Abstract
Brassinosteroid (BR)-6-oxidases mediate the bridge reactions that connect the late and early C-6 oxidation pathways by converting 6-deoxoBR to 6-oxoBRs. Two similar genes ofArabidopsis, CYP85A1 (At5g38970) andCYP85A2 (At3g30180), are proposed to encode BR-6-oxidases based on findings that heterologously expressed genes mediate BR-6-oxidation reactions in yeast. However, genetic evidence that both genes are critically involved in the BR-6-oxidation step inArabidopsis has been limited. Here, we show that a double mutant for the two genes displays dwarfism similar to that of typical BR biosynthesis-deficient mutants, suggesting that they are the major BR-6-oxidases inArabidopsis. Examination of endogenous BR levels and metabolism monitoring tests using this double mutant revealed a great reduction in the levels of 6-oxoBRs, e.g., TY and CS, due to a lack in the conversion reactions from 6-deoxoCS to CS, and from 6-deoxoTY to TY. Surprisingly, the double mutant accumulated a significant amount of 6-oxocampestanol, suggesting that the upstream C-6 oxidation of campestanol to 6-oxocampestanol is not catalyzed by the two BR-6-oxidases inArabidopsis, rather, by another enzyme yet to be discovered.
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Kwon, M., Fujioka, S., Jeon, J.H. et al. A double mutant for theCYP85A1 andCYP85A2 Genes ofArabidopsis exhibits a Brassinosteroid dwarf phenotype. J. Plant Biol. 48, 237–244 (2005). https://doi.org/10.1007/BF03030413
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DOI: https://doi.org/10.1007/BF03030413