This article reviews the current knowledge of the Zucchini yellow mosaic virus (ZYMV) specific physiological alterations within Styrian oil pumpkin plants with respect to glutathione metabolism. Reactive oxygen species (ROS), whose formation is accelerated under the virus infection, must be rapidly processed by antioxidants if oxidative damage is to be averted. Coupled with carbon, nitrogen and sulfur metabolism the reduced form of glutathione is known to play important protective roles in responses against viral pathogen infections, acting as an antioxidant, signal molecule and redox buffer. Biochemical analysis and immunocytochemical techniques were used, in order to demonstrate the alterations in the concentration and the distribution of glutathione in organs, tissues and within single cells of ZYMV infected Styrian oil pumpkin plants. The symptoms were preceded by a decline in total glutathione levels within whole leaves, whereas in single cells of dark-green leaf parts, close to the main leaf vein, increased glutathione concentrations were observed. Besides genetic engineering, possibilities to increase cellular glutathione contents in plants are the use of glutathione precursors or chemicals, which are stimulating glutathione synthesis. Experiments with L-2-oxothiazolidine-4-carboxylic acid (OTC) and salicylic acid (SA) demonstrated, that both chemicals were rapidly taken up by the plants since cotyledons, roots, leaf protoplasts and callus cells possessed a high affinity to assimilate these chemicals into thiol compounds. Furthermore, treatment with OTC and SA provided an enhanced tolerance against ZYMV induced symptoms and stimulated the synthesis, conversion and translocation of glutathione during advanced ZYMV infection in seedlings and regenerated plants. Since the characteristically thin, coated seed character of the Styrian oil pumpkin is a genetically recessive trait somatic embryogenesis discussed in this article would be important not only to obtain virus resistance by modulating the physiological properties of the plantlets, but also for the conservation of this local cultivar.

Key words: Cucurbita pepo, Styrian oil pumpkin, ZYMV, reactive oxygen species, systemic acquired resistance, glutathione, L-2-oxothiazolidine-4-carboxylic acid, salicylic acid, somatic embryogenesis, virus tolerance Abbreviations: GR, glutathione reductase; GSH, reduced glutathione; GSSG, oxidized glutathione; HIV, human immunodeficiency virus; H2O2, hydrogen peroxide; OTC, L-2-oxothia zolidine-4-carboxylic acid; ROS, reactive oxygen species; SA, salicylic acid; SAR, systemic acquired resistance; ZYMV, Zucchini yellow mosaic virus;

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