Plant adaptation to stress conditions: The case of glutathione S-transferases (GSTs)

Plants, unlike animals, are anchored to one place and, therefore, forced to sustain any environmental condition present. Unfavourable environmental conditions include abiotic (extreme temperatures, water deficits, floods, salinity, light intensities) and biotic (pests, viral, bacterial and fungal diseases) stress factors. Both types of stresses induce the production of reactive oxygen species (ROS), which damage macromolecules such as proteins, lipids, nucleic acids and cell structures like membranes. The effect of each stress factor depends on its intensity. When the stress is severe and the production of ROS is high, it might result to plant death. To avoid such event, plants have developed advanced physiological and chemical defence mechanisms of stress avoidance and/or tolerance, which allow growth only when the environmental conditions are optimum for each species, like in the case of seed dormancy. Plants have also evolved specific enzymatic defence mechanisms, including enzymes like catalase, peroxidase, super oxide dismutase and glutathione transferases. These defence mechanisms help plants either to avoid adverse environmental conditions or to combat their negative effects. A major defence mechanism involves the action of antioxidant enzymes. Glutathione transferases (GSTs) are antioxidant enzymes of great importance for the detoxification of plants from toxic compounds. GSTs have also important involvement in plant stress tolerance against biotic and abiotic stress tolerance like extreme heat, cold, salt and herbicides.