Analysis of brassinosteroids metabolites catalyzed by Arabidopsis CHIBI2 (CYP72C1)

Abstract

Brassinosteroids (BRs) are steroidal plant hormones that regulate growth and development. The Arabidopsis mutant chibi2 was obtained by activation T-DNA tagging and showed a dwarf phenotype due to BR-deficiency. The chibi2 mutant has been found to overexpress a cytochrome P450 gene (CYP72C1), suggesting that the P450 catalyzes the inactivation of endogenous BRs. To investigate the biochemical properties of CHIBI2, the recombinant CHIBI2 protein was expressed using baculovirus expression system in insect cells (Sf9). CHIBI2 activity was measured in an assay mixture reconstituted with the recombinant CHIBI2, NADPH-P450 reductase, and NADPH generating system. We have identified several metabolites of BRs catalyzed by CHIBI2. Analysis of the structures of the metabolites is in progress.