Abstract
Ascorbate (AsA) is a potent antioxidant protecting plants against oxidative damage imposed by environmental stresses such as ozone, drought and salt stress. In this study we demonstrated the enhancement of oxidative stress tolerance in transgenic tobacco (Nicotiana tabacum) overexpressing either cytosolic dehydroascorbate reductase (DHAR) or cytosolic monodehydroascorbate reductase (MDAR). Incorporation of the transgenes in the genome of tobacco plants was confirmed by PCR and Southern blot analysis and its expression was confirmed by Northern and Western blot analyses. DHAR transgenic plants exhibited 2.3 to 3.1 folds higher DHAR activity and 1.9 to 2.1 folds higher level of reduced AsA compared to non-transformed plants. MDAR transgenic plants exhibited 1.2 to 2.1 folds higher MDAR activity and 2.0 folds higher level of reduced AsA. These transgenic plants showed maintained redox status of AsA and exhibited an enhanced tolerance to ozone, drought, salt, and polyethylene glycol stresses in term of higher net photosynthesis.
