Cytosolic ascorbate peroxidase and Cu, Zn-superoxide dismutase improve seed germination, plant growth, nutrient uptake and drought tolerance in tobacco

The effects of over-expression of two cytosolic antioxidant enzymes (Cu, Zn-SOD and/or APX) on plant nutrition, gas exchange, chlorophyll fluorescence, seed viability and germination in transgenic tobacco (Nicotiana tabacum cv. Xanthi) under deficit irrigation or salinity conditions were investigated. Three transgenic lines of tobacco were used in this study: line 17, harboring 2 copies of the cytosolic CuZn-SOD (cytsod) gene; line 51, with 2 copies of the cytosolic APX (cytapx) gene and line 39, harboring one copy of each gene. Over-expression of cytosolic antioxidants enzymes in tobacco plants resulted in a better growth performance that correlated with an improved photosynthetic capacity and nutrient uptake. Moreover, cytsod or cytapx genes promoted seed germination, and enhanced tolerance to mild water stress. In addition, this enhanced antioxidant capacity protected seeds from ageing during prolonged storage, and stimulated germination under salt stress conditions. These results suggest that cytosolic antioxidant transgenes are useful tools to improve drought tolerance, nutrient uptake and seed germination under stressful conditions.