Light response of the circadian waves of the APRR1/TOC1 quintet: when does the quintet start singing rhythmically in Arabidopsis?
We previously identified a novel class of proteins, named A:rabidopsis pseudo-response regulators (APRRs), each of which (APRR1/TOC1, APRR3, APRR5, APRR7, APRR9) has an intriguing structural design containing an N-terminal pseudo-receiver domain and a C-terminal CONSTANS motif. Expression of these APRR1/TOC1 family members is under the control of a coordinate circadian rhythm at the level of transcription such that the APRR-mRNAs start accumulating sequentially after dawn with 2 to 3 h intervals in the order of APRR9-->APRR7-->APRR5-->APRR3-->APRR1/TOC1 in a given 24 h photo-period. Based on these data, we previously proposed that these sequential and rhythmic events of transcription, termed 'circadian waves of APRR1/TOC1 quintet', may be a basis of a presumed Arabidopsis biological clock (named 'bar code clock') [Matsushika et al. (2000) Plant and Cell Physiol. 41: 1002]. Here we further characterized the event of circadian waves, by demonstrating that certain light stimuli are crucial determinants to induce the robust circadian waves, and accordingly, the first-boosted and light-induced APRR9 appears to be primarily responsible for this light response of the circadian waves. Also, as such a light stimulus, a red light pulse that is presumably perceived by phytochromes appears to be sufficient to induce (or synchronize) the APRR1/TOC1 circadian waves.
Laboratory of Molecular Microbiology, School of Agriculture, Nagoya University, Chikusa-ku, Nagoya, 464-8601 Japan.
S
S
Makino
A
A
Matsushika
M
M
Kojima
Y
Y
Oda
T
T
Mizuno
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D029681:Arabidopsis Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D008027:Light; D055537:Light Signal Transduction / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics*; D014157:Transcription Factors
C091601:ABI3 protein, Arabidopsis; D029681:Arabidopsis Proteins; D010940:Plant Proteins; C411822:TOC1 protein, Arabidopsis; D014157:Transcription Factors