Response regulator homologues have complementary, light-dependent functions in the Arabidopsis circadian clock

Planta. 2003 Nov;218(1):159-62. doi: 10.1007/s00425-003-1106-4. Epub 2003 Sep 4.


TIMING OF CAB EXPRESSION 1 ( TOC1) functions with CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) in a transcriptional feedback loop that is important for the circadian clock in Arabidopsis thaliana (L.) Heynh. TOC1 and its four paralogues, the Arabidopsis PSEUDO-RESPONSE REGULATOR (PRR) genes, are expressed in an intriguing daily sequence. This was proposed to form a second feedback loop, similar to the interlocking clock gene circuits in other taxa. We show that prr9 and prr5 null mutants have reciprocal period defects for multiple circadian rhythms, consistent with subtly altered expression patterns of CCA1 and TOC1. The period defects are conditional on light quality and combine additively in double-mutant plants. Thus PRR9 and PRR5 modulate light input to the circadian clock but are neither uniquely required for rhythm generation nor form a linear series of mutual PRR gene regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / radiation effects
  • Circadian Rhythm / genetics*
  • DNA, Bacterial / genetics
  • DNA, Single-Stranded / genetics
  • Darkness
  • Light
  • Mutation
  • Phenotype
  • Phosphoproteins / physiology
  • Phosphoproteins / radiation effects
  • Polymerase Chain Reaction
  • Transcription Factors / genetics*
  • Transcription Factors / radiation effects


  • Arabidopsis Proteins
  • CCA1 protein, Arabidopsis
  • DNA, Bacterial
  • DNA, Single-Stranded
  • Phosphoproteins
  • T-DNA
  • TOC1 protein, Arabidopsis
  • Transcription Factors