The DWF4 gene of arabidopsis encodes a cytochrome P450 that mediates multiple 22 alpha-hydroxylation steps in brassinosteroid biosynthesis

• Published in: The Plant cell Vol. 10; no. 2; pp. 231 - 243
• Main Authors: Choe, S. (University of Arizona, Tucson, AZ.), Dilkes, B.P, Fujoka, S, Takatsuto, S, Sakurai, A, Feldmann, K.A
• Format: Journal Article
• Language: English
• Published: American Society of Plant Physiologists 01.02.1998
• Subjects: 22ALPHA-HYDROXYCAMPESTEROL; 6ALPHA-HYDROXYCASTASTERONE; 6ALPHA-HYDROXYCATHASTERONE; ALLELES; AMINO ACID SEQUENCES; ARABIDOPSIS THALIANA; BIOLOGICAL DIFFERENCES; BIOSYNTHESIS; BRASSINOSTEROIDS; CAMPESTEROL; Cephalopelvic disproportion; CHEMICAL COMPOSITION; CYTOCHROME P450; Cytochromes; DELETIONS; DERIVATIVES; DNA; DWARFS; EXONS; GENBANK/AF044216; GENES; Genetic mutation; INTRONS; MOLECULAR SEQUENCE DATA; MUTANTS; NUCLEOTIDE SEQUENCE; Oxidation; OXIDOREDUCTASES; PHYLOGENETICS; PHYTOSTEROLS; Plants; SEEDLINGS; SPECIES DIFFERENCES; STRUCTURAL GENES; UNSPECIFIC MONOOXYGENASE
• ISSN: 1040-4651; 1532-298X
• DOI: 10.1105/tpc.10.2.231

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 22 alpha-hydroxylated BRs rescued the dwf4 phenotype, confirming that DWF4 acts as a 22 alpha-hydroxylase