Laboratory of Plant Physiology and Biochemistry, Department of Botany, University of Delhi, Delhi 110007, India.
Research Unit Protein Science, Helmholtz Zentrum Muenchen, D-80939, München, Germany.
Physiol Plant. 2018 Jan;162(1):49-72. doi: 10.1111/ppl.12641. Epub 2017 Oct 26.
Nitric oxide (NO) and various reactive nitrogen species produced in cells in normal growth conditions, and their enhanced production under stress conditions are responsible for a variety of biochemical aberrations. The present findings demonstrate that sunflower seedling roots exhibit high sensitivity to salt stress in terms of nitrite accumulation. A significant reduction in S-nitrosoglutathione reductase (GSNOR) activity is evident in response to salt stress. Restoration of GSNOR activity with dithioerythritol shows that the enzyme is reversibly inhibited under conditions of 120 mM NaCl. Salt stress-mediated S-nitrosylation of cytosolic proteins was analyzed in roots and cotyledons using biotin-switch assay. LC-MS/MS analysis revealed opposite patterns of S-nitrosylation in seedling cotyledons and roots. Salt stress enhances S-nitrosylation of proteins in cotyledons, whereas roots exhibit denitrosylation of proteins. Highest number of proteins having undergone S-nitrosylation belonged to the category of carbohydrate metabolism followed by other metabolic proteins. Of the total 61 proteins observed to be regulated by S-nitrosylation, 17 are unique to cotyledons, 4 are unique to roots whereas 40 are common to both. Eighteen S-nitrosylated proteins are being reported for the first time in plant systems, including pectinesterase, phospholipase d-alpha and calmodulin. Further physiological analysis of glyceraldehyde-3-phosphate dehydrogenase and monodehydroascorbate reductase showed that salt stress leads to a reversible inhibition of both these enzymes in cotyledons. However, seedling roots exhibit enhanced enzyme activity under salinity stress. These observations implicate the role of S-nitrosylation and denitrosylation in NO signaling thereby regulating various enzyme activities under salinity stress in sunflower seedlings.
一氧化氮（NO）和各种活性氮物种在正常生长条件下在细胞中产生，其在应激条件下的增强产生负责各种生化异常。本研究结果表明，向日葵幼苗根在亚硝酸盐积累方面对盐胁迫表现出高度敏感性。在盐胁迫下，S-亚硝基谷胱甘肽还原酶（GSNOR）活性明显降低。用二硫苏糖醇恢复 GSNOR 活性表明，该酶在 120mM NaCl 条件下可被可逆抑制。使用生物素转换测定法在根和子叶中分析了盐胁迫介导的胞质蛋白 S-亚硝基化。LC-MS/MS 分析显示幼苗子叶和根中的 S-亚硝基化模式相反。盐胁迫增强了子叶中蛋白质的 S-亚硝基化，而根中蛋白质则发生去亚硝基化。经历 S-亚硝基化的蛋白质数量最多的属于碳水化合物代谢类别，其次是其他代谢蛋白。在受 S-亚硝基化调节的 61 种蛋白质中，有 17 种仅存在于子叶中，4 种仅存在于根中，而 40 种则存在于两者中。在植物系统中首次报道了 18 种 S-亚硝基化蛋白质，包括果胶酯酶、磷脂酶 D-α 和钙调蛋白。进一步对甘油醛-3-磷酸脱氢酶和单脱氢抗坏血酸还原酶的生理分析表明，盐胁迫导致子叶中这两种酶的可逆抑制。然而，幼苗根在盐胁迫下表现出增强的酶活性。这些观察结果表明 S-亚硝基化和去亚硝基化在 NO 信号转导中的作用，从而调节向日葵幼苗在盐胁迫下各种酶活性。
