Tebufenozide induces upregulation of an ABC-transporter but not cytochrome P450s in resistant smaller tea tortrix, Adoxophyes honmai

The smaller tea tortrix, Adoxophyes honmai, is a lepidopteran pest of tea in Japan. They have developed resistance to multiple insecticides including tebufenozide across the full range of Japan. Previous studies found that tebufenozide-resistant tea tortrix constitutively upregulates detoxification genes such as cytochrome P450s compared to susceptible strains. Defenses against stressors can be constitutive and/or inducible, and the inducible defenses against tebufenozide remain unknown in the smaller tea tortrix. To investigate the inducible responses to tebufenozide in the smaller tea tortrix, we exposed animals from a susceptible and a resistant strain to two doses of tebufenozide over six hours. We monitored the expression of hormone receptor 3 as a positive control of tebufenozide exposure. At each dose, susceptible animals upregulated the expression of hormone receptor 3 more than susceptible animals, indicating successful treatment as well as differential response between strains. We confirmed that resistant animals constitutively upregulated multiple cytochrome P450 genes associated with tebufenozide resistance, but these genes were not inducible by tebufenozide in either strain. Interestingly, we found that an ABC-transporter gene did not differ in constitutive expression between strains; however, it is induced by tebufenozide in a dose-dependent fashion only in the resistant strain. Our results suggest that plastic responses contribute to tebufenozide resistance in conjunction with constitutive defenses in the smaller tea tortrix, and may have implications for the dynamics of tebufenozide detoxification and the evolution of different resistance mechanisms.