Blue light-dependent interaction of CRY2 with SPA1 regulates COP1 activity and floral initiation in Arabidopsis

Curr Biol. 2011 May 24;21(10):841-7. doi: 10.1016/j.cub.2011.03.048. Epub 2011 Apr 21.


Cryptochromes are blue light receptors that mediate light regulation of gene expression in all major evolution lineages, but the molecular mechanism underlying cryptochrome signal transduction remains not fully understood. It has been reported that cryptochromes suppress activity of the multifunctional E3 ubiquitin ligase CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) to regulate gene expression in response to blue light. But how plant cryptochromes mediate light suppression of COP1 activity remains unclear. We report here that Arabidopsis CRY2 (cryptochrome 2) undergoes blue light-dependent interaction with the COP1-interacting protein SUPPRESSOR OF PHYTOCHROME A 1 (SPA1). We demonstrate that SPA1 acts genetically downstream from CRY2 to mediate blue light suppression of the COP1-dependent proteolysis of the flowering-time regulator CONSTANS (CO). We further show that blue light-dependent CRY2-SPA1 interaction stimulates CRY2-COP1 interaction. These results reveal for the first time a wavelength-specific mechanism by which a cryptochrome photoreceptor mediates light regulation of protein degradation to modulate developmental timing in Arabidopsis.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / growth & development*
  • Arabidopsis Proteins / metabolism*
  • Cell Cycle Proteins / metabolism*
  • Cryptochromes / metabolism*
  • DNA-Binding Proteins / metabolism
  • Flowers / growth & development*
  • Gene Expression Regulation, Plant / physiology*
  • Gene Expression Regulation, Plant / radiation effects
  • Immunoblotting
  • Immunoprecipitation
  • Light*
  • Polymerase Chain Reaction
  • Signal Transduction / physiology*
  • Transcription Factors / metabolism
  • Two-Hybrid System Techniques
  • Ubiquitin-Protein Ligases / metabolism*
  • beta-Galactosidase


  • Arabidopsis Proteins
  • CONSTANS protein, Arabidopsis
  • CRY2 protein, Arabidopsis
  • Cell Cycle Proteins
  • Cryptochromes
  • DNA-Binding Proteins
  • SPA1 protein, Arabidopsis
  • Transcription Factors
  • AT2G32950 protein, Arabidopsis
  • Ubiquitin-Protein Ligases
  • beta-Galactosidase