Abstract
WRKY proteins are a large family of plant-specific transcription factors that specifically bind to the W-box elements. Many WRKY proteins have been suggested to have a regulatory function in the response to pathogen infection and other stresses. OsWRKY53 is a rice WRKY gene identified by microarray analysis as a chitin oligosaccharide elicitor-induced gene. Previously we indicated that OsWRKY53 functions as a transcriptional activator, and overexpression of OsWRKY53 resulted in enhanced resistance to the rice blast fungus Magnaporthe grisea in rice plants. Transient gene expression assays were performed to identify an elicitor-responsive region in the OsWRKY53 promoter. Analysis of 5'-promoter deletions indicated that a region between -500 and -250 contained an elicitor-responsive cis-element. In this region, there are three tandem W-box elements. Site-directed mutagenesis to these W-boxes revealed that these W-box elements function as elicitor-responsive cis-elements. Moreover, chromatin immunoprecipitation analysis revealed that OsWRKY53 can bind to these W-box elements in vivo. These results strongly suggest that OsWRKY53 can induce the expression of its own gene via binding to the W-box elements in its own promoter. Now, we are trying to make transgenic rice cells which constitutively express a dominant negative form of OsWRKY53, and analyze the expression of native OsWRKY53 in the transgenic rice cells after treatment with the elicitor to support the above hypothesis.
