Attenuation of phytochrome A and B signaling pathways by the Arabidopsis circadian clock

Plant Cell. 1997 Oct;9(10):1727-43. doi: 10.1105/tpc.9.10.1727.


In higher plants, environmental cues such as light signals are integrated with circadian clock signals to control precisely the daily rhythms observed for many biological functions. We have used a fusion of the promoter of a chlorophyll a/b binding protein gene, CAB2, with firefly luciferase (cab2::luc) to monitor the detailed kinetics of transcription in response to photoreceptor activation in Arabidopsis. Using this marker in phototransduction and circadian-dysfunctional mutants, we studied how signals from phytochrome and the circadian clock are integrated for the regulation of CAB2 transcription. Results from these mutant studies demonstrate that similar expression features, namely, the acute and circadian responses, are present in both etiolated and green seedlings and that the acute and circadian responses are genetically separable. We also demonstrate that persistent Pfr signaling occurs in red light-pulsed etiolated seedlings, which suggests that the circadian clock antagonizes Pfr-mediated signal transduction. Based on these genetic studies, we propose a model for the regulation of CAB2 transcription in which individual photoreceptors and phototransduction components have been assigned to specific pathways for the regulation of discrete kinetic components of the CAB2 expression pattern.

Publication types

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

MeSH terms

  • Arabidopsis / metabolism*
  • Arabidopsis / physiology
  • Arabidopsis Proteins
  • Avena / genetics
  • Circadian Rhythm*
  • Light
  • Light-Harvesting Protein Complexes
  • Luciferases / genetics
  • Photoreceptor Cells*
  • Photosynthetic Reaction Center Complex Proteins / genetics
  • Phytochrome / metabolism*
  • Phytochrome A
  • Phytochrome B
  • Promoter Regions, Genetic
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction*
  • Transcription Factors*


  • Arabidopsis Proteins
  • Light-Harvesting Protein Complexes
  • PHYA protein, Arabidopsis
  • PHYB protein, Arabidopsis
  • Photosynthetic Reaction Center Complex Proteins
  • Phytochrome A
  • Recombinant Fusion Proteins
  • Transcription Factors
  • Phytochrome
  • Phytochrome B
  • Luciferases