The response of transgenic Nicotiana tabacum L. plants carrying the gene for potyviral non-structural P3 protein to Potato virus Y (strain NTN) infection was not significantly different from the wild type. The activities of antioxidant enzymes catalase (CAT), glutathion reductase (GR), ascorbate peroxidase (APOD) and superoxid dismutase (SOD), determined in systemically infected leaves at early stages of the infection did not change except for the transient increase in CAT and GR activities in

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... he wild type infected plants compared to the healthy ones. At the stages, when severe symptoms of the infection developed on the leaves and the virus content reached its maximum, a significant increase in the activities of several enzymes of anaplerotic metabolic pathways, NADP-dependent malic enzyme (NADP-ME), phosphoenolpyruvate carboxylase