Williamson MS


Full name : Williamson Martin S

First name : Martin S

Mail : Insecticides Department. Rothamsted Exptl., Station, Harpenden. Herts AL5 2JQ

Zip Code :

City :

Country : United Kingdom

Email : martin.williamson@rothamsted.ac.uk

Phone : (44)582-763133

Fax : 1582-762595

Website :

Directory :

References (52)

Title : Global patterns in genomic diversity underpinning the evolution of insecticide resistance in the aphid crop pest Myzus persicae - Singh_2021_Commun.Biol_4_847
Author(s) : Singh KS , Cordeiro EMG , Troczka BJ , Pym A , Mackisack J , Mathers TC , Duarte A , Legeai F , Robin S , Bielza P , Burrack HJ , Charaabi K , Denholm I , Figueroa CC , ffrench-Constant RH , Jander G , Margaritopoulos JT , Mazzoni E , Nauen R , Ramirez CC , Ren G , Stepanyan I , Umina PA , Voronova NV , Vontas J , Williamson MS , Wilson ACC , Xi-Wu G , Youn YN , Zimmer CT , Simon JC , Hayward A , Bass C
Ref : Commun Biol , 4 :847 , 2021
Abstract : The aphid Myzus persicae is a destructive agricultural pest that displays an exceptional ability to develop resistance to both natural and synthetic insecticides. To investigate the evolution of resistance in this species we generated a chromosome-scale genome assembly and living panel of >110 fully sequenced globally sampled clonal lines. Our analyses reveal a remarkable diversity of resistance mutations segregating in global populations of M. persicae. We show that the emergence and spread of these mechanisms is influenced by host-plant associations, uncovering the widespread co-option of a host-plant adaptation that also offers resistance against synthetic insecticides. We identify both the repeated evolution of independent resistance mutations at the same locus, and multiple instances of the evolution of novel resistance mechanisms against key insecticides. Our findings provide fundamental insights into the genomic responses of global insect populations to strong selective forces, and hold practical relevance for the control of pests and parasites.
ESTHER : Singh_2021_Commun.Biol_4_847
PubMedSearch : Singh_2021_Commun.Biol_4_847
PubMedID: 34234279

Title : Unravelling the Molecular Determinants of Bee Sensitivity to Neonicotinoid Insecticides - Manjon_2018_Curr.Biol_28_1137
Author(s) : Manjon C , Troczka BJ , Zaworra M , Beadle K , Randall E , Hertlein G , Singh KS , Zimmer CT , Homem RA , Lueke B , Reid R , Kor L , Kohler M , Benting J , Williamson MS , Davies TGE , Field LM , Bass C , Nauen R
Ref : Current Biology , 28 :1137 , 2018
Abstract : The impact of neonicotinoid insecticides on the health of bee pollinators is a topic of intensive research and considerable current debate [1]. As insecticides, certain neonicotinoids, i.e., N-nitroguanidine compounds such as imidacloprid and thiamethoxam, are as intrinsically toxic to bees as to the insect pests they target. However, this is not the case for all neonicotinoids, with honeybees orders of magnitude less sensitive to N-cyanoamidine compounds such as thiacloprid [2]. Although previous work has suggested that this is due to rapid metabolism of these compounds [2-5], the specific gene(s) or enzyme(s) involved remain unknown. Here, we show that the sensitivity of the two most economically important bee species to neonicotinoids is determined by cytochrome P450s of the CYP9Q subfamily. Radioligand binding and inhibitor assays showed that variation in honeybee sensitivity to N-nitroguanidine and N-cyanoamidine neonicotinoids does not reside in differences in their affinity for the receptor but rather in divergent metabolism by P450s. Functional expression of the entire CYP3 clade of P450s from honeybees identified a single P450, CYP9Q3, that metabolizes thiacloprid with high efficiency but has little activity against imidacloprid. We demonstrate that bumble bees also exhibit profound differences in their sensitivity to different neonicotinoids, and we identify CYP9Q4 as a functional ortholog of honeybee CYP9Q3 and a key metabolic determinant of neonicotinoid sensitivity in this species. Our results demonstrate that bee pollinators are equipped with biochemical defense systems that define their sensitivity to insecticides and this knowledge can be leveraged to safeguard bee health.
ESTHER : Manjon_2018_Curr.Biol_28_1137
PubMedSearch : Manjon_2018_Curr.Biol_28_1137
PubMedID: 29576476

Title : Mutation in the ace-1 gene of the tomato leaf miner (Tuta absoluta) associated with organophosphates resistance - Haddi_2017_J.Appl.Entomol_141_612
Author(s) : Haddi K , Berger M , Bielza P , Rapisarda C , Williamson MS , Moores GD , Bass C
Ref : J.Appl_Entomol , 141 :612 , 2017
Abstract : The tomato leaf miner, Tuta absoluta (Lepidoptera: Gelechiidae), is a major invasive pest that has spread throughout many countries in the Mediterranean basin and parts of Asia over the last decade. The control of T. absoluta has relied heavily on the use of chemical insecticides, a strategy that has led to the evolution of resistance. In this study, biological and molecular methods were used to determine the susceptibility of five strains of T. absoluta to the organophosphate chlorpyrifos and to investigate the molecular mechanisms underlying resistance to this class of insecticides. High levels of resistance to chlorpyrifos were observed in all five strains tested. Cloning and sequencing of the gene encoding the organophosphate target site, ace-1, of T. absoluta revealed the presence of an alanine to serine substitution at a position that has been previously linked with organophosphate resistance across a range of different insect and mite species. The presence of this mutation at high frequency in T. absoluta populations originating from various countries further supports the suggestion that the rapid expansion of this species is, in part, mediated by the resistance of this pest to chemical insecticides.
ESTHER : Haddi_2017_J.Appl.Entomol_141_612
PubMedSearch : Haddi_2017_J.Appl.Entomol_141_612
Gene_locus related to this paper: tutab-ACHE1

Title : Ryanodine receptor point mutations confer diamide insecticide resistance in tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae) - Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
Author(s) : Roditakis E , Steinbach D , Moritz G , Vasakis E , Stavrakaki M , Ilias A , Garcia-Vidal L , Martinez-Aguirre MD , Bielza P , Morou E , Silva JE , Silva WM , Siqueira Eta A , Iqbal S , Troczka BJ , Williamson MS , Bass C , Tsagkarakou A , Vontas J , Nauen R
Ref : Insect Biochemistry & Molecular Biology , 80 :11 , 2017
Abstract : Insect ryanodine receptors (RyR) are the molecular target-site for the recently introduced diamide insecticides. Diamides are particularly active on Lepidoptera pests, including tomato leafminer, Tuta absoluta (Lepidoptera: Gelechiidae). High levels of diamide resistance were recently described in some European populations of T. absoluta, however, the mechanisms of resistance remained unknown. In this study the molecular basis of diamide resistance was investigated in a diamide resistant strain from Italy (IT-GELA-SD4), and additional resistant field populations collected in Greece, Spain and Brazil. The genetics of resistance was investigated by reciprocally crossing strain IT-GELA-SD4 with a susceptible strain and revealed an autosomal incompletely recessive mode of inheritance. To investigate the possible role of target-site mutations as known from diamondback moth (Plutella xylostella), we sequenced respective domains of the RyR gene of T. absoluta. Genotyping of individuals of IT-GELA-SD4 and field-collected strains showing different levels of diamide resistance revealed the presence of G4903E and I4746M RyR target-site mutations. These amino acid substitutions correspond to those recently described for diamide resistant diamondback moth, i.e. G4946E and I4790M. We also detected two novel mutations, G4903V and I4746T, in some of the resistant T. absoluta strains. Radioligand binding studies with thoracic membrane preparations of the IT-GELA-SD4 strain provided functional evidence that these mutations alter the affinity of the RyR to diamides. In combination with previous work on P. xylostella our study highlights the importance of position G4903 (G4946 in P. xylostella) of the insect RyR in defining sensitivity to diamides. The discovery of diamide resistance mutations in T. absoluta populations of diverse geographic origin has serious implications for the efficacy of diamides under applied conditions. The implementation of appropriate resistance management strategies is strongly advised to delay the further spread of resistance.
ESTHER : Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
PubMedSearch : Roditakis_2017_Insect.Biochem.Mol.Biol_80_11
PubMedID: 27845250

Title : Insecticide resistance mediated by an exon skipping event - Berger_2016_Mol.Ecol_25_5692
Author(s) : Berger M , Puinean AM , Randall E , Zimmer CT , Silva WM , Bielza P , Field LM , Hughes D , Mellor I , Hassani-Pak K , Siqueira HA , Williamson MS , Bass C
Ref : Mol Ecol , 25 :5692 , 2016
Abstract : Many genes increase coding capacity by alternate exon usage. The gene encoding the insect nicotinic acetylcholine receptor (nAChR) alpha6 subunit, target of the bio-insecticide spinosad, is one example of this and expands protein diversity via alternative splicing of mutually exclusive exons. Here, we show that spinosad resistance in the tomato leaf miner, Tuta absoluta is associated with aberrant regulation of splicing of Taalpha6 resulting in a novel form of insecticide resistance mediated by exon skipping. Sequencing of the alpha6 subunit cDNA from spinosad selected and unselected strains of T. absoluta revealed all Taalpha6 transcripts of the selected strain were devoid of exon 3, with comparison of genomic DNA and mRNA revealing this is a result of exon skipping. Exon skipping cosegregated with spinosad resistance in survival bioassays, and functional characterization of this alteration using modified human nAChR alpha7, a model of insect alpha6, demonstrated that exon 3 is essential for receptor function and hence spinosad sensitivity. DNA and RNA sequencing analyses suggested that exon skipping did not result from genetic alterations in intronic or exonic cis-regulatory elements, but rather was associated with a single epigenetic modification downstream of exon 3a, and quantitative changes in the expression of trans-acting proteins that have known roles in the regulation of alternative splicing. Our results demonstrate that the intrinsic capacity of the alpha6 gene to generate transcript diversity via alternative splicing can be readily exploited during the evolution of resistance and identifies exon skipping as a molecular alteration conferring insecticide resistance.
ESTHER : Berger_2016_Mol.Ecol_25_5692
PubMedSearch : Berger_2016_Mol.Ecol_25_5692
PubMedID: 27748560

