Functional characterization of P450 genes associated with insecticide resistance in Anopheles funestus, malaria vector in Africa

Insecticide resistance in Anopheles funestus, one of the main vectors of malaria transmission, is disrupting malaria control in some areas of Africa. Using QTL mapping and microarray gene expression analysis with laboratory and field samples, we have shown that that pyrethroid resistance in An. funestus is mainly conferred by two duplicated P450 genes, CYP6P9 (CYP6P9a and CYP6P9b) and CYP6P4 (CYP6P4a and CYP6P4b). To establish their mode of action and their respective contribution to the resistance phenotype we functionally characterised these four genes by: I) in vitro metabolic assays with different allelic variants to prove whether they are able to metabolize pyrethroids and II) transgenic expression of the 4 P450 genes using the GAL4-UAS system in Drosophila melanogaster to determine whether the over-expression may confer resistance to a susceptible line. Significant variability in the amino acid sequences has been observed between susceptible and resistant mosquitoes. CYP6P9a and CYP6P9b have been shown to metabolise pyrethroids while CYP6P4 copies are less involved.