Overexpression of from Yam ( Thunb.) Enhances Cold Tolerance in Transgenic Tobacco.

β-amylase (BAM) plays an important role in plant development and response to abiotic stresses. In this study, 5 members were identified in yam ( Thunb.). A novel β-amylase gene , (named ), was isolated from yam varieties Bikeqi and Dahechangyu. The open reading frame (ORF) of is 2806 bp and encodes 543 amino acids. Subcellular localization analysis indicates that DoBAM1 localizes to the cell membrane and cytoplasm. In the yam variety Dahechangyu, the starch content, β-amylase activity, and expression of were characterized and found to all be higher than in Bikeqi. overexpression in tobacco is shown to promote the accumulation of soluble sugar and chlorophyll content and to increase the activities of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and β-amylase. Under cold treatment, we observed the induced upregulation of and lower starch content and malondialdehyde (MDA) accumulation than in WT plants. In conclusion, these results demonstrate that overexpression plays an advanced role in cold tolerance, at least in part by raising the levels of soluble sugars that are capable of acting as osmolytes or antioxidants.