Abstract
Salinity is the major environmental limiting factor of plant growth and productivity. Salt, as well as drought, chilling and extreme temperatures, increases the levels of reactive oxygen species (ROS). Excessive levels of ROS lead to oxidative damage to cellular molecules, ageing and cell death. The antioxidative system is important for the maintenance of intracellular ROS at appropriate levels. The antioxidant ascorbate is oxidized in antioxidative reactions, and a system for the regeneration of ascorbate is critical for maintaining the antioxidative system. Dehydroascorbate (DHA) reductase (DHAR) catalyses the re-reduction of DHA to ascorbate. The transcription levels and activity of DHAR are increased in response to various abiotic stresses. Mutant plants deficient in DHAR are hypersensitive to stress. Conversely, transgenic plants that overexpress DHAR show enhanced salt tolerance. Thus, manipulation of DHAR expression is important for genetic engineering of salt-tolerant plants.