Title : The global status of insect resistance to neonicotinoid insecticides - Bass_2015_Pestic.Biochem.Physiol_121_78
Author(s) : Bass C , Denholm I , Williamson MS , Nauen R
Ref : Pestic Biochem Physiol , 121 :78 , 2015
Abstract : The first neonicotinoid insecticide, imidacloprid, was launched in 1991. Today this class of insecticides comprises at least seven major compounds with a market share of more than 25% of total global insecticide sales. Neonicotinoid insecticides are highly selective agonists of insect nicotinic acetylcholine receptors and provide farmers with invaluable, highly effective tools against some of the world's most destructive crop pests. These include sucking pests such as aphids, whiteflies, and planthoppers, and also some coleopteran, dipteran and lepidopteran species. Although many insect species are still successfully controlled by neonicotinoids, their popularity has imposed a mounting selection pressure for resistance, and in several species resistance has now reached levels that compromise the efficacy of these insecticides. Research to understand the molecular basis of neonicotinoid resistance has revealed both target-site and metabolic mechanisms conferring resistance. For target-site resistance, field-evolved mutations have only been characterized in two aphid species. Metabolic resistance appears much more common, with the enhanced expression of one or more cytochrome P450s frequently reported in resistant strains. Despite the current scale of resistance, neonicotinoids remain a major component of many pest control programmes, and resistance management strategies, based on mode of action rotation, are of crucial importance in preventing resistance becoming more widespread. In this review we summarize the current status of neonicotinoid resistance, the biochemical and molecular mechanisms involved, and the implications for resistance management.
ESTHER : Bass_2015_Pestic.Biochem.Physiol_121_78
PubMedSearch : Bass_2015_Pestic.Biochem.Physiol_121_78
PubMedID: 26047114

Title : The evolution of insecticide resistance in the peach potato aphid, Myzus persicae - Bass_2014_Insect.Biochem.Mol.Biol_51_41
Author(s) : Bass C , Puinean AM , Zimmer CT , Denholm I , Field LM , Foster SP , Gutbrod O , Nauen R , Slater R , Williamson MS
Ref : Insect Biochemistry & Molecular Biology , 51 :41 , 2014
Abstract : The peach potato aphid, Myzus persicae is a globally distributed crop pest with a host range of over 400 species including many economically important crop plants. The intensive use of insecticides to control this species over many years has led to populations that are now resistant to several classes of insecticide. Work spanning over 40 years has shown that M. persicae has a remarkable ability to evolve mechanisms that avoid or overcome the toxic effect of insecticides with at least seven independent mechanisms of resistance described in this species to date. The array of novel resistance mechanisms, including several 'first examples', that have evolved in this species represents an important case study for the evolution of insecticide resistance and also rapid adaptive change in insects more generally. In this review we summarise the biochemical and molecular mechanisms underlying resistance in M. persicae and the insights study of this topic has provided on how resistance evolves, the selectivity of insecticides, and the link between resistance and host plant adaptation.
ESTHER : Bass_2014_Insect.Biochem.Mol.Biol_51_41
PubMedSearch : Bass_2014_Insect.Biochem.Mol.Biol_51_41
PubMedID: 24855024

Title : Development of a high-throughput real-time PCR assay for the detection of the R81T mutation in the nicotinic acetylcholine receptor of neonicotinoid-resistant Myzus persicae - Puinean_2013_Pest.Manag.Sci_69_195
Author(s) : Puinean AM , Elias J , Slater R , Warren A , Field LM , Williamson MS , Bass C
Ref : Pest Manag Sci , 69 :195 , 2013
Abstract : BACKGROUND: Myzus persicae is a globally important aphid pest that is mainly controlled through the application of chemical insecticides. Recently, a clone of M. persicae exhibiting control-compromising levels of resistance to neonicotinoid insecticides was described. The resistance of this clone was associated with reduced affinity of imidacloprid for the target site (the nicotinic acetylcholine receptor) as a result of mutation of a key amino acid residue (R81T) in the loop D region of a nAChR beta1 subunit. The potent levels of resistance conferred by this mechanism are cause for considerable concern, and the frequency and distribution of the mutation in worldwide populations of M. persicae require careful monitoring. In this study, a high-throughput assay has been developed that allows detection of the mutation in individual aphids.
RESULTS: A real-time TaqMan assay to detect the R81T substitution was developed that proved to be sensitive and specific in tests of analytical sensitivity and in a blind genotyping trial of DNA extracted from individual aphids comprising the three possible genotypes. The assay was then used to examine the frequency of the R81T mutation in aphids collected and stored in ethanol from peach orchards in southern France. The R81T frequency varied from 33 to 100% in seven populations from the department of Gard, France.
CONCLUSIONS: This study describes a rapid and sensitive assay that very effectively detects the R81T mutation in individual aphids. The results also have practical significance for the control of M. persicae in southern France and provide contemporary data to inform current resistance management strategies.
ESTHER : Puinean_2013_Pest.Manag.Sci_69_195
PubMedSearch : Puinean_2013_Pest.Manag.Sci_69_195
PubMedID: 22528746

Title : Investigating the molecular mechanisms of organophosphate and pyrethroid resistance in the fall armyworm Spodoptera frugiperda - Carvalho_2013_PLoS.One_8_e62268
Author(s) : Carvalho RA , Omoto C , Field LM , Williamson MS , Bass C
Ref : PLoS ONE , 8 :e62268 , 2013
Abstract : The fall armyworm Spodoptera frugiperda is an economically important pest of small grain crops that occurs in all maize growing regions of the Americas. The intensive use of chemical pesticides for its control has led to the selection of resistant populations, however, to date, the molecular mechanisms underlying resistance have not been characterised. In this study the mechanisms involved in the resistance of two S. frugiperda strains collected in Brazil to chlorpyrifos (OP strain) or lambda-cyhalothrin (PYR strain) were investigated using molecular and genomic approaches. To examine the possible role of target-site insensitivity the genes encoding the organophosphate (acetylcholinesterase, AChE) and pyrethroid (voltage-gated sodium channel, VGSC) target-site proteins were PCR amplified. Sequencing of the S. frugiperda ace-1 gene identified several nucleotide changes in the OP strain when compared to a susceptible reference strain (SUS). These result in three amino acid substitutions, A201S, G227A and F290V, that have all been shown previously to confer organophosphate resistance in several other insect species. Sequencing of the gene encoding the VGSC in the PYR strain, identified mutations that result in three amino acid substitutions, T929I, L932F and L1014F, all of which have been shown previously to confer knockdown/super knockdown-type resistance in several arthropod species. To investigate the possible role of metabolic detoxification in the resistant phenotype of the OP and PYR stains all EST sequences available for S. frugiperda were used to design a gene-expression microarray. This was then used to compare gene expression in the resistant strains with the susceptible reference strain. Members of several gene families, previously implicated in metabolic resistance in other insects were found to be overexpressed in the resistant strains including glutathione S-transferases, cytochrome P450s and carboxylesterases. Taken together these results provide evidence that both target-site and metabolic mechanisms underlie the resistance of S. frugiperda to pyrethroids and organophosphates.
ESTHER : Carvalho_2013_PLoS.One_8_e62268
PubMedSearch : Carvalho_2013_PLoS.One_8_e62268
PubMedID: 23614047
Gene_locus related to this paper: spolt-ACHE1

Title : Gene amplification and microsatellite polymorphism underlie a recent insect host shift - Bass_2013_Proc.Natl.Acad.Sci.U.S.A_110_19460
Author(s) : Bass C , Zimmer CT , Riveron JM , Wilding CS , Wondji CS , Kaussmann M , Field LM , Williamson MS , Nauen R
Ref : Proc Natl Acad Sci U S A , 110 :19460 , 2013
Abstract : Host plant shifts of herbivorous insects may be a first step toward sympatric speciation and can create new pests of agriculturally important crops; however, the molecular mechanisms that mediate this process are poorly understood. Certain races of the polyphagous aphid Myzus persicae have recently adapted to feed on tobacco (Myzus persicae nicotianae) and show a reduced sensitivity to the plant alkaloid nicotine and cross-resistance to neonicotinoids a class of synthetic insecticides widely used for control. Here we show constitutive overexpression of a cytochrome P450 (CYP6CY3) allows tobacco-adapted races of M. persicae to efficiently detoxify nicotine and has preadapted them to resist neonicotinoid insecticides. CYP6CY3, is highly overexpressed in M. persicae nicotianae clones from three continents compared with M. persicae s.s. and expression level is significantly correlated with tolerance to nicotine. CYP6CY3 is highly efficient (compared with the primary human nicotine-metabolizing P450) at metabolizing nicotine and neonicotinoids to less toxic metabolites in vitro and generation of transgenic Drosophila expressing CYP6CY3 demonstrate that it confers resistance to both compounds in vivo. Overexpression of CYP6CY3 results from the expansion of a dinucleotide microsatellite in the promoter region and a recent gene amplification, with some aphid clones carrying up to 100 copies. We conclude that the mutations leading to overexpression of CYP6CY3 were a prerequisite for the host shift of M. persicae to tobacco and that gene amplification and microsatellite polymorphism are evolutionary drivers in insect host adaptation.
ESTHER : Bass_2013_Proc.Natl.Acad.Sci.U.S.A_110_19460
PubMedSearch : Bass_2013_Proc.Natl.Acad.Sci.U.S.A_110_19460
PubMedID: 24218582

