Flavonoids are major polyphenol compounds in plants and contribute substantially to the health-promoting benefits of fruit and vegetables. Peach is rich in polyphenols with flavonols as the main flavonoids. To investigate the regulation of flavonol biosynthesis in peach fruit, two R2R3-MYB transcription factor (TF) genes, PpMYB15 and PpMYBF1, were isolated and characterized. Sequence analysis revealed that the PpMYB15 and PpMYBF1 proteins are members of the flavonol clade of the R2R3-MYB family. Real-time quantitative PCR analysis showed that PpMYB15 and PpMYBF1 transcript levels correlated well with the flavonol content and the expression of flavonol synthase (PpFLS1) in different fruit samples. Dual-luciferase assays indicated that both PpMYB15 and PpMYBF1 could trans-activate promoters of flavonoid biosynthesis genes, including chalcone synthase (PpCHS1), chalcone isomerase (PpCHI1), flavanone 3-hydroxylase (PpF3H), and PpFLS1. Transient overexpression of 35S::PpMYB15 or 35S::PpMYBF1 both triggered flavonol biosynthesis but not anthocyanin and proanthocyanidin biosynthesis in tobacco leaves. In transgenic tobacco flowers, overexpression of 35S::PpMYB15 or 35S::PpMYBF1 caused a significant increase in flavonol levels and significantly reduced anthocyanin accumulation, resulting in pale-pink or pure white flowers. These results suggest that PpMYB15 and PpMYBF1 are functional flavonol-specific positive regulators in peach fruit and are important candidates for biotechnological engineering flavonol biosynthesis in plants.

中文翻译：

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PpMYB15和PpMYBF1转录因子参与调节桃果实中黄酮醇的生物合成

类黄酮是植物中的主要多酚化合物，对水果和蔬菜的健康促进作用有很大贡献。桃子富含以黄酮醇为主要类黄酮的多酚。为了研究桃果实中黄酮醇的生物合成调控，分离并鉴定了两个R2R3-MYB转录因子（TF）基因PpMYB15和PpMYBF1。序列分析表明，PpMYB15和PpMYBF1蛋白是R2R3-MYB家族黄酮分子的成员。实时定量PCR分析表明PpMYB15和PpMYBF1转录水平与黄酮含量和黄酮合成酶（PpFLS1）的表达密切相关）放在不同的水果样本中。双重荧光素酶分析表明，PpMYB15和PpMYBF1都可以反激活黄酮类生物合成基因的启动子，包括查尔酮合酶（PpCHS1），查尔酮异构酶（PpCHI1），黄烷酮3-羟化酶（PpF3H）和PpFLS1。35S :: PpMYB15或35S :: PpMYBF1的瞬时过表达均触发了烟叶中的黄酮醇生物合成，但未触发花色素苷和原花色素生物合成。在转基因烟草花中，35S :: PpMYB15或35S :: PpMYBF1的过度表达导致黄酮醇含量显着增加，花青素积累显着减少，从而导致淡粉色或纯白色花朵。这些结果表明PpMYB15和PpMYBF1是桃果实中功能性黄酮醇特异性正调节剂，并且是植物中生物技术工程性黄酮醇生物合成的重要候选物。