记者日前从中国科学院植物研究所获悉，该所研究员庞永珍研究组以类黄酮含量丰富的茶叶和百脉根为研究对象，对类黄酮未知生物合成机理，特别是类黄酮糖基化的分子机制展开研究。揭示了特异的糖基转移酶（UGT）基因亚家族在类黄酮糖基化中的意义以及在植物生长发育中的功能。相关成果在线发表在国际学术期刊《实验植物学杂志》（Journal of Experimental Botany）上。 

　　研究人员在基因组水平上，从茶叶和百脉根中分别鉴定了178和188个UGT基因，通过对这些基因进行的系统进化、组织表达谱和分子对接分析，从中筛选了30多个UGT主要候选基因。通过体外酶活检测，研究人员最终发现了参与合成茶叶涩味类黄酮糖苷以及百脉根主要成分黄酮醇糖苷的关键UGT基因，并分析比较了这些糖基转移酶的酶动力学参数和体内外功能。 

　　据了解，类黄酮化合物是对植物、动物和人类健康都具有益处的一大类植物次生代谢产物，主要以糖基化的形式广泛存在于植物不同部位。类黄酮的糖基化是由UGT基因编码的糖基转移酶所催化的。UGT家族基因在植物进化的过程中不断扩增、分化和特化，形成了具有不同底物特异性和区域特异性的UGT基因家族，进而合成了不同植物中成分和功能多样的类黄酮糖苷。（来源：科学网 丁佳） 

　　Identification of UDP-glycosyltransferases involved in the biosynthesis of astringent taste compounds in tea (Camellia sinensis) 

　　Abstract 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. 

　　原文链接：http://jxb.oxfordjournals.org/content/67/8/2285.full.pdf+html