Effects of nicotinic acetylcholine receptor subunit deletion mutants on insecticide susceptibility and fitness in Drosophila melanogaster

Abstract

BACKGROUND: Nicotinic acetylcholine receptors (nAChRs) are major excitatory neurotransmitter receptors in insects and also the target site for many insecticides. Unfortunately, the effectiveness of these insecticides is diminishing as a consequence of the evolution of insecticide resistance. Further exploration of insecticide targets is important to sustainable pest management.RESULTS: In order to validate the role of nAChR subunits in insecticide susceptibility and test whether the subunit's absence imposes the fitness cost on insects, we determined the susceptibility of eight nAChR subunit deletion mutants of Drosophila melanogaster to nine insecticides. These findings highlighted the specific resistance of the D⊍6 deletion mutant to spinosyns. Although triflumezopyrim, dinotefuran and imidacloprid are competitive modulators of nAChRs, differences in susceptibility of the insect with different deletion mutants suggested that the target sites of these three insecticides do not overlap completely. Mutants showed decreased susceptibility to insecticides, accompanied by a reduction in fitness. The number of eggs produced by D⊍1 attP , D⊍2 attP , D⊎2 attP and D⊎3 attP females was significantly lesser than that of the vas-Cas9 strain as the control. In addition, adults of D⊍2 attP , D⊍3 attP and D⊍7 attP strains showed lower climbing performance. Meanwhile, males of D⊍3 attP , D⊍5 attP , D⊎2 attP and D⊎3 attP , and females of D⊎2 attP showed significantly shorter longevity than those of the vas-Cas9 strain.CONCLUSION: This study provides new insights into the interactions of different insecticides with different nAChRs subunit in D. melanogaster as a research model, it could help better understand such interaction in agricultural pests whose genetic manipulations for toxicological research are often challenging.