Cadmium Affects the Glutathione/Glutaredoxin System in Germinating Pea Seeds

The aim of this work was to investigate the effects of cadmium (Cd) on thiol and especially glutathione (GSH)-dependent reactions (glutathione content, glutaredoxin (Grx) content and activity, "glutathione" peroxidase (Gpx) activity, and glutathione reductase (GR) activity) in germinating pea seeds. Under Cd stress conditions, the overall activity as well as more specifically the expression of Grx C4 and Grx S12 increased. On the contrary, when incubated with Cd ions in vitro, the disulfide reductase activity of both isoforms was drastically inhibited. In the case of Grx C4, this correlated with the formation of protein dimers of 28 kDa as evidenced by electrophoresis analysis. Oxidative stress also affected the GSH status, since Cd treatment provoked (1) a pronounced stimulation in Gpx (a thioredoxin-dependent enzyme in plants) expression and (2) a drastic decrease in GR activity. These results are discussed in relation with the known contribution of Grx system to the thiol status during the germination of Cd-poisoned pea seeds.