Abstract
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 α‐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 μmol/L). High‐performance liquid chromatography analysis demonstrated that the recombinant UGT201D3 could effectively deplete abamectin (15.77% ± 3.72%) incubating with 150 μg protein for 6 h. These results provided direct evidence that UGT201D3 was involved in abamectin resistance in T. cinnabarinus.
Highlights
The carmine spider mite, Tetranychus cinnabarinus (Boisduval), is one of the major agricultural pests worldwide, infesting vegetables and many other crops including cotton, maize and tobacco (Guo et al, 1998; Cakmak & Baspinar, 2005)
The specific activities of UGTs were 1.73 nmol/mg protein/min in AbR strain and 0.74 nmol/mg protein/min in susceptible strain (SS), that is the activity of UGTs in AbR strain was 2.34-fold of that in SS (Table 1), which suggested that the increase of UGT activity was probably correlated with T. cinnabarinus’s resistance against abamectin
The toxicity of abamectin to SS changed without significance in the synergist test, that in AbR strain significantly increased by 56.98% in the synergist treatment
Summary
The carmine spider mite, Tetranychus cinnabarinus (Boisduval), is one of the major agricultural pests worldwide, infesting vegetables and many other crops including cotton, maize and tobacco (Guo et al, 1998; Cakmak & Baspinar, 2005). Many researchers believe that T. cinnabarinus and the two-spotted mite, Tetranychus urticae, are two forms (red and green) of a single species (T. urticae) because of their similarity in morphological, biological and molecular characteristics (de Mendonca et al, 2011; Auger et al, 2013). The control of phytophagous mites has mainly relied on chemical acaricides. The high reproductive potential and extremely short life cycle of these mites, result in rapid resistance development to many acaricides often after only a few applications, which is a major problem for the control of T. cinnabarinus (Devine et al, 2001; Stumpf & Nauen, 2001).
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