AUTHOR=Sun Wei , Liang Lingjie , Meng Xiangyu , Li Yueqing , Gao Fengzhan , Liu Xingxue , Wang Shucai , Gao Xiang , Wang Li 

TITLE=Biochemical and Molecular Characterization of a Flavonoid 3-O-glycosyltransferase Responsible for Anthocyanins and Flavonols Biosynthesis in Freesia hybrida

JOURNAL=Frontiers in Plant Science

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2016.00410

DOI=10.3389/fpls.2016.00410

ISSN=1664-462X

ABSTRACT=<p>The glycosylation of flavonoids increases their solubility and stability in plants. Flowers accumulate anthocyanidin and flavonol glycosides which are synthesized by UDP-sugar flavonoid glycosyltransferases (UFGTs). In our previous study, a cDNA clone (<italic>Fh3GT1</italic>) encoding UFGT was isolated from <italic>Freesia hybrida</italic>, which was preliminarily proved to be invovled in cyanidin 3-<italic>O</italic>-glucoside biosynthesis. Here, a variety of anthocyanin and flavonol glycosides were detected in flowers and other tissues of <italic>F. hybrida</italic>, implying the versatile roles of <italic>Fh3GT1</italic> in flavonoids biosynthesis. To further unravel its multi-functional roles, integrative analysis between gene expression and metabolites was investigated. The results showed expression of <italic>Fh3GT1</italic> was positively related to the accumulation of anthocyanins and flavonol glycosides, suggesting its potential roles in the biosynthesis of both flavonoid glycosides. Subsequently, biochemical analysis results revealed that a broad range of flavonoid substrates including flavonoid not naturally occurred in <italic>F. hybrida</italic> could be recognized by the recombinant Fh3GT1. Both UDP-glucose and UDP-galactose could be used as sugar donors by recombinant Fh3GT1, although UDP-galactose was transferred with relatively low activity. Furthermore, regiospecificity analysis demonstrated that Fh3GT1 was able to glycosylate delphinidin at the 3-, 4-′, and 7- positions in a sugar-dependent manner. And the introduction of <italic>Fh3GT1</italic> into <italic>Arabidopsis UGT78D2</italic> mutant successfully restored the anthocyanins and flavonols phenotypes caused by lost-of-function of the <italic>3GT</italic>, indicating that <italic>Fh3GT1</italic> functions as a flavonoid 3-<italic>O</italic>-glucosyltransferase <italic>in vivo</italic>. In summary, these results demonstrate that Fh3GT1 is a flavonoid 3-<italic>O</italic>-glycosyltransferase using UDP-glucose as the preferred sugar donor and may involve in flavonoid glycosylation in <italic>F. hybrida.</italic></p>