Arabidopsis HEMERA/pTAC12 initiates photomorphogenesis by phytochromes

Cell. 2010 Jun 25;141(7):1230-40. doi: 10.1016/j.cell.2010.05.007.


Light plays a profound role in plant development, yet how photoreceptor excitation directs phenotypic plasticity remains elusive. One of the earliest effects of light is the regulated translocation of the red/far-red photoreceptors, phytochromes, from the cytoplasm to subnuclear foci called phytochrome nuclear bodies. The function of these nuclear bodies is unknown. We report the identification of hemera, a seedling lethal mutant of Arabidopsis with altered phytochrome nuclear body patterns. hemera mutants are impaired in all phytochrome responses examined, including proteolysis of phytochrome A and phytochrome-interacting transcription factors. HEMERA was identified previously as pTAC12, a component of a plastid complex associated with transcription. Here, we show that HEMERA has a function in the nucleus, where it acts specifically in phytochrome signaling, is predicted to be structurally similar to the multiubiquitin-binding protein, RAD23, and can partially rescue yeast rad23mutants. Together, these results implicate phytochrome nuclear bodies as sites of proteolysis.

Publication types

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

MeSH terms

  • Arabidopsis / cytology
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / metabolism*
  • Cell Nucleus / metabolism
  • Chloroplasts / metabolism
  • DNA-Binding Proteins / metabolism
  • Green Fluorescent Proteins / analysis
  • Intracellular Signaling Peptides and Proteins
  • Light
  • Microscopy, Confocal
  • Nuclear Proteins / metabolism
  • Phytochrome A / metabolism*
  • Phytochrome B / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism
  • Seeds / metabolism
  • Signal Transduction
  • Transcription Factors / metabolism*


  • Arabidopsis Proteins
  • DET1 protein, Arabidopsis
  • DNA-Binding Proteins
  • HMR protein, Arabidopsis
  • Intracellular Signaling Peptides and Proteins
  • Nuclear Proteins
  • PHYB protein, Arabidopsis
  • Phytochrome A
  • RAD23 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Phytochrome B
  • Green Fluorescent Proteins