| Budget Amount *help |
¥25,480,000 (Direct Cost: ¥19,600,000、Indirect Cost: ¥5,880,000)
Fiscal Year 2009: ¥7,410,000 (Direct Cost: ¥5,700,000、Indirect Cost: ¥1,710,000)
Fiscal Year 2008: ¥7,410,000 (Direct Cost: ¥5,700,000、Indirect Cost: ¥1,710,000)
Fiscal Year 2007: ¥10,660,000 (Direct Cost: ¥8,200,000、Indirect Cost: ¥2,460,000)
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| Research Abstract |
The major achievement of this research is the finding that weak d2 mutations have probably been used in breeding programs that generated high-yielding cultivars. I also found an interesting phenomenon, namely that the genetic background controls the phenotypes of rice brassinosteroid-related mutants. I obtained some evidence that an insertion of mPing in the promoter of the brassinosteroid receptor gene, OsBRI1, causes this phenomenon. When I performed comprehensive gene-expression analyses of the brassinosteroid-related genes to identify the phenotype-controlling factor mentioned above, I found that auxin treatment transiently increases OsBRI1 expression. This result led to a striking finding: the auxin signal-transcription factor ARF controls the degree of brassinosteroid perception required for normal plant growth and development. I also found evidence of evolution of the genes for CYP734As, which acquired novel functions in brassinosteroid inactivation after the differentiation of monocot and dicot plants, and then increased in number in the rice genome. These genes are directly applicable for regulating the endogenous bioactive brassinosteroid content, and therefore for controlling rice developmental and physiological processes. I have isolated and characterized a novel brassinosteroid-signaling component, ELF1. This research led to an unexpected finding, namely that brassinosteroid and jasmonate signaling compete for the nuclear protein EIZ1. Although further analyses are needed, this will be a productive starting point from which to understand the extensive crosstalk between brassinosteroids and jasmonate, especially in terms of the mechanisms responsible for how plants acquire stress tolerance after brassinosteroid treatment.
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