Reciprocal Regulation Between TOC1 and LHY/CCA1 Within the Arabidopsis Circadian Clock
David Alabadí,1*
Tokitaka Oyama,1*
Marcelo J. Yanovsky,1*
Franklin G. Harmon,1
Paloma Más,1
Steve A. Kay1
The interactive regulation between clock genes is central for
oscillator function. Here, we show interactions between the Arabidopsis 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 and
CCA1 expression. Our results indicate that these
interactions form a loop critical for clock function in
Arabidopsis.
1 Department of Cell Biology and Institute for
Childhood and Neglected Diseases, The Scripps Research Institute, La
Jolla, CA 92037, USA.
*
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}scripps.edu
