Molecular Cloning, Characterization And Transgenic Analysis Of CDNAs For Salt Stress Tolerance Response In Arabidopsis Thaliana Using Schizosaccharomyces Pombe

Environmental factors that impose water-deficit stress, such as salinity, drought and temperature extremes, place major limits on plant productivity, and soil salinity is a major abiotic stress in plant agriculture worldwide. Might salt stress affect plant metabolism in a complex way that disrupts homeostasis in water potential and ion distribution. To achieve salt tolerance, the damage must be prevented or alleviated. At the same time, homeostatic conditions must be re-established and plant growth must be resumed. By far, many ion/proton transporters that involves in K+/Na+ uptake and transport, establishment of proton gradients, removal and sequestration of toxic ions from the cytoplasm and organelles have been isolated. Meanwhile, many proteins have also been isolated related to osmoprotectants, reactive oxygen scavengers, stress-induced proteins, heat shock proteins, membrane fluidity, water status, signaling components, transcription control and growth regulators. However, studies of stress adaptation have suggested a network of multiple signaling pathways in the course of physical adaptations and interactive molecular and cellular changes that begin after the onset of stress in plant .The most important task in the next few years remains to identify pathway components to establish their function by genetic approaches.Despite soil salinity is the major constraint for plant agriculture, few functional determinants of salt adaptation have been identified and the significance of their involvement characterized. The fission yeast Schizosaccharomyces pombe is a single cell eukaryotic organism. Taking advantage of the genetic simplicity of S. pombe and the functional conservation of some salt tolerance-related proteins, We used this organism as a simple system to identify Arabidopsis thaliana salt tolerance proteins by screening for cDNA clones that confer salt resistance when overexpressed. An Arabidopsis thaliana cDNA library was constructed in pREPSN vector under the control of the inducible nmt-1 promoter and transformed into S. pombe. Expression of the A. thaliana sequences were induced and clones showing strong salt stress wereidentified and analysed. By this 'cross-phylogenetic' screen, We have isolated some salt tolerance-related proteins such as glycine-rich protein, chlorophyll a/b-binding protein and some unknown protein. Overexpression of these proteins in the yeast cells afforded significantly increase in salt tolerance. Northern-blot analysis revealed that these genes were induced by NaCl and ABA. In addition, differentially regulated in various tissues. Transgenic Arabidopsis can develop better than wild type in salt tolerance. Taken together, these results undoubtedly suggest that these proteins are involved in the salt stress response in Arabidopsis. The AtGRP9 gene and the AtCab gene are first reported to salt stress response in Arabidopsis.