Localization of S-nitrosoglutathione and expression of S-nitrosoglutathione reductase in pea plants under cadmium stress.

S-nitrosoglutathione (GSNO) is considered a natural nitric oxide (NO.) reservoir and a reactive nitrogen intermediate in animal cells, but little is known about this molecule and its metabolism in plant systems. In this work, using pea plants as a model system, the presence of GSNO in collenchyma cells was demonstrated by an immunohistochemical method. When pea plants were grown with a toxic Cd concentration (50 microM) the content of GSNO in collenchyma cells was drastically reduced. Determination of the nitric oxide (NO.) and gluthathione contents in leaves by confocal laser scanning microscopy and HPLC, respectively, showed a marked decrease of both compounds in plants treated with cadmium. The analysis of the S-nitrosoglutathione reductase (GSNOR) activity and its transcript expression in leaves showed a reduction of 31% by cadmium. These results indicate that GSNO is associated with a specific plant cell type, and this metabolite and its related catabolic activity, GSNOR, are both down-regulated under Cd stress.