Isolation And Function Identification Of A Novel Mitogen-Activated Protein Kinase Gene, ZmOSMAPK1, In Maize Roots And Its Role In Plant Signal Transduction

Mitogen Activated Protein Kinase (MAPK) cascades are common signal transduction pathway in all eukaryotes. The MAPK cascades are composed of MAPK, MAPKK(MAPK kinase) and MAPKKK(MAPKK kinase). They transfer signals through phosphorylations of MAPKKK-MAPKK-MAPK in turn. In plants, MAPK cascades interlace with other signal transduction pathways and form a molecular interaction network, and regulate various cellular functions, including growth, development, biotic and abiotic stress responses.To date, numerous MAPKs have been isolated from different plants, and considerable progress has been made in understanding plant MAPKs. Though the regulation of MAPK signaling has been discussed most in dicot plant species (Arabidopsis, tobacco, and alfafa etc.), the study on maize MAPKs is virtually lacking. In this thesis, a series of studies based on the materials of maize Zheng 958 have been conducted on the gene isolation, sequence comparison, expression analysis, kinase activity analysis and the further study was carried on the signaling pathway in which ZmOSMAPK1 was involved. The main results are as follows:1. Analysis of MAPKs activity in maizeThe activity of MAPKs in maize roots was investigated by solution assay after various treatments. Results showed that drought, salt and cold stress induced the activitation of MAPKs rapidly, which indicated that the MAPK signaling pathway played important roles in maize under the three kinds of stress. The MAPKs activity reached a high level in 2 hours after three stress treatments and then declined obviously, which showed that there was an effective MAPK regulation mechanism in maize. The maximum activity of MAPKs and the time on which it appeared were different under three stress treatments, suggesting that the MAPK cascades would be diverse in different stress. The MAPKs activity also could be induced by exogenously signal molecules, such as H2O2, SA and ABA. The results all above indicated that the MAPK cascades had important functions in various stress signaling pathways. The further study found that the kinase activity induced by environmental stimulation could be inhibited by MEK inhibitor PD98059, and weakened by protein synthesis inhibitor CHX and enhanced by protein phosphatase inhibitor PAO.2. Isolation and characterization of ZmOSMAPK1 gene...