Gao Yongfeng, Liu Jikai, Chen Yongfu, Tang Hai, Wang Yang, He Yongmei, Ou Yongbin, Sun Xiaochun, Wang Songhu, Yao Yinan
1School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, 621010 China.
Yunnan Engineering Laboratory for Agro-environment Pollution Control and Eco-remediation, The Innovation Team for Farmland Non-pollution Production of Yunnan Province, Kunming, 650201 China.
Hortic Res. 2018 Jun 1;5:27. doi: 10.1038/s41438-018-0032-3. eCollection 2018.
The flavonoid compounds are important secondary metabolites with versatile human nutritive benefits and fulfill a multitude of functions during plant growth and development. The abundance of different flavonoid compounds are finely tuned with species-specific pattern by a ternary MBW complex, which consists of a MYB, a bHLH, and a WD40 protein, but the essential role of SlAN11, which is a WD40 protein, is not fully understood in tomato until now. In this study, a tomato WD40 protein named as SlAN11 was characterized as an effective transcription regulator to promote plant anthocyanin and seed proanthocyanidin (PA) contents, with late flavonoid biosynthetic genes activated in transgenic lines, while the dihydroflavonol flow to the accumulation of flavonols or their glycosylated derivatives was reduced by repressing the expression of in this -overexpressed lines. The above changes were reversed in transgenic lines except remained levels of flavonol compounds and expression. Interestingly, our data revealed that gene could affect seed dormancy by regulating the expressions of abscisic acid (ABA) signaling-related genes and , and the sensitivity to ABA treatment in seed germination is conversely changed by -overexpressed or -downregulated lines. Yeast two-hybrid assays demonstrated that SlAN11 interacted with bHLH but not with MYB proteins in the ternary MBW complex, whereas bHLH interacted with MYB in tomato. Our results indicated that low level of anthocyanins in tomato fruits, with low expression of bHLH () and MYB ( and ) genes, remain unchanged upon modification of gene alone in the transgenic lines. These results suggest that the tomato WD40 protein SlAN11, coordinating with bHLH and MYB proteins, plays a crucial role in the fine adjustment of the flavonoid biosynthesis and seed dormancy in tomato.
类黄酮化合物是重要的次生代谢产物，对人类具有多种营养益处，并在植物生长发育过程中发挥多种功能。不同类黄酮化合物的丰度由一个三元MBW复合体以物种特异性模式进行精细调控，该复合体由一个MYB、一个bHLH和一个WD40蛋白组成，但作为WD40蛋白的SlAN11在番茄中的重要作用至今尚未完全明确。在本研究中，一个名为SlAN11的番茄WD40蛋白被鉴定为一种有效的转录调节因子，可促进植物花青素和种子原花青素（PA）的含量，在转基因株系中激活了后期类黄酮生物合成基因，而在该过表达株系中，通过抑制相关基因的表达，二氢黄酮醇向黄酮醇或其糖基化衍生物积累的流动减少。在转基因株系中，除了黄酮醇化合物水平和相关基因表达保持不变外，上述变化发生了逆转。有趣的是，我们的数据表明，该基因可通过调节脱落酸（ABA）信号相关基因和的表达来影响种子休眠，而过表达或下调该基因的株系在种子萌发时对ABA处理的敏感性会发生相反的变化。酵母双杂交试验表明，在三元MBW复合体中，SlAN11与bHLH相互作用，但不与MYB蛋白相互作用，而在番茄中bHLH与MYB相互作用。我们的结果表明，番茄果实中花青素含量较低，bHLH（）和MYB（和）基因表达较低，在转基因株系中单独改变该基因时保持不变。这些结果表明，番茄WD40蛋白SlAN11与bHLH和MYB蛋白协同作用，在番茄类黄酮生物合成和种子休眠的精细调节中起关键作用。
