title: The DWF4 gene of Arabidopsis encodes a cytochrome P450 that mediates multiple 22alpha-hydroxylation steps in brassinosteroid biosynthesis.
abstract: dwarf4 (dwf4) mutants of Arabidopsis display a dwarfed phenotype due to a lack of cell elongation. Dwarfism could be rescued by the application of brassinolide, suggesting that DWF4 plays a role in brassinosteroid (BR) biosynthesis. The DWF4 locus is defined by four mutant alleles. One of these is the result of a T-DNA insertion. Plant DNA flanking the insertion site was cloned and used as a probe to isolate the entire DWF4 gene. Sequence analysis revealed that DWF4 encodes a cytochrome P450 monooxygenase with 43% identity to the putative Arabidopsis steroid hydroxylating enzyme CONSTITUTIVE PHOTOMORPHOGENESIS AND DWARFISM. Sequence analysis of two other mutant alleles revealed deletions or a premature stop codon, confirming that DWF4 had been cloned. This sequence similarity suggests that DWF4 functions in specific hydroxylation steps during BR biosynthesis. In fact, feeding studies utilizing BR intermediates showed that only 22alpha-hydroxylated BRs rescued the dwf4 phenotype, confirming that DWF4 acts as a 22alpha-hydroxylase.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: S
authors.initials: S
authors.lastname: Choe
authors.forename: B P
authors.initials: BP
authors.lastname: Dilkes
authors.forename: S
authors.initials: S
authors.lastname: Fujioka
authors.forename: S
authors.initials: S
authors.lastname: Takatsuto
authors.forename: A
authors.initials: A
authors.lastname: Sakurai
authors.forename: K A
authors.initials: KA
authors.lastname: Feldmann
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D018744:DNA, Plant / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D010641:Phenotype; D010840:Phytosterols / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D010940:Plant Proteins / Q000235:genetics*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: C111451:AT3G50660 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018744:DNA, Plant; D010840:Phytosterols; D010937:Plant Growth Regulators; D010940:Plant Proteins; D003577:Cytochrome P-450 Enzyme System