Stress-Inducible Overexpression of SlDDF2 Gene Improves Tolerance against Multiple Abiotic Stresses in Tomato Plant

Dehydration-responsive element-binding protein 1 (DREB1)/C-repeat binding factor (CBF) family plays a key role in plant tolerance against different abiotic stresses. In this study, an orthologous gene of the DWARF AND DELAYED FLOWERING (DDF) members in Arabidopsis, SlDDF2, was identified in tomato plants. The SlDDF2 gene expression was analyzed, and a clear induction in response to ABA treatment, cold, salinity, and drought stresses was observed. Furthermore, two transgenic lines (SlDDF2-IOE#6 and SlDDF2-IOE#9) with stress-inducible overexpression of SlDDF2 under Rd29a promoter were generated. Under stress conditions, the gene expression of SlDDF2 was significantly higher in both transgenic lines. The growth performance, as well as physiological parameters, were evaluated in wild-type and transgenic plants. The transgenic lines showed growth retardation phenotypes and had higher chlorophyll content under stress conditions in plants. However, the relative decrease in growth performance (plant height, leaf number, and leaf area) in stressed transgenic lines was lower than that in stressed wild-type plants, compared with nonstressed conditions. The reduction in the relative water content and water loss rate was also lower in the transgenic lines. Compared with wild-type plants, transgenic lines showed enhanced tolerance to different abiotic stresses including water deficit, salinity, and cold. In conclusion, stress-inducible expression of SlDDF2 can be a useful tool to improve tolerance against multiple abiotic stresses in tomato plants.