S-nitrosylation, the addition of nitric oxide (NO) moiety to a reactive cysteine thiol, to form an S-nitrosothiol (SNO), is emerging as a prototypic redox-based post-translational modification. S-nitrosoglutathione reductase (GSNOR) is thought to be the major regulator of total cellular SNO levels in plants. However, its role in excess nitrate stress has not been investigated in spinach. In this study, a spinach GSNOR gene (GenBank Accession No. KR381778) was amplified and designated as SoGSNOR. The transcript and protein level of SoGSNOR were reduced after excess nitrate treatment for 24 h. Addition of NO donor to the nitrate solution decreased the SoGSNOR expression, while supplementation inhibitor of nitrate reductase and nitric oxide synthase increased its expression. Overexpression of SoGSNOR in tobacco increased the germination rate of transgenic seeds, compared to the wild type (WT) under nitrate stress. Higher photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency and expression level of some stress-related genes were detected in the transgenic seedlings than the WT under nitrate stress. The transgenic tobacco seedlings have lower malondialdehyde content, reactive oxygen species (ROS) fluorescence, and higher activities and transcript level of superoxide dismutase, catalase, peroxidase under nitrate stress. SoGSNOR transgenic tobacco plants have lower NR activity and protein level, higher GSNOR and non-symbiotic class 1 hemoglobin (nsHb) protein level than the WT plants, leading to lower NO accumulation and SNOs contents under nitrate stress. These results suggested that overexpression of SoGSNOR increased nitrate stress tolerance of tobacco by regulating ROS and RNS metabolism.

S-亚硝基化，将一氧化氮（NO）部分添加到反应性半胱氨酸硫醇上形成S-亚硝基硫醇（SNO），是基于原型氧化还原的翻译后修饰。S-亚硝基谷胱甘肽还原酶（GSNOR）被认为是植物中总细胞SNO水平的主要调节剂。然而，菠菜中尚未研究其在过量硝酸盐胁迫中的作用。在这项研究中，菠菜GSNOR基因（GenBank登录号KR381778）被扩增并命名为SoGSNOR。过量的硝酸盐处理24小时后，SoGSNOR的转录本和蛋白质水平降低。在硝酸盐溶液中添加NO供体会降低SoGSNOR表达，而硝酸盐还原酶和一氧化氮合酶的补充抑制剂会增加其表达。SoGSNOR的过表达与硝酸盐胁迫下的野生型（WT）相比，烟草中的烟草增加了转基因种子的发芽率。在硝酸盐胁迫下，转基因幼苗的光合速率，蒸腾速率，气孔导度，水分利用效率和某些胁迫相关基因的表达水平均高于野生型。转基因烟草幼苗在硝酸盐胁迫下具有较低的丙二醛含量，活性氧（ROS）荧光，较高的活性和转录水平的超氧化物歧化酶，过氧化氢酶，过氧化物酶。索格诺与野生型植物相比，转基因烟草植物的NR活性和蛋白质水平较低，GSNOR和非共生1类血红蛋白（nsHb）蛋白水平较高，导致硝酸盐胁迫下NO积累和SNOs含量降低。这些结果表明，SoGSNOR的过表达通过调节ROS和RNS代谢而增加了烟草对硝酸盐胁迫的耐受性。