OsSGT1 Is a Glucosyltransferase Gene Involved in the Glucose Conjugation of Phenolics in Rice

Phenolics are a class of plant secondary metabolites that play important roles in plant growth and environmental adaptation. Glucosylation of phenolics is one of the molecular mechanisms controlling phenolics homeostasis. However, the relevant glucosyltransferases are largely unknown. In this study, a putative family 1 glucosyltransferase gene OsSGT1 was cloned from rice due to its close homology with the previously reported phenolics-related glucosyltransferases UGT84A1-A4, and the phylogenetic relationship of OsSGT1 with homologs from other species was investigated. Recombinant OsSGT1 protein showed strong activity towards phenolics to form their glucose conjugates. This is the first identified natural phenolics-related glucosyltransferase in rice. In addition, the expression patterns of OsSGT1 in different tissues of rice indicated that OsSGT1 was predominantly expressed in the old leaves and dough grains, suggesting that OsSGT1 might be involved in the maturation process of rice by regulating phenolic metabolism, and thus deepened our understanding on the roles of phenolics in rice growth and environmental adaptation.