Location: Tropical Crop and Commodity Protection ResearchTitle: Identification of a carboxylesterase associated with resistance to naled in Bactrocera dorsalis (Hendel)
|HSU, PO-KAI - National Taiwan University|
|HUANG, LI-HSIN - Taiwan Agricultural Chemicals And Toxic Substances Research Institute|
|HSU, JU-CHUN - National Taiwan University|
Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2016
Publication Date: 2/4/2016
Citation: Hsu, P., Huang, L., Geib, S.M., Hsu, J. 2016. Identification of a carboxylesterase associated with resistance to naled in Bactrocera dorsalis (Hendel). Pesticide Biochemistry and Physiology. 133:24-31.
Interpretive Summary: The oriental fruit fly (Bactrocera dorsalis) is an important pest fruit fly of many tropical and subtropical fruits and vegetables. Control of this insect includes the use of several different types of pesticides. One of the pesticides used in some regions of the world is naled (an organophosphate) which is often combined in traps or lures with an attractant, methyl eugenol. In this study, a strain of B.dorsalis that was developed to be resistant to naled what characterized to try to determine what mechanism evokes resistance in this line. Using a combination of gene and protein expression assays, the naled resistant line was compared to a susceptible line. It was found that a carboxylesterase was associated with resistance in this line, and the mode of resistance was suggested. These results have important implications in managing pesticide resistance in pest fruit fly species, and provides a basic understanding of resistance to this specific pesticide in this species.
Technical Abstract: Compared to other organophosphate-resistant and -susceptible (S) lines of Bactrocera dorsalis, the carboxylesterase (CBE) BdE5 in the naled-resistant(nal-r) line has been found to possess remarkable quantitative elevation. Our study attempts to identify the role of BdE5 in naled resistance, and we discovered several points of interest. Firstly, activity staining on native PAGE revealed that the percentage of flies with intensive BdE5 bands in the nal-r line was substantially higher than in the S line, indicating that the BdE5 band correlates with naled susceptibility. Secondly, in vitro and in vivo inhibition assays showed that BdE5 was inhibited by naled in both lines; under diagnostic doses of naled, the overall extent of inhibition on CBEs was much greater in the S line than in the nal-r line. Thirdly, NanoLC-nanoESi-MS/MS analysis used the NCBI database to identify and annotate BdE5 as an esterase FE4-like (XP_011200445.1) in B. dorsalis. Fourthly, rapid amplification of cDNA ends was used to obtain the 2012-bp full-length BdE5 cDNA, which contained an open reading frame of 1770 bp and encoded a putative protein of 590 amino acid residues. Phylogenetic analysis revealed that BdE5 is a secreted ß-esterase (E clade) closely related to CG6414 (NP_570089), a CBE in Drosophila melanogaster. Finally, our relative quantification real-time PCR data showed a significant elevation in transcript levels of the BdE5 gene in nal-r line. Our results confirmed that BdE5 is correlated with naled resistance and provides further understanding about the identification and molecular characteristics of BdE5 in B.dorsalis.