Field LM


Full name : Field Linda M

First name : Linda M

Mail : Centre for Sustainable Pest and Disease Management, Rothamsted Research, Harpenden

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Country : United Kingdom

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References (38)

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 : 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 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 : 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 : 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 : Identification of genes expressed in the sex pheromone gland of the black cutworm Agrotis ipsilon with putative roles in sex pheromone biosynthesis and transport - Gu_2013_BMC.Genomics_14_636
Author(s) : Gu SH , Wu KM , Guo YY , Pickett JA , Field LM , Zhou JJ , Zhang YJ
Ref : BMC Genomics , 14 :636 , 2013
Abstract : BACKGROUND: One of the challenges in insect chemical ecology is to understand how insect pheromones are synthesised, detected and degraded. Genome wide survey by comparative sequencing and gene specific expression profiling provide rich resources for this challenge. A. ipsilon is a destructive pest of many crops and further characterization of the genes involved in pheromone biosynthesis and transport could offer potential targets for disruption of their chemical communication and for crop protection.
RESULTS: Here we report 454 next-generation sequencing of the A. ipsilon pheromone gland transcriptome, identification and expression profiling of genes putatively involved in pheromone production, transport and degradation. A total of 23473 unigenes were obtained from the transcriptome analysis, 86% of which were A. ipsilon specific. 42 transcripts encoded enzymes putatively involved in pheromone biosynthesis, of which 15 were specifically, or mainly, expressed in the pheromone glands at 5 to 120-fold higher levels than in the body. Two transcripts encoding for a fatty acid synthase and a desaturase were highly abundant in the transcriptome and expressed more than 40-fold higher in the glands than in the body. The transcripts encoding for 2 acetyl-CoA carboxylases, 1 fatty acid synthase, 2 desaturases, 3 acyl-CoA reductases, 2 alcohol oxidases, 2 aldehyde reductases and 3 acetyltransferases were expressed at a significantly higher level in the pheromone glands than in the body. 17 esterase transcripts were not gland-specific and 7 of these were expressed highly in the antennae. Seven transcripts encoding odorant binding proteins (OBPs) and 8 encoding chemosensory proteins (CSPs) were identified. Two CSP transcripts (AipsCSP2, AipsCSP8) were highly abundant in the pheromone gland transcriptome and this was confirmed by qRT-PCR. One OBP (AipsOBP6) were pheromone gland-enriched and three OBPs (AipsOBP1, AipsOBP2 and AipsOBP4) were antennal-enriched. Based on these studies we proposed possible A. ipsilon biosynthesis pathways for major and minor sex pheromone components.
CONCLUSIONS: Our study identified genes potentially involved in sex pheromone biosynthesis and transport in A. ipsilon. The identified genes are likely to play essential roles in sex pheromone production, transport and degradation and could serve as targets to interfere with pheromone release. The identification of highly expressed CSPs and OBPs in the pheromone gland suggests that they may play a role in the binding, transport and release of sex pheromones during sex pheromone production in A. ipsilon and other Lepidoptera insects.
ESTHER : Gu_2013_BMC.Genomics_14_636
PubMedSearch : Gu_2013_BMC.Genomics_14_636
PubMedID: 24053512
Gene_locus related to this paper: agrip-u5kkb6 , agrip-u5kkb9 , agrip-u5kk05

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 : 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 : 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 : 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 : Gene amplification and insecticide resistance - Bass_2011_Pest.Manag.Sci_67_886
Author(s) : Bass C , Field LM
Ref : Pest Manag Sci , 67 :886 , 2011
Abstract : Pesticide resistance in arthropods has been shown to evolve by two main mechanisms, the enhanced production of metabolic enzymes, which bind to and/or detoxify the pesticide, and mutation of the target protein, which makes it less sensitive to the pesticide. One route that leads to enhanced metabolism is the duplication or amplification of the structural gene(s) encoding the detoxifying enzyme, and this has now been described for the three main families (esterases, glutathione S-transferases and cytochrome P450 monooxygenases) implicated in resistance. More recently, a direct or indirect role for gene duplication or amplification has been described for target-site resistance in several arthropod species. This mini-review summarises the involvement of gene duplication/amplification in the insecticide/acaricide resistance of insect and mite pests and highlights recent developments in this area in relation to P450-mediated and target-site resistance.
ESTHER : Bass_2011_Pest.Manag.Sci_67_886
PubMedSearch : Bass_2011_Pest.Manag.Sci_67_886
PubMedID: 21538802

