Engineering of Reactive Species Detoxification Pathways for Increasing Stress Tolerance in Plants

The productivity of plants is greatly affected by environmental stresses such as drought, high or low temperature, high salinity and UV-B irradiation, therefore there is a continuous need for the genetic improvement of stress tolerance in the agriculture. The abiotic stresses can disturb the homeostasis between assimilation and oxidative reactions, negatively influencing the photosynthetic yield of higher plants and resulting in oxidative damage. Reactive compounds produced under such conditions significantly increase the cytotoxic effect of environmental stresses. Beside the generated reactive oxygen species (ROS), reactive aldehydes (as 4-hydroxy-nonenal and methylglyoxal) can further increase the cellular damages mainly due to their better penetration through biological membranes and their rapid reaction with biomolecules such as proteins and DNA. Improvement of intracellular scavenging capacity of such toxic compounds provenly leads to increased stress tolerance. Plant aldo-keto reductases (AKRs) are important enzymes for such function since they have a wide range of activity on lipid peroxidation and glycolysis generated reactive aldehydes. AKRs can detoxify those lipid peroxidation products (e.g., 4-hydroxynon-2-enal) and glycolysis-derived reactive aldehydes (e.g., methylglyoxal) that contribute significantly to cellular damages caused by environmental stresses. Moreover, the specific members of this NADPH-dependent aldo-keto reductase superfamily are able to catalyze the production of sugar alcohols (like sorbitol or mannitol). The products of these reactions can act as radical scavengers even at low concentration and their accumulation as osmolytes can lead to improvement of osmotic adaptation.