title: Point mutations in the Drosophila sodium channel gene para associated with resistance to DDT and pyrethroid insecticides.
abstract: The gene para in Drosophila melanogaster encodes an alpha subunit of voltage-activated sodium channels, the presumed site of action of DDT and pyrethroid insecticides. We used an existing collection of Drosophila para mutants to examine the molecular basis of targetsite resistance to pyrethroids and DDT. Six out of thirteen mutants tested were associated with a largely dominant, 10- to 30-fold increase in DDT resistance. The amino acid lesions associated with these alleles defined four sites in the sodium channel polypeptide where a mutational change can cause resistance: within the intracellular loop between S4 and S5 in homology domains I and III, within the pore region of homology domain III, and within S6 in homology domain III. Some of these sites are analogous with those defined by knockdown resistance (kdr) and super-kdr resistance-associated mutations in houseflies and other insects, but are located in different homologous units of the channel polypeptide. We find a striking synergism in resistance levels with particular heterozygous combinations of para alleles that appears to mimic the super-kdr double mutant housefly phenotype. Our results indicate that the alleles analyzed from natural populations represent only a subset of mutations that can confer resistance. The implications for the binding site of pyrethroids and mechanisms of target-site insensitivity are discussed.
authors.affiliation: Department of Entomology, University of Wisconsin-Madison 53706, USA.
authors.forename: B
authors.initials: B
authors.lastname: Pittendrigh
authors.forename: R
authors.initials: R
authors.lastname: Reenan
authors.forename: R H
authors.initials: RH
authors.lastname: ffrench-Constant
authors.forename: B
authors.initials: B
authors.lastname: Ganetzky
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D003058:Cockroaches / Q000235:genetics; D003634:DDT / Q000494:pharmacology*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000187:drug effects / Q000235:genetics*; D018432:Drug Resistance, Multiple / Q000235:genetics; D005799:Genes, Dominant; D017344:Genes, Insect; D006793:Houseflies / Q000235:genetics; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010243:Paralysis / Q000235:genetics; D017354:Point Mutation; D011722:Pyrethrins / Q000494:pharmacology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D013045:Species Specificity; D013696:Temperature
chemical_list: D029721:Drosophila Proteins; D019476:Insect Proteins; D007306:Insecticides; D011722:Pyrethrins; D015222:Sodium Channels; C469950:para protein, Drosophila; D003634:DDT