Functional analysis of a carboxylesterase gene involved in beta‐cypermethrin and phoxim resistance in Plutella xylostella (L.)

Abstract

BACKGROUND Carboxylesterases (CarEs) are associated with detoxification of xenobiotics, including insecticides, in organism bodies. Overexpression of CarE genes is considered to have an important role in insecticide resistance in insects, however its involvement in multi‐insecticide resistance has rarely been reported. This study aimed to assess the function of a CarE gene (PxαE8) in resistance to five insecticides in Plutella xylostella. RESULTS Relative expression of PxαE8 in three multi‐insecticide‐resistant Plutella xylostella populations, GD‐2017, GD‐2019 and HN, was14.8‐, 19.5‐ and 28.0‐fold higher than that in the susceptible population. Exposure to lethal concentrations associated with 25% mortality (LC25) of beta‐cypermethrin, chlorantraniliprole, metaflumizone, phoxim and tebufenozide could induce the specific activity of CarEs and increase the relative expression of PxαE8. By contrast, knockdown of PxαE8 expression dramatically reduced the activity of CarEs and increased the resistance of P. xylostella (GD‐2019) larvae to beta‐cypermethrin and phoxim by 47.4% and 45.5%, respectively. Further, a transgenic line of Drosophila melanogaster overexpressing PxαE8 was constructed and the bioassay results showed that the tolerance of transgenic Drosophila to beta‐cypermethrin and phoxim was 3.93‐ and 3.98‐fold higher than that of the untransgenic line. CONCLUSION These results provide evidence that overexpression of PxαE8 is involved in resistance, at least to beta‐cypermethrin and phoxim, in multi‐insecticide‐resistant P. xylostella populations, which could help in further understanding the molecular mechanisms of multi‐insecticide resistance in this pest. © 2020 Society of Chemical Industry

Overexpression of PxαE14 Contributing to Detoxification of Multiple Insecticides in Plutella xylostella (L.)

“…Many CarE genes have been identified to be responsible for insecticide resistance in different pests due to overexpression and thus enhanced detoxification, especially in resistance to pyrethroids and organophosphates. 19,20,23 In P. xylostella, several CarE genes have also been reported to participate in insecticide resistance, such as PxCCE016b in chlorantraniliprole resistance, 43 Pxae18 and Pxae28 in chlorpyrifos resistance, 44 and PxαE8 in β-cypermethrin and phoxim resistance. 23,27 In this study, PxαE14 is found to be overexpressed in the GD population, a field-evolved resistant population with moderate to extremely high resistance to at least nine insecticides.…”

“…19,20,23 In P. xylostella, several CarE genes have also been reported to participate in insecticide resistance, such as PxCCE016b in chlorantraniliprole resistance, 43 Pxae18 and Pxae28 in chlorpyrifos resistance, 44 and PxαE8 in β-cypermethrin and phoxim resistance. 23,27 In this study, PxαE14 is found to be overexpressed in the GD population, a field-evolved resistant population with moderate to extremely high resistance to at least nine insecticides. The spatiotemporal expression profile assay with the SS population showed that PxαE14 was constitutively expressed in all body parts/tissues and abundant in the midgut, malpighian tubule, and fat body of fourth instars, which are the primary detoxification tissues and considered to be responsible for detoxification of xenobiotics including insecticides.…”

“…RNAi and transgenic D. melanogaster systems have been widely used for gene function exploration through “lose of function” and “gain of function,” respectively, especially in the functional characterization of insecticide resistance-related genes. ,, Both techniques were used to further explore the functions of PxαE14 in multiresistance. The repression of PxαE14 caused reduced resistance, and PxαE14 overexpression resulted in increased resistance, implying that the overexpression of PxαE14 was involved in resistance to three pyrethroid and three organophosphorus insecticides in the GD population of P.…”

“…8 Carboxylesterases (CarEs) are a kind of phase I detoxifying enzymes and capable of hydrolyzing a broad range of estercontaining xenobiotics including different classes of insecticides such as pyrethroids, 9 organophosphates, carbamates, 10 neonicotinoids, 11 oxadiazine, 12 and biogenic pesticides. 13 Overexpression and mutation are two major mechanisms for CarE-mediated insecticide resistance through enhanced detoxification of insecticides, 14,15 which has been widely reported in Myzus persicae, 16 Culex mosquitoes, 17 Drosophila melanogaster, 18 Bemisia tabaci, 19 Aphis gossypii, 20 Lucilia cuprina, 21 Nilaparvata lugens, 11 Tetranychus urticae, 22 P. xylostella, 23 and Spodoptera litura. 24 Generally, there are two ways for CarEs to contribute to insecticide metabolism; one is to delay or prevent the interaction between insecticides and the target site through sequestration, and the other is the enhanced metabolism of the insecticides.…”

“…Overexpression and mutation are two major mechanisms for CarE-mediated insecticide resistance through enhanced detoxification of insecticides, , which has been widely reported in Myzus persicae, Culex mosquitoes, Drosophila melanogaster, Bemisia tabaci, Aphis gossypii, Lucilia cuprina, Nilaparvata lugens, Tetranychus urticae, P. xylostella, and Spodoptera litura . Generally, there are two ways for CarEs to contribute to insecticide metabolism; one is to delay or prevent the interaction between insecticides and the target site through sequestration, and the other is the enhanced metabolism of the insecticides. , Although CarE-mediated insecticide resistance and the underlying mechanisms have been extensively investigated, the roles of CarEs in detoxification of multiple insecticides are rarely reported.…”