Lesions in the sterol Δ7 reductase gene of Arabidopsis cause dwarfism due to a block in brassinosteroid biosynthesis

Sunghwa Choe, Atsushi Tanaka, Takahiro Noguchi, Shozo Fujioka, Suguru Takatsuto, Amanda S. Ross, Frans E. Tax, Shigeo Yoshida, Kenneth A. Feldmann

Research output: Contribution to journalArticle

112 Scopus citations


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 Δ7 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 Δ7 reductase activity. All six independent alleles contain loss-of-function mutations in the sterol Δ7 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 Δ7 reductase gene, indicating that it is required for the proper growth and development of these two organisms.

Original languageEnglish (US)
Pages (from-to)431-443
Number of pages13
JournalPlant Journal
Issue number5
StatePublished - Mar 1 2000

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology

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