Responses Of Transgenic Tobacco With ZmPP2C2 To Environmental Stress

Protein phosphorylation and dephosphorylation, which are mainly done by protein kinases and phosphatases, two kinds of enzymes possessing converse functions, are most important aspects of signal transduction pathways in all kinds of organisms. Protein Phosphatase 2Cs (PP2Cs) are a subfamily of protein phosphatases and their biochemical properties and protein structures distinguish themselves from any other subgroups. Plant PP2Cs have been demonstrated to play important roles in abscisic acid (ABA) -activated multiple signal transductions, such as ABA-induced seed dormancy/ germination, guard cell closure, ion tunnel regulation and stress acclimation. Meanwhile, plant PP2Cs have also been shown to be involved in signaling in wound response, development and pathogen resistance. As negative regulatory factors of many signaling events, PP2Cs can interact with kinases, other regulatory proteins, or directly combine with DNA to regulate expression of corresponding genes.Transgenic tobacco with ZmPP2C2 gene and wild type tobacco were taken as material in our research. They were cultivated by solution in the mode of sitmulated treatments with low-temperature, salt and water stresss. We investigated the responses of transgenic tobacco with ZmPP2C2 to environmental stress .The main results were as follows:1.The transgenic tobaccos with ZmPP2C2 gene were identified by genome-PCR. The positive plants were selected which were used for physiological measurement.2.Under environmental stress (low temperature, salt and drought),the relative electrical conductivity and MDA content in both wild type and transgenic tobacco increased, which resulted in the increase membrane permeability and electrolyte leakage. The structure and function of cell membrane was damaged .But the MDA and relative electrical conductivity of transgenic tobacco was lower than that of wild type tobacco, that indicated the extent of the membrance lipid perioxidation in transgenic tobacco was smaller than that in wild type tobacco. It is favorable to maintain the function of cell membrane.3. Under environmental stress (low temperature, salt and drought),the contents of proline and soluble sugar in transgenic tobacco accumulated more than in wild type tobacco. Under low temperature stress , the anti-oxidant enzyme( SOD) activities of both wild type and transgenic tobacco increased, while the transgenic type increased more. Similary results observed in POD activaty under salt or drought stress. Interestingly, the SOD activity in both transgenic and wild type tobacco reached a peak and then decreased under salt or water stress, so POD activity was the same under low temperature.4. Under salt or drought stress, Pn and Gs in both wile type tobacco and transgenic tobacco decreased, while there was no obvious difference between wild-type and transgenic plants. However, the level of Fv/Fm in transgenic tobacco decreased less compared with wild type tobacco under salt stress. It indicated that injury of PS II was lower in transgenic tobacco plants.5. Under salt or drought stress, the change of soluble proteins content was similar in two type tobacco, exhibiting decreased and then increased. The Car content of transgenic tobacco increased, while that in wild type tobacco decreased under 150mM NaCl stress.