20. イネにおけるジテルペン環化酵素について

概要

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We have isolated and characterized cDNAs, OsCyc1, OsCyc2, OsKS4, OsKS7, OsKS8, OsKS10, encoding syn-CDP synthase, ent-CDP synthase, 9β-pimara-7, 15-diene synthase, ent-cassa-12, 15-diene synthase, stemar-13-ene synthase, and ent-sandaracopimaradiene synthase, responsible for rice (Oryza sativa) diterpene phytoalexin biosynthesis. In rice genome sequences, we found other translatable diterpene cyclase genes; OsCPS1, OsKS1, OsKS5, and OsKS6. It has already been suggested that OsCPS1 and OsKS1 are responsible for gibberellin biosynthesis. In this study, we show that recombinant proteins expressed in E.coli from OsKS5 and OsKS6 converted ent-CDP into ent-pimara-8(14), 15-diene and ent-kaur-15-ene like substance, respectively. These results suggest that the two genes are responisible for biosynthesis of neither gibberellins nor phytoalexines. In addition, we attempted to investigate the subcelluar localization of diterpen cyclases, responsible for biosynthesis of gibberellins or phytoalexins, using GFP system. Our results suggest that OsCyc2, OsKS1, OsKS8, OsKS10 shoud localize in plastids, like gibberellin biosyntheis ditrpene cyclases in other plants. Studies on the subcelluar localization of OsCyc1, OsCPS1, OsKS4, and OsKS7 are now progressing.
2005-10-13