Photoconversion and nuclear trafficking cycles determine phytochrome A's response profile to far-red light

Cell. 2011 Sep 2;146(5):813-25. doi: 10.1016/j.cell.2011.07.023.


Phytochrome A (phyA) is the only photoreceptor in plants, initiating responses in far-red light and, as such, essential for survival in canopy shade. Although the absorption and the ratio of active versus total phyA are maximal in red light, far-red light is the most efficient trigger of phyA-dependent responses. Using a joint experimental-theoretical approach, we unravel the mechanism underlying this shift of the phyA action peak from red to far-red light and show that it relies on specific molecular interactions rather than on intrinsic changes to phyA's spectral properties. According to our model, the dissociation rate of the phyA-FHY1/FHL nuclear import complex is a principle determinant of the phyA action peak. The findings suggest how higher plants acquired the ability to sense far-red light from an ancestral photoreceptor tuned to respond to red light.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus*
  • Arabidopsis / cytology
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / metabolism
  • Light
  • Models, Biological
  • Phytochrome A / genetics
  • Phytochrome A / metabolism*


  • Arabidopsis Proteins
  • PHYA protein, Arabidopsis
  • Phytochrome A