Isolation and Expression of a Gene Encoding CBF/DREB1 Transcription Factor from Chorispora bungeana Physiological responses of Chorispora bungeana seedings in vitro to drought stress simulated by PEG-6000 Cloning and Prokaryotic Expression of Chorispora bungeana CbMAPK3 Gene Effect of Drought Stress on Antioxidant System and Reactive Oxygen in Chorispora bungeana Plantlets in vitro