Due to the effects of climate changes, stress related research has a major focus in the field of plant physiology. Increasing number of extreme weather events cause severe losses in agricultural production. Plants are constantly exposed to the effects of the environmental factors, extreme changes some of these factors may be detrimental to them, cause stress. Due to environmental stresses, oxidative stress is also appear as a secondary stress. During this, the accumulation of reactive oxygen species (ROS) can easily overturn the reduction state of the plants, therefore damages the membranes, proteins and nucleic acids, thus impairing plants’ growth and development. To avoid this, plants are protected by the complete antioxidant defence system.
Plant glutathione peroxidase-like enzymes (GPXL) are members of the antioxidant enzymes, and are able to reduce H2O2 and organic hydroperoxides to water or the corresponding alcohols by using thioredoxin (TRX) (or glutathione (GSH)) as reducing substrates. GPXLs are similar to animal phospholipid hydroperoxide glutathione peroxidases (PHGPX), but they contain a cysteine in their catalytic site instead of selenocysteines. Because of the chemical properties of cysteine, the activity of these enzymes is lower compared to selenocysteine-containing enzymes. This raises the possibility that they may be involved in processes other than enzymatic antioxidant functions. In Arabidopsis thaliana 8 isoenzymes were identified in different subcellular particles, they are localized in the cytoplasm, nucleus, plasma membrane, mitochondria, chloroplasts and Golgi. Arabidopsis is a commonly used model plant of physiological research, since its genetic background is known and many mutants are available. In our experiments Atgpxl T-DNA insertional mutant plants were used to investigate the role of AtGPXL proteins in stress responses. We compared the sensitivity of wild-type (Col-0) and mutant plants to abiotic stress through H2O2 and malondialdehyde (MDA) contents, and we investigated some antioxidant enzyme activities and levels of non-enzymatic antioxidants in the plants. The effect of the lack of one AtGPXL on glutathione redox potential (EGSH) was studied using a redox sensor protein (roGFP2), expressed in selected Atgpxl mutant plants. Experiments of the biochemical properties of GPXL proteins were performed with purified recombinant enzymes