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 : 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 : 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 : 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 : A novel assay reveals the blockade of esterases by piperonyl butoxide - Khot_2008_Pest.Manag.Sci_64_1139
Author(s) : Khot AC , Bingham G , Field LM , Moores GD
Ref : Pest Manag Sci , 64 :1139 , 2008
Abstract : BACKGROUND: Conventional in vitro assays sometimes fail to reveal esterase inhibition by piperonyl butoxide (PBO), although synergism studies suggest loss of esterase-mediated sequestration of insecticide does take place. A new in vitro assay has been devised that routinely reveals binding between PBO and these esterases. RESULTS: The new 'esterase interference' assay detects the blockade of resistance-associated esterases in a species, Myzus persicae Slzer, where this has not previously been seen. The assay also demonstrates directly the protective effect esterases may confer to target sites of insecticides. CONCLUSION: The new assay reveals esterase blockade by PBO and thus has the potential to be used as a high-throughput screening method for other potential synergists.
ESTHER : Khot_2008_Pest.Manag.Sci_64_1139
PubMedSearch : Khot_2008_Pest.Manag.Sci_64_1139
PubMedID: 18481337

Title : Temporal synergism can enhance carbamate and neonicotinoid insecticidal activity against resistant crop pests - Bingham_2008_Pest.Manag.Sci_64_81
Author(s) : Bingham G , Gunning RV , Delogu G , Borzatta V , Field LM , Moores GD
Ref : Pest Manag Sci , 64 :81 , 2008
Abstract : BACKGROUND: Piperonyl butoxide (PBO) effectively synergises synthetic pyrethroids, rendering even very resistant insect pests susceptible, provided a temporal element is included between exposure to synergist and insecticide. This concept is now applied to carbamates and neonicotinoids. RESULTS: A microencapsulated formulation of PBO and pirimicarb reduced the resistance factor in a clone of Myzus persicae (Sulzer) from >19 000- to 100-fold and in Aphis gossypii (Glover) from >48 000- to 30-fold. Similar results were obtained for a strain of Bemisia tabaci Gennadius resistant to imidacloprid and acetamiprid, although a second resistant strain did not exhibit such a dramatic reduction, presumably owing to the presence of target-site insensitivity and the absence of metabolic resistance. Synergism was also observed in laboratory susceptible insects, suggesting that, even when detoxification is not enhanced, there is degradation of insecticides by the background enzymes. Use of an analogue of PBO, which inhibits esterases but has reduced potency against microsomal oxidases, suggests that acetamiprid resistance in whiteflies is largely oxidase based. CONCLUSION: Temporal synergism can effectively enhance the activity of carbamates and neonicotinoids against resistant insect pests. Although the extent of this enhancement is dependent upon the resistance mechanisms present, inhibition of background enzymes can confer increased sensitivity against target-site resistance as well as increased metabolism.
ESTHER : Bingham_2008_Pest.Manag.Sci_64_81
PubMedSearch : Bingham_2008_Pest.Manag.Sci_64_81
PubMedID: 17926308

Title : Temporal synergism by microencapsulation of piperonyl butoxide and -cypermethrin overcomes insecticide resistance in crop pests - Bingham_2007_Pest.Manag.Sci_63_276
Author(s) : Bingham G , Gunning RV , Gorman K , Field LM , Moores GD
Ref : Pest Manag Sci , 63 :276 , 2007
Abstract : A microencapsulated formulation that gives a burst release of piperonyl butoxide (PBO) several hours before a burst release of a conventional pyrethroid can effectively overcome metabolic resistance in Bemisia tabaci Gennadius, Helicoverpa armigera (Hbner), Aphis gossypii Glover and Myzus persicae Sulzer. This increase in efficacy against resistant pests was reflected in a field trial against B. tabaci on cotton, eliminating the need for two treatments. The ratio between the active insecticide and the synergist was found to be crucial in reducing resistance factors.
ESTHER : Bingham_2007_Pest.Manag.Sci_63_276
PubMedSearch : Bingham_2007_Pest.Manag.Sci_63_276

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 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 : 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 : 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 : 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 : 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 : Amplified esterase genes and their relationship with other insecticide resistance mechanisms in English field populations of the aphid, Myzus persicae (Sulzer) - Field_2002_Pest.Manag.Sci_58_889
Author(s) : Field LM , Foster SP
Ref : Pest Manag Sci , 58 :889 , 2002
Abstract : Myzus persicae samples were collected from populations present on a range of field crops between 1997 and 2000. A combination of biochemical, DNA-based diagnostics and bioassays was used to assess the presence of three insecticide resistance mechanisms: elevated carboxylesterase (E4 or FE4), insensitive acetylcholinesterase and insensitive sodium channels (knockdown resistance, kdr). For the carboxylesterases, both the levels of enzyme and the type of gene present (E4 or FE4) were determined. The results showed that during the time period studied there was a dramatic reduction in the proportion of aphids with very high levels of E4 and an increase in those with lower levels of FE4. There was also a slightly different E4 gene present in a limited number of samples. The change in esterase genes was accompanied by a virtual loss of the insensitive AChE variant and a maintenance of aphids with kdr. The selection pressures and other factors leading to these changes in field populations of M persicae are discussed.
ESTHER : Field_2002_Pest.Manag.Sci_58_889
PubMedSearch : Field_2002_Pest.Manag.Sci_58_889
PubMedID: 12233178