Title : Chlorpyrifos resistance is associated with mutation and amplification of the acetylcholinesterase-1 gene in the tomato red spider mite, Tetranychus evansi - Carvalho_2012_Pestic.Biochem.Physiol_104_143
Author(s) : Carvalho RA , Yang Y , Field LM , Gorman K , Moores GD , Williamson MS , Bass C
Ref : Pesticide Biochemistry and Physiology , 104 :143 , 2012
Abstract : The tomato red spider mite, Tetranychus evansi is an invasive pest of many African countries where it causes significant damage to a range of solanaceous crops. In Malawi the control of T. evansi relies heavily on the use of chemical pesticides and this species has evolved resistance to members of the pyrethroid and organophosphate (OP) classes. In this study the molecular mechanisms underlying resistance to the organophosphate chlorpyrifos were investigated in two resistant strains of T. evansi from Malawi and France. Cloning and sequencing of the gene encoding the OP target (ace-1) revealed an amino acid substitution at just one of the positions (331) previously implicated in OP resistance across a range of different insect and mite species. The amino acid residue usually found at this position in susceptible insects and mites is a phenylalanine (F) but was a tyrosine (Y) in all sequenced clones of the France strain and a tyrosine or tryptophan (W) in sequenced clones of the Malawi strain. Additionally we found evidence that the ace-1 locus is amplified in the resistant strains, with direct measurement of gene copy number by quantitative PCR showing there are around 8-10 copies of the gene in both the France and the Malawi strain. Sequencing of clones of ace-1 from the Malawi strain indicated that individual mites have fewer copies of the W331 allele than the Y331 allele. The enhanced copy number of the ace-1 gene in T. evansi and copy number variation of the two alleles seen in the Malawi strain may be a mechanism to compensate for fitness costs associated with the mutant alleles as has been proposed for T. urticae.
ESTHER : Carvalho_2012_Pestic.Biochem.Physiol_104_143
PubMedSearch : Carvalho_2012_Pestic.Biochem.Physiol_104_143
Gene_locus related to this paper: 9acar-k9m8p0

Title : Identification of mutations associated with pyrethroid resistance in the voltage-gated sodium channel of the tomato leaf miner (Tuta absoluta) - Haddi_2012_Insect.Biochem.Mol.Biol_42_506
Author(s) : Haddi K , Berger M , Bielza P , Cifuentes D , Field LM , Gorman K , Rapisarda C , Williamson MS , Bass C
Ref : Insect Biochemistry & Molecular Biology , 42 :506 , 2012
Abstract : The tomato leaf miner, Tuta absoluta (Lepidoptera) is a significant pest of tomatoes that has undergone a rapid expansion in its range during the past six years and is now present across Europe, North Africa and parts of Asia. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study insecticide bioassays were used to determine the susceptibility of five T. absoluta strains established from field collections from Europe and Brazil to pyrethroids. High levels of resistance to lambda cyhalothrin and tau fluvalinate were observed in all five strains tested. To investigate whether pyrethroid resistance was mediated by mutation of the para-type sodium channel in T. absoluta the IIS4-IIS6 region of the para gene, which contains many of the mutation sites previously shown to confer knock down (kdr)-type resistance to pyrethroids across a range of different arthropod species, was cloned and sequenced. This revealed that three kdr/super-kdr-type mutations (M918T, T929I and L1014F), were present at high frequencies within all five resistant strains at known resistance 'hot-spots'. This is the first description of these mutations together in any insect population. High-throughput DNA-based diagnostic assays were developed and used to assess the prevalence of these mutations in 27 field strains from 12 countries. Overall mutant allele frequencies were high (L1014F 0.98, M918T 0.35, T929I 0.60) and remarkably no individual was observed that did not carry kdr in combination with either M918T or T929I. The presence of these mutations at high frequency in T. absoluta populations across much of its range suggests pyrethroids are likely to be ineffective for control and supports the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this pest to chemical insecticides.
ESTHER : Haddi_2012_Insect.Biochem.Mol.Biol_42_506
PubMedSearch : Haddi_2012_Insect.Biochem.Mol.Biol_42_506
PubMedID: 22504519

Title : Mutation of a nicotinic acetylcholine receptor beta subunit is associated with resistance to neonicotinoid insecticides in the aphid Myzus persicae - Bass_2011_BMC.Neurosci_12_51
Author(s) : Bass C , Puinean AM , Andrews M , Cutler P , Daniels M , Elias J , Paul VL , Crossthwaite AJ , Denholm I , Field LM , Foster SP , Lind R , Williamson MS , Slater R
Ref : BMC Neurosci , 12 :51 , 2011
Abstract : BACKGROUND: Myzus persicae is a globally important aphid pest with a history of developing resistance to insecticides. Unusually, neonicotinoids have remained highly effective as control agents despite nearly two decades of steadily increasing use. In this study, a clone of M. persicae collected from southern France was found, for the first time, to exhibit sufficiently strong resistance to result in loss of the field effectiveness of neonicotinoids.
RESULTS: Bioassays, metabolism and gene expression studies implied the presence of two resistance mechanisms in the resistant clone, one based on enhanced detoxification by cytochrome P450 monooxygenases, and another unaffected by a synergist that inhibits detoxifying enzymes. Binding of radiolabeled imidacloprid (a neonicotinoid) to whole body membrane preparations showed that the high affinity [3H]-imidacloprid binding site present in susceptible M. persicae is lost in the resistant clone and the remaining lower affinity site is altered compared to susceptible clones. This confers a significant overall reduction in binding affinity to the neonicotinoid target: the nicotinic acetylcholine receptor (nAChR). Comparison of the nucleotide sequence of six nAChR subunit (Mpalpha1-5 and Mpbeta1) genes from resistant and susceptible aphid clones revealed a single point mutation in the loop D region of the nAChR beta1 subunit of the resistant clone, causing an arginine to threonine substitution (R81T). CONCLUSION: Previous studies have shown that the amino acid at this position within loop D is a key determinant of neonicotinoid binding to nAChRs and this amino acid change confers a vertebrate-like character to the insect nAChR receptor and results in reduced sensitivity to neonicotinoids. The discovery of the mutation at this position and its association with the reduced affinity of the nAChR for imidacloprid is the first example of field-evolved target-site resistance to neonicotinoid insecticides and also provides further validation of exisiting models of neonicotinoid binding and selectivity for insect nAChRs.
ESTHER : Bass_2011_BMC.Neurosci_12_51
PubMedSearch : Bass_2011_BMC.Neurosci_12_51
PubMedID: 21627790

Title : Overexpression of a cytochrome P450 monooxygenase, CYP6ER1, is associated with resistance to imidacloprid in the brown planthopper, Nilaparvata lugens - Bass_2011_Insect.Mol.Biol_20_763
Author(s) : Bass C , Carvalho RA , Oliphant L , Puinean AM , Field LM , Nauen R , Williamson MS , Moores GD , Gorman K
Ref : Insect Molecular Biology , 20 :763 , 2011
Abstract : The brown planthopper, Nilaparvata lugens, is an economically significant pest of rice throughout Asia and has evolved resistance to many insecticides including the neonicotinoid imidacloprid. The resistance of field populations of N. lugens to imidacloprid has been attributed to enhanced detoxification by cytochrome P450 monooxygenases (P450s), although, to date, the causative P450(s) has (have) not been identified. In the present study, biochemical assays using the model substrate 7-ethoxycoumarin showed enhanced P450 activity in several resistant N. lugens field strains when compared with a susceptible reference strain. Thirty three cDNA sequences encoding tentative unique P450s were identified from two recent sequencing projects and by degenerate PCR. The mRNA expression level of 32 of these was examined in susceptible, moderately resistant and highly resistant N. lugens strains using quantitative real-time PCR. A single P450 gene (CYP6ER1) was highly overexpressed in all resistant strains (up to 40-fold) and the level of expression observed in the different N. lugens strains was significantly correlated with the resistance phenotype. These results provide strong evidence for a role of CYP6ER1 in the resistance of N. lugens to imidacloprid.
ESTHER : Bass_2011_Insect.Mol.Biol_20_763
PubMedSearch : Bass_2011_Insect.Mol.Biol_20_763
PubMedID: 21929695

Title : Amplification of a cytochrome P450 gene is associated with resistance to neonicotinoid insecticides in the aphid Myzus persicae - Puinean_2010_PLoS.Genet_6_e1000999
Author(s) : Puinean AM , Foster SP , Oliphant L , Denholm I , Field LM , Millar NS , Williamson MS , Bass C
Ref : PLoS Genet , 6 :e1000999 , 2010
Abstract : The aphid Myzus persicae is a globally significant crop pest that has evolved high levels of resistance to almost all classes of insecticide. To date, the neonicotinoids, an economically important class of insecticides that target nicotinic acetylcholine receptors (nAChRs), have remained an effective control measure; however, recent reports of resistance in M. persicae represent a threat to the long-term efficacy of this chemical class. In this study, the mechanisms underlying resistance to the neonicotinoid insecticides were investigated using biological, biochemical, and genomic approaches. Bioassays on a resistant M. persicae clone (5191A) suggested that P450-mediated detoxification plays a primary role in resistance, although additional mechanism(s) may also contribute. Microarray analysis, using an array populated with probes corresponding to all known detoxification genes in M. persicae, revealed constitutive over-expression (22-fold) of a single P450 gene (CYP6CY3); and quantitative PCR showed that the over-expression is due, at least in part, to gene amplification. This is the first report of a P450 gene amplification event associated with insecticide resistance in an agriculturally important insect pest. The microarray analysis also showed over-expression of several gene sequences that encode cuticular proteins (2-16-fold), and artificial feeding assays and in vivo penetration assays using radiolabeled insecticide provided direct evidence of a role for reduced cuticular penetration in neonicotinoid resistance. Conversely, receptor radioligand binding studies and nucleotide sequencing of nAChR subunit genes suggest that target-site changes are unlikely to contribute to resistance to neonicotinoid insecticides in M. persicae.
ESTHER : Puinean_2010_PLoS.Genet_6_e1000999
PubMedSearch : Puinean_2010_PLoS.Genet_6_e1000999
PubMedID: 20585623

