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Review
. 2010 Oct;13(5):594-603.
doi: 10.1016/j.pbi.2010.05.004.

Similarities in the circadian clock and photoperiodism in plants

Young Hun Song  1 , Shogo Ito, Takato Imaizumi
Affiliations
Review

Similarities in the circadian clock and photoperiodism in plants

Young Hun Song et al. Curr Opin Plant Biol. 2010 Oct.

Abstract

Plants utilize circadian clocks to synchronize their physiological and developmental events with daily and yearly changes in the environment. Recent advances in Arabidopsis research have provided a better understanding of the molecular mechanisms of the circadian clock and photoperiodism. One of the most important questions is whether the mechanisms discovered in Arabidopsis are conserved in other plant species. Through the identification of many Arabidopsis clock gene homologs and the characterization of some gene functions, a strong resemblance between the circadian clocks in plants has been observed. On the contrary, based on our recent increased knowledge of photoperiodic flowering mechanisms in cereals and other plants, the day-length sensing mechanisms appear to have diverged more between long-day plants and short-day plants.

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Figures

Figure 1
Figure 1
Photoperiodic flowering pathways in long-day and short-day plants. Long-day plants (Arabidopsis, barley and wheat) sense day-length increases and promote flowering in late spring and/or early summer. In these plants, photoperiodic flowering responses are regulated by the CO-FT modules. The circadian clocks regulate CO expression through the function of PRRs, FKF1, GI, and CDFs in Arabidopsis, and Ppd1 (a homolog of PRR7) in barley and wheat. Vernalization represses FLC expression in Arabidopsis, while it induces VRN1 expression in barley and wheat. VRN1 depresses the expression of VRN2, which represses FT expression. Therefore, vernalization releases the strong repression of FT and enables these plants to promote flowering in LD. In the short-day plant rice, the circadian clock regulates Hd1 (a homolog of CO) expression through OsGI function. Hd1 represses the expression of a rice FT (Hd3a) in LD, while it promotes the expression of Hd3a and RFT1 (another rice FT homolog) in SD. Phytochromes and SE5 signaling promotes Hd1-dependent repression of Hd3a in LD. The expression of a rice-specific floral inducer Ehd1 is regulated by activators (OsMADS50, OsMADS51, OsGI, and Ehd2/OsId1/RID) and repressors (Ghd7, SE5, and phys). To promote flowering Ehd1 induces RFT1 expression in LD and both Hd3a and RFT1 expression in SD. Cultivated rice plants grow in a wider range of latitudes with different changes in day-length conditions. Depending on where they grow, either the long-day or the short-day pathways control flowering. Grey dotted lines indicate potential interaction.
Figure 2
Figure 2
The expression patterns of CO and FT in various plant species. CO expression profiles are similar in long-day and short-day plants under both long day (LD) and short day (SD) conditions. Even in the day neutral plant maize, conz1 (a homolog of rice Hd1) expression showed similar patterns [77]. These results suggest that the molecular mechanisms of CO transcriptional regulation may also be highly conserved among plants. In long-day plants, FT mRNA levels are high at the end of the day in LD and extremely low throughout the day in SD. In contrast, in short-day plants, FT mRNA levels are high in the morning in SD. White and black boxes designate day and night, respectively.
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References

    1. Harmer SL. The circadian system in higher plants. Annu Rev Plant Biol. 2009;60:357–377. - PubMed
    1. Imaizumi T. Arabidopsis circadian clock and photoperiodism: time to think about location. Curr Opin Plant Biol. 2010;13:83–89. - PMC - PubMed
    1. Más P, Yanovsky MJ. Time for circadian rhythms: plants get synchronized. Curr Opin Plant Biol. 2009;12:574–579. - PubMed
    1. Farré EM, Harmer SL, Harmon FG, Yanovsky MJ, Kay SA. Overlapping and distinct roles of PRR7 and PRR9 in the Arabidopsis circadian clock. Curr Biol. 2005;15:47–54. - PubMed
    1. Alabadí D, Oyama T, Yanovsky MJ, Harmon FG, Más P, Kay SA. Reciprocal regulation between TOC1 and LHY/CCA1 within the Arabidopsis circadian clock. Science. 2001;293:880–883. - PubMed

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