Abstract
Herbivore attack is a major type of biotic stress that greatly affects the development and quality of tea plant [Camellia sinensis (L) O. Kuntze]. Tea plant produces many glycosylated compounds that enhance resistance to herbivores. An example is quercetin, one of the major flavonols of tea plants, which was glycosylated to involve responses to various environmental stresses. However, not much is known about the biosynthesis of glycosylated quercetin derivatives in tea plant in response to herbivorous attack. Here, we found that E. grisescens attack significantly increased the contents of quercetin 3-O-glucoside and quercetin 7-O-glucoside in tea leaves, and exogenous application of these two compounds improved the E. grisescens resistance of tea plant. Integrated transcriptome and phylogenetic analyses identified CsUGT95B11 gene, encoding a quercetin glycosyltransferase, which was upregulated in response to E. grisescens attack. Enzymatic assays showed that CsUGT95B11 preferentially glycosylated quercetin to produce quercetin 7-O-glucoside with a kcat·Km–1 value of 9655.52 M–1·s–1. Subcellular localization analysis indicated that CsUGT95B11 was dispersed in the cytoplasm of Nicotiana benthamiana leaves and Arabidopsis protoplast. Suppression of CsUGT95B11 reduced the quercetin glucoside content of tea leaves and impaired resistance of tea plant to E. grisescens. These results indicate that CsUGT95B11 is a quercetin glycosyltransferase that enhances resistance of tea plant to E. grisescens, providing insights into the mechanism of flavonol glycosylation regulating interactions between plants and herbivores.
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