<br>从无色花青素到花青素和原花青素 (PA) 的代谢通量的综合分析,Journal of Agricultural and Food Chemistry

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从无色花青素到花青素和原花青素 (PA) 的代谢通量的综合分析
Journal of Agricultural and Food Chemistry ( IF 5.7 ) Pub Date : 2020-12-12 , DOI: 10.1021/acs.jafc.0c05048
Peiqiang Wang _{1,

2} , Lingjie Zhang ₃ , Lei Zhao ₁ , Xinfu Zhang ₁ , Hanghang Zhang ₁ , Yahui Han ₁ , Xiaolan Jiang ₂ , Yajun Liu ₃ , Liping Gao ₃ , Tao Xia ₂

Affiliation

花青素和 PA 是两种最常见的黄酮类化合物，广泛存在于不同物种中。它们的合成和调控取得了巨大进展。在这项研究中，我们分析了其合成前体无色花青素的代谢通量，这些前体是通过体外和体内二氢黄酮醇 4-还原酶 (DFR) 的过表达获得的。 CsDFRa酶促反应中产生的不稳定产物无色花青素在弱酸性条件下很容易转化为C型碳正离子，可进一步参与体外C型PA的合成。此外，还研究了过表达CsDFRa的烟草和拟南芥DFR 和花青素合酶 (ANS) 突变体的代谢物。在CsDFRa转基因烟草中，花瓣中花青素的含量大大增加，但没有检测到儿茶素或PA。在拟南芥中，EC型碳正离子主要在野生型(WT)中积累，而C型碳正离子仅在ans突变体中检测到。在茶树中，C型PA的积累与CsDFRa的表达呈强正相关。综上所述，无色花青素不仅参与下游花青素和表儿茶素的合成，还可以转化为C型碳正离子参与C型PA的合成。因此，无色花青素形成了朝向儿茶素、花青素和 C 型碳正离子的三种代谢流。这些结果丰富了无色花青素的代谢通量，并进一步阐明了DFR在C型PA形成过程中的作用。

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Comprehensive Analysis of Metabolic Fluxes from Leucoanthocyanins to Anthocyanins and Proanthocyanidins (PAs)

Anthocyanins and PAs are the two most common flavonoids, which are widely present among diverse species. Great progress has been made in their synthesis and regulation. In this study, we analyzed the metabolic fluxes from their synthetic precursor leucoanthocyanins, which were obtained by overexpression of dihydroflavonol 4-reductase (DFR) in vitro and in vivo. The unstable product leucocyanidin generated in the CsDFRa enzymatic reaction was easily converted into C-type carbocations under weak acidic conditions, which could be further involved in the synthesis of C-type PAs in vitro. Additionally, the metabolites in tobacco overexpressing CsDFRa and Arabidopsis thaliana DFR and anthocyanidin synthase (ANS) mutants were investigated. In CsDFRa transgenic tobacco, the content of anthocyanins in the petals was greatly increased, but no catechin or PA was detected. In A. thaliana, EC-type carbocation was mainly accumulated in the wild type (WT), and the C-type carbocation was only detected in the ans mutant. In tea plant, the accumulation of C-type PAs is strong positively correlated with the expression of CsDFRa. In summary, leucocyanidin is not only involved in the synthesis of downstream anthocyanin and epicatechin but also can be converted into C-type carbocation to participate in the synthesis of C-type PAs. Hence, from leucocyanidin, three metabolic fluxes were formed toward catechin, cyanidin, and C-type carbocation. These results enriched the metabolic fluxes of leucoanthocyanins and further elaborated the roles of DFR in the process of C-type PA formation.

更新日期：2020-12-23

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