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A nicotinic acetylcholine receptor transmembrane point mutation (G275E) associated with resistance to spinosad in F rankliniella occidentalis
Author(s) -
Puinean Alin M.,
Lansdell Stuart J.,
Collins Toby,
Bielza Pablo,
Millar Neil S.
Publication year - 2013
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/jnc.12029
Subject(s) - spinosad , nicotinic acetylcholine receptor , biology , allosteric regulation , transmembrane domain , point mutation , acetylcholine receptor , mutation , nicotinic agonist , biochemistry , amino acid , receptor , pesticide , gene , ecology
Abstract High levels of resistance to spinosad, a macrocyclic lactone insecticide, have been reported previously in western flower thrips, Frankliniella occidentalis , an economically important insect pest of vegetables, fruit and ornamental crops. We have cloned the nicotinic acetylcholine receptor (nAChR) α6 subunit from F. occidentalis (Foα6) and compared the nucleotide sequence of Foα6 from susceptible and spinosad‐resistant insect populations ( MLFOM and R1S respectively). A single nucleotide change has been identified in Foα6, resulting in the replacement of a glycine (G) residue in susceptible insects with a glutamic acid (E) in resistant insects. The resistance‐associated mutation (G275E) is predicted to lie at the top of the third α‐helical transmembrane domain of Foα6. Although there is no direct evidence identifying the location of the spinosad binding site, the analogous amino acid in the C. elegans glutamate‐gated chloride channel lies in close proximity (4.4 Å) to the known binding site of ivermectin, another macrocyclic lactone pesticide. The functional consequences of the resistance‐associated mutation have been examined in the human nAChR α7 subunit. Introduction of an analogous (A272E) mutation in α7 abolishes the modulatory effects of spinosad whilst having no significant effect upon activation by acetylcholine, consistent with spinosad having an allosteric mechanism of action.