ブラシノステロイドの生合成および受容体遺伝子の単離と機能に関する研究(奨励賞)
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Brassinosteroids (BRs) are essential plant growth hormones. In order to obtain compelling evidence that BRs are prerequisite hormones, we aimed to find out dwarf mutants. As the result, we discovered dwarf pea mutants lka and lkb as BR-insensitive and BR-deficient mutants, respectively. The dwarf phenotype of the lkb mutant was rescued by exogenous application of BRs. GC-MS analysis showed that dwarfism of the lkb mutant is due to BR deficiency caused by blocked synthesis of plant sterol, campesterol. The lka mutant was insensitive to exogenous BRs, but it accumulated castasterone to a great extent. The responsible gene was determined to be a BRI1 homolog encoding a BR receptor. Overproduction of castasterone in the lka mutant was ascribed to the depletion of a feedback control mechanism due to the impaired BR receptor. In this work, a new cytochrome P450 was also discovered that catalyzes the synthesis of brassinolide. A null mutation in the cytochrome P450 CYP85A1 gene of tomato (d^x) causes severe dwarfism due to BR deficiency, but the d^x mutant still produces normal fruits. I found that d^x fruits contain brassinolide at high level and that a new CYP85A gene, CYP85A3, is preferentially expressed in tomato fruits. Tomato CYP85A3 expressed in yeast catalyzed the Baeyer-Villiger oxidation to produce brassinolide from 6-deoxocastasterone and castasterone. In summary, the present work demonstrated that BRs are essential plant growth hormones and provided much information on the roles and functions of the biosynthesis and signaling genes of BRs.
- 2005-10-13
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- ブラシノステロイドの生合成および受容体遺伝子の単離と機能に関する研究(奨励賞)
- ブラシノステロイドの生合成および受容体遺伝子の単離と機能に関する研究(奨励賞,受賞業績)