title: Mutation of a nicotinic acetylcholine receptor β subunit is associated with resistance to neonicotinoid insecticides in the aphid Myzus persicae.
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 (Mpα1-5 and Mpβ1) genes from resistant and susceptible aphid clones revealed a single point mutation in the loop D region of the nAChR β1 subunit of the resistant clone, causing an arginine to threonine substitution (R81T).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Centre for Sustainable Pest and Disease Management, Rothamsted Research, Harpenden, AL5 2JQ, UK. chris.bass@rothamsted.ac.uk
authors.forename: Chris
authors.initials: C
authors.lastname: Bass
authors.forename: Alin M
authors.initials: AM
authors.lastname: Puinean
authors.forename: Melanie
authors.initials: M
authors.lastname: Andrews
authors.forename: Penny
authors.initials: P
authors.lastname: Cutler
authors.forename: Miriam
authors.initials: M
authors.lastname: Daniels
authors.forename: Jan
authors.initials: J
authors.lastname: Elias
authors.forename: Verity Laura
authors.initials: VL
authors.lastname: Paul
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Crossthwaite
authors.forename: Ian
authors.initials: I
authors.lastname: Denholm
authors.forename: Linda M
authors.initials: LM
authors.lastname: Field
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Foster
authors.forename: Rob
authors.initials: R
authors.lastname: Lind
authors.forename: Martin S
authors.initials: MS
authors.lastname: Williamson
authors.forename: Russell
authors.initials: R
authors.lastname: Slater
mesh_terms: D000818:Animals; D001042:Aphids / Q000235:genetics* / Q000378:metabolism; D018678:Cholinergic Agents / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology*; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides / Q000494:pharmacology*; D009154:Mutation; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000494:pharmacology*; D011978:Receptors, Nicotinic / Q000235:genetics* / Q000378:metabolism
chemical_list: D018678:Cholinergic Agents; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D011978:Receptors, Nicotinic; C082359:imidacloprid