Effects of exogenous NO donor on glutathione-dependent antioxidative system in wheat seedling leaf under salt stress

中国人. 研究了外源一氧化氮（NO）供体SNP对150mmol／L NaCl胁迫下小麦幼苗叶片谷胱甘肽抗氧化酶系统的影响。结果表明，与单独盐胁迫相比，0．1mmol／L的SNP处理明显提高了小麦幼苗叶片还原型谷胱甘肽（GSH）的含量，略微降低了氧化型谷胱甘肽（GSSG）的含量，明显提高了GSH／GSSG，这可能与其诱导谷胱甘肽还原酶（GR）的活性有部分关系。同时，SNP处理亦显著促进了谷胱甘肽-S-转移酶（GST）的活性，通过参与降解因盐胁迫而过量产生的过氧化产物，实现细胞解毒功能。此外，外源NO供体SNP还提高了盐胁迫下小麦幼苗叶片抗坏血酸（ASC）的含量以及抗坏血酸过氧化物酶（APX）的活性，协助清除活性氧。

英语. Accumulation of salts in irrigated soil is one of the primary factors limiting yield in wheat production in Southeast Asia. It is well known that salinity could affect any process in the plant＇s life cycle, so that tolerance will involve a complex interplay of characters. For example, overproduction of reactive oxygen species （ROS）, if they are not rapidly removed, they easily cause considerable structural and functional oxidative damage in plant cells under salinity. Meanwhile, a lot of recent researches found that nitric oxide （NO） plays an important role in mediating some biotic and abiotic stress-induced oxidative stresses in plant kingdom. However, it remains unknown about the role of NO in glutathione-dependent antioxidative system under salt stress. In this report, effects of exogenous NO donor SNP on metabolism of glutathione in wheat seedling leaf under 150 mmol/L NaCl salt stress were investigated. Results showed that 0.1 mmol/L SNP treatment apparently increased the reduced glutathione （GSH） contents （ Fig. 1-A）, slightly decreased the contents of oxidized glutathione （GSSG） （Fig. 1-B）, therefore resulting in elevating the ratio of GSH/GSSG in wheat seedling leaves subjected to salt stress （Fig. 1-C）. Further results indicated that these might be partially due .to the increased activities of glutathione reductase （GR） exerted by exogenous NO donor （ Fig. 2-A）. Meanwhile, exogenous NO donor SNP also promoted the activities of GSH-dependent glutathione-S-transferase （GST） in wheat seedling leaves （ Fig. 2- B）, participating the degradation of peroxides caused by salt stress and achieving its cell detoxification function. Also, employment of exogenous SNP induced the APX activities and ASC contents （ Fig. 3）, which were both benefit for the scavenging of reactive oxygen species （ROS） in wheat seedling leaves under salinity. Based on the present results, it is inferred that NO could strongly up-regulate glutathione-dependent antioxidative system, ultimately resulting in promoting the salt tolerance against salt stress. In view of the fact that NO is the byproduct of metabolism in high plants, it will be more available if some applied approaches, which could modulate the activities of nitric oxide synthase （NOS） or/and NR to enhance appropriate endogenous NO level, would ultimately alleviate the oxidative damage caused by salt stress.