Contribution of multiple overexpressed carboxylesterase genes to indoxacarb resistance in Spodoptera litura

Abstract

BACKGROUND As an important family of detoxification enzymes, carboxylesterases (CarEs) have important roles in the development of insecticide resistance in almost all agricultural pests. Previous studies have suggested that enhancement of CarE activity is an important mechanism mediating indoxacarb resistance in Spodoptera litura, and several CarE genes have been found to be overexpressed in indoxacarb‐resistant strains. However, the functions of these CarE genes in indoxacarb resistance needs to be further investigated. RESULTS The synergist triphenyl phosphate effectively reduced the resistance of S. litura to indoxacarb, suggesting an involvement of CarEs in indoxacarb resistance. Among seven identified S. litura CarE genes (hereafter SlituCOE), six were overexpressed in two indoxacarb‐resistant strains, but there were no significant differences in gene copy number. Knockdown of SlituCOE009 and SlituCOE050 enhanced indoxacarb sensitivity in both susceptible and resistant strains, whereas knockdown of SlituCOE090, SlituCOE093 and SlituCOE074 enhanced indoxacarb sensitivity in only the resistant strain. Knockdown of the sixth gene, SlituCOE073, did not have any effect. Furthermore, simultaneous knockdown of the five SlituCOE genes had a greater effect on increasing indoxacarb sensitivity than silencing them individually. By contrast, overexpression of the five SlituCOE genes individually in Drosophila melanogaster significantly decreased the toxicity of indoxacarb to transgenic fruit flies. Furthermore, modeling and docking analysis indicated that the catalytic pockets of SlituCOE009 and SlituCOE074 were ideally shaped for indoxacarb and N‐decarbomethoxylated metabolite (DCJW), but the binding affinity for DCJW was stronger than for indoxacarb. CONCLUSION This study reveals that multiple overexpressed CarE genes are involved in indoxacarb resistance in S. litura.

Characterization of Indoxacarb Resistance in the Fall Armyworm: Selection, Inheritance, Cross-Resistance, Possible Biochemical Mechanisms, and Fitness Costs

“…Indoxacarb is a potent novel insecticide for crop protection because to its safety for humans and non-target organisms, superior environmental and residual qualities, broad spectrum, and quick reduction in insect feeding [ 24 ]. However, numerous studies have indicated that a number of insects have recently evolved resistance to indoxacarb due to its widespread use, including S. litura [ 29 ], such as C. rosaceana [ 30 ], M. domestica [ 31 ], S. exigua [ 32 ], P. xylostella [ 33 ] and H. armigera [ 34 ] have developed a significant level of resistance. Furthermore, resistance to several Bt maize products expressing Cry1F and Cry1Ab proteins has been reported in the field, increasing the use of chemical insecticides against S. frugiperda in maize [ 13 , 35 ].…”

Effects of Methyl Jasmonate Fumigation on the Growth and Detoxification Ability of Spodoptera litura to Xanthotoxin

“…However, despite its function in interplant communication, the specific role of MeJA in insect defense responses is poorly understood. The tobacco cutworm, Spodoptera litura (Fabricius), is a major widespread and broadly polyphagous pest that feeds on a variety of important economic crops, such as tomato, cotton, soybean, tobacco, and peanut [ 44 ]. In this study, we analyzed the growth of S. litura and its detoxification ability against xanthotoxin after exposure to different concentrations of MeJA fumigation, and the effective role of MeJA in inducing insects’ defense responses to the toxin was studied.…”

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

“…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.…”