Avaliação da resposta ao stresse oxidativo induzido por cádmio e cobre em plantas de tabaco transformadas e não transformadas

Abstract

The response of tobacco plants (Nicotiana tabacum L.) non-transformed (WT) and transformed (B1F and B5H) with AtTPS1, the trehalose-6-phosphate-synthase gene from Arabidopsis, to cadmium (50, 200 μM) and copper (100, 400 μM) was compared. Protein content, antioxidative enzymes (CAT, POD, SOD, APX), lipid peroxidation and hydrogen peroxide were determined in leaves. WT showed a significant increase in malondialdehyde content both with Cd and Cu, indicating occurrence of lipid peroxidation. B5H and B1F showed lower incidence of lipid peroxidation. SOD activity showed no significant variation both with Cd and Cu, indicating that superoxide formation was not induced by these heavy metals. POD role in the scavenging of H2O2 was more relevant in WT than in B5H and B1F.CAT seems to be more important in B5H and B1F than in WT, with higher activity compared to WT. APX showed a significant increase in activity levels in B5H, both with Cd and Cu, indicating an important role in the elimination of H2O2. However, H2O2 removal by APX was not capable of reducing H2O2 levels that remained significantly higher than the control. In conclusion, B1F plants seem to be less affected by oxidative stress induced by Cd and Cu than B5H or WT.