Study On Tolerances Of DREB Transgenic BY-2 Cells To Salt And Osmotic Stresses

Abiotic stresses such as drought, salt and cold exert severe influences on growth and development of plant. Plants have evolved to perceive different stress signals from their surroundings, to integrate them and to respond to these different stresses by modulating the expression of related genes. The products of these genes induced by drought stress can be classified into two groups: those that directly protect against environmental stresses, and those that regulate gene expression and signal transduction in the stress response. The first group includes proteins and enzymes that likely function by protecting cells from dehydration, such as late embryogenesis abundant (LEA) proteins, enzymes required for biosynthesis of proline.and aquaporins(AQP), et al. The second group of gene products includes transcription factors, protein kinases, and enzymes involved in phosphoinositide metabolism, such as bZIP, MYC. Plants sense the environmental changes through many ways, and then transform these changes into the cell signals. The transcription factors accepting this signal after a series of actions will act with cis-acting element and promote the expression of stress-responsive genes, resulting in an enhance of stress-tolerance in plants. The transcription factor plays an important role on transcriptional control.The transcription factors accepting this signal after a series of actions will act with cis-acting element and promote the expression of stress-responsive genes, resulting in an enhance of stress-tolerance in plants. In plants, the expression of many genes is regulated at transcriptional level, and mostly by cis- and traps-acting elements. DREB, encodes a transcriptional factor that responds to drought stress and induces the expression of certain stresses tolerances genes and plays important roles in stress signal transduction, gene expression modulation and phase transition during Arabidopsis thaliana development.In this study, an expression plasmid pBACI28F carrying transcriptional factor gene from Arabidopsis driven by drought inducing promoter rd29B, was transformed with BY-2 (bright yellow 2) suspension cells of tobacco by particle bombardment. The research work and the main conclusions are as follows:1. By particle bombardment of PDS1000/He system, plasmid pBACI28F was transformed with BY-2 (bright yellow 2) suspension cells of tobacco. After screen by Bialaphos, transgenic suspension cell lines were produced.2. PCR and PCR-Southern blotting identification were conduced to screen the transgenic cells. The results showed that foreign DREB gene were well integrated into some transgenic BY-2's genome.3. After 14d stress treatments under solid-culture supplementing of as high as 300mM NaCl or15% PEG6000, transgenic cell lines could grow and WT was near to death. Our research suggested that transferring foreign DREB gene can greatly improve tolerances of transgenic BY-2 to Salt and Osmotic stresses.4. Proline and MDA content and SOD activities were measured to test the resistance of transgenic cell lines to osmotic (PEG6000) and salt (NaCl) stresses treatments. The results showed that there was no significant difference between transgenic cell lines and the wild type (WT) under normal growth conditions. Proline content was higher in transgenic cell lines than that in WT under osmotic and salt stresses, but opposite result in MDA accumulation was obtained. SOD activities in transgenic cell lines were increased significantly comparison with that in WT under different concentration of NaCl and PEG6000 treatments.In conclusion, transcription factor DREB gene can activate the expression of array of downstream stress defense genes. The transgenic BY-2 over-expressing DREB gene show significant improvement in tolerance to abiotic stresses. Furthermore, studies of physiology and metabolism in transgenic BY-2 would be advantaged to uncover mechanism that DREB gene improve drought tolerance of transgenic plants. And these results lay the foundation to research on expression regulation of DREB in monocotyledonous plant and breed wheat materials with stress resistance.