Functional analysis of UGT201D3 associated with abamectin resistance in Tetranychus cinnabarinus (Boisduval)

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are widely distributed within living organisms and share roles in biotransformation of various lipophilic endo- and xenobiotics with activated UDP sugars. In this study, it was found that the activity of UGTs in abamectin-resistant (AbR) strain was significantly higher (2.35-fold) than that in susceptible strain (SS) of Tetranychus cinnabarinus. Further analysis showed that 5-nitrouracil, the inhibitor of UGTs, could enhance the lethal effect of abamectin on mites. From the previous microarray results, we found an UGT gene (UGT201D3) overexpressed in AbR strain. Quantitative PCR analysis showed that UGT201D3 was highly expressed and more inducible with abamectin exposure in the AbR strain. After silencing the transcription of UGT201D3, the activity of UGTs was decreased and the susceptibility to abamectin was increased in AbR strain whereas it was not in SS. Furthermore, UGT201D3 gene was then successfully expressed in Escherichia coli. The recombinant UGT201D3 exhibited alpha-naphthol activity (2.81 +/- 0.43 nmol/mg protein/min), and the enzyme activity could be inhibited by abamectin (inhibitory concentration at 50%: 57.50 +/- 3.54 mu mol/L). High-performance liquid chromatography analysis demonstrated that the recombinant UGT201D3 could effectively deplete abamectin (15.77% +/- 3.72%) incubating with 150 mu g protein for 6 h. These results provided direct evidence that UGT201D3 was involved in abamectin resistance in T. cinnabarinus.