Biological diversities of cytochrome P450 monooxygenases that catalyze the C-6 oxidation in brassinosteroid biosynthesis

Abstract

The CYP85A family of P450s plays a key role in the regulation of biologically active brassinosteroid (BR) levels in the plant. We have shown that Arabidopsis and tomato CYP85A1s catalyze the C-6 oxidation of 6-deoxocastasterone (6-deoxoCS) to castasterone (CS), while Arabidopsis CYP85A2 and tomato CYP85A3 catalyze the further conversion (Baeyer-Villiger oxidation) of CS to BL that is the most biologically active BR. Recently we have isolated two CYP85As (CYP85A1 and CYP85A6) from pea. However, unlike Arabidopsis and tomato, the two CYP85As in pea both act principally to convert 6-DeoxoCS to CS. The isolation of these CYP85A genes in dicotyledonous species highlights the species-specific differences associated with C-6 oxidation. Phylogenetic analysis of these P450s in several dicotyledonous species shows that the Baeyer-Villiger reaction catalyzed by the CYP85A family may have evolved independently.