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 : Relationship between amount of esterase and gene copy number in insecticide-resistant Myzus persicae (Sulzer) - Field_1999_Biochem.J_339 ( Pt 3)_737
Author(s) : Field LM , Blackman RL , Tyler-Smith C , Devonshire AL
Ref : Biochemical Journal , 339 ( Pt 3) :737 , 1999
Abstract : Overproduction of the insecticide-degrading esterases, E4 and FE4, in peach-potato aphids, Myzus persicae (Sulzer), depends on both gene amplification and transcriptional control, the latter being associated with changes in DNA methylation. The structure and function of the aphid esterase genes have been studied but the determination of their copy number has proved difficult, a common problem with gene amplification. We have now used a combination of pulsed-field gel electrophoresis and quantitative competitive PCR to determine relative esterase gene copy numbers in aphid clones with different levels of insecticide resistance (R1, R2 and R3). There are approx. 4-fold increases between susceptible, R1, R2 and R3 aphids, reaching a maximum of approx. 80 times more genes in R3; this gives proportionate increases in esterase protein relative to susceptible aphids. Thus there is no overexpression of the amplified genes, in contrast with what was thought previously. For E4 genes, the loss of 5-methylcytosine is correlated with a loss of expression, greatly decreasing the amount of enzyme relative to the copy number.
ESTHER : Field_1999_Biochem.J_339 ( Pt 3)_737
PubMedSearch : Field_1999_Biochem.J_339 ( Pt 3)_737
PubMedID: 10215614

Title : Amplification and methylation of an esterase gene associated with insecticide-resistance in greenbugs, Schizaphis graminum (Rondani) (Homoptera: Aphididae) - Ono_1999_Insect.Biochem.Mol.Biol_29_1065
Author(s) : Ono M , Swanson JJ , Field LM , Devonshire AL , Siegfried BD
Ref : Insect Biochemistry & Molecular Biology , 29 :1065 , 1999
Abstract : The greenbug aphid, Schizaphis graminum (Rondani) has developed resistance to organophosphorus insecticides by the over-production of esterases that have been classified as Type I and Type II. The first twenty N-terminal amino acids of the Type I esterase were determined and used to design an oligonucleotide, which in conjunction with an active site primer derived from conserved sequences of other insect esterases and two internal primers specific for esterases from another aphid species resulted in a 0.85 kb genomic DNA fragment from resistant greenbugs. This was extended by 5' RACE which provided approximately 1.2 kb of the 5' end of the esterase gene. The 5' DNA sequence corresponded to 19 of the 20 known amino acids of the Type I esterase, with the last needing only a one base change (probably resulting from a PCR artifact). Furthermore, the sequence showed very close similarity to the amplified E4/FE4 esterase genes of Myzus persicae (Sulzer). A comparison of sequences suggested that the S. graminum gene has introns in the same positions as the first two introns of E4/FE4, with the second intron being considerably larger in S. graminum. Probing of Southern blots with the 0.85 kb esterase fragment showed that the gene encoding the Type I esterase is amplified 4- to 8-fold in resistant S. graminum and that the amplified sequences contain 5-methylcytosine at MspI/HpaII sites, again in agreement with previous findings for M. persicae genes.
ESTHER : Ono_1999_Insect.Biochem.Mol.Biol_29_1065
PubMedSearch : Ono_1999_Insect.Biochem.Mol.Biol_29_1065
PubMedID: 10612041

