Xenobiotic-induced expression of detoxification genes, CYP4H28v2 and CYP4H31v2 in the dengue mosquito Aedes aegypti

ABSTRACT

Synthetic insecticides and other xenobiotic compounds are usually used to abate the effects of insect pests/vectors of agricultural and medical importance by adversely affecting the insects. The xenobiotics are also capable of inducing the expression of detoxification genes such as the cytochrome P450 (CYP) gene in targeted insects like mosquitoes (Feyereisen, 2012). The high expression levels of CYPs in insecticide-resistant and exposed mosquitoes have been linked with a potential role in xenobiotic resistance. This study investigated the induction potential of leaf litter infusions and insecticides on the expressions of CYP4H28v2 and CYP4H31v2 in the dengue mosquito Aedes aegypti using Reverse Transcription-quantitative Polymerase Chain Reaction. Exposure of Ae. aegypti larvae to leaf litter infusions demonstrated that CYP4H28v2 and CYP4H31v2 were significantly induced by Lagerstroemia speciosa but not Ficus benjamina, Plumeria obtusa, Millettia pinnata and Pithecellobium dulce. None of the genes was significantly highly expressed in adult females exposed to d-allethrin and d-trans allethrin products. CYP4H28v2 was significantly induced in Ae. aegypti exposed to DDT, malathion and permethrin for both 5 and 10 min. DDT, malathion and permethrin significantly induced CYP4H31v2 only in Ae. aegypti exposed to the insecticides for 10 min. Exposure to the insecticides for 5 min displayed different levels of CYP4H31v2 expression with significantly higher (DDT-exposed) and lower (permethrin-exposed) levels in the mosquito. The results show that natural and synthetic xenobiotics can induce significant expression of CYP4H28v2 and CYP4H31v2 in the mosquito, indicating the potential role of the genes in mediating xenobiotic resistance. This may enhance the survival capabilities of the mosquito when in contact with phytotoxins of leaf litter in their natural ecosystem and synthetic insecticides in adulticide spray regimens.