The ratio of campesterol to sitosterol that modulates growth in Arabidopsis is controlled by STEROL METHYLTRANSFERASE 2;1

Plant J. 2001 Mar;25(6):605-15. doi: 10.1046/j.1365-313x.2001.00994.x.

Abstract

The Arabidopsis genome contains three distinct genes encoding sterol-C24-methyltransferases (SMTs) involved in sterol biosynthesis. The expression of one of them, STEROL METHYLTRANSFERASE 2;1, was modulated in 35S:SMT2;1 Arabidopsis in order to study its physiological function. Plants overexpressing the transgene accumulate sitosterol, a 24-ethylsterol which is thought to be the typical plant membrane reinforcer, at the expense of campesterol. These plants displayed a reduced stature and growth that could be restored by brassinosteroid treatment. Plants showing co-suppression of SMT2;1 were characterized by a predominant 24-methylsterol biosynthetic pathway leading to a high campesterol content and a depletion in sitosterol. Pleiotropic effects on development such as reduced growth, increased branching, and low fertility of high-campesterol plants were not modified by exogenous brassinosteroids, indicating specific sterol requirements to promote normal development. Thus SMT2;1 has a crucial role in balancing the ratio of campesterol to sitosterol in order to fit both growth requirements and membrane integrity.

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / enzymology
  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Blotting, Northern
  • Brassinosteroids
  • Cholestanols / antagonists & inhibitors
  • Cholestanols / metabolism
  • Cholesterol / analogs & derivatives*
  • Cholesterol / biosynthesis*
  • Fruit / growth & development
  • Gene Expression Regulation, Plant*
  • Methyltransferases / genetics
  • Methyltransferases / physiology*
  • Molecular Sequence Data
  • Phenotype
  • Phytosterols*
  • Plant Growth Regulators / antagonists & inhibitors
  • Plant Growth Regulators / metabolism
  • Plant Roots / growth & development
  • Plant Stems / growth & development
  • Plants, Genetically Modified / enzymology
  • Plants, Genetically Modified / growth & development
  • Sitosterols / metabolism*
  • Steroids, Heterocyclic / antagonists & inhibitors
  • Steroids, Heterocyclic / metabolism
  • Sterols / biosynthesis
  • Transgenes

Substances

  • Brassinosteroids
  • Cholestanols
  • Phytosterols
  • Plant Growth Regulators
  • Sitosterols
  • Steroids, Heterocyclic
  • Sterols
  • campesterol
  • gamma-sitosterol
  • Cholesterol
  • Methyltransferases
  • delta 24-sterol methyltransferase
  • brassinolide