Key message

The simultaneous expression of AmRosea1 and AmDelila transcription factors from snapdragon can activate the anthocyanin pathway in orange carrots, leading to the synthesis and accumulation of anthocyanins in the taproots.

Abstract

Anthocyanins are phenolic compounds produced in various parts of plants. They are used as natural food dyes and are reported as beneficial antioxidants for humans. Black carrot is an important source for anthocyanins; however, the reason for the lack of anthocyanin production in the orange carrot is unknown. Anthocyanins are synthesized by a specific branch of the phenylpropanoid pathway that has previously been reported to be activated by a triad of R2R3-MYB, basic helix-loop helix (bHLH) and WD40 transcription factors (TFs). In the current study, orange carrots were turned purple by simultaneous expression of R2R3-MYB and bHLH TFs, i.e. AmRosea1 and AmDelila from snapdragon (Antirrhinum majus). Simultaneous transgenic expression of the TFs under a constitutive promoter in the orange carrot cultivar ‘Danvers 126’ lead to consistent upregulation of anthocyanin-related biosynthetic genes and significant accumulation of anthocyanins in leaves, stems and taproots. Highest overall content of soluble anthocyanins in the taproot among the transformants amounted to 44.38 mg g⁻¹ dry weight. The anthocyanin profile of the transformants were significantly different from the profile in the reference black carrot ‘Deep Purple’. The main anthocyanins present in the transformed taproots were cyanidin 3-xylosyl(sinapoylglucosyl)galactoside, whereas the main anthocyanin present in Deep Purple was cyanidin 3-xylosyl(feruloylglucosyl)galactoside. This study confirms the presence of the necessary biosynthetic genes in orange carrots for production of anthocyanins and demonstrates the absence of suitable R2R3-MYB and bHLH TFs for stimulating anthocyanin biosynthesis in the orange carrot.

中文翻译：

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通过 AmRosea1 和 AmDelila、MYB 和 bHLH 转录因子的表达恢复橙胡萝卜中基于花青素的花青素生物合成。

关键信息

金鱼草中AmRosea1和AmDelila转录因子 的同时表达可以激活橙胡萝卜中的花青素途径，导致花青素在主根中的合成和积累。

抽象的

花青素是植物不同部位产生的酚类化合物。它们被用作天然食用染料，据报道是对人类有益的抗氧化剂。黑胡萝卜是花青素的重要来源；然而，橙色胡萝卜中缺乏花青素产生的原因尚不清楚。花青素是由苯丙素途径的一个特定分支合成的，此前据报道该分支被 R2R3-MYB、基本螺旋-环螺旋 (bHLH) 和 WD40 转录因子 (TF) 的三联体激活。在目前的研究中，橙色胡萝卜通过同时表达 R2R3-MYB 和 bHLH TFs，即来自金鱼草的AmRosea1和AmDelila（金鱼草）。在橙色胡萝卜品种“Danvers 126”的组成型启动子下，TFs 的同时转基因表达导致花青素相关生物合成基因的一致上调和花青素在叶、茎和主根中的显着积累。转化体中主根中可溶性花青素总含量最高为44.38 mg g ^-1净重。转化体的花青素谱与参考黑胡萝卜'深紫'中的谱显着不同。转化的主根中存在的主要花青素是花青素 3-xylosyl(sinapoylglucosyl)galactoside，而 Deep Purple 中存在的主要花青素是花青素 3-xylosyl(feruloylglucosyl)galactoside。这项研究证实了橙色胡萝卜中存在产生花青素所需的生物合成基因，并证明了在橙色胡萝卜中不存在刺激花青素生物合成的合适的 R2R3-MYB 和 bHLH TF。