Identification of the glucosyltransferase gene that supplies the p-hydroxybenzoyl-glucose for 7-polyacylation of anthocyanin in delphinium
Identification of the glucosyltransferase gene that supplies the p-hydroxybenzoyl-glucose for 7-polyacylation of anthocyanin in delphinium
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DOI：
10.1093/jxb/eru134
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发表时间：
2014-06-01
影响因子：
6.9
通讯作者：
Ozeki, Yoshihiro
中科院分区：
文献类型：
--
作者：
Nishizaki, Yuzo;Sasaki, Nobuhiro;Ozeki, Yoshihiro
在飞燕草（Delphinium grandflorum）中，蓝色的花朵是由7-聚酰基化花青素产生的。聚酰基部分由葡萄糖和对羟基苯甲酸（pHBA）组成。花青素的7-多酰化是由两种不同的酶催化的，一种是葡萄糖基转移酶，另一种是酰基转移酶；这两种酶都利用对羟基苯甲酰葡萄糖（pHBG）作为双功能（Zwitter）供体。然而，迄今为止，合成pHBG的酶和编码它的基因还没有被阐明。本文对5个飞燕草品种进行了研究，发现其7-聚酰基化活性降低或检测不到；这些品种合成飞燕草苷3- o -芦丁苷（Dp3R）产生淡紫色萼片。其中一个品种缺乏介导7-聚酰基化第一步所需的酰基葡萄糖依赖花青素7- o -葡萄糖基转移酶（AA7GT）。其余4个品种AA7GT活性和DgAA7GT均有表达；然而，与野生型品种相比，pHBG积累显著减少，而对葡萄糖基氧苯甲酸（pGBA）积累较多。鉴定了三个候选cdna，编码udp -葡萄糖依赖的pHBAGT。对DgpHBAGT氨基酸序列的系统发育分析表明，DgpHBAGT与其他植物中参与酰基葡萄糖合成的ugt密切相关。重组DgpHBAGT蛋白在体外合成了pHBG，对pHBA具有较高的亲和性。积累pGBA的突变品种DgpHBAGT的表达量非常低，而在野生品种萼片和组织发育过程中，DgpHBAGT的表达与pHBG的积累水平密切相关。这些结果支持DgpHBAGT参与飞燕草体内pHBG合成的结论。
In delphiniums (Delphinium grandiflorum), blue flowers are produced by the presence of 7-polyacylated anthocyanins. The polyacyl moiety is composed of glucose and p-hydroxybenzoic acid (pHBA). The 7-polyacylation of anthocyanin has been shown to be catalysed by two different enzymes, a glucosyltransferase and an acyltransferase; both enzymes utilize p-hydroxybenzoyl-glucose (pHBG) as a bi-functional (Zwitter) donor. To date, however, the enzyme that synthesizes pHBG and the gene that encodes it have not been elucidated. Here, five delphinium cultivars were investigated and found to show reduced or undetectable 7-polyacylation activity; these cultivars synthesized delphinidin 3-O-rutinoside (Dp3R) to produce mauve sepals. One cultivar showed a deficiency for the acyl-glucose-dependent anthocyanin 7-O-glucosyltransferase (AA7GT) necessary for mediating the first step of 7-polyacylation. The other four cultivars showed both AA7GT activity and DgAA7GT expression; nevertheless, pHBG accumulation was significantly reduced compared with wild-type cultivars, whereas p-glucosyl-oxybenzoic acid (pGBA) was accumulated. Three candidate cDNAs encoding a UDP-glucose-dependent pHBA glucosyltransferase (pHBAGT) were identified. A phylogenetic analysis of DgpHBAGT amino acid sequences showed a close relationship with UGTs that act in acyl-glucose synthesis in other plant species. Recombinant DgpHBAGT protein synthesized pHBG and had a high preference for pHBA in vitro. Mutant cultivars accumulating pGBA had very low expression of DgpHBAGT, whereas expression during the development of sepals and tissues in a wild cultivar showed a close correlation to the level of accumulation of pHBG. These results support the conclusion that DgpHBAGT is responsible for in vivo synthesis of pHBG in delphiniums.