水稻气孔高效的分子机制及其生理意义研究

Our previous work on the molecular responses of rice roots to varied ammonium availabilities and feed-back regulations during ammonium uptake revealed that carbon synthesis and accumulation in the plant are strongly demanded in coordinating with efficient nitrogen use capability and gain in grain yield. Therefore, in this proposal we test and realize the hypothesis of “promoting nitrogen use efficiency by enhanced carbon acquisition” in rice. The hypothesis can finds, to certain extent, experimental supports from recent reports of rice yield gains under elevated CO2 treatments with FACE platforms. However, the FACE treatments could cause lowering of the stomatal apertures and was consequently disadvangeous in driving ammonium uptake. The proposal targets the stomata as the major approach of facilitated CO2 entrance. The dominant K+ uptake channel OsK2.1 in the guard cell of rice leaves is to be analyzed to the respects of mode-of-action and mechanisms of functional regulation in order to obtain molecular insights that restricting rice stomata from efficient opening, a phenomenon we previously found with OsK2.1, a pre-requisition of K+ accumulation for channel’s activation. We then evaluate the contribution of molecular manipulation on OsK2.1, by analyzing the phenotypes of the knockout and transgenic rice, to the improvement of nitrogen use efficiency and gain in grain yields of genetically modified rice.

申请在前期对水稻铵响应和吸收机制研究中，发现体内碳的高效协同是提高其氮素利用效率与增加产量的关键之一，因此提出“增碳促氮”的氮高效假设。近年来FACE平台通过增加大气CO2浓度使得水稻显著增产的研究屡有报道，侧面验证了水稻对增碳的需求。鉴于FACE增碳途径往往会导致气孔开度降低而降低氮素利用效率，本项目拟从光合CO2输入的主要门户—气孔入手，通过对主导水稻气孔开放的OsK2.1通道的功能与调控研究，解析因该通道功能对K+的依赖性而限制水稻气孔高效开放的分子机制。在此基础上通过突变体和转基因水稻材料验证由OsK2.1通道主导的气孔增碳途径对提高水稻氮钾养分利用率和产量的实际效果。

明确了OsK2.1(OsKAT3)对高钾的依赖性是保证其钾吸收和行使气孔开放控制功能的关键。发现了该通道独特的钙调控特征及其结构基础。揭示了基于OsK2.1(OsKAT3)和玉米ZmK2.1通道基因的水稻气孔分子调控的运作机制及其对提高水稻氮素利用效率和籽粒增产的田间效果。由OsKAT1.1和OsAKT2所介导的根-茎K+长距离传输与分配，对满足OsK2.1(OsKAT3)的功能及其控制的水稻气孔开放的叶片高钾需求，具有重要的支撑作用。