Comparative analyses of six cytochrome P450 genes and their roles in differential insecticide susceptibilities between the red flour beetle and the confused flour beetle

Abstract

The red flour beetle (Tribolium castaneum Herbst) and the confused flour beetle (Tribolium confusum Jacquelin du Val) are closely related species commonly infesting stored grains and milled grain products. Although the same insecticides are used to control both species, their susceptibilities to those insecticides often vary considerably. To explore possible contributions of cytochrome P450 (CYP) genes to the differential insecticide susceptibilities between T. castaneum and T. confusum, we selected six CYP orthologous genes to explore their possible contributions to differential insecticide susceptibilities to each of three commonly used insecticides (dichlorvos, pyrethrins, and esfenvalerate). After the expression of each CYP gene was suppressed by RNA interference (RNAi) in late larvae, we examined larval susceptibility to each insecticide. Our results showed that although T. castaneum were more susceptible to dichlorvos than T. confusum, none of these CYP genes appeared to play any significant role in differential dichlorvos susceptibility between the two species. In contrast, there were no significant differences in larval susceptibility to pyrethrins between the two species. However, suppression of CYP4BR3 expression increased larval susceptibility to pyrethrins in T. castaneum at 24 and 72 h after the insecticide exposure, but not in T. confusum. Furthermore, RNAi-mediated suppression of CYP4G7, CYP9Z5, CYP4BR3, and CYP345A1/6 significantly increased larval susceptibility to esfenvalerate in T. castaneum but not in T. confusum at 72 h. In addition, the suppression of CYP4G7 expression increased larval susceptibility to esfenvalerate at 96 h in both species. These results suggest that although CYP4G7 may play some role in esfenvalerate susceptibility in T. confusum, CYP4G7, CYP9Z5, CYP4BR3, and CYP345A1 significantly contribute to differential esfenvalerate susceptibilities between two Tribolium species. This study represents the first study to reveal molecular mechanisms causing differential insecticide susceptibilities between the two Tribolium species.