抄録
Momilactones and phytocassanes are major diterpenoid phytoalexins, which are produced in elicitor-treated rice cells. Two cytochrome P450 monooxigenases (P450s) and a dehydrogenase whose genes are found to be clustered on chromosome 4, are involved in momilactone biosynthesis. Likewise, six P450 genes form a gene cluster on chromosome 2 with the diterpene cyclase genes OsCPS2 and OsKSL7 for phytocassane biosynthesis. However, functions of these P450s have not yet been clarified. Here, we report functional identification of two P450 genes, CYP71Z6 and CYP71Z7, of the six P450 genes organized in the gene cluster on chromosome 2. As CYP71Z6 and CYP71Z7 genes are highly homologous to each other, we attempted to generate their double knockdown RNAi lines. The CYP71Z6/CYP71Z7 double knockdown suppressed the elicitor-inducible production of phytocassanes A, B, and D, suggesting that either or both of CYP71Z6 and CYP71Z7 genes are required for hydroxylation at 2-position of the biosynthetic intermediates of phytocassane A, B, and D. These results provide strong evidence for the presence on chromosome 2 of a gene cluster involved in phytocassane biosynthesis.
