Biosynthesis of brassinosteroids in cultured cells of Catharanthus roseus

Abstract Precursor administration experiments with 2 H -labeled 6-oxocampestanol, 6-deoxocastasterone and 6α-hydroxycastasterone in cultured cells of Catharanthus roseus were performed and the metabolites were analyzed by GC-MS. [ 2 H 6 ]Cathasterone was identified as a metabolite of [ 2 H 6 ]6-oxocampestanol, whereas [ 2 H 6 ]6α-hydroxycastasterone and [ 2 H 6 ]castasterone were identified as metabolites of [ 2 H 6 ]6-deoxocastasterone, and [ 2 H 6 ]castasterone was identified as a metabolite of [ 2 H 6 ]6α-hydroxycastasterone, indicating that 6-deoxocastasterone is converted to castasterone via 6α-hydroxycastasterone. In addition, 6-deoxocathasterone, a putative biosynthetic intermediate in the late C6-oxidation pathway, was identified as an endogenous brassinosteroid. These studies provide further evidence supporting our proposed biosynthetic pathways for brassinolide.