Title : Development of high-throughput real-time PCR assays for the identification of insensitive acetylcholinesterase (ace-1R) in Anopheles gambiae - Bass_2010_Pestic.Biochem.Physiol_96_80
Author(s) : Bass C , Nikou D , Vontas J , Williamson MS , Field LM
Ref : Pesticide Biochemistry and Physiology , 96 :80 , 2010
Abstract : Resistance to the organophosphate and carbamate insecticides through insensitivity of the target site enzyme, acetylcholinesterase has recently been reported in Anopheles gambiae populations in West Africa. To date, screening for the mutation (G119S of the ace-1 gene) conferring this insensitivity has employed a simple PCR-RFLP diagnostic. However, this has the disadvantage of requiring digestion of the amplified fragment and subsequent gel electrophoresis of the products. To overcome this, and thus increase throughput and reduce costs, we have developed two assays based on real-time PCR (TaqMan and melt-curve) that represent true [`]closed-tube' approaches. The two new platforms were compared to PCR-RFLP to genotype over 280 samples. The two new methods compared favourably with PCR-RFLP with the TaqMan assay delivering the greatest specificity and sensitivity of the three approaches. This assay is also cheaper to run than PCR-RFLP and results are obtained in a single step.
ESTHER : Bass_2010_Pestic.Biochem.Physiol_96_80
PubMedSearch : Bass_2010_Pestic.Biochem.Physiol_96_80
Gene_locus related to this paper: anoga-ACHE1

Title : Functional and evolutionary insights from the genomes of three parasitoid Nasonia species - Werren_2010_Science_327_343
Author(s) : Werren JH , Richards S , Desjardins CA , Niehuis O , Gadau J , Colbourne JK , Beukeboom LW , Desplan C , Elsik CG , Grimmelikhuijzen CJ , Kitts P , Lynch JA , Murphy T , Oliveira DC , Smith CD , van de Zande L , Worley KC , Zdobnov EM , Aerts M , Albert S , Anaya VH , Anzola JM , Barchuk AR , Behura SK , Bera AN , Berenbaum MR , Bertossa RC , Bitondi MM , Bordenstein SR , Bork P , Bornberg-Bauer E , Brunain M , Cazzamali G , Chaboub L , Chacko J , Chavez D , Childers CP , Choi JH , Clark ME , Claudianos C , Clinton RA , Cree AG , Cristino AS , Dang PM , Darby AC , de Graaf DC , Devreese B , Dinh HH , Edwards R , Elango N , Elhaik E , Ermolaeva O , Evans JD , Foret S , Fowler GR , Gerlach D , Gibson JD , Gilbert DG , Graur D , Grunder S , Hagen DE , Han Y , Hauser F , Hultmark D , Hunter HCt , Hurst GD , Jhangian SN , Jiang H , Johnson RM , Jones AK , Junier T , Kadowaki T , Kamping A , Kapustin Y , Kechavarzi B , Kim J , Kiryutin B , Koevoets T , Kovar CL , Kriventseva EV , Kucharski R , Lee H , Lee SL , Lees K , Lewis LR , Loehlin DW , Logsdon JM, Jr. , Lopez JA , Lozado RJ , Maglott D , Maleszka R , Mayampurath A , Mazur DJ , McClure MA , Moore AD , Morgan MB , Muller J , Munoz-Torres MC , Muzny DM , Nazareth LV , Neupert S , Nguyen NB , Nunes FM , Oakeshott JG , Okwuonu GO , Pannebakker BA , Pejaver VR , Peng Z , Pratt SC , Predel R , Pu LL , Ranson H , Raychoudhury R , Rechtsteiner A , Reese JT , Reid JG , Riddle M , Robertson HM , Romero-Severson J , Rosenberg M , Sackton TB , Sattelle DB , Schluns H , Schmitt T , Schneider M , Schuler A , Schurko AM , Shuker DM , Simoes ZL , Sinha S , Smith Z , Solovyev V , Souvorov A , Springauf A , Stafflinger E , Stage DE , Stanke M , Tanaka Y , Telschow A , Trent C , Vattathil S , Verhulst EC , Viljakainen L , Wanner KW , Waterhouse RM , Whitfield JB , Wilkes TE , Williamson MS , Willis JH , Wolschin F , Wyder S , Yamada T , Yi SV , Zecher CN , Zhang L , Gibbs RA , Williamson M
Ref : Science , 327 :343 , 2010
Abstract : We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and developmental genetics. Key findings include the identification of a functional DNA methylation tool kit; hymenopteran-specific genes including diverse venoms; lateral gene transfers among Pox viruses, Wolbachia, and Nasonia; and the rapid evolution of genes involved in nuclear-mitochondrial interactions that are implicated in speciation. Newly developed genome resources advance Nasonia for genetic research, accelerate mapping and cloning of quantitative trait loci, and will ultimately provide tools and knowledge for further increasing the utility of parasitoids as pest insect-control agents.
ESTHER : Werren_2010_Science_327_343
PubMedSearch : Werren_2010_Science_327_343
PubMedID: 20075255
Gene_locus related to this paper: nasvi-ACHE1 , nasvi-ACHE2 , nasvi-k7in31 , nasvi-k7iwl9 , nasvi-k7iyk8 , nasvi-k7jlv1 , nasvi-k7in32 , nasvi-k7ind2 , nasvi-k7inh0 , nasvi-k7inh1 , nasvi-k7inh2 , nasvi-k7inp9 , nasvi-k7iun7 , nasvi-k7iv21 , nasvi-k7ivn5 , nasvi-k7ivn6 , nasvi-k7iw29 , nasvi-k7iwk5 , nasvi-k7iwl8 , nasvi-k7iz24 , nasvi-k7izb4 , nasvi-k7j5u6 , nasvi-k7j6y1 , nasvi-k7j6y2 , nasvi-k7j6y4 , nasvi-k7j718 , nasvi-k7j755 , nasvi-k7j756 , nasvi-k7j757 , nasvi-k7j7k5 , nasvi-k7j7n7 , nasvi-k7j7r8 , nasvi-k7j7s8 , nasvi-k7j7s9 , nasvi-k7j811 , nasvi-k7iny8 , nasvi-k7izf2 , nasvi-k7iwe2 , nasvi-k7j6w4 , nasvi-k7izl9 , nasvi-k7jf39 , nasvi-k7izl8 , nasvi-k7irf1 , nasvi-k7j7l1

Title : Identification of ion channel genes in the Acyrthosiphon pisum genome - Dale_2010_Insect.Mol.Biol_19 Suppl 2_141
Author(s) : Dale RP , Jones AK , Tamborindeguy C , Davies TG , Amey JS , Williamson S , Wolstenholme A , Field LM , Williamson MS , Walsh TK , Sattelle DB
Ref : Insect Molecular Biology , 19 Suppl 2 :141 , 2010
Abstract : Aphids are major pests of crops, causing hundreds of millions of dollars worth of damage annually. Ion channel proteins are often the targets of modern insecticides and mutations in ion channel genes can lead to resistance to many leading classes of insecticides. The sequencing of the pea aphid, Acyrthosiphon pisum, genome has now allowed detailed in silico analysis of the aphid ion channels. The study has revealed significant differences in the composition of the ion channel families between the aphid and other insects. For example A. pisum does not appear to contain a homologue of the nACh receptor alpha 5 gene whilst the calcium channel beta subunit has been duplicated. These variations could result in differences in function or sensitivity to insecticides. The genome sequence will allow the study of aphid ion channels to be accelerated, leading to a better understanding of the function of these economically important channels. The potential for identifying novel insecticide targets within the aphid is now a step closer.
ESTHER : Dale_2010_Insect.Mol.Biol_19 Suppl 2_141
PubMedSearch : Dale_2010_Insect.Mol.Biol_19 Suppl 2_141
PubMedID: 20482646

Title : High-throughput allelic discrimination of B and Q biotypes of the whitefly, Bemisia tabaci, using TaqMan allele-selective PCR - Jones_2008_Pest.Manag.Sci_64_12
Author(s) : Jones CM , Gorman K , Denholm I , Williamson MS
Ref : Pest Manag Sci , 64 :12 , 2008
Abstract : BACKGROUND: B and Q biotypes of the whitefly, Bemisia tabaci (Gennadius), are generally regarded as the most significant given their global distribution and strong resistance to insecticides. Since these biotypes can coexist and differ markedly in their insecticide resistance profiles, a rapid but reliable means of discriminating between them would be a valuable complement to resistance monitoring and management programmes. Recently, PCR-based methods have been developed to determine the biotype status of B. tabaci populations. However, these require post-amplification procedures, which increase time and labour. RESULTS: The authors have developed an allelic discrimination real-time PCR assay using fluorescent dye-labelled probes to distinguish the B and Q biotypes. The assay targets a single nucleotide polymorphism (SNP) in the mitochondrial cytochrome oxidase I (mtCOI) gene. To evaluate the assay, DNA was extracted from individual whiteflies of six known biotype strains, and all scored correctly as either a B or Q biotype. As further validation, 72 individuals from field samples collected in different parts of the world were also tested by the assay. No failed reactions were observed, with all 72 samples scoring clearly as either the B or Q biotype. CONCLUSION: The development of this rapid and high-throughput assay has important potential for routine monitoring of B and Q biotypes on ornamental plants and for the screening of B. tabaci populations in countries where these biotypes are not yet established.
ESTHER : Jones_2008_Pest.Manag.Sci_64_12
PubMedSearch : Jones_2008_Pest.Manag.Sci_64_12
PubMedID: 17972303

