AcB6抑制洋葱鳞茎中花青素合成的分子机制

洋葱因营养丰富被誉为“蔬菜皇后”，挖掘控制花青素积累的关键基因，创制花青素富集的新种质是目前洋葱品质育种的重要内容。项目组基于转录组分析，在洋葱中鉴定了激活花青素积累的MBW复合体成员AcMYB1和AcB2，并发掘了首个bHLH负调控因子AcB6；敲除AcB6促进洋葱鳞茎中花青素积累；酵母双杂显示AcB6与花青素激活因子AcMYB1互作。由此推测，AcB6通过与AcMYB1竞争性结合，抑制了MBW复合体形成，从而降低了洋葱鳞茎中花青素的积累。本项目拟利用过表达和敲除AcB6验证其抑制花青素合成的功能；通过酵母三杂等实验探索AcB6对 AcMYB1-AcB2复合体形成的干扰作用，并基于RNA-seq和EMSA等挖掘MBW复合体及AcB6调控的下游关键基因，明确AcB6抑制花青素途径的基因调控网络。研究结果将揭示花青素途径新的抑制机制，为通过基因编辑创制花青素富集的洋葱新种质提供理论依据。

Onions are known as the "Queen of Vegetables" because of their rich nutrition. It is an important part of onion quality breeding to identify the key genes that control the anthocyanin biosynthesis and create new germplasm enriched with anthocyanin. Based on transcriptome analysis of red- and white-onion, we identified AcMYB1 and AcB2, members of the MBW complex that activate anthocyanin biosynthesis in onion, and identified the first bHLH repressor AcB6. Knock-out of AcB6 resulted in the increasing accumulation of anthocyanin in onion bulbs. AcB6 interacted with the anthocyanin activator, AcMYB1, in yeast two-hybrid assays. It is speculated that AcB6 represses the formation of MBW complex by competitively binding with AcMYB1, thereby reducing the accumulation of anthocyanins in onion bulbs. In this project, AcB6 will be overexpressed and knocked out to verify its function of repressing anthocyanin synthesis. We will perform experiments such as Y3H to explore the interference effect of AcB6 on the formation of AcMYB1-AcB2 complex. RNA-seq and EMSA will be performed to identify the key downstream genes regulated by MBW complex and AcB6, so as to clarify the gene regulation network of AcB6 repressing the anthocyanin synthesis pathway. The results will reveal a new repression mechanism of the anthocyanin synthesis pathway and provide a theoretical basis for creating new anthocyanin-enriched onion germplasm by gene editing.