When plants are attacked by pathogenic microorganisms, they respond with a variety of defense reactions including production of PR proteins. We identified OsWRKY53 by microarray analysis as a chitin oligosaccharide elicitor-induced gene, and indicated that OsWRKY53 functions as a transcriptional activator, and that overexpression of OsWRKY53 resulted in enhanced resistance to the rice blast fungus Magnaporthe grisea in rice plants. It has been suggested that MAPK-mediated phosphorylation of orthologs of OsWRKY53 in other plant species results in increase in transactivation acitivity. To examine the effect of phosphorylation of OsWRKY53 on its transactivation activity, we performed reporter gene assay in rice calli using a reporter plasmid containing a GAL4 binding site fused to LUC gene and an effector plasmid encoding a fusion protein of the GAL4 DNA binding domain and native, phospho-mimic, or alanine-substituted OsWRKY53. LUC activity was highest when the effector was the phospho-mimic OsWRKY53, followed by native OsWRKY53, and then the alanine-substituted OsWRKY53. These results may suggest that MAPK-mediated phosphorylation of OsWRKY53 function to increase in its transactivation activity in rice. Now, we are trying to determine whether MAPK cascades are involved in phosphorylation of OsWRKY53 in rice by in vitro phosphorylation assay. Also, we are trying gel-shift assays to examine the effect of phosphorylation of OsWRKY53 on its DNA-binding activity.
抄録全体を表示