Reciprocal Regulation Between TOC1 and LHY/CCA1 Within the Arabidopsis Circadian Clock

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Science  03 Aug 2001:
Vol. 293, Issue 5531, pp. 880-883
DOI: 10.1126/science.1061320

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The interactive regulation between clock genes is central for oscillator function. Here, we show interactions between theArabidopsis clock genes LATE ELONGATED HYPOCOTYL(LHY), CIRCADIAN CLOCK ASSOCIATED 1(CCA1), and TIMING OF CAB EXPRESSION 1(TOC1). The MYB transcription factors LHY and CCA1 negatively regulate TOC1 expression. We show that both proteins bind to a region in the TOC1 promoter that is critical for its clock regulation. Conversely, TOC1 appears to participate in the positive regulation of LHY andCCA1 expression. Our results indicate that these interactions form a loop critical for clock function inArabidopsis.

  • * These authors contributed equally to this work.

  • Present address: Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan.

  • To whom correspondence should be addressed. E-mail: stevek{at}

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