title: Directionally selected cytochrome P450 alleles are driving the spread of pyrethroid resistance in the major malaria vector Anopheles funestus.
abstract: Pyrethroid insecticides are critical for malaria control in Africa. However, resistance to this insecticide class in the malaria vector Anopheles funestus is spreading rapidly across Africa, threatening the success of ongoing and future malaria control programs. The underlying resistance mechanisms driving the spread of this resistance in wild populations remain largely unknown. Here, we show that increased expression of two tandemly duplicated P450 genes, CYP6P9a and CYP6P9b, is the main mechanism driving pyrethroid resistance in Malawi and Mozambique, two southern African countries where this insecticide class forms the mainstay of malaria control. Genome-wide transcription analysis using microarray and quantitative RT-PCR consistently revealed that CYP6P9a and CYP6P9b are the two genes most highly overexpressed (>50-fold; q < 0.01) in permethrin-resistant mosquitoes. Transgenic expression of CYP6P9a and CYP6P9b in Drosophila melanogaster demonstrated that elevated expression of either of these genes confers resistance to both type I (permethrin) and type II (deltamethrin) pyrethroids. Functional characterization of recombinant CYP6P9b confirmed that this protein metabolized both type I (permethrin and bifenthrin) and type II (deltamethrin and Lambda-cyhalothrin) pyrethroids but not DDT. Variability analysis identified that a single allele of each of these genes is predominantly associated with pyrethroid resistance in field populations from both countries, which is suggestive of a single origin of this resistance that has since spread across the region. Urgent resistance management strategies should be implemented in this region to limit a further spread of this resistance and minimize its impact on the success of ongoing malaria control programs.
authors.affiliation: Vector Biology Department,  Liverpool School of Tropical Medicine, Liverpool L3 5QA,  United Kingdom.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Riveron
authors.forename: Helen
authors.initials: H
authors.lastname: Irving
authors.forename: Miranda
authors.initials: M
authors.lastname: Ndula
authors.forename: Kayla G
authors.initials: KG
authors.lastname: Barnes
authors.forename: Sulaiman S
authors.initials: SS
authors.lastname: Ibrahim
authors.forename: Mark J I
authors.initials: MJ
authors.lastname: Paine
authors.forename: Charles S
authors.initials: CS
authors.lastname: Wondji
mesh_terms: D000483:Alleles; D000818:Animals; D000852:Anopheles / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004331:Drosophila melanogaster; D004351:Drug Resistance / Q000235:genetics*; D007303:Insect Vectors / Q000201:enzymology / Q000235:genetics*; D008288:Malaria / Q000517:prevention & control*; D008295:Malawi; D046228:Microarray Analysis; D008969:Molecular Sequence Data; D009073:Mozambique; D011722:Pyrethrins; D060888:Real-Time Polymerase Chain Reaction; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D011722:Pyrethrins; D003577:Cytochrome P-450 Enzyme System