The genetics of phenylpyrazole resistance in Drosophila melanogaster

Fipronil is an insecticide of the phenylpyrazole class of chemicals which has been widely used in agriculture and animal health. Phenylpyrazoles exert their lethal effects on insects by binding to and inhibiting the actions of ligand-gated chloride channels (LGCCs). The precise interactions of these insecticides with specific protein subunits of LGCCs is not well understood, yet is crucial to the elucidation of target site resistance mechanisms which may develop in insect pests. A mutagenesis approach is currently underway to generate resistance to fipronil and a related structural analogue of the phenylpyrazole class. Both ethylmethanesulfonate (EMS) mutagenesis and site-directed mutagenesis will be used to generate and investigate mutations in LGCC subunits which may alter the resistance phenotype of susceptible insects. This approach is aided by the use of homology modelling of insect receptors and docking studies to predict important residues for binding of the insecticides. Consideration of the LGCC gene family as a whole, both phylogenetically using bioinformatics, and physiologically using gene expression and RNAi knockdown studies, will assess the importance of this family as potential insecticide targets. This research will contribute to the understanding of the LGCC neural system in insects, which remains to provide crucial insecticide targets for past, present and future insecticides.