Disease relevance of DWF4

• Dwarfism could be rescued by the application of brassinolide, suggesting that DWF4 plays a role in brassinosteroid (BR) biosynthesis [1].
• To better understand the role of DWF4 in BR biosynthesis, transgenic Arabidopsis plants ectopically overexpressing DWF4 (AOD4) were generated, using the cauliflower mosaic virus 35S promoter, and their phenotypes were characterized [2].
• Recombinant CYP90B1 was produced in Escherichia coli, and CYP90B1 activity was measured in an in vitro assay reconstituted with NADPH-cytochrome P450 reductase [3].

High impact information on DWF4

• Sequence analysis revealed that DWF4 encodes a cytochrome P450 monooxygenase with 43% identity to the putative Arabidopsis steroid hydroxylating enzyme CONSTITUTIVE PHOTOMORPHOGENESIS AND DWARFISM [1].
• This sequence similarity suggests that DWF4 functions in specific hydroxylation steps during BR biosynthesis [1].
• dwarf4 (dwf4) mutants of Arabidopsis display a dwarfed phenotype due to a lack of cell elongation [1].
• Selective interaction of triazole derivatives with DWF4, a cytochrome P450 monooxygenase of the brassinosteroid biosynthetic pathway, correlates with brassinosteroid deficiency in planta [4].
• Thus, it is likely that the DWF4 promoter serves as a focal point in maintaining homeostasis of endogenous bioactive BR pools in specific tissues of Arabidopsis [5].

Biological context of DWF4

• We report the catalytic activity and substrate specificity of CYP90B1 [3].
• CYP724B2 showed 42% and 62% amino acid sequence identity with Arabidopsis DWARF4/CYP90B1 and rice DWARF11/CYP724B1 respectively [6].

Associations of DWF4 with chemical compounds

• Among several triazole derivatives, brassinazole had both the highest binding affinity to DWF4 and the highest growth inhibitory activity [4].
• These results strongly suggest that triadimefon inhibits the reaction catalysed by DWF4 protein and induces BR deficiency in plants [7].
• In particular, the catalytic efficiency (k(cat)/K(m)) of CYP90B1 for campesterol (CR) was 325 times greater than that for CN [3].
• Arabidopsis dwf4 was shown to be defective in a steroid 22alpha hydroxylase (CYP90B1) step that is the putative rate-limiting step in the BR biosynthetic pathway [2].

Regulatory relationships of DWF4

• Moreover, a weak response in the mutant suggests that DWF4 alone is likely to be regulated in other way(s) in addition to BRI1 mediation [8].

Other interactions of DWF4

• The DWF4 gene of Arabidopsis encodes a cytochrome P450 that mediates multiple 22alpha-hydroxylation steps in brassinosteroid biosynthesis [1].
• However, their response to fluctuation of BR levels was highly reduced (DWF4) or nullified (the other eight genes) in a bri1 mutant [8].
• Both show a mild phenotype in comparison with BR-deficient mutants such as cpd/cbb3, det2, and dwf4 [9].

Analytical, diagnostic and therapeutic context of DWF4

• Sequence analysis of two other mutant alleles revealed deletions or a premature stop codon, confirming that DWF4 had been cloned [1].

References