背景回顾：Enhancing fruit sugar contents, especially for high-flavonoid apples with a sour taste, is one of the main goals of horticultural crop breeders. 

主要发现：This study analyzed sugar accumulation and the underlying mechanisms in the F2 progenies of a hybridization between the high-sugar apple (Malus × domestica) variety ‘Gala’ and high-flavonoid apple germplasm ‘CSR6R6’. We revealed that MdSWEET9b (sugars will eventually be exported transporter) helps mediate sugar accumulation in fruits. 

结果1-MdSEWWT9b蔗糖转运活性：Functional characterization of MdSWEET9b in yeast mutants lacking sugar transport as well as in overexpressing and CRISPR/Cas9 knockdown apple calli revealed MdSWEET9b could transport sucrose specifically, ultimately promoting normal yeast growth and accumulation of total sugar contents. 

结果2-ABA-MdWRKY9-MdSEWWT9b：Moreover, MdWRKY9 bound to the MdSWEET9b promoter and regulated its activity, which responded to abscisic acid (ABA) signaling. Furthermore, MdWRKY9 interacted with MdbZIP23 (basic leucine zipper) and MdbZIP46, key ABA signal transducers, at the protein and DNA levels to enhance its regulatory effect on MdSWEET9b expression, thereby influencing sugar accumulation. 

结果3-ABA与糖积累：Based on the contents of ABA in lines with differing sugar contents and the effects of ABA treatments on fruits and calli, we revealed ABA as one of the main factors responsible for the diversity in apple fruit sugar content. 

结论：The results of this study have clarified how MdSWEET9b influences fruit sugar accumulation, while also further elucidating the regulatory effects of the ABA signaling network on fruit sugar accumulation. This work provides a basis for future explorations of the cross-talk between hormone and sugar metabolism pathways.

增加果实的糖含量，尤其是对那些类黄酮含量较高、味道偏酸的果实，是园艺作物育种者的主要目标。本文利用糖含量较高的苹果品种‘嘎啦’和类黄酮含量较高的苹果种质‘CSR6R6’进行杂交获得的F2子代群体，分析了糖积累及其潜在的分子调控机制。作者发现，糖转运蛋白MdSWEET9b有助于果实中的糖积累。在糖转运缺陷型的酵母突变体中对MdSWEET9b的功能鉴定，以及在苹果愈伤组织中过表达和敲除MdSWEET9b基因，发现MdSWEET9b能够特异性地转运蔗糖，促进了酵母的正常生长以及总糖含量的积累。此外，MdWRKY9能够响应于ABA信号转导途径，直接结合到MdSWEET9b基因启动子上并调控后者的转录活性。此外，MdWRKY9能够与ABA信号的关键传导者MdbZIP23和MdbZIP46在蛋白和DNA层面互作，增强其对于MdSWEET9b表达的调控作用，从而影响糖积累。基于对不同糖含量株系中的ABA含量测定以及对果实和愈伤组织的ABA处理，作者发现ABA是苹果果实糖含量多样性的一个主要影响因子。本文的研究结果揭示了MdSWEET9b是如何影响苹果果实的糖积累，同时也解析了ABA信号转导网络对于苹果果实糖积累的调控作用。本文的工作为将来进一步解析植物激素与糖代谢途径直接的交联提供了基础。

** 王 楠 **