TIME FOR COFFEE encodes a nuclear regulator in the Arabidopsis thaliana circadian clock.
The plant circadian clock is required for daily anticipation of the diurnal environment. Mutation in Arabidopsis thaliana TIME FOR COFFEE (TIC) affects free-running circadian rhythms. To investigate how TIC functions within the circadian system, we introduced markers for the evening and morning phases of the clock into tic and measured evident rhythms. The phases of evening clock genes in tic were all advanced under light/dark cycles without major expression level defects. With regard to morning-acting genes, we unexpectedly found that TIC has a closer relationship with LATE ELONGATED HYPOCOTYL (LHY) than with CIRCADIAN CLOCK ASSOCIATED1, as tic has a specific LHY expression level defect. Epistasis analysis demonstrated that there were no clear rhythms in double mutants of tic and evening-acting clock genes, although double mutants of tic and morning-acting genes exhibited a similar free-running period as tic. We isolated TIC and found that its mRNA expression is continuously present over the diurnal cycle, and the encoded protein appears to be strictly localized to the nucleus. Neither its abundance nor its cellular distribution was found to be clock regulated. We suggest that TIC encodes a nucleus-acting clock regulator working close to the central oscillator.
Ding
Zhaojun
Z
Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne D-50829, Germany.
Millar
Andrew J
AJ
Davis
Amanda M
AM
Davis
Seth J
SJ
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D001683:Biological Clocks / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D030821:Plants, Genetically Modified; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D004268:DNA-Binding Proteins; C113192:LHY protein, Arabidopsis; D009687:Nuclear Proteins; D012333:RNA, Messenger; C523534:TIC protein, Arabidopsis; D014157:Transcription Factors