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Published on: January 24, 2013
Circadian rhythms in insecticide susceptibility, metabolic enzyme activity, and gene expression in Cimex lectularius
Muhammad Fazli Khalid1, Chow-Yang Lee2, Stephen L Doggett3
1Centre for Chemical Biology, Universiti Sains Malaysia, Bayan Lepas, Penang, Malaysia.
Abstract:
Many insect species display daily variation of sensitivity to insecticides when they are exposed to the same concentration at different times during the day. To date, this has not been investigated in bed bugs. To address this, we explored circadian rhythms in insecticide susceptibility, xenobiotic metabolizing (XM) gene expressions, and metabolic detoxification in the common bed bug, Cimex lectularius. An insecticide susceptible Monheim strain of C. lectularius was most tolerant of deltamethrin during the late photophase at ZT9 (i.e. nine hours after light is present in the light-dark cycle (LD) cycle) and similarly repeated at CT9 (i.e. nine hours into the subjective day in constant darkness (DD)) suggesting endogenous circadian involvement in susceptibility to deltamethrin. No diel rhythm was observed against imidacloprid insecticide despite significant daily susceptibility in both LD and DD conditions. Rhythmic expressions of metabolic detoxification genes, GSTs1 and CYP397A1 displayed similar expression patterns with total GST and P450 enzyme activities in LD and DD conditions, respectively. The oscillation of mRNA levels of GSTs1 and CYP397A1 was found consistent with peak phases of deltamethrin susceptibility in C. lectularius. This study demonstrates that circadian patterns of metabolic detoxification gene expression occur within C. lectularius. As a consequence, insecticide efficacy can vary dramatically throughout a 24 hour period.
Insights
Bed bugs show daily changes in insecticide sensitivity, with tolerance to deltamethrin peaking at specific times. This variation is linked to circadian rhythms in detoxification genes, impacting insecticide effectiveness.
Area of Science:
- Entomology
- Chronobiology
- Pest Management
Background:
- Insecticide resistance is a growing problem in pest control.
- Daily variations in insecticide sensitivity have been observed in many insect species.
- Circadian rhythms influence physiological processes, potentially affecting insecticide metabolism.
Purpose of the Study:
- To investigate circadian rhythms in insecticide susceptibility in the common bed bug, Cimex lectularius.
- To examine the daily expression patterns of xenobiotic metabolizing (XM) genes and enzyme activities.
- To determine if circadian rhythms influence metabolic detoxification and insecticide efficacy in bed bugs.
Main Methods:
- Exposure of susceptible bed bugs (Monheim strain) to deltamethrin and imidacloprid at different times of day under light-dark and constant darkness conditions.
- Quantification of mRNA levels for detoxification genes (GSTs1 and CYP397A1).
- Measurement of total GST and P450 enzyme activities.
Main Results:
- Bed bugs exhibited peak tolerance to deltamethrin during the late photophase (ZT9/CT9), suggesting circadian involvement.
- No diel rhythm in susceptibility was observed for imidacloprid.
- Rhythmic expression of GSTs1 and CYP397A1 correlated with deltamethrin susceptibility, indicating circadian control of detoxification.
Conclusions:
- Circadian rhythms significantly influence deltamethrin susceptibility in Cimex lectularius.
- Metabolic detoxification gene expression oscillates, impacting the timing of peak insecticide efficacy.
- Understanding these rhythms can optimize bed bug control strategies.
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