Antioxidant enzyme activities and isozyme pattern in hairy roots and regenerated tobacco plants

Hairy root disease is caused by infection of wounded higher plants with Agrobacterium rhizogenes. Transformation of tissues or plants with A. rhizogenes, as well as transformation with rol genes, in addition to hairy roots, may produce alterations in the plant secondary metabolism. H2O2 and other ROS are involved as signals in secondary metabolite production pathways and play a key role in plant defense reactions. In this work the effects of A. rhizogenes rol genes on nicotine content, antioxidant enzymes activity, H2O2 production, the pattern of peroxidase (POX) and superoxide dismutase (SOD) isozymes in hairy roots and regenerated Nicotiana tabacum plants were studied. The rise in SOD and POX activities in the transformed lines TRa and TRb and the resulting regenerated plants and a decreased level of H2O2 in them as compared with the untransformed lines indicates that rol gene expression decreases H2O2 level probably by increasing production of antioxidant enzymes. A decreased H2O2 content in TRc line, in spite of similarity of antioxidant enzyme activity as compared to normal roots, indicates that rol genes activate other mechanisms except SOD and POX enzymes for reducing H2O2.