Abstract: Glutathione transferases (GSTs) are a diverse group of antioxidant enzymes. Their most known function is the detoxification of endogenous or exogenous harmful molecules by conjugation of glutathione (GSH). Numerous GSTs also have glutathione peroxidase (GPOX) activity reducing lipid peroxides, and are involved in membrane integrity maintenance. Glutathione is the master regulator of the reduction - oxidation (redox) states in cells, but reactive oxygen species (ROS), non-enzymatic and enzymatic antioxidants all contribute to the redox homeostasis. Cytosolic GSTs may represent up to 2% of the soluble protein in plant cells. In Solanum lycopersicum a total of 90 GST genes were identified. We aimed to compare the stress responses of two tomato cultivars (Moneymaker and Ailsa Craig), particularly regarding to the relationship between the redox potential and the diverse GST enzyme family. Osmotic and salt stresses and salicylic acid treatments were applied to trigger redox changes. Generally, cv. Moneymaker can be characterized by lower ROS and lipid peroxide levels, higher ascorbate (ASC) and GSH contents, more negative glutathione redox potential and higher GST and GPOX activities than cv. Ailsa Craig. Besides higher transcript abundance of genes involved in recycling of ASC and GSH pools, large number of SlGSTs were expressed at higher level in cv. Moneymaker even under control conditions compared to those in cv. Ailsa Craig and were induced more by the stresses. However, several genes expressed in cv. Moneymaker on extremely high level were induced by stress treatments also in cv. Ailsa Craig and stronger correlation with redox changes was observed in that cultivar. SlGSTs with high expression levels or showing strong positive or negative correlations with redox potentials presumably have important roles in stress responses. Their further investigations and molecular characterization may lead to new insight in improving stress tolerance of tomato and other crops.

Biography: She was awarded by PhD degree in 2003 (the title of the thesis: Control of the stress responses in auxin heterotrophic and autotrophic tobacco tissue cultures). Besides having active roles in teaching, her main research interest is the investigation of the effect of abiotic stresses (drought, osmotic stress, NaCl, heavy metal) on physiological processes, water relations of different plant species (Arabidopsis, wheat, tomato, tobacco, poplar). In the focus of their research is the antioxidant mechanisms and their roles in stress tolerance. Among the antioxidative enzymes especially the glutathione-related enzymes (glutathione transferase, glutathione reductase, glutathione peroxidase) are estimated. They reported that the enhanced and/or maintained antioxidant activity, among them that of glutathione transferases and peroxidases under stress conditions are important features of the priming effect of salicylic acid on Arabidopsis and tomato plants. She habilitated in 2019 (the title of the thesis: Role of glutathione and glutathione-related enzyme systems in plant stress responses). They also adapt a recently developed fluorescent reporter system and use a redox sensitive green fluorescent protein (roGFP), allowing monitoring of the dynamic changes of redox state in living plants or tissues using real time fluorescence imaging.