The dynamics of pyrethroid residues and Cyp P450 gene expression in insects depends on the circadian clock

Abstract

A circadian clock may underlie pesticide resistance mechanisms in organisms that are very important for humans, for example, in the honey bee (Apis mellifera). Using the gas chromatography, we evaluated the daily variability in the λ-cyhalothrin degradation rate in bodies of guards and forager bees, Apis mellifera. Additionally, using the RT-qPCR method, we studied expression levels of selected cytochrome P450 genes after exposure to λ-cyhalothrin. During 48-h-tests, we exposed bees to λ-cyhalothrin at four crucial times of the day: at 04:30 a.m., 11:30 a.m., 06:30 p.m., and 11:30 p.m. The results obtained indicate that in bees the intensity of the λ-cyhalothrin degradation is the highest during first 6 h after intoxication, when it disappeared at the rate of 14.29% h−1, 11.43% h−1, 13.15% h−1, and 12.50% h−1 in bees treated at noon, sunset, midnight, and sunrise, respectively. In the later period (6–48 h of the experiment), the degradation stopped and its rate did not exceed 1.0% h−1. In the control group of bees we demonstrated that the increase in the Cyp9Q1 and Cyp9Q3 expression was the highest during the experiments started at 04:30 a.m., while the highest elevation in the Cyp9Q2 expression was observed in the group for which the experiments started at 11:30 p.m.In intoxicated honey bees, the highest increase in the Cyp9Q1 expression occurred in the group treated with the pesticide at 11:30 a.m. In the case of genes encoding Cyp9Q2 and Cyp9Q3, the highest rise in the expression took place at 06:30 p.m.The obtained results indicate that honey bees activate detoxifying mechanisms partly protecting them against the effects of hazardous substances absorbed from the environment more efficiently during foraging than at other times of the day.