Abstract
When plants are attacked by pathogenic microorganisms, they respond with a variety of defense reactions including production of PR proteins or phytoalexins. 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 homologs of OsWRKY53 in other plant species results in increase in transactivation acitivity. Using a transient reporter gene assays in rice cells, we found that a phospho-mimic OsWRKY53 (S/D), a constitutively active form, has higher transactivation activity than the native OsWRKY53 and an alanine-substituted OsWRKY53 (S/A). Now, we are trying to determine whether OsMKK4-OsMPK6 cascades are involved in phosphorylation of recombinant OsWRKY53 by in vitro kinase assay. We are also trying microarray analysis to compare downstream responses between OsWRKY53-overexpressing lines and phospho-mimic OsWRKY53-overexpressing lines.