Title : The promise of insect genomics - Grimmelikhuijzen_2007_Pest.Manag.Sci_63_413
Author(s) : Grimmelikhuijzen CJ , Cazzamali G , Williamson MS , Hauser F
Ref : Pest Manag Sci , 63 :413 , 2007
Abstract : Insects are the largest animal group in the world and are ecologically and economically extremely important. This importance of insects is reflected by the existence of currently 24 insect genome projects. Our perspective discusses the state-of-the-art of these genome projects and the impacts that they have on basic insect science and pest control.
ESTHER : Grimmelikhuijzen_2007_Pest.Manag.Sci_63_413
PubMedSearch : Grimmelikhuijzen_2007_Pest.Manag.Sci_63_413
PubMedID: 17377971

Title : Molecular characterisation of nicotinic acetylcholine receptor subunits from the cat flea, Ctenocephalides felis (Siphonaptera: Pulicidae) - Bass_2006_Insect.Biochem.Mol.Biol_36_86
Author(s) : Bass C , Lansdell SJ , Millar NS , Schroeder I , Turberg A , Field LM , Williamson MS
Ref : Insect Biochemistry & Molecular Biology , 36 :86 , 2006
Abstract : As part of a program to monitor the susceptibility of cat flea populations to the insecticide imidacloprid we have examined the cat flea nicotinic acetylcholine receptor, the target site protein of the neonicotinoid group of insecticides. Seven nAChR subunits (six alpha-type and one beta-type) were identified in cat flea using a degenerate PCR-based strategy. Five of these were expressed in vitro by creating chimeras containing the N-terminal ligand-binding domain of the cat flea subunits and the C-terminal region of the Drosophila Dalpha2 (SAD) subunit. Two of the five chimeric subunits, Cfalpha1/Dalpha2 and Cfalpha3/Dalpha2, when co-expressed with rat beta2 in Drosophila S2 cells, showed high-affinity binding of both epibatidine (Kd=1.6+/-0.6 and 0.13+/-0.06nM, respectively), and imidacloprid (Ki=142+/-34 and 28.7+/-2.4nM, respectively). It is likely therefore that Cfalpha1 and Cfalpha3 contribute to nAChR populations in vivo that are sensitive to imidacloprid. The identification of cat flea nAChR subunits that have a high affinity for imidacloprid presents candidate genes in which to look for resistance-associated mutations if target-site resistance to imidacloprid arises in domestic pet flea populations.
ESTHER : Bass_2006_Insect.Biochem.Mol.Biol_36_86
PubMedSearch : Bass_2006_Insect.Biochem.Mol.Biol_36_86
PubMedID: 16360954

Title : A nicotinic acetylcholine receptor mutation (Y151S) causes reduced agonist potency to a range of neonicotinoid insecticides - Liu_2006_J.Neurochem_99_1273
Author(s) : Liu Z , Williamson MS , Lansdell SJ , Han Z , Denholm I , Millar NS
Ref : Journal of Neurochemistry , 99 :1273 , 2006
Abstract : Neonicotinoid insecticides are potent selective agonists of insect nicotinic acetylcholine receptors (nAChRs). Since their introduction in 1991, resistance to neonicotinoids has been slow to develop, but it is now established in some insect field populations such as the planthopper, Nilaparvata lugens, a major rice pest in many parts of Asia. We have reported recently the identification of a target-site mutation (Y151S) within two nAChR subunits (Nlalpha1 and Nlalpha3) from a laboratory-selected field population of N. lugens. In the present study, we have examined the influence of this mutation upon the functional properties of recombinant nAChRs expressed in Xenopus oocytes (as hybrid nAChRs, co-expressed with a rat beta2 subunit). The agonist potency of several nicotinic agonists has been examined, including all of the neonicotinoid insecticides that are currently licensed for either crop protection or animal health applications (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam). The Y151S mutation was found to have no significant effect on the maximal current (I(max)) observed with the endogenous agonist, acetylcholine. In contrast, a significant reduction in I(max) was observed for all neonicotinoids (the I(max) for mutant nAChRs ranged from 13 to 81% of that observed on wild-type receptors). In addition, nAChRs containing the Y151S mutation caused a significant rightward shift in agonist dose-response curves for all neonicotinoids, but of varying magnitude (shifts in EC(50) values ranged from 1.3 to 3.6-fold). The relationship between neonicotinoid structure and their potency on nAChRs containing the Y151S target-site mutation is discussed.
ESTHER : Liu_2006_J.Neurochem_99_1273
PubMedSearch : Liu_2006_J.Neurochem_99_1273
PubMedID: 16981889

Title : Acetylcholinesterase genes and insecticide resistance in aphids -
Author(s) : Dong SL , Andrews MC , Li F , Moores GD , Han ZJ , Williamson MS
Ref : Chemico-Biological Interactions , 157-158 :373 , 2005
PubMedID: 16429498

Title : A nicotinic acetylcholine receptor mutation conferring target-site resistance to imidacloprid in Nilaparvata lugens (brown planthopper) - Liu_2005_Proc.Natl.Acad.Sci.U.S.A_102_8420
Author(s) : Liu Z , Williamson MS , Lansdell SJ , Denholm I , Han Z , Millar NS
Ref : Proc Natl Acad Sci U S A , 102 :8420 , 2005
Abstract : Neonicotinoids, such as imidacloprid, are nicotinic acetylcholine receptor (nAChR) agonists with potent insecticidal activity. Since its introduction in the early 1990s, imidacloprid has become one of the most extensively used insecticides for both crop protection and animal health applications. As with other classes of insecticides, resistance to neonicotinoids is a significant threat and has been identified in several pest species, including the brown planthopper, Nilaparvata lugens, a major rice pest in many parts of Asia. In this study, radioligand binding experiments have been conducted with whole-body membranes prepared from imidacloprid-susceptible and imidacloprid-resistant strains of N. lugens. The results reveal a much higher level of [3H]imidacloprid-specific binding to the susceptible strain than to the resistant strain (16.7 +/- 1.0 and 0.34 +/- 0.21 fmol/mg of protein, respectively). With the aim of understanding the molecular basis of imidacloprid resistance, five nAChR subunits (Nlalpha1-Nlalpha4 and Nlbeta1) have been cloned from N. lugens.A comparison of nAChR subunit genes from imidacloprid-sensitive and imidacloprid-resistant populations has identified a single point mutation at a conserved position (Y151S) in two nAChR subunits, Nlalpha1 and Nlalpha3. A strong correlation between the frequency of the Y151S point mutation and the level of resistance to imidacloprid has been demonstrated by allele-specific PCR. By expression of hybrid nAChRs containing N. lugens alpha and rat beta2 subunits, evidence was obtained that demonstrates that mutation Y151S is responsible for a substantial reduction in specific [3H]imidacloprid binding. This study provides direct evidence for the occurrence of target-site resistance to a neonicotinoid insecticide.
ESTHER : Liu_2005_Proc.Natl.Acad.Sci.U.S.A_102_8420
PubMedSearch : Liu_2005_Proc.Natl.Acad.Sci.U.S.A_102_8420
PubMedID: 15937112

Title : Poster (65) A single amino acid substitution found in pirimicarb-insensitive acetylcholinesterase (AChE) of the peach-potato aphid, Myzus persicae (sulz.) -
Author(s) : Andrews MC , Williamson MS , Callaghan A , Field LM , Moores GD
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :355 , 2004

Title : A single amino acid substitution found in pirimicarb-insensitive acetylcholinesterase (AChE) of the peach-potato Aphid Myzus persicae (Sulz.) -
Author(s) : Andrews MC , Callaghan A , Williamson MS , Field LM , Moores GD
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :229 , 2004

Title : Identification of mutations conferring insecticide-insensitive AChE in the cotton-melon aphid, Aphis gossypii Glover - Andrews_2004_Insect.Mol.Biol_13_555
Author(s) : Andrews MC , Callaghan A , Field LM , Williamson MS , Moores GD
Ref : Insect Molecular Biology , 13 :555 , 2004
Abstract : We have identified two mutations in the ace1 gene of Aphis gossypii that are associated with insensitivity of acetylcholinesterase (AChE) to carbamate and organophosphate insecticides. The first of these, S431F (equivalent to F331 in Torpedo californica), is associated with insensitivity to the carbamate insecticide pirimicarb in a range of A. gossypii clones. The S431F mutation is also found in the peach-potato aphid, Myzus persicae (Sulzer), and a rapid RFLP diagnostic allows the identification of individuals of both aphid species with a resistant genotype. This diagnostic further revealed the presence of S431 in several other pirimicarb-susceptible aphid species. The serine at this position in the wild-type enzyme has only been reported for aphids and provides a molecular explanation of why pirimicarb has a specific aphicidal action. A less specific insensitivity to a wide range of carbamates and organophosphates is associated with a second mutation, A302S (A201 in T. californica).
ESTHER : Andrews_2004_Insect.Mol.Biol_13_555
PubMedSearch : Andrews_2004_Insect.Mol.Biol_13_555
PubMedID: 15373812
Gene_locus related to this paper: aphgo-ACHE1

Title : Poster (29) Insecticide-insensitive AChE in myzus persicae - a tale of two genes. -
Author(s) : Moores GD , Andrews MC , Javed N , Williamson MS , Viner R
Ref : In: Cholinesterases in the Second Millennium: Biomolecular and Pathological Aspects , (Inestrosa NC, Campos EO) P. Universidad Catolica de Chile-FONDAP Biomedicina :335 , 2004

