Document Detail

Phase-resetting mechanism of the circadian clock in Chlamydomonas reinhardtii.
MedLine Citation:
PMID:  23898163     Owner:  NLM     Status:  MEDLINE    
Although the circadian clock is a self-sustaining oscillator having a periodicity of nearly 1 d, its period length is not necessarily 24 h. Therefore, daily adjustment of the clock (i.e., resetting) is an essential mechanism for the circadian clock to adapt to daily environmental changes. One of the major cues for this resetting mechanism is light. In the unicellular green alga Chlamydomonas reinhardtii, the circadian clock is reset by blue/green and red light. However, the underlying molecular mechanisms remain largely unknown. In this study, using clock protein-luciferase fusion reporters, we found that the level of RHYTHM OF CHLOROPLAST 15 (ROC15), a clock component in C. reinhardtii, decreased rapidly after light exposure in a circadian-phase-independent manner. Blue, green, and red light were able to induce this process, with red light being the most effective among them. Expression analyses and inhibitor experiments suggested that this process was regulated mainly by a proteasome-dependent protein degradation pathway. In addition, we found that the other clock gene, ROC114, encoding an F-box protein, was involved in this process. Furthermore, we demonstrated that a roc15 mutant showed defects in the phase-resetting of the circadian clock by light. Taken together, these data strongly suggest that the light-induced degradation of ROC15 protein is one of the triggers for resetting the circadian clock in C. reinhardtii. Our data provide not only a basis for understanding the molecular mechanisms of light-induced phase-resetting in C. reinhardtii, but also insights into the phase-resetting mechanisms of circadian clocks in plants.
Yoshimi Niwa; Takuya Matsuo; Kiyoshi Onai; Daisaku Kato; Makoto Tachikawa; Masahiro Ishiura
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2013-07-29
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  110     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2013 Aug 
Date Detail:
Created Date:  2013-08-14     Completed Date:  2013-11-11     Revised Date:  2014-02-13    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  13666-71     Citation Subset:  IM    
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MeSH Terms
Algal Proteins / metabolism*
Base Sequence
Chlamydomonas reinhardtii / physiology*
Circadian Clocks / physiology*,  radiation effects
Circadian Rhythm / physiology*
Gene Expression Regulation, Plant / physiology*,  radiation effects
Luciferases / genetics,  metabolism
Luminescent Measurements
Molecular Sequence Data
Time Factors
Reg. No./Substance:
0/Algal Proteins; EC 1.13.12.-/Luciferases

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