Journal Article

The APRR1/TOC1 Quintet Implicated in Circadian Rhythms of <i>Arabidopsis thaliana</i>: I. Characterization with APRR1-Overexpressing Plants

Seiya Makino, Akinori Matsushika, Masaya Kojima, Takafumi Yamashino and Takeshi Mizuno

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 43, issue 1, pages 58-69
Published in print January 2002 | ISSN: 0032-0781
Published online January 2002 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcf005
The APRR1/TOC1 Quintet Implicated in Circadian Rhythms of Arabidopsis thaliana: I. Characterization with APRR1-Overexpressing Plants

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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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: APRR9APRR7APRR5APRR3 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.

Keywords: Key words: Arabidopsis — Circadian rhythm — Clock components — Transgenic plants.

Journal Article.  8271 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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