Role of Reactive Oxygen Species and Antioxidant Enzymes in Systemic Virus Infections of Plants

Oxidative stress in compatible virus‐host plant interactions was studied in cucumber mosaic virus and zucchini yellow mosaic virus‐infected Cucumis sativus and Cucurbita pepo plants. Both cucumber mosaic virus‐ and zucchini yellow mosaic virus‐infected plants showed an enhanced peroxidation of polyunsaturated fatty acids indicating an advanced disintegration of membranes. Radical intermediates formed during lipid peroxidation co‐oxidize pigment molecules and might thus account for virus‐induced yellowing symptoms. Furthermore in infected plants an induction of superoxide dismutases, catalases, total peroxidases and ascorbate peroxidases was observed. All the peroxidase isoforms detected in Cucumis sativus and Cucurbita pepo , however, not only functioned as radical scavengers but also catalysed the formation of H 2 O 2 . Thus it can be presumed that the enhancement of peroxidases contributes to the oxidative stress in systemic plant‐virus interactions. By way of oxidation of indole‐3‐acetic acid upregulated peroxidases might also be responsible for growth reductions and malformations in virus‐infected plants.