Controlled expression of nicotinic acetylcholine receptor-encoding genes in insects uncovers distinct mechanisms of action of the neonicotinoid insecticide dinotefuran

Abstract

Dinotefuran, a neonicotinoid, is a unique insecticide owing to its structure and action. We took two approaches that employed insects with controlled expression of nicotinic acetylcholine receptor (nAChR)-encoding genes to gain insight into the uniqueness of dinotefuran. First, we examined the insecticidal activity of dinotefuran and imidacloprid against brown planthoppers (Nilaparvata lugens), in which the expression of eight (of 13) individual subunit-encoding genes was specifically reduced using RNA interference. Knockdown of the tested gene, except one, resulted in a decrease in sensitivity to imidacloprid, whereas the sensitivity of N. lugens to dinotefuran decreased only when two of the eight genes were knocked down. These findings imply that a major dinotefuran-targeted nAChR subtype may contain specific subunits although imidacloprid acts on a broad range of receptor subtypes. Next, we examined the effects of knockout of Drosophila α1 subunit-encoding gene (Dα1) on the insecticidal effects of dinotefuran and imidacloprid. Dα1-deficient flies (Dα1KO) demonstrated the same sensitivity to dinotefuran as control flies, but a decreased sensitivity to imidacloprid. This difference was attributed to a reduction in imidacloprid-binding sites in Dα1KO flies, whereas the binding of dinotefuran remained unchanged. RNA sequencing analysis indicated that Dα2 expression was specifically enhanced in Dα1KO flies. These findings suggest that changes in Dα1 and Dα2 expression contribute to the differences in the insecticidal activity of dinotefuran and imidacloprid in Dα1KO flies. Overall, our findings suggest that dinotefuran acts on distinct nAChR subtypes.