Arabidopsis GIGANTEA protein is post-transcriptionally regulated by light and dark

FEBS Lett. 2006 Feb 20;580(5):1193-7. doi: 10.1016/j.febslet.2006.01.016. Epub 2006 Jan 18.


GIGANTEA (GI) is a key regulator of photoperiodic flowering in Arabidopsis and encodes a protein with no domains of known biochemical function. Expression of GI mRNA is controlled by the circadian clock, but GI protein accumulation has not been previously investigated. We generated plants that produced functional epitope-tagged GI to enable us to track the protein through the daily cycle. Here we show that GI protein levels oscillate when either constitutively overexpressed or driven by its promoter and that its accumulation is modulated by day length as well as by phase-specific factors. Also, we demonstrate that one of the mechanisms underlying GI protein oscillation occurs post-translationally via dark-induced proteolysis by the 26S proteasome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins / analysis
  • Arabidopsis Proteins / biosynthesis*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Circadian Rhythm
  • Gene Expression Regulation, Plant / radiation effects*
  • Light*
  • Photoperiod
  • Plants, Genetically Modified
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Processing, Post-Translational*


  • Arabidopsis Proteins
  • GI protein, Arabidopsis
  • Proteasome Endopeptidase Complex