我国苹果园土壤贫瘠，氮素缺乏且利用率低，提高植株氮素利用效率有助于我国苹果产业提质增效。根皮苷是苹果中最主要的二氢查尔酮和含量最高的多酚，且仅在苹果属植物中有大量积累。申请者发现，MdUGT88F1介导合成的根皮苷通过干扰氮素积累，阻碍苹果对氮的利用。在此基础上，本项目拟利用MdUGT88F1过表达苹果植株（根皮苷含量增加）的组合嫁接分析和苹果根MdUGT88F1干扰验证，综合评价苹果根皮苷在地上部和根系对氮素积累的作用；随后以MdUGT88F1过表达和干扰苹果植株叶片或根系为材料，在确定碳代谢变化的基础上，利用转录组和蛋白质组学以及基因网络预测分析，并结合苹果愈伤组织或根转基因技术，发掘苹果根皮苷在地上部或根系介导氮素积累过程（吸收、转运或同化）中的调控位点。本项目旨在提升对苹果氮素利用生物学基础的理解，为苹果氮高效利用遗传改良提供新理论依据

In China, the soil of apple orchards is barren and featured with nitrogen deficiency and low nitrogen utilization. Thus, it is of significance to improve nitrogen use efficiency (NUE) for apple cultivation. Phloridzin is the predominant dihydrochalcone and the most abundant phenolic compound in apple (Malus domestica). This makes apple unique in the plant kingdom because phloridzin does not accumulate such high amounts outside Malus spp. Previously, we found that MdUGT88F1-mediated phloridzin biosynthesis could impede apple nitrogen utilization by interfering with nitrogen accumulation. In this project, we plan to use MdUGT88F1 overexpression apple lines for analysis of recombinational grafting to determine the role of phloridzin in nitrogen accumulation of roots and aerial parts, in association with the verification of MdUGT88F1 knockdown in apple roots. Subsequently, based on the analysis of carbon metabolism, we will mine phloridzin-mediated regulatory genes affecting nitrogen accumulation processes, i.e. absorption, translocation, or assimilation, via gene network analysis on basis of both transcriptome and proteomics from MdUGT88F1 transgenic apple leaves or roots. Furthermore, these genes will be functionally verified by using transgenic apple callus or root. Taken together, this study aims to deepen the biological basis of nitrogen utilization and service for prospective NUE genetic improvement in apple.