The APRR1/TOC1 quintet implicated in circadian rhythms of Arabidopsis thaliana: I. Characterization with APRR1-overexpressing plants.
Several Arabidopsis genes have been proposed to encode potential clock-associated components, including the Myb-related CCA1 and LHY transcription factors and a member of the novel family of pseudo response regulators (APRR1/TOC1). We previously showed that mRNAs of the APRR1/TOC1 family of genes start accumulating after dawn rhythmically and sequentially at ... approximately 2 h intervals in the order: APRR9--> APRR7-->APRR5-->APRR3-->APRR1/TOC1. Here we constructed APRR1-overexpressing (APRR1-ox) plants, and examined certain circadian profiles for APRRs, CCA1, LHY, GI, CCR2, and CAB2. The free-running circadian rhythms of the APRR1/TOC1 family of genes, including APRR1, were dampened in APRR1-ox plants. In particular, the light-inducible expression of APRR9 was severely repressed in APRR1-ox plants, suggesting that there is a negative APRR1-->APRR9 regulation. The free-running robust rhythm of CAB2 was also dampened in APRR1-ox. The circadian profiles of potential clock-associated genes, CCA1, LHY, GI, and CCR2 were all markedly altered in APRR1-ox, each in characteristic fashion. To gain further insight into the molecular function of APRR1, we then identified a novel Myc-related bHLH transcription factor, which physically associated with APRR1. This protein (named PIL1) is similar in its amino acid sequence to PIF3, which has been identified as a phytochrome-interacting transcription factor. These results are discussed in relation to the current idea that APRR1 (TOC1) plays a role within, or close to, the Arabidopsis central oscillator.
Mesh Terms:
Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Blotting, Northern, Carrier Proteins, Circadian Rhythm, DNA-Binding Proteins, Gene Expression Regulation, Plant, Light-Harvesting Protein Complexes, Molecular Sequence Data, Multigene Family, Plant Proteins, Plants, Genetically Modified, Protein Binding, Sequence Homology, Amino Acid, Transcription Factors, Two-Hybrid System Techniques
Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Blotting, Northern, Carrier Proteins, Circadian Rhythm, DNA-Binding Proteins, Gene Expression Regulation, Plant, Light-Harvesting Protein Complexes, Molecular Sequence Data, Multigene Family, Plant Proteins, Plants, Genetically Modified, Protein Binding, Sequence Homology, Amino Acid, Transcription Factors, Two-Hybrid System Techniques
Plant Cell Physiol.
Date: Jan. 01, 2002
PubMed ID: 11828023
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