Abstract
Both fusicoccin A (FC) and structurally related cotylenin A (CN) are diterpene glucosides and show a phytohormone-like activity. However, only CN induces the differentiation of human myeloid leukemia cells. Since the CN producer lost its ability to proliferate during preservation, a study on the relationship between structure and activity was carried out and an elimination of hydroxyl group at 12-position of FC was essential to have the CN-like activity. Moreover, modified FC with hydroxyl group at 3-position was recently shown to be more effective. Therefore, we tried to identify a gene catalyzing 12-hydroxylation and to breed a mutant producing a modified FC without hydroxyl group at 12-position by a disruption of the gene. Previous identification of fusicocca-2,10(14)-diene synthase gene in Phomopsis amygdali, a FC producer, enabled us to identify a partial gene cluster for bisoynthesis of FC. However, other biosynthetic genes still remained unknown. In this study, we identified another gene cluster containing nine genes by draft genome sequencing. Of these, two cytochrome P450s catalyzing 813 and 9-hydrozylations, glycosylation, methylation, prenylation, and acetylation genes were confirmed to encode enzymes with the expected activities. We also identified a cytochrome P450 catalyzing 12-hydroxylations by a gene disruption experiment. The remaining one cytochrome P450 gene therefore probably catalyzes hydroxylation at the 19-position.
