背景回顾：DSugar and anthocyanin are important indicators of fruit quality, and understanding the mechanism underlying their accumulation is essential for breeding high-quality fruit. 

主要发现：We identified an R2R3-MYB transcription factor (TF) MdMYB305 in the red-fleshed apple progeny, which was positively correlated with fruit sugar content but negatively correlated with anthocyanin content. 

结果1-MdMYB305基因功能：Transient injection, stable expression (overexpressing and CRISPR/Cas9 knockdown) and heterologous transformation tomato confirmed that MdMYB305 promotes the accumulation of sugar and inhibits the synthesis of anthocyanin. 

结果2-MdMYB305下游基因：Through a series of molecular experiments (such as EMSA, LUC) confirmed that MdMYB305 combines with sugar-related genes (MdCWI1/MdVGT3/MdTMT2) and anthocyanin-related genes (MdF3H/MdDFR/MdUFGT), promote and inhibit their activities, and finally regulate the sugar and anthocyanin content of fruits. 

结果3-MdMYB305和MdMYB10竞争结合MdbHLH33：In addition, this study also found that MdMYB305 competes with MdMYB10 for the MdbHLH33 binding site to balance sugar and anthocyanin accumulation in the fruits, which provides a reference value for exploring more functions of MYB-bHLH-MYB complex and the balance relationship between sugar and anthocyanin in the future.

糖和花色苷是果实质量的重要指标，理解其积累的分子机制对于高质量果实育种是十分重要的。本文中，作者在红色果肉的苹果中，鉴定到了一个R2R3-MYB转录因子MdMYB305，其与果实的糖含量呈正相关，但是和花色苷含量呈负相关。通过注射法瞬时转化、过表达和CRISPR/Cas9基因编辑等稳定转化，以及在番茄中的异源转化，作者发现MdMYB305缺失可以促进糖的积累，并抑制花色苷的生物合成。通过EMSA、LUC等一系列分子试验，作者确认了MdMYB305可以结合并促进糖相关基因MdCWI1/MdVGT3/MdTMT2的转录活性，结合并抑制花色苷相关基因MdF3H/MdDFR/MdUFGT的转录活性，从而调控果实中的糖和花色苷含量。另外，本研究中作者还发现MdMYB305与MdMYB10竞争结合MdbHLH33，从而平衡果实中糖和花色苷的积累。本文的研究结果为进一步探索MYB-bHLH-MYB复合体的功能提供了参考，同时也为未来苹果果实中的糖-花色苷平衡调控提供了候选靶标。

** 王 楠 **