Functional analysis of a novel -glycosyltransferase in the orchid .

Flavonoids, which are a diverse class of phytonutrients, are used by organisms to respond to nearly all abiotic stresses and are beneficial for human health. Glycosyltransferase, used during the last step of flavonoid biosynthesis, is important in flavonoid enrichment. However, little is known about glycosyltransferase in the orchid (). In this study, we isolated a novel -glycosyltransferase (designated ) from the orchid by identifying and analyzing 82 putative genes in the GT1 family. DcaCGT could specifically catalyze not only di-glycosylation but also glycosylation. Apart from the normal function of catalyzing 2-hydroxynaringenin and phloretin to the respective di--glycosides, DcaCGT also catalyzes apigenin to cosmosiin. Targeted metabolic profiling of the substrates (2-hydroxynaringenin, phloretin, and apigenin) and products (vitexin, isovitexin, vicenin-2, nothofagin, 3',5'-di--glucosylphloretin, and cosmosiin) in different tissues showed that vicenin-2 was the most abundant product of this novel enzyme. Cosmosiin was detected in flowers and flower buds. We also established that functions expanded throughout the evolution of . Residual OGT activity may help resist drought stress. Our study illustrates the function, origin, and differentiation of and provides insights into glycosylation and molecular propagation processes, which can be used to improve the production of flavonoids by the cultivated medicinal plant .