BACKGROUND Citrus fruits are consumed freshly or as juice to directly provide various dietary flavonoids to humans. Diverse metabolites are present among Citrus genera, and many flavonoids biosynthetic genes were induced after abiotic stresses. To better understand the underlying mechanism, we designed experiments to overexpress a UDP-GLUCOSYL TRANSFERASE gene from sweet orange (Citrus sinensis) to evaluate its possible function in metabolism and response to stress. RESULTS Our results demonstrated that overexpression of Cs-UGT78D3 resulted in high accumulation of proanthocyanidins in the seed coat and a dark brown color to transgenic Arabidopsis seeds. In addition, the total contents of flavonoid and anthocyanin were significantly enhanced in the leaves of overexpressed lines. Gene expression analyses indicated that many flavonoid (flavonol) and anthocyanin genes were up-regulated by 4-15 folds in transgenic Arabidopsis. Moreover, after 14 days of high light stress, the transgenic Arabidopsis lines showed strong antioxidant activity and higher total contents of anthocyanins and flavonoids in leaves compared with the wild type. CONCLUSION Our study concluded that the citrus Cs-UGT78D3 gene contributes to proanthocyanidins accumulation in seed coats and confers tolerance to high light stress by accumulating the total anthocyanin and flavonoid contents with better antioxidant potential (due to photoprotective activity of anthocyanin) in the transgenic Arabidopsis.

中文翻译：

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柑橘UDP-葡糖基转移酶基因的异位表达增强了拟南芥中的花色苷和原花色素含量，并赋予了较高的耐光性。

背景技术柑橘类水果是新鲜食用的或作为果汁食用，以直接向人类提供各种饮食中的类黄酮。柑橘属植物中存在多种代谢产物，非生物胁迫后诱导了许多类黄酮生物合成基因。为了更好地了解其潜在机制，我们设计了实验来过量表达甜橙（Citrus sinensis）的UDP-葡萄糖基转移酶基因，以评估其在代谢和应激反应中的可能功能。结果我们的结果表明，Cs-UGT78D3的过表达导致原花青素在种皮中大量积累，并向转基因拟南芥种子呈深棕色。此外，过表达品系叶片中类黄酮和花色苷的总含量显着增加。基因表达分析表明，在转基因拟南芥中，许多类黄酮（黄酮醇）和花色苷基因上调了4-15倍。此外，经过14天的高光胁迫后，与野生型相比，转基因拟南芥品系显示出强大的抗氧化活性以及叶片中花色苷和类黄酮的总含量更高。结论我们的研究得出结论，柑橘中的Cs-UGT78D3基因通过在转基因拟南芥中积累花青素和类黄酮的总含量并具有更好的抗氧化能力（由于花青素的光保护活性），从而促进了种皮中原花青素的积累，并赋予了其对高光胁迫的耐受性。与野生型相比，转基因拟南芥品系具有较强的抗氧化活性，叶片中花色苷和类黄酮的总含量较高。结论我们的研究得出结论，柑橘中的Cs-UGT78D3基因通过在转基因拟南芥中积累花青素和类黄酮的总含量并具有更好的抗氧化能力（由于花青素的光保护活性），从而促进了种皮中原花青素的积累，并赋予了其对高光胁迫的耐受性。与野生型相比，转基因拟南芥品系具有较强的抗氧化活性，且叶片中花色苷和类黄酮的总含量较高。结论我们的研究得出结论，柑橘中的Cs-UGT78D3基因通过在转基因拟南芥中积累花青素和类黄酮的总含量并具有更好的抗氧化能力（由于花青素的光保护活性），从而促进了种皮中原花青素的积累，并赋予了其对高光胁迫的耐受性。