Lesions in the sterol delta reductase gene of Arabidopsis cause dwarfism due to a block in brassinosteroid biosynthesis

Plant J. 2000 Mar;21(5):431-43. doi: 10.1046/j.1365-313x.2000.00693.x.


The brassinosteroid (BR) biosynthetic pathway, and the sterol pathway which is prerequisite to the BR pathway, are rapidly being characterized because of the availability of a large number of characteristic dwarf mutants in Arabidopsis. Here we show that the Arabidopsis dwarf5 mutants are disrupted in a sterol Delta7 reduction step. dwf5 plants display the characteristic dwarf phenotype typical of other BR mutants. This phenotype includes small, round, dark-green leaves, and short stems, pedicels, and petioles. Metabolite tracing with 13C-labeled precursors in dwf5 verified a deficiency in a sterol Delta7 reductase activity. All six independent alleles contain loss-of-function mutations in the sterol Delta7 reductase gene. These include a putative mRNA instability mutation in dwf5-1, 3' and 5' splice-site mutations in dwf5-2 and dwf5-6, respectively, premature stop codons in dwf5-3 (R400Z) and dwf5-5 (R409Z), and a mis-sense mutation in dwf5-4 (D257N). The dwf5 plant could be restored to wild type by ectopic overexpression of the wild-type copy of the gene. Both the Arabidopsis dwf5 phenotype and the human Smith-Lemli-Opitz syndrome are caused by loss-of-function mutations in a sterol Delta7 reductase gene, indicating that it is required for the proper growth and development of these two organisms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alleles
  • Amino Acid Sequence
  • Animals
  • Arabidopsis / enzymology*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis Proteins*
  • Base Sequence
  • Blotting, Northern
  • Cloning, Molecular
  • DNA, Complementary
  • Humans
  • Molecular Sequence Data
  • Mutation
  • Oxidoreductases / genetics*
  • Oxidoreductases Acting on CH-CH Group Donors*
  • Plant Growth Regulators / biosynthesis*
  • Plant Proteins / chemistry
  • Plant Proteins / genetics*
  • RNA Splicing
  • RNA, Messenger / genetics
  • Sequence Homology, Amino Acid
  • Steroids / biosynthesis*


  • Arabidopsis Proteins
  • DNA, Complementary
  • Plant Growth Regulators
  • Plant Proteins
  • RNA, Messenger
  • Steroids
  • lathosterol delta-5-dehydrogenase
  • Oxidoreductases
  • Oxidoreductases Acting on CH-CH Group Donors
  • DWF5 protein, Arabidopsis