Alternative splicing of a carboxyl/choline esterase gene enhances the fenpropathrin tolerance of Tetranychus cinnabarinus

Detoxification plays a crucial role in agricultural pests to withstand pesticides, and cytochrome P450s, carboxyl/choline esterases (CCEs), and glutathione-S-transferases are the main proteins responsible for their detoxification ability. The activity of CCEs can be upregulated, downregulated, or modified by mutation. However, few studies have examined the role of alternative splicing in altering the properties of CCEs. We identified 2 variants of TcCCE23 in Tetranychus cinnabarinus: a long version (CCE23-V1) and a short version that is 18 nucleotides shorter than CCE23-V1 (CCE23-V2). Whether splicing affects the activity of TcCCE23 remains unclear. Overexpression of CCE23-V2 in fenpropathrin-resistant T. cinnabarinus revealed that splicing affected the detoxification of fenpropathrin by CCE23-V2. The mortality of mites was significantly higher when the expression of CCE23-V2 was knocked down (43.2% ± 3.3%) via injection of CCE23-dsRNA (double-stranded RNA) compared with the control group injected with green fluorescent protein-dsRNA under fenpropathrin exposure; however, the downregulation of CCE23-V1 (61.3% ± 6.3%) by CCE23-small interfering RNA had no such effect, indicating CCE23-V2 plays a greater role in xenobiotic metabolism than CCE23-V1. The tolerance of flies overexpressing CCE23-V2 to fenpropathrin (50% lethal dose [LD50 ] = 19.47 μg/g) was significantly higher than that of Gal4/UAS-CCE23-V1 transgenic flies (LD50 = 13.11 μg/g). Molecular docking analysis showed that splicing opened a "gate" that enlarges the substrate binding cavity of CCE23-V2, might enhance the ability of CCE23-V2 to harbor fenpropathrin molecules. These findings suggest that splicing might enhance the detoxifying capability of TcCCE23. Generally, our data improve the understanding of the diversity and complexity of the mechanisms underlying the regulation of CCEs.