Glutathione peroxidase expression and activity in barley root tip after short-term treatment with cadmium, hydrogen peroxide and t-butyl hydroperoxide

The purpose of this study was to analyse the alterations of glutathione peroxidase (GPX) expression and activity during the recovery period after a short-term treatment of barley root tip with cadmium (Cd) and hydrogen peroxide (H2O2). The transcript level of GPX increased as early as 1 h and GPX activity 3 h after short-term treatment independently of Cd concentration. In 15 mu M Cd-treated roots, its expression reached a peak within 2 h and sustained until 3 h, after which it gradually declined. After 6 h of short-term Cd treatment, the activity of GPX was the highest in the 15-mu M Cd-treated roots. At higher Cd concentrations, the activity of GPX was lower than in 15 mu M Cd-treated roots, but still higher than in control roots. A considerable increase in H2O2 production was observed even after only 1 h of short-term exposure of roots to 30 and 60 mu M Cd, while after 15 mu M Cd exposure, its production increased 3 h after the treatment. Lipid peroxidation increased even 1 h after short-term treatment in a Cd concentration-dependent manner. A considerable decrease of GPX activity was observed after the exposure of roots to H2O2 or t-butyl hydroperoxide in a concentration-dependent manner despite that its expression increased even 1 h after short-term treatment. Presumable, under high acute Cd stress, rapid accumulation of H2O2 leads to the disturbance of basal metabolic processes affecting also GPX activity. In contrast, high GPX activity under moderate Cd stress maintains cell function despite the high rate of H2O2 metabolism in root tip.