Characterization of UDP-Glucuronosyltransferases and the Potential Contribution to Nicotine Tolerance in .

Uridine diphosphate (UDP)-glycosyltransferases (UGTs) are major phase II detoxification enzymes involved in glycosylation of lipophilic endobiotics and xenobiotics, including phytoalexins. Nicotine, one of the most abundant secondary plant metabolites in tobacco, is highly toxic to herbivorous insects. Plant-herbivore competition is the major impetus for the evolution of large superfamilies of and other detoxification enzymes. However, UGT functions in green peach aphid () adaptation are unknown. In this study, we show that UGT inhibitors (sulfinpyrazone and 5-nitrouracil) significantly increased nicotine toxicity in , suggesting that UGTs may be involved in nicotine tolerance. In total, 101 transcripts identified in the genome/transcriptome were renamed according to the UGT Nomenclature Committee guidelines and grouped into 11 families, UGT329, UGT330, UGT339, UGT341-UGT345, and UGT348-UGT350, with UGT344 containing the most (57). Ten (, , , , , , , , , and ) were highly expressed in compared to sensu stricto. Knockdown of four UGTs (, , , and ) significantly increased sensitivity to nicotine, suggesting that expression in this subspecies may be associated with nicotine tolerance and thus host adaptation. This study reveals possible relevant to nicotine adaptation in tobacco-consuming , and the findings will facilitate further validation of the roles of these in nicotine tolerance.