Abstract
Flavonoids are one of the well-studied secondary metabolites with over 6,000 known structures. The huge diversity is derived from modifications such as glycosylation, acylation and methylation. The structures of nineteen flavonoids in Arabidopsis suggest that at least nine family 1-type glycosyltransferases (UGT) are involved in flavonoid modification pathway. However, only four UGT genes were identified. In Arabidopsis, UGTs are encoded by 107 genes. Their huge diversity makes it difficult to estimate their physiological functions distinctively.
By coexpression analysis of public microarray datasets, we found a UGT gene, UGT1, which is highly correlated with flavonoid biosynthetic genes. The deduced amino acid sequence and flavonoid target analysis of the mutants suggest that UGT1 encodes flavonoid 7-O-rhamnosyltransferase (7RhaT). We identified that UGT1 functions as flavonol 7RhaT by UGT1 recombinant protein and a complementation test of the T-DNA insertion mutants. Substrate specificity of UGT1 and putative flavonol glycosylation pathway are also discussed.
