The CYP88A cytochrome P450, ent-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway

The CYP88A cytochrome P450, ent-kaurenoic acid oxidase, catalyzes three steps of the gibberellin biosynthesis pathway

CSIRO Plant Industry, GPO Box 1600, Canberra 2601, Australia

Contributed by W. James Peacock

Abstract

We have shown that ent-kaurenoic acid oxidase, a member of the CYP88A subfamily of cytochrome P450 enzymes, catalyzes the three steps of the gibberellin biosynthetic pathway from ent-kaurenoic acid to GA₁₂. A gibberellin-responsive barley mutant, grd5, accumulates ent-kaurenoic acid in developing grains. Three independent grd5 mutants contain mutations in a gene encoding a member of the CYP88A subfamily of cytochrome P450 enzymes, defined by the maize Dwarf3 protein. Mutation of the Dwarf3 gene gives rise to a gibberellin-responsive dwarf phenotype, but the lesion in the gibberellin biosynthesis pathway has not been identified. Arabidopsis thaliana has two CYP88A genes, both of which are expressed. Yeast strains expressing cDNAs encoding each of the two Arabidopsis and the barley CYP88A enzymes catalyze the three steps of the GA biosynthesis pathway from ent-kaurenoic acid to GA₁₂. Sequence comparison suggests that the maize Dwarf3 locus also encodes ent-kaurenoic acid oxidase.

Footnotes

↵ * To whom reprint requests should be addressed. E-mail: chris.helliwell{at}pi.csiro.au.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AF318500, AF318501, and AF326277).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.041588998.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.041588998
Abbreviations:

GA,

gibberellin;

KA,

ent-kaurenoic acid;

7OH-KA,

ent-7α-hydroxy-kaurenoic acid;

KO,

ent-kaurene oxidase;

KAO,

KA oxidase;

Me,

methyl ester