Transcriptional and enzymatic regulation of antioxidant enzymes in aluminium induced oxidative stress in sorghum roots and leaves

Aluminum (Al) is amongst the most abundant elements of the planet and exposure to this metal can cause oxidative stress and lead to various signs of toxicity in plants resulting in decreased crop productivity. In this experiment we have studied the effect of Al treatment (100 µmol/L and 250 µmol/L) on induction of oxidative stress and changes in antioxidant gene expression in sorghum bicolor (cv AN 2000). Al treatment increased superoxide and H2O2 content and protein oxidation in both roots and leaves of sorghum. The lipid peroxide levels increased only in roots. The catalase (CAT) activity decreased both in roots and leaves while ascorbic peroxidase (APX) activity decreased in roots and increased in leaves. The activities of guaicol peroxidase (GPX) and superoxide dismutase (SOD) increased in dose dependent manner both in roots and leaves. The antioxidant gene expression analysis showed up regulation of SOD and GPX genes in roots and leaves while CAT showed decrease in expression. APX was down regulated in roots and up regulated in leaves. Our results indicate that Al toxicity generated oxidative damage in roots as indicated by increased level of lipid peroxidation but stimulated antioxidant enzymes conferred protection from oxidative damage in leaves.