title: The independent gene amplification of electrophoretically indistinguishable B esterases from the insecticide-resistant mosquito Culex quinquefasciatus.
abstract: Resistance to organophosphates in Culex mosquitoes is typically associated with increased activity of non-specific esterases. The commonest phenotype involves two elevated esterases, A2 and B2, while some strains have elevation of esterase B1 alone. Overexpression of the two B esterase electromorphs is due to gene amplification. Full-length cDNAs coding for amplified esterase B genes from a resistant Cuban strain (MRES, with amplified B1 esterase) and a Sri Lankan strain (PelRR, with amplified B2 esterase) of C. quinquefasciatus have been sequenced. In addition, a partial-length cDNA coding for a B esterase from an insecticide-susceptible Sri Lankan strain (PelSS) has been sequenced. All the nucleotide sequences and the inferred amino acid sequences show a high level of identify (> 95% at the nucleotide and amino acid level), confirming that they are an allelic series. The two B1 esterase nucleotide sequences (MRES and the previously published TEM-R [Mouches, Pauplin, Agarwal, Lemieux, Herzog, Abadon, Beyssat-Arnaouty, Hyrien, De Saint Vincent, Georghiou and Pasteur (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 2574-2578]) showed the lowest identity, and restriction-fragment-length-polymorphism analysis of the two strains was different. On the basis of these data we suggest that the two electrophoretically identical B1 esterase isoenzymes from California and Cuba have been amplified independently. Alternatively, if amplification has occurred only once, the original amplification has not occurred recently.
authors.affiliation: Department of Pure and Applied Biology, University of Wales College of Cardiff, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Vaughan
authors.forename: M
authors.initials: M
authors.lastname: Rodriguez
authors.forename: J
authors.initials: J
authors.lastname: Hemingway
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D043182:Carboxylesterase; D002265:Carboxylic Ester Hydrolases / Q000235:genetics*; D003465:Culex / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D005784:Gene Amplification; D016678:Genome; D007305:Insecticide Resistance / Q000235:genetics* / Q000502:physiology; D007527:Isoenzymes / Q000235:genetics*; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D000002:Temefos / Q000494:pharmacology*
chemical_list: D018076:DNA, Complementary; D007527:Isoenzymes; D002265:Carboxylic Ester Hydrolases; D043182:Carboxylesterase; D000002:Temefos