Light and brassinosteroid signals are integrated via a dark-induced small G protein in etiolated seedling growth

Cell. 2001 Jun 1;105(5):625-36. doi: 10.1016/s0092-8674(01)00370-1.


Plant growth and development are regulated through coordinated interactions between light and phytohormones. Here, we demonstrate that a dark-induced small G protein, pea Pra2, regulates a variant cytochrome P450 that catalyzes C-2 hydroxylation in brassinosteroid biosynthesis. The cytochrome P450 is dark-induced and predominantly expressed in the rapidly elongating zone of etiolated pea epicotyls, where Pra2 is also most abundant. Transgenic plants with reduced Pra2 exhibit a dark-specific dwarfism, which is completely rescued by exogenous brassinolide. Overexpression of the cytochrome P450 results in enhanced hypocotyl growth even in the light, which phenocopies the etiolated hypocotyls. We therefore propose that Pra2 and its orthologs are molecular mediators for the cross-talk between light and brassinosteroids in the etiolation process in plants.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis
  • Conserved Sequence
  • Cytochrome P-450 Enzyme System / analysis
  • Cytochrome P-450 Enzyme System / genetics*
  • Cytochrome P-450 Enzyme System / metabolism*
  • Darkness
  • Endoplasmic Reticulum / chemistry
  • Endoplasmic Reticulum / enzymology
  • Guanosine Triphosphate / metabolism
  • Hydroxylation
  • Hypocotyl / growth & development
  • Hypocotyl / physiology
  • Light*
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism
  • Molecular Sequence Data
  • Phytosterols / biosynthesis
  • Phytosterols / metabolism*
  • Plant Development
  • Plant Proteins*
  • Plants / enzymology*
  • Plants, Genetically Modified
  • Plants, Toxic
  • Tobacco
  • rab GTP-Binding Proteins / analysis
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*


  • DDWF1 protein, Pisum sativum
  • PRA3 protein, Pisum sativum
  • Phytosterols
  • Plant Proteins
  • Guanosine Triphosphate
  • Cytochrome P-450 Enzyme System
  • Mixed Function Oxygenases
  • PRA2 protein, Pisum sativum
  • rab GTP-Binding Proteins

Associated data

  • GENBANK/AF218296