Transcription of the Arabidopsis CPD gene, encoding a steroidogenic cytochrome P450, is negatively controlled by brassinosteroids

Plant J. 1998 Jun;14(5):593-602. doi: 10.1046/j.1365-313x.1998.00158.x.


The Arabidopsis CPD gene encodes a cytochrome P450 steroid side-chain hydroxylase (CYP90) that plays an essential role in the biosynthesis of the plant hormone brassinolide. Expression of the CPD gene is confined to cotyledons and leaf primordia in etiolated seedlings and detectable in the adaxial parenchyma of expanding leaves in light-grown plants. Transcription of the CPD gene is not affected by the plant growth factors auxin, ethylene, gibberellin, cytokinin, jasmonic acid and salicylic acid, but is specifically down-regulated by brassinolide in both dark and light. Steady-state mRNA levels of a CPD promoter-driven uidA reporter gene correlate with the expression of resident CPD gene in transgenic plants. Intermediates of the early and late C-6 oxidation pathways of brassinolide, carrying C-22 and C-23 side-chain hydroxyls, efficiently inhibit the activity of the CPD promoter. Repression of CPD transcription by brassinosteroids is sensitive to the protein synthesis inhibitor cycloheximide, indicating a requirement for de novo synthesis of a regulatory factor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis Proteins*
  • Brassinosteroids
  • Cholestanols / pharmacology*
  • Cotyledon
  • Cytochrome P-450 Enzyme System / biosynthesis*
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Plant* / drug effects
  • Genes, Reporter
  • Kinetics
  • Plant Growth Regulators / pharmacology*
  • Plant Leaves
  • Promoter Regions, Genetic
  • RNA, Messenger / biosynthesis
  • Recombinant Fusion Proteins / biosynthesis
  • Steroid Hydroxylases / biosynthesis*
  • Steroid Hydroxylases / genetics
  • Steroid Hydroxylases / metabolism
  • Steroids, Heterocyclic / pharmacology*
  • Substrate Specificity
  • Transcription, Genetic* / drug effects


  • Arabidopsis Proteins
  • Brassinosteroids
  • Cholestanols
  • Plant Growth Regulators
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • Steroids, Heterocyclic
  • Cytochrome P-450 Enzyme System
  • CPD protein, Arabidopsis
  • Steroid Hydroxylases
  • brassinolide