Study on Osmotic Stress Resistance of Tobacco by Overexpressing NsAKT1 and AtDWF4

In order to study the role of potassium and BRs in regulating plant resistance to stresses, the transgenic tobaccos overexpressing the K⁺ absorption gene NsAKT1 and the BRs synthetic gene AtDWF4 were used to analyze the effects of PEG osmotic stress on morphology and resistance-related physicochemical indexes of transgenic tobaccos. The results showed that SOD activities of the transgenic tobacco plants reached the maximum values at 3 d after PEG treatment, which was significantly higher than that of non-transgenic tobacco (Wt). Among them, the highest SOD enzyme activity was in plants co-transformed with AKT1/DWF4. The POD enzyme activities of the three transgenic plants were significantly higher than that of Wt plants at 1 d after PEG stress (p<0.05), and the POD enzyme activities in the AKT1/DWF4 co-transformed tobacco plants were 1.28 folds, 1.40 folds and 1.90 folds higher than that of trans-AKT1 plants, trans-DWF4 plants and Wt plants, respectively. Three days after PEG treatment, CAT enzyme activities in the AKT1/DWF4 plants increased the most, up to 59.18%, which was significantly higher than the other two transgenic tobaccos. Meanwhile, the determination of H₂O₂ and MDA contents showed that the maximum values of MDA and H₂O₂ in Wt were 58.52 nmol/g and 38.21 μg/g, respectively. Five days after PEG stress, these values were significantly higher than those in transgenic tobacco plants. Additionally, the expression analysis of characteristic genes indicated that NsAKT1 and AtDWF4 might synergistically regulate the resistance to PEG osmotic stress of the AKT1/DWF4 tobacco lines. The results of this study provided a theoretical basis for further understanding of the mechanism of K and BRs synergistically mediated tobacco response to stresses and the creation of excellent new tobacco germplasm.