State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Landscaping, Ministry of Agriculture and Rural Affairs, College of Horticulture, Nanjing Agricultural University, Weigang No. 1, Nanjing, 210095, Jiangsu Province, People's Republic of China.
Plant Mol Biol. 2022 Jan;108(1-2):51-63. doi: 10.1007/s11103-021-01206-z. Epub 2021 Oct 29.
An R2R3-MYB transcription factor, CmMYB9a, activates floral coloration in chrysanthemum by positively regulating CmCHS, CmDFR and CmFNS, but inhibiting the expression of CmFLS. Chrysanthemum is one of the most popular ornamental plants worldwide. Flavonoids, such as anthocyanins, flavones, and flavonols, are important secondary metabolites for coloration and are involved in many biological processes in plants, like petunia, snapdragon, Gerbera hybrida, as well as chrysanthemum. However, the metabolic regulation of flavonoids contributing to chrysanthemum floral coloration remains largely unexplored. Here, an R2R3-MYB transcription factor, CmMYB9a, was found to be involved in flavonoid biosynthesis. Phylogenetic analysis and amino acid sequence analysis suggested that CmMYB9a belonged to subgroup 7. Transient overexpression of CmMYB9a in flowers of chrysanthemum cultivar 'Anastasia Pink' upregulated the anthocyanin-related and flavone-related genes and downregulated CmFLS, which led to the accumulation of anthocyanins and flavones. We further demonstrated that CmMYB9a independently activates the expression of CmCHS, CmDFR and CmFNS, but inhibits the expression of CmFLS. Overexpression of CmMYB9a in tobacco resulted in increased anthocyanins and decreased flavonols in the petals by upregulating NtDFR and downregulating NtFLS. These results suggest that CmMYB9a facilitates metabolic flux into anthocyanin and flavone biosynthesis. Taken together, this study functionally characterizes the role of CmMYB9a in regulating the branched pathways of flavonoids in chrysanthemum flowers.
一个 R2R3-MYB 转录因子，CmMYB9a，通过正向调控 CmCHS、CmDFR 和 CmFNS 来激活菊花的花色，同时抑制 CmFLS 的表达。菊花是全球最受欢迎的观赏植物之一。类黄酮，如花色苷、类黄酮和类黄酮醇，是花色形成的重要次生代谢物，参与植物的许多生物学过程，如矮牵牛、金鱼草、非洲菊以及菊花。然而，菊花花色形成中类黄酮代谢调控的研究还很大程度上未被探索。在这里，我们发现一个 R2R3-MYB 转录因子 CmMYB9a 参与类黄酮生物合成。系统发育分析和氨基酸序列分析表明 CmMYB9a 属于第 7 亚组。在菊花品种“Anastasia Pink”的花朵中瞬时过表达 CmMYB9a 上调了花色苷相关和类黄酮相关基因，并下调了 CmFLS，导致花色苷和类黄酮的积累。我们进一步证明 CmMYB9a 可以独立激活 CmCHS、CmDFR 和 CmFNS 的表达，同时抑制 CmFLS 的表达。在烟草中过表达 CmMYB9a 通过上调 NtDFR 和下调 NtFLS 导致花瓣中花色苷增加和类黄酮醇减少。这些结果表明 CmMYB9a 促进了花色苷和类黄酮生物合成的代谢流。综上所述，本研究功能表征了 CmMYB9a 在调控菊花花色分支途径中的作用。
