title: Metabolic and target-site mechanisms combine to confer strong DDT resistance in Anopheles gambiae.
abstract: The development of resistance to insecticides has become a classic exemplar of evolution occurring within human time scales. In this study we demonstrate how resistance to DDT in the major African malaria vector Anopheles gambiae is a result of both target-site resistance mechanisms that have introgressed between incipient species (the M- and S-molecular forms) and allelic variants in a DDT-detoxifying enzyme. Sequencing of the detoxification enzyme, Gste2, from DDT resistant and susceptible strains of An. gambiae, revealed a non-synonymous polymorphism (I114T), proximal to the DDT binding domain, which segregated with strain phenotype. Recombinant protein expression and DDT metabolism analysis revealed that the proteins from the susceptible strain lost activity at higher DDT concentrations, characteristic of substrate inhibition. The effect of I114T on GSTE2 protein structure was explored through X-ray crystallography. The amino acid exchange in the DDT-resistant strain introduced a hydroxyl group nearby the hydrophobic DDT-binding region. The exchange does not result in structural alterations but is predicted to facilitate local dynamics and enzyme activity. Expression of both wild-type and 114T alleles the allele in Drosophila conferred an increase in DDT tolerance. The 114T mutation was significantly associated with DDT resistance in wild caught M-form populations and acts in concert with target-site mutations in the voltage gated sodium channel (Vgsc-1575Y and Vgsc-1014F) to confer extreme levels of DDT resistance in wild caught An. gambiae.
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Sara N
authors.initials: SN
authors.lastname: Mitchell
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rigden
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Dowd
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Fang
authors.initials: F
authors.lastname: Lu
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Wilding
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Weetman
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Noguchi Memorial Institute for Medical Research, University of Ghana, Legon, Ghana.
authors.forename: Samuel
authors.initials: S
authors.lastname: Dadzie
authors.affiliation: Boston College, Chestnut Hill, Massachusetts, United States of America.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Jenkins
authors.affiliation: Boston College, Chestnut Hill, Massachusetts, United States of America.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Regna
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Pelagie
authors.initials: P
authors.lastname: Boko
authors.affiliation: Institut Régional de Santé Publique de Ouidah/Université d'Abomey-Calavi, Cotonou, Bénin.
authors.forename: Luc
authors.initials: L
authors.lastname: Djogbenou
authors.affiliation: Boston College, Chestnut Hill, Massachusetts, United States of America; Harvard School of Public Health, Boston, Massachusetts, United States of America.
authors.forename: Marc A T
authors.initials: MA
authors.lastname: Muskavitch
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Hilary
authors.initials: H
authors.lastname: Ranson
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Mark J I
authors.initials: MJ
authors.lastname: Paine
authors.affiliation: Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Mayans
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom; Malaria Programme, Wellcome Trust Sanger Institute, Hinxton, Cambridge, United Kingdom.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Donnelly
mesh_terms: D000349:Africa; D000483:Alleles; D019943:Amino Acid Substitution; D000818:Animals; D000852:Anopheles / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D002384:Catalysis; D003634:DDT / Q000494:pharmacology*; D004789:Enzyme Activation; D005260:Female; D015870:Gene Expression; D017344:Genes, Insect; D014644:Genetic Variation; D006239:Haplotypes; D007305:Insecticide Resistance / Q000235:genetics*; D007306:Insecticides / Q000494:pharmacology*; D008958:Models, Molecular; D009154:Mutation; D058974:Phylogeography; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins
chemical_list: D007306:Insecticides; D011994:Recombinant Proteins; D003634:DDT