Title : High-throughput detection of knockdown resistance in Myzus persicae using allelic discriminating quantitative PCR - Anstead_2004_Insect.Biochem.Mol.Biol_34_871
Author(s) : Anstead JA , Williamson MS , Eleftherianos I , Denholm I
Ref : Insect Biochemistry & Molecular Biology , 34 :871 , 2004
Abstract : The peach-potato aphid Myzus persicae (Sulzer) has developed resistance to pyrethroid insecticides as a result of a mechanism conferring reduced nervous system sensitivity, termed knockdown resistance (kdr). This reduced sensitivity is caused by two mutations, L1014F (kdr) and M918T (super-kdr), in the para-type voltage-gated sodium channel. We have developed a diagnostic dose bioassay to detect kdr and provide preliminary information on the genotype present. We also developed two allelic discrimination PCR assays to determine precisely the genotypes of the two mutations (L1014F and M918T) in individual M. persicae using fluorescent Taqman MGB probes. In combination with assays for elevated carboxylesterase levels and modified acetylcholinesterase (MACE), this suite of assays allows for rapid high-throughput diagnosis, in individual aphids, of the three main resistance mechanisms of practical importance in the UK.
ESTHER : Anstead_2004_Insect.Biochem.Mol.Biol_34_871
PubMedSearch : Anstead_2004_Insect.Biochem.Mol.Biol_34_871
PubMedID: 15262290

Title : A single amino acid substitution found in pirimicarb-insensitive acetylcholinesterase of the peach-potato aphid, Myzus persicae (Sulz. -
Author(s) : Andrews MC , Bass CG , Williamson MS , Field LM , Callaghan A , Moores GD
Ref : Cholinergic Mechanisms, CRC Press :453 , 2004

Title : Investigating the diversity of acetylcholinesterase in insect species. -
Author(s) : Javed N , Williamson MS , Viner R , Lewis T , Moores GD
Ref : Cholinergic Mechanisms, CRC Press :595 , 2004

Title : Mutations of the para sodium channel of Drosophila melanogaster identify putative binding sites for pyrethroids - Vais_2003_Mol.Pharmacol_64_914
Author(s) : Vais H , Atkinson S , Pluteanu F , Goodson SJ , Devonshire AL , Williamson MS , Usherwood PN
Ref : Molecular Pharmacology , 64 :914 , 2003
Abstract : The effects of two pyrethroids on recombinant wild-type and mutant (pyrethroid-resistant) Na+ channels of Drosophila melanogaster have been studied. Three mutations that confer resistance (kdr/superkdr) to pyrethroids were inserted, either individually or in combination, into the para Na+ channel of D. melanogaster: L1014F in domain IIS6, M918T in the IIS4-S5 linker, and T929I in domain IIS5. Channels were expressed in Xenopus laevis oocytes and the effects of the pyrethroids permethrin (type I) and deltamethrin (type II) on Na+ currents were investigated using voltage clamp. The Na+ channels deactivated slowly after deltamethrin treatment, the resultant "tail" currents being used to quantify the effects of this pyrethroid. The Hill slope of 2 for deltamethrin action on the wild-type channel and the mutant L1014F channel is indicative of cooperative binding at two or more sites on these channels. In contrast, binding to the mutants M918T and T929I is noncooperative. Tail currents for the wild-type channel and L1014F channel decayed biphasically, whereas those for M918T and T929I mutants decayed monophasically. The L1014F mutant was approximately 20-fold less sensitive than the wild-type to deltamethrin. Surprisingly, the sensitivity of the double mutant M918T+L1014F to deltamethrin was similar to that of M918T alone, whereas the sensitivity of T929I+L1014F was >30,000-fold lower than that of T929I. Permethrin was less potent than deltamethrin, and its binding to all channel types was noncooperative. The decays of permethrin-induced tail currents were exclusively monophasic. These findings are discussed in terms of the properties and possible locations of pyrethroid binding sites on the D. melanogaster Na+ channel.
ESTHER : Vais_2003_Mol.Pharmacol_64_914
PubMedSearch : Vais_2003_Mol.Pharmacol_64_914
PubMedID: 14500748

Title : Characterization of acetylcholinesterases, and their genes, from the hemipteran species Myzus persicae (Sulzer), Aphis gossypii (Glover), Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) - Javed_2003_Insect.Mol.Biol_12_613
Author(s) : Javed N , Viner R , Williamson MS , Field LM , Devonshire AL , Moores GD
Ref : Insect Molecular Biology , 12 :613 , 2003
Abstract : Gene sequences encoding putative acetylcholinesterases have been reported for four hemipteran insect species. Although acetylcholinesterase insensitivity occurs in insecticide-resistant populations of each of these species, no mutations were detected in the gene sequences from the resistant insects. This, coupled with a series of experiments using novel reversible inhibitors to compare the biochemical characteristics of acetylcholinesterase from a range of insect species, showed that the cloned cDNA fragments are unlikely to encode the hemipteran synaptic acetylcholinesterases, and there is likely to be a second ace locus.
ESTHER : Javed_2003_Insect.Mol.Biol_12_613
PubMedSearch : Javed_2003_Insect.Mol.Biol_12_613
PubMedID: 14986922
Gene_locus related to this paper: aphgo-ACHE2 , bemta-ACHE2 , myzpe-ACHE , triva-ACHE

Title : The molecular interactions of pyrethroid insecticides with insect and mammalian sodium channels - Vais_2001_Pest.Manag.Sci_57_877
Author(s) : Vais H , Williamson MS , Devonshire AL , Usherwood PN
Ref : Pest Manag Sci , 57 :877 , 2001
Abstract : Recent progress in the cloning of alpha (para) and beta (TipE) Na channel sub-units from Drosophila melanogaster (fruit fly) and Musca domestica (housefly) have facilitated functional expression studies of insect Na channels in Xenopus laevis oocytes, assayed by voltage clamp techniques. The effects of Type I and Type III pyrethroids on the biophysical properties of these channels are critically reviewed. Pyrethroid resistance mutations (termed kdr and super-kdr) that reduce the sensitivity of the insect Na channel to pyrethroids have been identified in a range of insect species. Some of these mutations (e.g. L1014F, M918T and T929I) have been incorporated into the para Na channel of Drosophila, either individually or in combination, to investigate their effects on the sensitivity of this channel to pyrethroids. The kdr mutation (L1014F) shifts the voltage dependence of both activation and steady-state inactivation by approximately 5 mV towards more positive potentials and facilitates Na channel inactivation. Incorporation of the super-kdr mutation (M918T) into the Drosophila Na channel also increases channel inactivation and causes a > 100-fold reduction in deltamethrin sensitivity. These effects are shared by T929I, an alternative mutation that confers super-kdr-like resistance. Parallel studies have been undertaken using the rat IIA Na channel to investigate the molecular basis for the low sensitivity of mammalian brain Na channels to pyrethroids. Rat IIA channels containing the mutation L1014F exhibit a shift in their mid-point potential for Na activation, but their overall sensitivity to permethrin remains similar to that of the wild-type rat channel (i.e. both are 1000-fold less sensitive than the wild-type insect channel). Mammalian neuronal Na channels have an isoleucine rather than a methionine at the position (874) corresponding to the super-kdr (M918) residue of the insect channel. Replacement of the isoleucine of the wild-type rat IIA Na channel with a methionine (I874M) increases deltamethrin sensitivity 100-fold. In this way, studies of wild-type and mutant Na channels of insects and mammals are providing a molecular understanding of kdr and super-kdr resistance in insects, and of the low pyrethroid sensitivity of most mammalian Na channels. They are also giving valuable insights into the binding sites for pyrethroids on these channels.
ESTHER : Vais_2001_Pest.Manag.Sci_57_877
PubMedSearch : Vais_2001_Pest.Manag.Sci_57_877
PubMedID: 11695180

Title : Identification and characterization of mutations in housefly (Musca domestica) acetylcholinesterase involved in insecticide resistance - Walsh_2001_Biochem.J_359_175
Author(s) : Walsh SB , Dolden TA , Moores GD , Kristensen M , Lewis T , Devonshire AL , Williamson MS
Ref : Biochemical Journal , 359 :175 , 2001
Abstract : Acetylcholinesterase (AChE) insensitive to organophosphate and carbamate insecticides has been identified as a major resistance mechanism in numerous arthropod species. However, the associated genetic changes have been reported in the AChE genes from only three insect species; their role in conferring insecticide insensitivity has been confirmed, using functional expression, only for those in Drosophila melanogaster. The housefly, Musca domestica, was one of the first insects shown to have this mechanism; here we report the occurrence of five mutations (Val-180-->Leu, Gly-262-->Ala, Gly-262-->Val, Phe-327-->Tyr and Gly-365-->Ala) in the AChE gene of this species that, either singly or in combination, confer different spectra of insecticide resistance. The baculovirus expression of wild-type and mutated housefly AChE proteins has confirmed that the mutations each confer relatively modest levels of insecticide insensitivity except the novel Gly-262-->Val mutation, which results in much stronger resistance (up to 100-fold) to certain compounds. In all cases the effects of mutation combinations are additive. The mutations introduce amino acid substitutions that are larger than the corresponding wild-type residues and are located within the active site of the enzyme, close to the catalytic triad. The likely influence of these substitutions on the accessibility of the different types of inhibitor and the orientation of key catalytic residues are discussed in the light of the three-dimensional structures of the AChE protein from Torpedo californica and D. melanogaster.
ESTHER : Walsh_2001_Biochem.J_359_175
PubMedSearch : Walsh_2001_Biochem.J_359_175
PubMedID: 11563981
Gene_locus related to this paper: musdo-ACHE

Title : A single amino acid change makes a rat neuronal sodium channel highly sensitive to pyrethroid insecticides - Vais_2000_FEBS.Lett_470_135
Author(s) : Vais H , Atkinson S , Eldursi N , Devonshire AL , Williamson MS , Usherwood PN
Ref : FEBS Letters , 470 :135 , 2000
Abstract : Two amino acid substitutions in a housefly sodium channel, L1014F in domain IIS6 and M918T in the IIS4-S5 linker, have been identified in kdr and super-kdr pyrethroid-resistant phenotypes, respectively. Unlike their native insect counterparts, mammalian sodium channels are only weakly sensitive to pyrethroids. Do the sodium channels of mammal and pyrethroid-resistant housefly share similar structural characteristics that account for their low pyrethroid sensitivities? We report here that substitution of isoleucine for methionine at position 874 (equivalent to the super-kdr site 918 in the housefly) in the rat IIA alpha-subunit causes a 100-fold increase in sensitivity.
ESTHER : Vais_2000_FEBS.Lett_470_135
PubMedSearch : Vais_2000_FEBS.Lett_470_135
PubMedID: 10734222

