大白菜叶球是一个经过长期驯化而形成的复杂性状。结球与不结球白菜的基因组重测序分析表明，叶片背腹性基因BrARF3在叶球驯化过程中产生了等位变异，且与叶球形成高度选择相关。我们发现过表达BrARF3使不结球白菜获得结球性，但BrARF3在大白菜叶球形成中的调控机制尚不清楚。本项目拟以白菜转基因植株为材料，分析植物激素和叶片解剖结构的差异，明确BrARF3对大白菜结球的影响；利用RNA-seq与miRNA-seq分析、酵母双杂、双分子荧光互补等技术解析BrARF3上游ta-siRNA对其梯度调控机制和下游的互作蛋白；结合CRISPR基因编辑技术，确定BrARF3等位变异对基因功能的影响，揭示其等位变异与大白菜结球性选择驯化的关系。研究结果将为系统分析以叶球为产品的蔬菜作物的结球机制奠定基础；不同亚种基因组背景结球白菜的获得将为实现利用亚种间杂交优势进行结球白菜的生产提供重要材料与理论实践依据。

The leafy head of Chinese cabbage (Brassica rapa ssp. pekinensis) is a polygene-controlled trait formed after long-term domestication. The genome re-sequencing analyses on heading and non-handing types of B. rapa shows that BrARF3, a leaf ad/abaxial polarity gene, underwent allelic variation during the domestication, which is highly related to the leafy head formation. As our previous study showed, over-expressing BrARF3 leads to non-heading B. rapa forming leafy heads, but it remains unclear that the regulation mechanism of BrARF3 in leafy head formation and the effect of allelic variation on the gene function in Chinese cabbage. In this project, the BrARF3 transformed Chinese cabbage plants will be used as the experimental material to analyze the differences in leafy head development, plant hormones and leaf anatomical structure among different transgenic plants and wild type, meanwhile, to understand the effect of BrARF3 on the leafy head formation of Chinese cabbage. RNA-seq and miRNA-seq joint analysis, yeast two hybrid (Y2H), bimolecular fluorescence complementation (BiFC), etc. will be applied to reveal, in the upstream region of BrARF3, the gradient regulation pattern of TAS3–ta-siRNA–ARF3 pathway on BrARF3 and, in the downstream region of BrARF3, the protein-protein interaction. Besides, this project will understand the effect of BrARF3 allelic variation on gene function and uncover the relationship between the difference in BrARF3 alleles and the leafy head formation and domestication in Chinese cabbage via combining the CRISPR gene editing technique. The study results will lay a foundation for systematic studying the mechanism of leafy head formation in vegetable crops with leafy heads as product organs. Furthermore, the obtention of heading Chinese cabbage with different subspecies genome backgrounds will provide vital materials as well as a theoretical and practical basis for producing heading Chinese cabbage by utilization of heterosis of intersubspecific combination.