title: Acetylcholinesterase point mutations in European strains of Tetranychus urticae (Acari: Tetranychidae) resistant to organophosphates.
abstract: BACKGROUND
  In Tetranychus urticae Koch, acetylcholinesterase insensitivity is often involved in organophosphate (OP) and carbamate (CARB) resistance. By combining toxicological, biochemical and molecular data from three reference laboratory and three OP selected strains (OP strains), the AChE1 mutations associated with resistance in T. urticae were characterised.
  
  
  RESULTS
  The resistance ratios of the OP strains varied from 9 to 43 for pirimiphos-methyl, from 78 to 586 for chlorpyrifos, from 8 to 333 for methomyl and from 137 to 4164 for dimethoate. The insecticide concentration needed to inhibit 50% of the AChE1 activity was, in the OP strains, at least 2.7, 55, 58 and 31 times higher for the OP pirimiphos-methyl, chlorpyrifos oxon, paraoxon and omethoate respectively, and 87 times higher for the CARB carbaryl. By comparing the AChE1 sequence, four amino acid substitutions were detected in the OP strains: (1) F331W (Torpedo numbering) in all the three OP strains; (2) T280A found in the three OP strains but not in all clones; (3) G328A, found in two OP strains; (4) A201S found in only one OP strain.
  
  
  CONCLUSIONS
  Four AChE1 mutations were found in resistant strains of T. urticae, and three of them, F331W, G328A and A201S, are possibly involved in resistance to OP and CARB insecticides. Among them, F331W is probably the most important and the most common in T. urticae. It can be easily detected by the diagnostic PCR-RLFP assay developed in this study.
authors.affiliation: Laboratory of Agrozoology, Department of Crop Protection, Ghent University, Coupure links 653, 9000 Ghent, Belgium.
authors.forename: Jahangir
authors.initials: J
authors.lastname: Khajehali
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Leeuwen
authors.forename: Maria
authors.initials: M
authors.lastname: Grispou
authors.forename: Evangelia
authors.initials: E
authors.lastname: Morou
authors.forename: Haoués
authors.initials: H
authors.lastname: Alout
authors.forename: Mylène
authors.initials: M
authors.lastname: Weill
authors.forename: Luc
authors.initials: L
authors.lastname: Tirry
authors.forename: John
authors.initials: J
authors.lastname: Vontas
authors.forename: Anastasia
authors.initials: A
authors.lastname: Tsagkarakou
mesh_terms: D056810:Acaricides / Q000494:pharmacology*; D000110:Acetylcholinesterase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D004351:Drug Resistance; D005060:Europe; D008969:Molecular Sequence Data; D010755:Organophosphates / Q000494:pharmacology*; D017354:Point Mutation; D016415:Sequence Alignment; D040102:Tetranychidae / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics
chemical_list: D056810:Acaricides; D010755:Organophosphates; D000110:Acetylcholinesterase