Identification of UDP-glycosyltransferases involved in the biosynthesis of astringent taste compounds in tea (Camellia sinensis).
Identification of UDP-glycosyltransferases involved in the biosynthesis of astringent taste compounds in tea (Camellia sinensis).
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茶（Camellia sinensis）中涩味化合物生物合成所涉及的 UDP-糖基转移酶的鉴定
DOI：
10.1093/jxb/erw053
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发表时间：
2016-04
影响因子：
6.9
通讯作者：
Xia T
中科院分区：
文献类型：
--
作者：
Cui L;Yao S;Dai X;Yin Q;Liu Y;Jiang X;Wu Y;Qian Y;Pang Y;Gao L;Xia T
茶叶中涩味物质没食子酰化儿茶素和糖基化黄酮醇生物合成中三种UDP-糖基转移酶的鉴定。没食子酰化儿茶素和黄酮醇3-O-糖苷是茶叶中特有的涩味化合物。这些代谢物的形成机制在茶树中仍然未知。本研究共鉴定出178个UGT基因（CsUGTs）。基于对茶树转录组数据的分析，系统发育分析表明，其中132个基因被聚为15个已建立的系统发育群（A至M、O和P）和一个新发现的R群。11个重组UGT蛋白中有3个参与β-glucogallin和糖基化黄酮醇的体外生物合成。CsUGT 84 A22对酚酸，特别是没食子酸，表现出催化活性，以产生β-葡萄糖没食子酸，其是茶树中没食子酰化儿茶素生物合成的直接前体。CsUGT 78 A14和CsUGT 78 A15分别负责黄酮醇3-O-葡萄糖苷和黄酮醇3-O-半乳糖苷的生物合成。CsUGT 78 A14的Q373 H取代的定点突变表明Q（Gln）残基对类黄酮3-O-葡萄糖基转移酶活性起催化关键作用。CsUGT 84 A22、CsUGT 78 A14和CsUGT 78 A15基因的表达谱与β-glucogallin和糖基化黄酮醇的积累模式相关，表明这3个CsUGT基因参与了C. sinensis。
The identification of three UDP-glycosyltransferases involved in the biosynthesis of galloylated catechins and glycosylated flavonols which are astringent taste compounds in tea. Galloylated catechins and flavonol 3-O-glycosides are characteristic astringent taste compounds in tea (Camellia sinensis). The mechanism involved in the formation of these metabolites remains unknown in tea plants. In this paper, 178 UGT genes (CsUGTs) were identified in C. sinensis based on an analysis of tea transcriptome data. Phylogenetic analysis revealed that 132 of these genes were clustered into 15 previously established phylogenetic groups (A to M, O and P) and a newly identified group R. Three of the 11 recombinant UGT proteins tested were found to be involved in the in vitro biosynthesis of β-glucogallin and glycosylated flavonols. CsUGT84A22 exhibited catalytic activity toward phenolic acids, in particular gallic acid, to produce β-glucogallin, which is the immediate precursor of galloylated catechin biosynthesis in tea plants. CsUGT78A14 and CsUGT78A15 were found to be responsible for the biosynthesis of flavonol 3-O-glucosides and flavonol 3-O-galactosides, respectively. Site-directed mutagenesis of the Q373H substitution for CsUGT78A14 indicated that the Q (Gln) residue played a catalytically crucial role for flavonoid 3-O-glucosyltransferase activity. The expression profiles of the CsUGT84A22, CsUGT78A14, and CsUGT78A15 genes were correlated with the accumulation patterns of β-glucogallin and the glycosylated flavonols which indicated that these three CsUGT genes were involved in the biosynthesis of astringent compounds in C. sinensis.