle populations that showed differing levels of resistance to pyrethroids in bioassays. The study revealed a single P450 gene, CYP6BQ23, which is significantly and highly overexpressed (up to ∼900-fold) in adults and larvae of pyrethroid resistant strains compared to susceptible strains. CYP6BQ23 overexpression is significantly correlated with both the level of resistance and with the rate of deltamethrin metabolism in microsomal preparations of these populations. Functional recombinant expression of full length CYP6BQ23 along with cytochrome P450 reductase in an insect (Sf9) cell line showed that it is able to efficiently metabolise deltamethrin to 4-hydroxy deltamethrin. Furthermore we demonstrated by detection of 4-hydroxy tau-Fluvalinate using ESI-TOF MS/MS that functionally expressed CYP6BQ23 also metabolizes tau-Fluvalinate. A protein model was generated and subsequent docking simulations revealed the predicted substrate-binding mode of both deltamethrin and tau-Fluvalinate to CYP6BQ23. Taken together these results strongly suggest that the overexpression of CYP6BQ23 is the primary mechanism conferring pyrethroid resistance in pollen beetle populations throughout much of Europe.
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an amino acid substitution l925v associated with resistance to pyrethroids in varroa destructor
PLOS ONE, 2013Co-Authors: Joel Gonzalezcabrera, T Emyr G Davies, L M Field, Peter J Kennedy, Martin S WilliamsonAbstract:The Varroa mite, Varroa destructor, is an important pest of honeybees and has played a prominent role in the decline in bee colony numbers over recent years. Although pyrethroids such as tau-Fluvalinate and flumethrin can be highly effective in removing the mites from hives, their intensive use has led to many reports of resistance. To investigate the mechanism of resistance in UK Varroa samples, the transmembrane domain regions of the V. destructor voltage-gated sodium channel (the main target site for pyrethroids) were PCR amplified and sequenced from pyrethroid treated/untreated mites collected at several locations in Central/Southern England. A novel amino acid substitution, L925V, was identified that maps to a known hot spot for resistance within the domain IIS5 helix of the channel protein; a region that has also been proposed to form part of the pyrethroid binding site. Using a high throughput diagnostic assay capable of detecting the mutation in individual mites, the L925V substitution was found to correlate well with resistance, being present in all mites that had survived tau-Fluvalinate treatment but in only 8 % of control, untreated samples. The potential for using this assay to detect and manage resistance in Varroa-infected hives is discussed.