Host-Specific Induction and Functional Characterization of the Carboxylesterase TtCarE-4 in Tetranychus truncatus Adaptation to Woody Host Plants

Abstract

Carboxylesterases (CarEs) are detoxification enzymes that play important roles in xenobiotic metabolism and host adaptation in the polyphagous spider mite Tetranychus truncatus. However, the specific carboxylesterase proteins involved in host plant detoxification in Tetranychus truncatus remain poorly characterized. In this study, we investigated the activities of glutathione S-transferase (GST), carboxylesterase (CarE), and cytochrome P450 (CYP450) in T. truncatus reared on three host plants—common bean, cucumber, and jujube. CarE activity was significantly higher in mites fed on jujube, while CYP450 content increased in mites fed on cucumber. GST activity did not differ significantly among the three host plants, indicating that different hosts induce distinct detoxification responses in T. truncatus. Expression profiling of 24 CarE genes revealed that the carboxylesterase gene TtCarE-4 exhibited the strongest host-specific response, with expression levels 8-fold and 160-fold higher on jujube than on bean and cucumber, respectively, consistent with changes in total CarE enzyme activity. RNAi-mediated silencing of TtCarE-4 reduced its transcript abundance by 32.8%, significantly increased mite mortality, and decreased female fecundity. Off-target analysis indicated that the gene is specifically targeted to T. truncatus and is safe for non-target organisms such as natural enemies. This study provides new insights into the physiological mechanisms of host adaptation in spider mites and identifies the carboxylesterase gene TtCarE-4 as a potential RNAi target for sustainable pest management.