一个钙/阳离子交换体蛋白调控水稻籽粒Cd积累的机制研究

水稻Cd污染危害食品安全，低Cd基因挖掘和种质资源创新为低Cd水稻育种提供基础。但低Cd品种中Cd与微量元素的关系也引起关注，低Cd基因在降Cd的同时影响微量元素积累，产生不利性状，使生产上能应用的基因很少。因此，发掘不影响农艺性状的低Cd基因，研究其机理，具有重要理论和应用价值。申请者前期鉴定了首个参与水稻Cd积累的Ca/阳离子交换蛋白CCX2，发现异源过表达增强酵母对Cd的耐受性；粳稻和籼稻敲除突变体中籽粒Cd含量都明显下降，但其他金属离子不受影响，不影响生长发育和产量；CCX2在水稻茎节中调控Cd/Ca根-茎的转移和节间分配，但其具体的调控机制尚不清楚。在此基础上，本项目拟采用细胞、生化和遗传等技术手段，详细分析CCX2的Cd/Ca转运活性及其生理功能，阐明CCX2调控籽粒低Cd的细胞和分子机制。研究结果将加深对水稻Cd运输和积累机制的理解，为低Cd水稻分子育种提供新的遗传种质资源。

Cadmium pollution of rice endangers food safety. Low Cd gene mining and germplasm resource innovation provide the basis for low Cd rice breeding. However, the relationship between Cd and microelements in low Cd varieties has also attracted attention. The low Cd gene not only reduces Cd, but also affects the accumulation of microelements, resulting in adverse characters, so that few genes can be used in production. Therefore, it is of great theoretical and practical value to explore the low Cd gene which does not affect agronomic characters and study its mechanism. The applicant initially identified the first Ca/cation exchanger CCX2 involved in Cd accumulation in rice. It was found that heterologous overexpression enhanced the tolerance of yeast to Cd. Grain Cd content in japonica rice and indica rice knockout mutant decreased significantly, but other metal ions were not affected, and growth and yield were not affected. CCX2 regulates Cd/Ca root-to-shoot transfer and internode allocation in rice stem node. But its specific regulatory mechanism is not clear. On this basis, the project plans to use cell, biochemical and genetic techniques to analyze the Cd/Ca transport activity and physiological function of CCX2 in detail, and clarify the cell and molecular mechanism of CCX2 regulating low Cd in grains. The results will deepen the understanding of the mechanism of Cd transport and accumulation in rice, and provide new genetic germplasm resources for low Cd rice molecular breeding.