Title : Activation of Drosophila sodium channels promotes modification by deltamethrin. Reductions in affinity caused by knock-down resistance mutations - Vais_2000_J.Gen.Physiol_115_305
Author(s) : Vais H , Williamson MS , Goodson SJ , Devonshire AL , Warmke JW , Usherwood PN , Cohen CJ
Ref : Journal of General Physiology , 115 :305 , 2000
Abstract : kdr and super-kdr are mutations in houseflies and other insects that confer 30- and 500-fold resistance to the pyrethroid deltamethrin. They correspond to single (L1014F) and double (L1014F+M918T) mutations in segment IIS6 and linker II(S4-S5) of Na channels. We expressed Drosophila para Na channels with and without these mutations and characterized their modification by deltamethrin. All wild-type channels can be modified by <10 nM deltamethrin, but high affinity binding requires channel opening: (a) modification is promoted more by trains of brief depolarizations than by a single long depolarization, (b) the voltage dependence of modification parallels that of channel opening, and (c) modification is promoted by toxin II from Anemonia sulcata, which slows inactivation. The mutations reduce channel opening by enhancing closed-state inactivation. In addition, these mutations reduce the affinity for open channels by 20- and 100-fold, respectively. Deltamethrin inhibits channel closing and the mutations reduce the time that channels remain open once drug has bound. The super-kdr mutations effectively reduce the number of deltamethrin binding sites per channel from two to one. Thus, the mutations reduce both the potency and efficacy of insecticide action.
ESTHER : Vais_2000_J.Gen.Physiol_115_305
PubMedSearch : Vais_2000_J.Gen.Physiol_115_305
PubMedID: 10694259

Title : Cloning, heterologous expression and co-assembly of Mpbeta1, a nicotinic acetylcholine receptor subunit from the aphid Myzus persicae - Huang_2000_Neurosci.Lett_284_116
Author(s) : Huang Y , Williamson MS , Devonshire AL , Windass JD , Lansdell SJ , Millar NS
Ref : Neuroscience Letters , 284 :116 , 2000
Abstract : Nicotinic acetylcholine receptors (nAChRs) play a major role in excitatory synaptic transmission in insects and are also the target site for chloronicotinyl insecticides such as imidacloprid. Here we report the cloning and characterization of a novel nAChR beta subunit, Mpbeta1, from the aphid Myzus persicae, an economically important pest species. Sequence analysis has identified an open reading frame of 509 amino acids with features typical of nAChR subunits. The Mpbeta1 gene is expressed as a single major transcript of 4.6 kb, considerably larger than the predicted length of the Mpbeta1 open reading frame (1527 bp). By heterologous expression in Drosophila S2 cells, the Mpbeta1 subunit has been shown to co-assemble with the previously cloned nAChR subunits Mpalpha1 and Mpalpha2. In contrast, no co-assembly of Mpbeta1 could be detected with either Mpalpha3 or Mpalpha4. With the aim of gaining a clearer insight into the influence of subunit composition upon assembly, the ability of M. persicae nAChR subunits to co-assemble with vertebrate nAChR subunits has also been examined.
ESTHER : Huang_2000_Neurosci.Lett_284_116
PubMedSearch : Huang_2000_Neurosci.Lett_284_116
PubMedID: 10771176

Title : A sodium channel point mutation is associated with resistance to DDT and pyrethroid insecticides in the peach-potato aphid, Myzus persicae (Sulzer) (Hemiptera: Aphididae) - Martinez-Torres_1999_Insect.Mol.Biol_8_339
Author(s) : Martinez-Torres D , Foster SP , Field LM , Devonshire AL , Williamson MS
Ref : Insect Molecular Biology , 8 :339 , 1999
Abstract : The voltage-gated sodium channel is the primary target site of DDT and pyrethroid insecticides, and point mutations in the domain II region of the channel protein have been implicated in the knockdown resistant (kdr ) phenotype of several insect species. Here, we report that one of these mutations, a leucine-to-phenylalanine replacement in transmembrane segment IIS6, is also found in certain insecticide-resistant clones of the peach-potato aphid, Myzus persicae. The mutation was present in four clones with amplified E4 esterase genes, but was absent from both susceptible clones and those with amplified FE4 genes. The inferred presence of kdr-type resistance in the four E4 clones was subsequently confirmed by bioassays that showed this to be the primary mechanism of resistance to deltamethrin and DDT, although the esterase-based mechanism also contributes to the overall level of deltamethrin resistance. The kdr mutation on its own conferred 35-fold resistance to deltamethrin and this was enhanced up to 540-fold when it was present in a high (E4) esterase background. The esterase (FE4) mechanism was far less effective without the kdr mutation, conferring just 3-4-fold resistance to deltamethrin. These findings, and the linkage disequilibrium of the kdr mutation within clones overproducing the E4 esterase, have important implications for the evolution of resistance in this insect and for the use of pyrethroid sprays in the management of M. persicae populations in the field.
ESTHER : Martinez-Torres_1999_Insect.Mol.Biol_8_339
PubMedSearch : Martinez-Torres_1999_Insect.Mol.Biol_8_339
PubMedID: 10469251

Title : Molecular characterization and imidacloprid selectivity of nicotinic acetylcholine receptor subunits from the peach-potato aphid Myzus persicae - Huang_1999_J.Neurochem_73_380
Author(s) : Huang Y , Williamson MS , Devonshire AL , Windass JD , Lansdell SJ , Millar NS
Ref : Journal of Neurochemistry , 73 :380 , 1999
Abstract : The recent introduction of the chloronicotinyl insecticide imidacloprid, targeting insect nicotinic acetylcholine receptors (nAChRs), emphasises the importance of a detailed molecular characterisation of these receptors. We are investigating the molecular diversity of insect nAChR subunit genes in an important agricultural pest, the peach-potato aphid Myzus persicae. Two M. persicae alpha-subunit cDNAs, Mp alpha1 and Mp alpha2, have been cloned previously. Here we report the isolation of three novel alpha-subunit genes (Mp alpha3-5) with overall amino acid sequence identities between 43 and 76% to characterised insect nAChR subunits. Alignment of their amino acid sequences with other invertebrate and vertebrate nAChR subunits suggests that the insect alpha subunits evolved in parallel to the vertebrate neuronal nAChRs and that the insect non-alpha subunits are clearly different from vertebrate neuronal beta and muscle non-alpha subunits. The discovery of novel subtypes in M. persicae is a further indicator of the complexity of the insect nAChR gene family. Heterologous co-expression of M. persicae nAChR alpha-subunit cDNAs with the rat beta2 in Drosophila S2 cells resulted in high-affinity binding of nicotinic radioligands. The affinity of recombinant nAChRs for [3H]imidacloprid was influenced strongly by the alpha subtype. This is the first demonstration that imidacloprid selectively acts on Mp alpha2 and Mp alpha3 subunits, but not Mp alpha1, in M. persicae.
ESTHER : Huang_1999_J.Neurochem_73_380
PubMedSearch : Huang_1999_J.Neurochem_73_380
PubMedID: 10386991

Title : Biochemical and Molecular Characterisation of Insecticide Insensitive Acetylcholinesterase in Resistant Insects -
Author(s) : Devonshire AL , Byrne FJ , Moores GD , Williamson MS
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :491 , 1998

Title : Purification and Biochemical Characterization of Affinity-Tagged Musca Domestica Acetylcholinesterase Secreted from Baculovirus Infected Cells -
Author(s) : Moores GD , Williamson MS , Hadonou M , Devonshire AL , Kataja K , Uitto J , Oker-Blom C
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :547 , 1998

Title : Mutations in the Housefly Acetylcholinesterase Gene that Confer Resistance to Insecticides -
Author(s) : Williamson MS , Moores GD , Walsh S , Dolden T , Mullaley A , Taylor R , Devonshire AL
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :548 , 1998

Title : An Insensitive ACHE Confers Insecticide Resistance in Myzus Persicae -
Author(s) : Moores GD , Javed N , Williamson MS , Devonshire AL , Lewis T
Ref : In: Structure and Function of Cholinesterases and Related Proteins - Proceedings of Sixth International Meeting on Cholinesterases , (Doctor, B.P., Taylor, P., Quinn, D.M., Rotundo, R.L., Gentry, M.K. Eds) Plenum Publishing Corp. :549 , 1998

Title : Molecular characterization of pyrethroid knockdown resistance (kdr) in the major malaria vector Anopheles gambiae s.s - Martinez-Torres_1998_Insect.Mol.Biol_7_179
Author(s) : Martinez-Torres D , Chandre F , Williamson MS , Darriet F , Berge JB , Devonshire AL , Guillet P , Pasteur N , Pauron D
Ref : Insect Molecular Biology , 7 :179 , 1998
Abstract : Pyrethroid-impregnated bednets are playing an increasing role for combating malaria, especially in stable malaria areas. More than 90% of the current annual malaria incidence (c. 500 million clinical cases with up to 2 million deaths) is in Africa where the major vector is Anopheles gambiae s.s. As pyrethroid resistance has been reported in this mosquito, reliable and simple techniques are urgently needed to characterize and monitor this resistance in the field. In insects, an important mechanism of pyrethroid resistance is due to a modification of the voltage-gated sodium channel protein recently shown to be associated with mutations of the para-type sodium channel gene. We demonstrate here that one of these mutations is present in certain strains of pyrethroid resistant A. gambiae s.s. and describe a PCR-based diagnostic test allowing its detection in the genome of single mosquitoes. Using this test, we found this mutation in six out of seven field samples from West Africa, its frequency being closely correlated with survival to pyrethroid exposure. This diagnostic test should bring major improvement for field monitoring of pyrethroid resistance, within the framework of malaria control programmes.
ESTHER : Martinez-Torres_1998_Insect.Mol.Biol_7_179
PubMedSearch : Martinez-Torres_1998_Insect.Mol.Biol_7_179
PubMedID: 9535162

