title: The APRR1/TOC1 quintet implicated in circadian rhythms of Arabidopsis thaliana: I. Characterization with APRR1-overexpressing plants.
abstract: 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.
authors.affiliation: Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
authors.forename: Seiya
authors.initials: S
authors.lastname: Makino
authors.forename: Akinori
authors.initials: A
authors.lastname: Matsushika
authors.forename: Masaya
authors.initials: M
authors.lastname: Kojima
authors.forename: Takafumi
authors.initials: T
authors.lastname: Yamashino
authors.forename: Takeshi
authors.initials: T
authors.lastname: Mizuno
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002940:Circadian Rhythm / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D005810:Multigene Family; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: C091601:ABI3 protein, Arabidopsis; C448162:APRR3 protein, Arabidopsis; C448160:APRR5 protein, Arabidopsis; C448161:APRR7 protein, Arabidopsis; C448159:APRR9 protein, Arabidopsis; D029681:Arabidopsis Proteins; C423618:CAB2 protein, Arabidopsis; C114425:CCA1 protein, Arabidopsis; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C121183:GI protein, Arabidopsis; C113192:LHY protein, Arabidopsis; D045342:Light-Harvesting Protein Complexes; C456844:PIL1 protein, Arabidopsis; D010940:Plant Proteins; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors