Exogenous nitric oxide-mediated GSH-PC synthesis pathway in tomato under copper stress

Nitric oxide (NO) is a bioactive molecule that is extensively used at various biotic and abiotic stresses. This study investigated the law governing the variation of related enzymatic activity and metabolites in exogenous NO-mediated GSH-PC synthesis pathway in tomato solution culture subjected to copper stress. Results demonstrated that relative to control copper stress was more effective in the activation of gamma-ECS and GS in tomato. Moreover, sharp increases in root GSH and PCs were observed, which keep upward as the process continued. Moreover, adding exogenous SNP (NO donor) can further improve gamma-ECS and GS activities in tomato roots and facilitate the synthesis of GSH and PCs, thereby enhancing its peroxide removal ability, chelating excessive Cu2+, and reducing its biotoxicity. The GSH-PC metabolism in the tomato leaves lagged behind that in the roots to a certain extent. Although exogenous GSH synthesis inhibitor BSO inhibited gamma-ECS activity in tomato roots, as well as GSH and PC syntheses, adding SNP can counteract this effect by lessening the influence to the PCs in leaves. Under copper stress, exogenous NO may stimulate a signaling mechanism and reduce the biotoxicity and oxidative damage caused by excessive Cu2+ through activating or enhancing the enzymatic and non-enzymatic systems in the GSH-PC synthesis pathway.