Studies On Salt Tolerance Of Zmmpk7-overexpression Tobacco

The MAPK cascade is an important signaling pathway among eukaryotic organisms. It is composed of MAPK, MAPKK (MAPK kinase) and MAPKKK (MAPKK kinase). The intracellular signals were relayed and amplified through sequential phosphorylations of MAPKKK→MAPKK→MAPK. The phosphorylation events finally regulate gene expression and cell response to stimuli. In our research, transgenic tobacco with ZmMPK7 gene and wild type tobacco were used to study the responses of transgenic tobacco to salt stress. The main results are as follows:1. Incubated in the MS medium supplemented with different NaCl concentrations, transgenic tobacco lines germinated and grew normally while the wild type tobacco were severely inhibited. This result showed that Overexpressing ZmMPK7 gene enhanced salt tolerance in the transgenic tobacco.2. Under salt stress, the relative electrical conductivity and MDA content in both wild type tobacco and transgenic tobacco increased, which resulted in the increase of membrane permeability and electrolyte leakage. The structure and function of cell membrane was damaged. However, the MDA and relative electrical conductivity in transgenic tobacco was lower than that of wild type tobacco, indicating the extent of the membrance lipid perioxidation in transgenic tobacco was smaller than that in wild type tobacco. Overexpressing ZmMPK7 gene may protect the membrane integrity and stability in transgenic tobacco.3. Under salt stress, transgenic tobacco with ZmMPK7 gene maintained optimal photochemical efficiency of PSⅡ(Fv/Fm) and photosynthetic rate effectively. It showed that overexpression of ZmMPK7 may alleviate the chloroplast degradation and maintain the function of photosynthetic machine in thylakoid membrane .4. Under salt stress, the antioxidant enzyme activities of SOD, POD, CAT and APX in transgenic tobacco changed coordinately. Accumulation of H2O2 in transgenic tobacco was lower than that in wild type tobacco, suggesting that ZmMPK7 was involved in removing ROS to enhance salt tolerance.5. Under salt stress, while the soluble sugar in both transgenic tobacco and wild type tobacco accumulated, the amount showed no obvious difference between transgenic and wild type plants. The transgenic plants accumulated more proline which is favorable to osmotic regulation.