Flavonoids are natural antioxidants in plants that affect the color of plant tissues. Flavonoids can be divided into eight subgroups, including flavonols, anthocyanins, and proanthocyanidins. The mechanisms of flavonoid synthesis in model plants have been widely studied. However, there are a limited number of reports on the synthesis of flavonoids in the red leaf varieties of woody plants. In this study, we combined morphological observation, pigment content determination, metabolomics, and transcriptomics to investigate the metabolites and gene regulation present in the red and green leaves of Eucommia ulmoides Oliv. The results showed that the red leaves have a lower chlorophyll content and a higher anthocyanin content. Metabonomic analysis identified that the relative content of most flavonoids is up-regulated in red leaves based on UPLC-ESI-MS/MS, which included the apigenin class, quercetin class, kaempferol class, and procyanidins. Transcriptome data suggested that the differentially up-regulated genes are enriched in flavonoid and anthocyanin synthesis pathways, ABC transport, and GST pathways. The integrative analysis of the transcriptome and metabolome showed that the up-regulation of flavonoid metabolism and a high expression of chlorophyll degradation with the down-regulation of chlorophyll biosynthesis genes are detected in E. ulmoides red leaves compared with green leaves. In addition, the co-expression networks implied that cyanidin 3-5-O-diglucoside, EuDR5, EuPAL2, EuDFR11, Eu3MaT1, and EuF3′H are likely associated with the red leaf coloration of E. ulmoides. In summary, this research provided a reference for studying the mechanism of red leaf coloration in woody plants and the use of E. ulmoides red leaves as feedstock for bioactive products.

中文翻译：

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代谢组和转录组分析揭示了杜仲红叶和绿叶之间不同的类黄酮生物合成和叶绿素代谢特征

类黄酮是植物中的天然抗氧化剂，会影响植物组织的颜色。类黄酮可分为八个亚组，包括黄酮醇、花青素和原花青素。模式植物中类黄酮合成的机制已被广泛研究。然而，关于木本植物红叶品种中黄酮类化合物合成的报道数量有限。在这项研究中，我们结合形态学观察，色素含量测定，代谢组学，转录和调查中的红色和绿色叶子的代谢物和基因调控目前杜仲杜仲奥利夫。结果表明，红叶叶绿素含量较低，花青素含量较高。代谢组学分析发现，基于 UPLC-ESI-MS/MS，红叶中大多数黄酮类化合物的相对含量上调，其中包括芹菜素类、槲皮素类、山奈酚类和原花青素类。转录组数据表明差异上调的基因富含类黄酮和花青素合成途径、ABC 转运和 GST 途径。转录组和代谢组的综合分析表明，与绿叶相比，在 E. ulmoides 红叶中检测到黄酮类代谢的上调和叶绿素降解的高表达以及叶绿素生物合成基因的下调。此外，EuDR5，EuPAL2，EuDFR11，Eu3MaT1，和氟化铕3' ħ有可能用的红色着色叶相关联E.杜仲，总之，这项研究为研究的红叶变色木本植物机制和使用提供参考E.杜仲红叶作为原料用于生物活性物质。