Biotransformation of 6-Deoxo Type Brassinosteroids in Yeast (Saccharomyces cerevisiae) WAT21 Cells

Abstract

We recently demonstrated that non-plant cells, yeast WAT21, produce a steroidal plant hormone, castasterone. To understand how castasterone is generated in WAT21 cells, deuterium-labeled (26, 28-H-2(6)) 6-deoxoteasterone, 6-deoxotyphasterol and 6-deoxocastasterone were fed to WAT21 cells, and their metabolites were analyzed by gas chromatography-mass spectrometry. When [H-2(6)]-6-deoxoteasterone was fed, [H-2(6)]-6-deoxo-3-dehydroteasterone and [H-2(6)]-6-deoxotyphasterol were identified as metabolites. When [H-2(6)]-6-deoxotyphasterol was used, [H-2(6)]-6-deoxoteasterone and [H-2(6)]-6-deoxo-3-dehydroteasterone and [H-2(6)]-6-deoxocastasterone were detected. When [H-2(6)]-6-deoxocastasterone was added, [H-2(6)]-castasterone was identified. Taken together, a biosynthetic sequence, 6-deoxoteasterone <-> 6-deoxo-3-dehydroteasterone <-> 6-deoxotyphasterol -> 6-deoxocastasterone -> castasterone seems to function to produce brassinosteroids in WAT21 cells. Coupled with the presence of a biosynthetic sequence, teasterone -> 3-dehydroteasterone <-> typhasterol -> castasterone, this suggests that brassinosteroids in WAT21 cells were biosynthesized via the same kind of pathways established in plants. This study provides a clue for possible mass-production of brassinosteroids in non-plant cells, yeast WAT21 for commercial use in agriculture.