Title : Evidence that the E4 and FE4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer) are part of a gene family - Field_1998_Biochem.J_330 ( Pt 1)_169
Author(s) : Field LM , Devonshire AL
Ref : Biochemical Journal , 330 ( Pt 1) :169 , 1998
Abstract : The amplification of genes encoding the esterases E4 and FE4 is a widespread mechanism of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer). We present evidence that in susceptible aphids the two genes are adjacent to each other in a head-to-tail arrangement with E4 upstream of FE4 and with approx. 19 kb of intervening sequence. There are also at least two other closely related sequences which might come from other members of an esterase gene family, in line with reports of other insect gene families encoding detoxifying enzymes. The close identity between E4 and FE4 genes indicates a recent duplication and divergence. The subsequent amplifications giving multiple copies of either E4 or FE4 must have involved two separate events, each probably occurring once and then being selected by insecticide exposure and spread by migration. The cloning of sequences upstream of the FE4 gene suggest, by comparison with E4, that the two genes are regulated in different ways. FE4 has sequences corresponding to a conventional promoter (TATA box and CAP site) that are not present in E4; on the other hand, FE4 lacks the CpG island present 5' of E4 genes that may control expression through changes in DNA methylation. The differences are likely to have occurred by the duplication event that gave rise to E4 and FE4 leading to different 5' sequences.
ESTHER : Field_1998_Biochem.J_330 ( Pt 1)_169
PubMedSearch : Field_1998_Biochem.J_330 ( Pt 1)_169
PubMedID: 9461506

Title : Structure and organization of amplicons containing the E4 esterase genes responsible for insecticide resistance in the aphid Myzus persicae (Sulzer) - Field_1997_Biochem.J_322 ( Pt 3)_867
Author(s) : Field LM , Devonshire AL
Ref : Biochemical Journal , 322 ( Pt 3) :867 , 1997
Abstract : Insecticide resistance in the aphid Myzus persicae results primarily from the amplification of genes encoding the insecticide-detoxifying esterase, E4. Here we report the analysis of flanking DNA co-amplified with the E4 gene. The 5' end of this gene has an untranslated leader sequence interspersed by two introns, and the promoter region lacks TATA and CAAT boxes. The DNA breakpoint involved in the generation of the amplification is just upstream (approx. 250 bp) of the putative E4 transcription start site; thus the E4 gene is very close to the 5' end of the approx. 24 kb amplicon. PCR primers specific to the 'novel joint' generated during the amplification have been used to show that a wide range of aphid clones have the same amplicons, arranged as a series of head-to-tail direct repeats. Long-distance mapping has revealed the structure of these repeats. This has important implications for understanding both the generation of the amplified genes and the origin and spread of insecticide resistance in M. persicae.
ESTHER : Field_1997_Biochem.J_322 ( Pt 3)_867
PubMedSearch : Field_1997_Biochem.J_322 ( Pt 3)_867
PubMedID: 9148762

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 : Polymerase chain reaction-based identification of insecticide resistance genes and DNA methylation in the aphid Myzus persicae (Sulzer) - Field_1996_Insect.Mol.Biol_5_197
Author(s) : Field LM , Crick SE , Devonshire AL
Ref : Insect Molecular Biology , 5 :197 , 1996
Abstract : The ability of a peach-potato aphid (Myzus persicae) to resist insecticides can depend on both the presence of amplified esterase genes and on differences in their expression. Here we report a polymerase chain reaction-restriction enzyme (PCR-REN) technique which can detect the presence of amplified esterase genes and distinguish between the two possible types of amplified gene (E4 and FE4) and a homologous fragment from susceptible aphids. The technique is quick and sensitive enough to be used on a fraction of an aphid or an individual embryo. Furthermore, it can be combined with a pre-PCR digestion using a methylation-sensitive enzyme (Hpall) to determine whether or not the esterase genes contain 5-methylcytosine, the presence or absence of which is known to correlate with changes in gene expression.
ESTHER : Field_1996_Insect.Mol.Biol_5_197
PubMedSearch : Field_1996_Insect.Mol.Biol_5_197
PubMedID: 8799738

Title : Analysis of amplicons containing the esterase genes responsible for insecticide resistance in the peach-potato aphid Myzus persicae (Sulzer) - Field_1996_Biochem.J_313 ( Pt 2)_543
Author(s) : Field LM , Devonshire AL , Tyler-Smith C
Ref : Biochemical Journal , 313 ( Pt 2) :543 , 1996
Abstract : The amplification of genes encoding an insecticide-detoxifying esterase (E4) in the peach-potato aphid Myzus persicae is one of the few examples where this genetic phenomenon has been shown to be involved in the response of an intact higher organism to artificial selection. Here we report quantitative and qualitative studies of the repeat units (amplicons) containing the E4 genes in a highly resistant aphid clone. Initial studies to quantify esterase sequences showed a 5-11-fold increase in resistant aphids compared with susceptible aphids, suggesting the presence of 10-22 gene copies per diploid genome. A more incisive analysis by pulsed-field gel electrophoresis confirmed the presence of about 12 copies of the E4 gene and showed them to be on about 24 kb amplicons, arranged as a tandem array of direct repeats. This, together with previous results from crossing experiments and with recent in situ hybridization studies, confirms that the E4 gene amplification in this aphid clone is heterozygous at a single locus. However, these data show that the gene amplification alone cannot account for the approx. 60 times higher levels of E4 protein and its mRNA present in this aphid clone, and therefore resistance must involve changes in both esterase gene copy number and gene expression.
ESTHER : Field_1996_Biochem.J_313 ( Pt 2)_543
PubMedSearch : Field_1996_Biochem.J_313 ( Pt 2)_543
PubMedID: 8573090

