低温冷害是影响水稻生产的主要障碍之一。一氧化氮(Nitric oxide,NO)作为一个具有广泛作用的重要信号分子，参与植物许多重要的生理过程。硝酸还原酶是目前被证实植物体内能合成NO的主要酶类，然而硝酸还原酶介导的内源NO调控水稻耐冷的作用机制尚不清楚。本项目拟利用水稻硝酸还原酶基因OsNia1和OsNia2单敲除与双敲除突变体及野生型，采用水培和盆栽的方法，设定不同浓度钼素、硝态氮营养、ABA、H2O2等处理，研究不同生育时期冷胁迫下突变体与野生型叶片与根系NO含量、硝酸还原酶活性、活性氧水平、抗氧化酶活性、激素含量及冷胁迫相关基因表达差异，从生理水平、酶学水平和转录组学水平系统解析硝酸还原酶介导产生的NO调控水稻耐冷的作用机理，以及探讨体外调控硝酸还原酶酶促途径调节NO水平增强耐冷的可能措施，为丰富水稻低温冷害防控措施与培育耐冷品种提供理论依据。

Low temperature is one of the most important abiotic stress factors affecting rice growth. Nitric oxide is an important signal molecule, and is involved in many essential physiological processes in plants. Nitrate reductase (NR) has been confirmed as the major enzyme for the synthesis of nitric oxide (NO) in plant. However, the mechanism of endogenous NO mediated by nitrate reductase on cold tolerance is not clear. In this research, the NO content, nitrate reductase activity, reactive oxygen species, antioxidant enzyme activity, hormone content and cold stress related gene expression will be studied in the NR single and double mutant line nia1,nia2,nia1nia2 and wild type under treatment of different concentrations of molybdenum, nitrate nitrogen, ABA, H2O2, etc. The mechanism of how NO generated by nitrate reductase mediates the regulation of cold tolerance will be analyzed in physiological, enzymatic and transcriptome levels, as well as the possible methods to enhance the cold tolerance by regulating NR activity will be explored in vitro. These results will provide a theoretical basis for cold tolerance prevention and varieties breeding in rice.