Tyrosine phosphorylation regulates the activity of phytochrome photoreceptors

Cell Rep. 2013 Jun 27;3(6):1970-9. doi: 10.1016/j.celrep.2013.05.006. Epub 2013 Jun 6.


Phytochromes are red/far-red light receptors that function in photomorphogenesis of plants. Photoisomerization of phytochrome by red light leads to its translocation to the nucleus, where it regulates gene expression. We examined whether phytochrome is phosphorylated in response to light, and we report that phytochrome B (phyB)'s N terminus contains a region with a number of phosphoserines, threonines, and tyrosines. The light-dependent phosphorylation of tyrosine 104 (Y104) appears to play a negative role in phyB's activity, because a phosphomimic mutant, phyBY104E, is unable to complement any phyB-related phenotype, is defective in binding to its signaling partner PIF3, and fails to form stable nuclear bodies even though it retains normal photochemistry in vitro. In contrast, plants stably expressing a nonphosphorylatable mutant, phyBY104F, are hypersensitive to light. The proper response to changes in the light environment is crucial for plant survival, and our study brings tyrosine phosphorylation to the forefront of light-signaling mechanisms.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / cytology
  • Arabidopsis / metabolism
  • Humans
  • Molecular Sequence Data
  • Phosphorylation
  • Photoreceptor Cells / cytology
  • Photoreceptor Cells / metabolism*
  • Phytochrome / metabolism*
  • Plants, Genetically Modified
  • Signal Transduction
  • Tyrosine / metabolism*


  • Phytochrome
  • Tyrosine