80. イネのジテルペン型ファイトアレキシン生合成酵素遺伝子クラスターに存在するP450遺伝子の機能解析(口頭発表,植物化学調節学会第46回大会)

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Antimicrobial diterpenoid compounds such as momilactones and phytocassanes are major phytoalexins produced in rice upon pathogen attack. Previously, we reported that a novel gene cluster for phytocassane biosynthesis is organized in rice chromosome 2, which consists of two diterpene cyclase genes for phytocassanes (OsCPS2 and OsKSL7) and six cytochrome P450 monooxygenase (P450) genes (CYP71Z6, CYP71Z7, CYP76M5, CYP76M6, CYP76M7 and CYP76M8). RNAi experiment has suggested that CYP71Z7 is involved in biosynthesis of phytocassanes A, B and D (C-2 oxygenated phytocassanes), and CYP76M8 is involved in biosynthesis of phytocassanes B, C and E (C-1 oxygenated phytocassanes). In this report, we show the results of analysis of phytocassane levels in the leaves of a null T-DNA mutant of CYP71Z7. This T-DNA mutant exhibited impaired production of phytocassanes A, B and D (C-2 oxygenated phytocassanes), whereas accumulated levels of phytocassanes C and E (C-2 non-oxygenated phytocassanes) were increased compared with wild-type as well as RNAi lines in which expression of CYP71Z7 was suppressed. Furthermore, we detected a novel diterpenoid compound accumulated in this mutant after copper chloride treatment, and identified it as 2-deoxyphytocassane A, which is likely to be a novel biosynthesis intermediate of phytocassanes.
2011-10-03