水稻qZn7基因提高精米锌含量抑制镉积累的调控机制

Grains of rice (Oryza sativa L.) not only work as seeds which are basic materials for rice production in agriculture, but also offer the raw materials for the industry of rice products. The grain mineral concentration (GMC), especially the balance between zinc and cadmium (Zn/Cd balance) in the milled grains plays key roles in the decision of rice nutrient quality and food safety, as well as in seed quality including germination and seedling vigor. We have identified a gene nominated as qZn7 from T124, with function of Zn-increasing and Cd-suppressing in milled grains. The derived amino acid (A.A.) sequence of qZn7 belongs to a C3H zinc finger protein (TZF) family with two A.A. mutations (Leu550→Arg550和Thr560→Ser560) in the C end. As well, a coordinated expression pattern was found between qZn7 and OsHMA3 gene. On this basis, we would further: 1) clarify the relationships between qZn7 and OsHMA3 with qZn7 / OsHMA3 double mutant; 2) identify more interacting factors for qZn7 by yeast two-way hybrid; 3) screening the coordinated expression genes by ChIP-Seq and RNA-Seq; 3) verify the function of key genes identified in 2) and 3) by CRISPR and / or RNAi; 4) exploring the endosperm genetics model and the affects of qZn7 on the seed quality. Taking together, both the molecular and genetic mechanisms of reciprocal regulation underlying the Zn/Cd balance controlled by qZn7 would be elucidated by this project.

水稻种子矿质元素含量（GMC）尤其锌和镉的含量不仅影响种子质量，而且决定稻米产品的营养和安全特性。项目组已从资源T124中克隆了增加精米锌含量抑制镉积累的qZn7基因，它编码一个C3H类锌指蛋白（TZF），其C端存在两个氨基酸突变；分析发现qZn7与OsHMA3有协同表达趋势。本项目拟在此基础上：1) 借助qZn7 / OsHMA3双突变体分析，明确二者之间的作用关系；2) 用酵母双杂+BiFC分析获得更多的qZn7互作因子；3) 用ChIP-Seq结合转录组测序全面筛选qZn7下游及共表达相关基因；4) 用CRISPR与RNAi等对部分参与互作的重点基因开展功能验证；5) 用qZn7转基因系/近等基因系与保持系正反交探讨qZn7基因的胚乳遗传与种子质量的关系。最终整合上述证据，初步探明qZn7提高精米锌含量抑制镉积累的调控机制。

本项目工作开展期间（2019-2022年），项目组通过学术交流和文献检索，发现与qZn7密切相关的籽粒镉积累机理已经被揭示并发表(Liu et al., 2020)，从而遇到项目原计划失去新颖性的问题。项目组根据这个情况并综合考虑自然基金探索属性，适时调整了研究方案。项目组在本项目和其它国家科研经费的联合支持下，在籽粒微量元素（GMC）新基因位点及其单倍型挖掘方法、适用于GMC研究显性早熟材料创制及其机理解析等方面取得了一定的进展并获得了阶段性成果。对照发表论文1-2篇的研究目标，本项目实际发表标注SCI论文3篇（累计影响因子35.007，其中影响因子大于8论文2篇）。其它研究成果还包括：发明专利获得授权3项，新申请3项；新品种权授权2项，新申请12项；合作审定品种1个；培养毕业研究生1名，联合培养出站博士后1名，外国留学生博士1名；发布全球共享单倍型挖掘数据库1个(https://www.rmbreeding.cn)，年均访问量过万。总之，本项目较好的完成了调整后的研究目标，为后续研究打下了较好的工作基础。