Ectopic expression of FaDREB2 enhances osmotic tolerance in paper mulberry

Dehydration-responsive element binding (DREB) proteins are a subfamily of AP2/ERF transcription factors that have been shown to improve tolerance to osmotic stresses in plants. To improve the osmotic stress tolerance of paper mulberry (Broussonetia papyrifera L. Vent), an economically important tree, we transformed it with a plasmid carrying tall fescue (Festuca arundinacea Schreb) FaDREB2 under the control of CaMV 35S. The ectopic expression of FaDREB2 did not cause growth retardation, and the paper mulberry seedlings expressing FaDREB2 showed higher salt and drought tolerance than wild-type plants (WT). After 13 d of withholding water, or 15 d in the presence of 250 mM NaCl, all the WT plants died, while the plants expressing FaDREB2 survived. The FaDREB2 transgenic plants had higher leaf water and chlorophyll contents, accumulated more proline and soluble sugars, and had less membrane damage than the WT plants under high salt and water-deficient conditions. Taken together, the results indicate the feasibility of improving tolerance to multiple environmental stresses in paper mulberry seedlings via genetic engineering, by introducing FaDREB2, which promotes the increased accumulation of osmolytes (soluble sugars and proline), to counter osmotic stresses caused by abiotic factors.