Abstract
Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are major phase II enzymes that conjugate a variety of small lipophilic molecules with UDP sugars and alter them into more water-soluble metabolites. Therefore, glucosidation plays a major role in the inactivation and excretion of a great variety of both endogenous and exogenous compounds. In this study, two inhibitors of UGT enzymes, sulfinpyrazone and 5-nitrouracil, significantly increased the toxicity of thiamethoxam against the resistant strain of Aphis gossypii, which indicates that UGTs are involved in thiamethoxam resistance in the cotton aphid. Based on transcriptome data, 31 A. gossypii UGTs belonging to 11 families (UGT329, UGT330, UGT341, UGT342, UGT343, UGT344, UGT345, UGT348, UGT349, UGT350, and UGT351) were identified. Compared with the thiamethoxam-susceptible strain, the transcripts of 23 UGTs were elevated, and the transcripts of 13 UGTs (UGT344J2, UGT348A2, UGT344D4, UGT341A4, UGT343B2, UGT342B2, UGT350C3, UGT344N2, UGT344A14, UGT344B4, UGT351A4, UGT344A11, and UGT349A2) were increased by approximately 2.0-fold in the resistant cotton aphid. The suppression of selected UGTs significantly increased the insensitivity of resistant aphids to thiamethoxam, suggesting that the up-regulated UGTs might be associated with thiamethoxam tolerance. This study provides an overall view of the possible metabolic factor UGTs that are relevant to the development of insecticide resistance. The results might facilitate further work to validate the roles of these UGTs in thiamethoxam resistance.
Highlights
Uridine diphosphate (UDP)-glycosyltransferases (UGTs, EC 2.4.1.17) catalyze the conjugation of a range of small lipophilic compounds with sugars to produce glycosides, which are soluble in water and can be efficiently excreted (Mackenzie et al, 1997)
Due to the extensive use of the neonicotinoid insecticide imidacloprid for controlling cotton aphids in the field, the resistance to imidacloprid ranged from 1.48 to >1,200-fold among different A. gossypii populations collected from various Bt cotton planting areas in China in 2014, and the LC50value of imidacloprid was >5,000 mg/L in the population from Yuncheng of Shanxi Province (Chen et al, 2017)
Thiamethoxam has been used as an alternative neonicotinoid insecticide for the control of cotton aphids
Summary
Uridine diphosphate (UDP)-glycosyltransferases (UGTs, EC 2.4.1.17) catalyze the conjugation of a range of small lipophilic compounds with sugars to produce glycosides, which are soluble in water and can be efficiently excreted (Mackenzie et al, 1997). Research studies have indicated that enhanced detoxification caused by P450 gene overexpression accounts for neonicotinoids in Bemisia tabaci, Myzus persicae, and Nilaparvata lugens (Karunker et al, 2008, 2009; Puinean et al, 2010; Bao et al, 2016; Zhang et al, 2016). Consistent with these reports, our previous synergism analysis demonstrated that P450s are involved in thiamethoxam resistance in A. gossypii (Wei et al, 2017). The results might facilitate further study of the functions in UGTs in the insecticide resistance of A. gossypii
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