Title : Functional analysis of a rat sodium channel carrying a mutation for insect knock-down resistance (kdr) to pyrethroids - Vais_1997_FEBS.Lett_413_327
Author(s) : Vais H , Williamson MS , Hick CA , Eldursi N , Devonshire AL , Usherwood PN
Ref : FEBS Letters , 413 :327 , 1997
Abstract : Pyrethroid insensitivity in resistant (kdr) insects has been correlated with a leucine to phenylalanine replacement in the S6 transmembrane segment of domain II of the axonal sodium channel alpha(para)-subunit. An alpha-subunit of rat brain type II sodium channel containing this mutation has been expressed and its sensitivity to permethrin compared with that of the wild-type channel. The steady-state activation curve of the mutant was shifted 14 mV in the depolarizing direction. We propose that an equivalent shift of the sodium current activation curve in kdr insects could account for their low sensitivity to permethrin toxicity.
ESTHER : Vais_1997_FEBS.Lett_413_327
PubMedSearch : Vais_1997_FEBS.Lett_413_327
PubMedID: 9280307

Title : Use of biochemical and DNA diagnostics for characterising multiple mechanisms of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer) - Field_1997_Pest.Sci_51_283
Author(s) : Field LM , Anderson AP , Denholm I , Foster SP , Harling ZK , Javed N , Martinez-Torres D , Moores GD , Williamson MS , Devonshire AL
Ref : Pest Sci , 51 :283 , 1997
Abstract : The peach-potato aphid Myzus persicae (Sulzer) can resist a range of insecticides by over-producing detoxifying esterase and having mutant-insensitive forms of the target proteins, acetylcholinesterase (AChE), and the sodium channel. Using a combination of bioassays, biochemical and DNA diagnostics, it is now possible to diagnose all three mechanisms in individual aphids, and thereby establish their spatial distributions and temporal dynamics. A survey of 58 samples of wide geographic origin showed that all 46 resistant clones had amplified esterase genes (E4 or FE4) conferring broad-spectrum resistance to pyrethroids, organophosphates and carbamates. These occurred in combination with insensitive AChE (11 clones), conferring resistance to pirimicarb and triazamate, and/or mutant sodium channel genes (25 clones), conferring knockdown (kdr) resistance to pyrethroids and DDT. Amplified esterase genes were in linkage disequilibrium with both insensitive AChE and the kdr mutation, reflecting tight physical linkage, heavy selection favouring aphids with multiple mechanisms, and/or the prominence of parthenogenesis in many M. persicae populations. An ability to monitor individual mechanisms with contrasting cross-resistance profiles has important implications for the development of resistance management recommendations.
ESTHER : Field_1997_Pest.Sci_51_283
PubMedSearch : Field_1997_Pest.Sci_51_283

Title : Characterization of the acetylcholinesterase gene from insecticide-resistant houseflies (Musca domestica) - Huang_1997_Chin.J.Biotechnol_13_177
Author(s) : Huang Y , Qiao C , Williamson MS , Devonshire AL
Ref : Chin J Biotechnol , 13 :177 , 1997
Abstract : Acetylcholinesterase (AChE) is the target site for the organophosphates and carbamates in insects. Widespread use of these two classes of insecticides has led to the selection of resistance. Target modification was regarded as a molecular mechanism in some resistance species. The altered AChEs with reduced sensitivity to inhibition are related to this resistance. AChE genes from two insecticide-resistant housefly (Musca domestica) strains D3 and Kash were isolated and sequenced using RT-PCR and streptavidin-linked magnetic bead techniques. The cDNAs have a 2082-bp open reading frame from which the complete amino acid sequence of AChE has been deduced. Some differences in nucleotide sequence and four-point mutations of amino acid were found compared to a susceptible strain, i.e., the Cooper strain. Three substitutions are likely to confer insecticide insensitivity, which seems that D3 and Kash belong to CH2 pattern of resistance.
ESTHER : Huang_1997_Chin.J.Biotechnol_13_177
PubMedSearch : Huang_1997_Chin.J.Biotechnol_13_177
PubMedID: 9429779
Gene_locus related to this paper: musdo-ACHE

Title : Identification of mutations in the housefly para-type sodium channel gene associated with knockdown resistance (kdr) to pyrethroid insecticides - Williamson_1996_Mol.Gen.Genet_252_51
Author(s) : Williamson MS , Martinez-Torres D , Hick CA , Devonshire AL
Ref : Molecular & General Genetics , 252 :51 , 1996
Abstract : We report the isolation of cDNA clones containing the full 6.3-kb coding sequence of the para-type sodium channel gene of the housefly, Musca domestica. This gene has been implicated as the site of knockdown resistance (kdr), an important resistance mechanism that confers nerve insensitivity to DDT and pyrethroid insecticides. The cDNAs predict a polypeptide of 2108 amino acids with close sequence homology (92% identity) to the Drosophila para sodium channel, and around 50% homology to vertebrate sodium channels, Only one major splice form of the housefly sodium channel was detected, in contrast to the Drosophila para transcript which has been reported to undergo extensive alternative splicing. Comparative sequence analysis of housefly strains carrying kdr or the more potent super-kdr factor revealed two amino acid mutations that correlate with these resistance phenotypes. Both mutations are located in domain II of the sodium channel. A leucine to phenylalanine replacement in the hydro-phobic IIS6 transmembrane segment was found in two independent kdr strains and six super-kdr strains of diverse geographic origin, while an additional methionine to threonine replacement within the intracellular IIS4-S5 loop was found only in the super-kdr strains. Neither mutation was present in five pyrethroid-sensitive strains. The mutations suggest a binding site for pyrethroids at the intracellular mouth of the channel pore in a region known to be important for channel inactivation.
ESTHER : Williamson_1996_Mol.Gen.Genet_252_51
PubMedSearch : Williamson_1996_Mol.Gen.Genet_252_51
PubMedID: 8804403

Title : Knockdown resistance (kdr) to DDT and pyrethroid insecticides maps to a sodium channel gene locus in the housefly (Musca domestica) - Williamson_1993_Mol.Gen.Genet_240_17
Author(s) : Williamson MS , Denholm I , Bell CA , Devonshire AL
Ref : Molecular & General Genetics , 240 :17 , 1993
Abstract : The voltage-sensitive sodium channel is generally regarded as the primary target site of dichloro-diphenyl-trichloro-ethane (DDT) and pyrethroid insecticides, and has been implicated in the widely reported mechanism of nerve insensitivity to these compounds. This phenomenon is expressed as knockdown resistance (kdr) and has been best characterised in the housefly where several putative alleles, including the more potent super-kdr factor, have been identified. We report the isolation of cDNA clones containing part of a housefly sodium channel gene, designated Msc, which show close homology to the para sodium channel of Drosophila (99% amino acid identity within the region of overlap). Using Southern blots of insect DNA, restriction fragment length polymorphisms (RFLPs) at the Msc locus were identified in susceptible, kdr and super-kdr housefly strains. These RFLPs showed tight linkage to resistance in controlled crosses involving these strains, thus providing clear genetic evidence that kdr, and hence pyrethroid mode of action, is closely associated with the voltage-sensitive sodium channel.
ESTHER : Williamson_1993_Mol.Gen.Genet_240_17
PubMedSearch : Williamson_1993_Mol.Gen.Genet_240_17
PubMedID: 8101963

Title : Cloning and analysis of the esterase genes conferring insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer) - Field_1993_Biochem.J_294 ( Pt 2)_569
Author(s) : Field LM , Williamson MS , Moores GD , Devonshire AL
Ref : Biochemical Journal , 294 ( Pt 2) :569 , 1993
Abstract : Full-length cDNA clones encoding the esterases (E4 and FE4) that confer insecticide resistance in the peach-potato aphid [Myzus persicae (Sulzer)] were isolated and characterized. The E4 cDNA contained an open reading frame of 1656 nucleotides, coding for a protein of 552 amino acids. The FE4 cDNA shared 99% identity with E4 over this region, the most important difference being a single nucleotide substitution resulting in the FE4 mRNA having an extra 36 nucleotides at the 3' end. The derived amino acid sequences for the N-terminus of E4 and FE4 were identical, with the first 23 residues being characteristic of a signal peptide and the next 40 residues being an exact match to the N-terminal sequence determined by Edman degradation of both purified proteins. The predicted molecular masses of 58.8 and 60.2 kDa for the E4 and FE4 polypeptides were consistent with those previously observed by in vitro translation of mRNA. Five potential N-linked glycosylation sites were present in both polypeptides, in accordance with earlier evidence that the native esterases are glycoproteins. Comparison of the aphid esterase protein sequences with other serine hydrolases provided evidence that their activity involves a charge-relay system with a catalytic triad the same as that found in acetylcholinesterase. Restriction mapping and sequencing of cloned genomic DNA showed that the E4 gene is spread over 4.3 kb with six introns and that the previously reported differences between the 3' ends of the E4 and FE4 genes result from single nucleotide substitutions and not gross differences in the DNA sequences.
ESTHER : Field_1993_Biochem.J_294 ( Pt 2)_569
PubMedSearch : Field_1993_Biochem.J_294 ( Pt 2)_569
PubMedID: 8373371
Gene_locus related to this paper: myzpe-este4 , myzpe-estf4

Title : Altered Forms of Acetylcholinesterase in Insecticide-Resistant Houseflies (Musca Domestica) -
Author(s) : Williamson MS , Moores GD
Ref : In Multidisciplinary approaches to cholinesterase functions - Proceedings of Fourth International Meeting on Cholinesterases , (Shafferman, A. and Velan, B., Eds) Plenum Press, New York :83 , 1992
Gene_locus related to this paper: musdo-ACHE