Improvement of freezing tolerance in tobacco plants expressing a cold-responsive and chloroplast-targeting protein WCOR15 of wheat

Cold acclimation, an adaptive process for developing freezing tolerance in overwintering plants, is associated with increased expression levels of a series of cold-responsive (Cor)/late embryogenesis abundant (Lea) genes. To investigate the function of Wcor15, a member of the wheat Cor/Lea gene family, for improvement of freezing tolerance, two types of transgenic tobacco tines expressing Wcor15-containing chimeric genes were produced and characterized. Immunoblot and gene expression analyses of a transgenic tobacco tine expressing the Wcor15-GFP fusion gene under control of the CaMV35S promoter showed transport and abundant accumulation of the WCOR15 protein in the stromal compartment of the chloroplasts. The 5' upstream region of Wcor15 induced expression of the GFP reporter gene under low-temperature conditions in the transgenic tobacco. Both transgenic lines expressing the Wcor15-GFP fusion gene showed a similar and significantly improved level. of freezing tolerance compared with the wild-type tobacco plants. Our results demonstrate that the induced expression of the wheat Wcor15 gene positively contributes to the development of freezing tolerance in the heterologous tobacco plants. (C) 2005 Elsevier GmbH. All rights reserved.