| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2005: ¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2004: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2003: ¥7,800,000 (Direct Cost: ¥7,800,000)
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| Research Abstract |
In this project, in order to have basic information on jasmonic acid (JA) functions and its signal transduction pathways, we have performed extensive studies including promoter analysis of a jasmonic acid (JA)-responsive gene, functional identification of a JA biosynthetic enzyme gene, and detailed characterization of JA/elicitor-responsive transcription factors that play key roles in the regulation of defense responses in rice. The principal conclusions are as follows: (l) We identified a TGACG-containing sequence that is a cis element involved in the JA-responsiveness of OsOPR1 in suspension-cultured rice cells, suggesting that a basic leucine zipper (bZIP) transcription factor is involved in the JA-responsive expression of OsOPR1 transcription. (2) We provided evidence that an OPR family gene in rice chromosome 8, OsOPR7, encodes the enzyme involved in the JA biosynthesis. The expression of OsOPR7mRNA was induced and reached maximum levels within 0.5 h of mechanical wounding and dro
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ught stress, and the endogenous JA level started to increase in accordance with the increase in OsOPR7expression. (3) We indicated that the JA-responsive bHLH transcription factor gene RERJ1 isolated from suspension-cultured rice cells was expressed in response to exogenous JA in leaves, leaf sheaths, and roots of rice in a vegetative stage, and that RERJ1 expression in the leaves was up-regulated by exposure to wounding and drought stress. In our recent studies including microarray analysis using transgenic rice overexpressing sense-RERJ1 mRNA, it has been shown that RERJ1 is involved in regulation of pathogenesis-related protein genes expression. (4) We provided strong evidence for the involvement of OsWRKY53 and OsWRKY71 in regulating the expression of defense-related genes induced by chitin oligosaccharide and fungal cerebroside elicitors in rice. Although OsWRKY53 was suggested to be a transcriptional activator, OsWRKY71 showed features characteristic of a transcriptional repressor, indicating that the activation of defense-related genes by OsWRKY71 was probably indirect. Less
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