Abstract
We have identified that feruloyl-CoA ortho-(6'-) hydroxylase (AtF6'H1) catalyzes the key step of scopoletin biosynthesis in Arabidopsis thaliana. AtF6'H1 exhibits the high substrate specificity for feruloyl-CoA. Arabidopsis mainly accumulates scopoletin. These results indicate that the substrate specificity of the ortho-hydroxylases in the respective plants seems to determine the accumulation patterns of the coumarins.
Many AtF6'H1 homologs are found in the EST database of the plants. Of these plants, sweet potato and tobacco accumulate both scopoletin and umbelliferone. It is, therefore, assumed that the AtF6'H1 homologs from sweet potato and tobacco are involved in biosynthesis of the respective coumarins. These homologs may also exhibit the substrate specificities different from that of AtF6'H1. In order to investigate the substrate specificity of these homologs, we performed cloning and functional analysis of these AtF6'H1 homologs from sweet potato and tobacco. The total sequences of the homologs were obtained by RT-PCR, 3'- and 5'-RACE methods.
