Cloning and Stress Expression of AlDREB2 Gene from Aloe vera L. var.chinensis Isolation and Identification of pndreb1-A New DREB Transcription Factor from Peanut(Arachis hypogaea L.) DREB Gene Expression in Leaves of Broussonetia papyrifera Seedlings under Salt Stress Detected by Real-Time Fluorescent Quantitative PCR Cloning and Stress Expression of AlDREB2 Gene from Aloe vera L. var.chinensis