Overexpression of two α-esterase genes mediates metabolic resistance to malathion in the oriental fruit fly,Bactrocera dorsalis(Hendel)

Abstract

Esterase has been reported to be involved in malathion resistance in the oriental fruit fly, Bactrocera dorsalis (Hendel). However, the underlying molecular mechanism of the esterase-mediated resistance remains largely unknown in this species. Here, with the use of a strain selected for malathion resistance in the laboratory (MR), we found that two overexpressed α-esterase genes, namely BdCarE4 and BdCarE6, predominant in the adult midgut and fat body, function in conferring malathion resistance in B. dorsalis. Notably, these two genes were found to be mostly close to the esterase E3, which are usually implicated in detoxifying organophosphate insecticides. The transcript levels of BdCarE4 and BdCarE6 were investigated and compared between the MR and a susceptible (MS) strain of B. dorsalis. Both genes were significantly up-regulated in the MR strain, which was consistent with the enhanced esterase activity in the MR strain. However, no changes in either the coding sequence or gene copy number were observed between the two strains. Subsequently, heterologous expression combined with cytotoxicity assay in Sf9 cells demonstrated that BdCarE4 and BdCarE6 can probably detoxify malathion. Furthermore, RNA interference-mediated knockdown of each of these two genes significantly increased malathion susceptibility in the MR strain adults. In conclusion, these results expand our molecular understanding of the important role of α-esterases during the development of resistance to organophosphorous insecticides in B. dorsalis.

Involvement of Three Esterase Genes from Panonychus citri (McGregor) in Fenpropathrin Resistance

“…The up-regulation of two α-esterase genes mediated metabolic resistance to malathion in the oriental fruit fly, Bactrocera dorsalis [35]. The increased transcription levels and gene copy numbers of CarE were responsible for malathion resistance of the cotton aphid [32].…”

“…In T. cinnabarinus , TCE2 gene was successfully expressed by E. coli expression system, and subsequent biochemical analysis found the recombinant protein presented 2-fold of the activity of the crude enzyme extracts [41]. As insecticides have previously been reported to express cytotoxic effects, such as oxidative stress in Sf9 cells [35], treatment with fenpropathrin in Sf9 cells can cause cell mortality unless cells are protected by detoxification or sequestration of fenpropathrin. Thus, cell-based inhibition assays employing MTT cytotoxicity assays were conducted to further clarify the detoxification capabilities of recombinant CarEs to fenpropathrin.…”

“…In Anopheles minimus , CYP6P7- or CYP6AA3-expressing cells showed higher detoxification capabilities than parental Sf9 cells against cytotoxicity of pyrethroids [43]. Heterologous expression combined with MTT assay revealed the detoxification role of BdCarE4 and BdCarE6 against malathion [35]. …”

Characterization of a β-Adrenergic-Like Octopamine Receptor in the Oriental Fruit Fly, Bactrocera dorsalis (Hendel)

“…B. dorsalis has greatly expanded its geographical distribution adaptability also due to a powerful reproductive ability [13]. B. dorsalis has evolved high levels of resistance against most commonly used insecticides [14]. Therefore, it is urgent to discover novel targets for the development of insecticides.…”

Biochemical Characterization of Detoxifying Enzymes in Dimethoate-Resistant Strains of Melon Aphid, <i>Aphis gossypii</i>(Hemiptera: Aphididae)

“…Detoxification is conferred by esterases (CarE and AChE), GSTs and MFOs. These enzymes are very important in many OP-resistant insect pests [15] [52] [53]. In this study, biochemical results revealed that an additive interaction of increased CarE, GSTs and PNOD activities in A. gossypii is correlated with resistance to dimethoate indicating metabolic resistance is the one of the means of dimethoate detoxification in the resistant strains.…”