Abstract
BackgroundPyrethroid insecticides, especially permethrin and deltamethrin, have been used extensively worldwide for mosquito control. However, insecticide resistance can spread through a population very rapidly under strong selection pressure from insecticide use. The upregulation of aldehyde dehydrogenase (ALDH) has been reported upon pyrethroid treatment. In Aedes aegypti, the increase in ALDH activity against the hydrolytic product of pyrethroid has been observed in DDT/permethrin-resistant strains. The objective of this study was to identify the role of individual ALDHs involved in pyrethroid metabolism.Methodology/Principal FindingsThree ALDHs were identified; two of these, ALDH9948 and ALDH14080, were upregulated in terms of both mRNA and protein levels in a DDT/pyrethroid-resistant strain of Ae. aegypti. Recombinant ALDH9948 and ALDH14080 exhibited oxidase activities to catalyse the oxidation of a permethrin intermediate, phenoxybenzyl aldehyde (PBald), to phenoxybenzoic acid (PBacid).Conclusions/SignificanceALDHs have been identified in association with permethrin resistance in Ae. aegypti. Characterisation of recombinant ALDHs confirmed the role of this protein in pyrethroid metabolism. Understanding the biochemical and molecular mechanisms of pyrethroid resistance provides information for improving vector control strategies.
Highlights
Pyrethroids, synthetic insecticides analogous to natural pyrethrin, have been widely used throughout the world for the control of insects
Identification of Ae. aegypti aldehyde dehydrogenase (ALDH) The DNA sequence of ALDH (AAEL014080) in Ae. aegypti was retrieved from VectorBase, and it is located in supercontig 1.1002
Close paralogues of ALDH (AAEL014080), ALDH (AAEL009948) and ALDH (AAEL009029) were included in the experiment to expand for genes of interest that were found on supercontigs 1.440 and 1.363, respectively (Figure S1)
Summary
Pyrethroids, synthetic insecticides analogous to natural pyrethrin, have been widely used throughout the world for the control of insects. The extensive use of these insecticides has led to insecticide resistance in insect populations [1,2,3]. Resistance to pyrethroids can be divided into two main mechanisms: an alteration in the target site of the insecticide or increased expression of metabolic detoxification enzymes. Pyrethroids act by targeting sodium channels, leading to neurotoxic effects [4]. In metabolic resistance, enhanced activity of enzymes in metabolic pathways in insects leads to insecticides being detoxified or sequestered before they reach the target site. Pyrethroid insecticides, especially permethrin and deltamethrin, have been used extensively worldwide for mosquito control. In Aedes aegypti, the increase in ALDH activity against the hydrolytic product of pyrethroid has been observed in DDT/permethrin-resistant strains. The objective of this study was to identify the role of individual ALDHs involved in pyrethroid metabolism
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