ジベレリン活性を制御する酵素の分子生物学的研究(奨励賞,受賞業績)

概要

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Analysis of gibberellin (GA)-deficient dwarf mutants contributed to the identification of GA biosynthesis genes. Meanwhile, additional GA-related genes that have not been discovered by conventional forward genetic approach are likely to be present. We identified such genes by analysis of an activation tagged mutant (1), and by reverse genetic approach (2). (1) A dominant dwarf mutant designated dwarf and delayed-flowering1 (ddf1) was isolated from a library of activation-tagged Arabidopsis. Genetic and molecular analyses revealed that the ddf1 phenotypes are caused by increased expression of GA2-oxidase7 gene (GA2ox7), which encodes a C20-GA inactivation enzyme, through increased expression of a high salinity responsive AP2 transcription factor, DDF1. (2) A rice P450 gene, EUI (CYP714D1) encodes a novel class of GA inactivation enzyme. We examined the possible involvement of other CYP714 members of Arabidopsis and rice in GA metabolism. We found the gene products that have GA13-hydroxylation activity from Arabidopsis (one gene) and rice (two genes). GA measurements of a rice double mutant of these genes indicated that the levels of 13-hydroxy GAs were decreased, whereas those of non 13-hydroxy GAs were increased in the double mutants. These results strongly suggest that these two cytochrome P450 genes play a major role in GA13-hydroxylation in rice.
2011-05-31