LUX ARRHYTHMO encodes a Myb domain protein essential for circadian rhythms

Proc Natl Acad Sci U S A. 2005 Jul 19;102(29):10387-92. doi: 10.1073/pnas.0503029102. Epub 2005 Jul 8.


In higher plants, the circadian clock orchestrates fundamental processes such as light signaling and the transition to flowering. We isolated mutants of the circadian clock from an Arabidopsis thaliana mutagenized reporter line by screening for seedlings with long hypocotyl phenotypes and subsequently assaying for abnormal clock-regulated CAB2::LUC expression. This screen identified five mutant alleles of a clock gene, LUX ARRHYTHMO (LUX), that significantly affect amplitude and robustness of rhythms in both constant white light and dark conditions. In addition, the transition from vegetative to floral development is accelerated and hypocotyl elongation is accentuated in these mutants under light:dark cycles. We genetically mapped the mutations by bulk segregant analysis with high-density oligonucleotide array genotyping to a small putative Myb transcription factor related to other clock components and response regulators in Arabidopsis. The negative arm of the Arabidopsis circadian clock, CIRCADIAN CLOCK ASSOCIATED (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), is repressed in the lux mutants, whereas TIMING OF CAB2 EXPRESSION (TOC1) is activated. We demonstrate that CCA1 and LHY bind to the evening element motif in the LUX promoter, which strongly suggests that these proteins repress LUX expression, as they do TOC1. The data are also consistent with LUX being necessary for activation of CCA1 and LHY expression.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / growth & development
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Biological Clocks / genetics*
  • Chromosome Mapping
  • Circadian Rhythm / genetics*
  • DNA Primers
  • DNA-Binding Proteins / metabolism
  • Electrophoretic Mobility Shift Assay
  • Gene Expression Regulation, Plant / genetics*
  • Oligonucleotide Array Sequence Analysis
  • Photoperiod
  • Reverse Transcriptase Polymerase Chain Reaction
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism


  • Arabidopsis Proteins
  • CCA1 protein, Arabidopsis
  • DNA Primers
  • DNA-Binding Proteins
  • LHY protein, Arabidopsis
  • Lux Arrhythmo protein, Arabidopsis
  • TOC1 protein, Arabidopsis
  • Transcription Factors