Abstract
S-Nitrosothiols (SNO) are redox-activated molecules formed through reactions between thiol compounds and reactive nitrogen oxides (NOx) such as NO. S-Nitrosoglutathione (GSNO), a representative SNO with biological relevance, is regarded as a vital substance mediating protein S-nitrosylation in animal NO signaling. Although little is known of plant biochemistry and physiology of SNO, we recently found that SNO constitutes a part of "unidentified nitrogen"-bearing compounds, a largely unexplored group of ubiquitous plant metabolites. When exposed to NOx, Arabidopsis plants significantly increased the level of SNO most of which were recovered in high-molecular fractions. Overexpression of Arabidopsis GSNO reductase (GSNOR), the only known plant enzyme possibly involved in SNO metabolism, led to a significant SNO reduction in transgenic Arabidopsis. In contrast, knocking out the GSNOR gene resulted in SNO accumulation and severe growth inhibition. These results strongly indicate GSNOR as a key enzyme in SNO metabolism and its potential importance in plant physiology.
