Characterization of a gene cluster on chromosome 2 that is involved in biosynthesis of diterpenpoid phytoalexins in rice

Abstract

Momilactones and phytocassanes are major diterpenoid phytoalexins in rice. In momilactones biosynthesis, two cytochrome P450 monooxigenases (P450s) and a dehydrogenase have been found to be involved and the genes encoding these enzymes are clustered on chromosome 4. Likewise, six P450 genes form a gene cluster on chromosome 2 with the diterpene cyclase genes for phytocassanes biosynthesis, although functions of these P450s have not yet been clarified. Here, we report functional analysis of two P450s, CYP71Z6 and CYP71Z7, of the six P450s encoded by the gene cluster on chromosome 2. As CYP71Z6 and CYP71Z7 are highly homologous to each other, we attempted to generate their double knockdown RNAi lines. The CYP71Z6/CYP71Z7 double knockdown suppressed elicitor-inducible production of phytocassanes A and B, strongly suggesting that either or both of CYP71Z6 and CYP71Z7 are involved in phytocassane A and B biosynthesis.