Abstract
Coumarins are often found as secondary metabolites in various plant species. Hydroxylation of cinnamates at the ortho-position is a key step to form the coumarin structure, and however ortho-hydroxylase still remains to be characterized. We previously reported the high accumulation of scopolin, a β-glucoside of scopoletin, in the roots of Arabidopsis. We have also found that scopoletin biosynthesis strongly depends on CCoAMT1, which catalyzes methylation of the 3'-hydroxy group of caffeoyl CoA. We therefore selected several oxidase genes, which show co-expression with CCoAOMT1, as candidates of ortho-hydroxylase, and their T-DNA insertion mutants were obtained from SALK institute. One of the mutants exhibited severe reduction in scopolin/scopoletin levels in the roots. The recombinant protein expressed in E. coli exhibited ortho-hydroxylase activity. Biochemical characterization of the recombinant protein is in progress.
