78. イネのジテルペン型フィトアレキシン生合成を制御する新規遺伝子の同定(口頭発表,植物化学調節学会第46回大会)

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We have been studying about brassinosteroid upregulated genes in rice using BR defective mutant brdl. In the process, overexpression of BU2 gene showed a phenotype of severe inclination of lamina joints and lesion mimic in the late growth stage. Because it has been reported that some lesion mimic mutants like Sp118 accumulate momilactones, a kind of diterpenoid phytoalexins, we analyzed the expression levels of genes involved in the biosynthesis of diterpenoid phytoalexins in BU2 overexpressing plants with lesion mimic. Expression levels of the genes involved in momilactone and phytocassane biosynthesis were remarkably increased. In addition, accumulation levels of diterpenoid phytoalexins containing momilactones A and B and phytocassanes A to E in BU2 overexpressing plants were greatly increased compared to those in wild-type plants. The accumulation levels in the leaves with lesion mimic were higher than those without lesion mimic. Next, we investigated the tissue specificity of the BU2 gene expression in wild-type plants. BU2 expression was detected in leaves, roots and panicles but not in young panicles before heading. Furthermore, the expression level of BU2 increased in the leaves infected with the blast fungus Magnaporthe oryzae. Because diterpenoid phytoalexins are known to accumulate in blast infected leaves, BU2 may positively regulate the blast inducible phytoalexin biosynthesis.
2011-10-03