Title : Changes in the methylation of amplified esterase DNA during loss and reselection of insecticide resistance in peach-potato aphids, Myzus persicae - Hick_1996_Insect.Biochem.Mol.Biol_26_41
Author(s) : Hick CA , Field LM , Devonshire AL
Ref : Insect Biochemistry & Molecular Biology , 26 :41 , 1996
Abstract : Insecticide resistance in peach-potato aphids, Myzus persicae, results from the amplification of genes encoding an esterase that hydrolyses and sequesters insecticides. Resistance is normally stable, but highly resistant aphid clones sometimes lose resistance when insecticidal selection pressure is removed. This loss of resistance, termed reversion, arises from a loss of elevated esterase enzyme through transcriptional control, i.e. without loss of the amplified esterase DNA sequences. We have shown that loss of the elevated enzyme occurred simultaneously with loss of methylation at CCGG sites in the amplified DNA sequences. During reselection of resistance in these revertant clones, enzyme levels increased, but there was no corresponding return of methylation to DNA sequences. Thus, although DNA methylation is closely correlated with expression of the amplified esterase genes during reversion, it may not be a factor in the reverse process.
ESTHER : Hick_1996_Insect.Biochem.Mol.Biol_26_41
PubMedSearch : Hick_1996_Insect.Biochem.Mol.Biol_26_41
PubMedID: 8673078

Title : The peach-potato aphid Myzus persicae and the tobacco aphid Myzus nicotianae have the same esterase-based mechanisms of insecticide resistance - Field_1994_Insect.Mol.Biol_3_143
Author(s) : Field LM , Javed N , Stribley MF , Devonshire AL
Ref : Insect Molecular Biology , 3 :143 , 1994
Abstract : Biochemical and molecular studies have established that in the peach-potato aphid, Myzus persicae, insecticide resistance is conferred by amplification of genes encoding the insecticide-detoxifying esterases E4 or FE4. Here we report that two insecticide-resistant clones of the closely related tobacco aphid Myzus nicotianae have elevated esterases indistinguishable from E4 and FE4 and amplified esterase DNA sequences, and flanking regions, with identical restriction maps to the M. persicae genes. Furthermore, the DNA sequences of c. 630 bp fragments of the E4 and FE4 genes of M. persicae are different from each other but identical to the fragment from corresponding M. nicotianae clones. The existence of apparently identical insecticide resistance genes in the two species can be best explained by the selection of the amplified genes in M. persicae, transfer to hybrids of M. persicae and M. nicotianae by sexual reproduction and subsequent spread through M. nicotianae populations.
ESTHER : Field_1994_Insect.Mol.Biol_3_143
PubMedSearch : Field_1994_Insect.Mol.Biol_3_143
PubMedID: 7894746

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 : Gene amplification and insecticide resistance -
Author(s) : Devonshire AL , Field LM
Ref : Annual Review of Entomology , 36 :1 , 1991
PubMedID: 2006866

Title : Molecular evidence that insecticide resistance in peach-potato aphids (Myzus persicae Sulz.) results from amplification of an esterase gene - Field_1988_Biochem.J_251_309
Author(s) : Field LM , Devonshire AL , Forde BG
Ref : Biochemical Journal , 251 :309 , 1988
Abstract : cDNA clones for the esterase (E4) responsible for broad insecticide resistance in peach-potato aphids (Myzus persicae Sulz.) were isolated and used to study the molecular basis of resistance. Increased esterase synthesis by resistant aphids was found to be associated with amplification of the structural gene for the esterase (E4 or its closely related variant, FE4), the degree of amplification being correlated with the activity of the esterase and the level of resistance. Hybridization of the cDNA clones to genomic Southern blots showed that only some of the esterase-related restriction fragments are amplified. Qualitative differences between restriction patterns in different clones of resistant aphids correlated with the presence or absence of a specific chromosome translocation and with production of E4 or FE4.
ESTHER : Field_1988_Biochem.J_251_309
PubMedSearch : Field_1988_Biochem.J_251_309
PubMedID: 3390158