title: Resistance to spiromesifen in Trialeurodes vaporariorum is associated with a single amino acid replacement in its target enzyme acetyl-coenzyme A carboxylase.
abstract: Spiromesifen is a novel insecticide and is classed as a tetronic acid derivative. It targets the insects' acetyl-coenzyme A carboxylase (ACCase) enzyme, causing a reduction in lipid biosynthesis. At the time of this publication, there are no reports of resistance to this class of insecticides in insects although resistance has been observed in several mite species. The greenhouse whitefly Trialeurodes vaporariorum (Westwood) is a serious pest of protected vegetable and ornamental crops in temperate regions of the world and spiromesifen is widely used in its control. Mortality rates of UK and European populations of T. vaporariorum to spiromesifen were calculated and up to 26-fold resistance was found. We therefore sought to examine the molecular mechanism underlying spiromesifen resistance in this important pest. Pre-treatment with piperonyl butoxide did not synergize spiromesifen, suggesting a target-site resistance mechanism. The full length ACCase gene was sequenced for a range of T. vaporariorum strains and a strong association was found between spiromesifen resistance and a glutamic acid substitution with lysine in position 645 (E645K) of this gene. A TaqMan allelic discrimination assay confirmed these findings. Although this resistance is not considered sufficient to compromise the field performance of spiromesifen, this association of E645K with resistance is the first report of a potential target site mechanism affecting an ACCase inhibitor in an arthropod species.
authors.affiliation: Rothamsted Research, West Common, Harpenden, UK. nikolaos.karatolos@rothamsted.ac.uk
authors.forename: N
authors.initials: N
authors.lastname: Karatolos
authors.forename: M S
authors.initials: MS
authors.lastname: Williamson
authors.forename: I
authors.initials: I
authors.lastname: Denholm
authors.forename: K
authors.initials: K
authors.lastname: Gorman
authors.forename: R
authors.initials: R
authors.lastname: ffrench-Constant
authors.forename: R
authors.initials: R
authors.lastname: Nauen
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D017124:Conserved Sequence / Q000235:genetics; D005260:Female; D006430:Hemiptera / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics*; D007305:Insecticide Resistance / Q000187:drug effects / Q000235:genetics*; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000201:enzymology; D008297:Male; D008969:Molecular Sequence Data; D010882:Piperonyl Butoxide / Q000633:toxicity; D017354:Point Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013141:Spiro Compounds / Q000633:toxicity*; D016019:Survival Analysis
chemical_list: D007306:Insecticides; D013141:Spiro Compounds; D000103:Acetyl-CoA Carboxylase; D010882:Piperonyl Butoxide; C521569:spiromesifen