title: Functional characterization of an α-esterase gene involving malathion detoxification in Bactrocera dorsalis (Hendel).
abstract: Extensive use of insecticides in many orchards has prompted resistance development in the oriental fruit fly, Bactrocera dorsalis (Hendel). In this study, a laboratory selected strain of B. dorsalis (MR) with a 21-fold higher resistance to malathion was used to examine the resistance mechanisms to this organophosphate insecticide. Carboxylesterase (CarE) was found to be involved in malathion resistance in B. dorsalis from the synergism bioassay by CarE-specific inhibitor triphenylphosphate (TPP). Molecular studies further identified a previously uncharacterized α-esterase gene, BdCarE2, that may function in the development of malathion resistance in B. dorsalis via gene upregulation. This gene is predominantly expressed in the Malpighian tubules, a key insect tissue for detoxification. The transcript levels of BdCarE2 were also compared between the MR and a malathion-susceptible (MS) strain of B. dorsalis, and it was significantly more abundant in the MR strain. No sequence mutation or gene copy changes were detected between the two strains. Functional studies using RNA interference (RNAi)-mediated knockdown of BdCarE2 significantly increased the malathion susceptibility in the adult files. Furthermore, heterologous expression of BdCarE2 combined with cytotoxicity assay in Sf9 cells demonstrated that BdCarE2 could probably detoxify malathion. Taken together, the current study bring new molecular evidence supporting the involvement of CarE-mediated metabolism in resistance development against malathion in B. dorsalis and also provide bases on functional analysis of insect α-esterase associated with insecticide resistance.
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Luo-Luo
authors.initials: LL
authors.lastname: Wang
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Xue-Ping
authors.initials: XP
authors.lastname: Lu
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Meng
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Wei
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China.
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China; Department of Crop Protection, Ghent University, B-9000 Ghent, Belgium.
authors.forename: Guy
authors.initials: G
authors.lastname: Smagghe
authors.affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing 400716, China. Electronic address: jjwang7008@yahoo.com.
authors.forename: Jin-Jun
authors.initials: JJ
authors.lastname: Wang
mesh_terms: D000818:Animals; D043182:Carboxylesterase / Q000235:genetics* / Q000378:metabolism; D055785:Gene Knockdown Techniques; D017344:Genes, Insect / Q000235:genetics*; D007305:Insecticide Resistance / Q000235:genetics*; D008294:Malathion / Q000378:metabolism*; D010802:Phylogeny; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D033621:Tephritidae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*
chemical_list: D043182:Carboxylesterase; D008294:Malathion
keywords: Carboxylesterase; Cytotoxicity assay; Heterologous expression; Malathion resistance; RNAi