Genetic and Molecular Analysis of Circadian Rhythms

Dunlap, Jay C.

doi:10.1146/annurev.genet.30.1.579

Cited by 242 publications

(162 citation statements)

References 104 publications

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“…Since the day/night cycles of life on Earth are important in determining the priorities of existence for most organisms, their biological or circadian clocks have become adjusted to run with a period of roughly 24 h. However, the input of a photoreceptor is necessary in order to synchronise this clock with the environmental light / dark cycle (Dunlap, 1996). In plants, it has been known for some time that the red / far red reversible photoreceptor family, the phytochromes, are involved in this process of entrainment (Simon et al, 1976).…”

Section: Introductionmentioning

confidence: 99%

The phytochrome B encoded by the HLG locus of Nicotiana plumbaginifolia is required for detection of photoperiod: hlg mutants show altered regulation of flowering and circadian movement

Hudson

Smith

1998

The Plant Journal

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SummaryThe sensitivity of the Nicotiana plumbaginifolia wild-type and phytochrome B (hlg) mutant to photoperiod was investigated. Leaf number at bolting and rosette-leaf movement were measured under conditions of different light quality and photoperiod. Bolting in wild-type plants was slightly delayed under short days (SD), compared to plants grown under long days (LD). The hlg mutant bolted later than the wild-type under LD, but not under SD. An endogenous rhythm of rosette-leaf movement in the wildtype was present under SD, but suppressed under LD. The hlg mutant behaved indistinguishably from the wild-type under SD conditions, but the movements were not suppressed under LD in the mutants. The endogenous rhythm appeared to be entrained normally in the mutants under all the conditions investigated. It was concluded that the B-type phytochrome absent in the hlg mutant is required for the measurement of photoperiod duration in N. plumbaginifolia, but is not required for entrainment of the circadian clock.

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Section: Introductionmentioning

confidence: 99%

The phytochrome B encoded by the HLG locus of Nicotiana plumbaginifolia is required for detection of photoperiod: hlg mutants show altered regulation of flowering and circadian movement

Hudson

Smith

1998

The Plant Journal

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“…According to current models, circadian clocks regulating these rhythms consist of input pathways, a central oscillator, and output pathways (1)(2)(3). Oscillators are thought to generate rhythms by a transcription-translation negative feedback loop (4)(5)(6)(7)(8).…”

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confidence: 99%

“…In addition, posttranscriptional and posttranslational regulation play important roles in circadian clocks in Drosophila and Neurospora (7)(8)(9)(10). The oscillator can be entrained by input pathways from environmental cues such as light and temperature, and, in turn, regulates specific cellular events such as expression of clock-controlled genes (1)(2)(3).…”

mentioning

confidence: 99%

The protein kinase CK2 is involved in regulation of circadian rhythms in Arabidopsis

Sugano

Andronis²,

Ong³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

212

183

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A wide range of processes in plants, including expression of certain genes, is regulated by endogenous circadian rhythms. The circadian clock-associated 1 (CCA1) and the late elongated hypocotyl (LHY) proteins have been shown to be closely associated with clock function in Arabidopsis thaliana. The protein kinase CK2 can interact with and phosphorylate CCA1, but its role in the regulation of the circadian clock remains unknown. Here we show that plants overexpressing CKB3, a regulatory subunit of CK2, display increased CK2 activity and shorter periods of rhythmic expression of CCA1 and LHY. CK2 is also able to interact with and phosphorylate LHY in vitro. Additionally, overexpression of CKB3 shortened the periods of four known circadian clock-controlled genes with different phase angles, demonstrating that many clock outputs are affected. This overexpression also reduced phytochrome induction of an Lhcb gene. Finally, we found that the photoperiodic flowering response, which is influenced by circadian rhythms, was diminished in the transgenic lines, and that the plants flowered earlier on both long-day and short-day photoperiods. These data demonstrate that CK2 is involved in regulation of the circadian clock in Arabidopsis. C ircadian rhythms are driven by endogenous biological clocks that regulate many biochemical, physiological, and behavioral processes in a wide variety of organisms. According to current models, circadian clocks regulating these rhythms consist of input pathways, a central oscillator, and output pathways (1-3). Oscillators are thought to generate rhythms by a transcription-translation negative feedback loop (4-8). Studies in cyanobacteria, Neurospora, Drosophila, and mouse have found that both positive and negative elements that activate and inhibit the transcription of clock genes are required to maintain the loop. In addition, posttranscriptional and posttranslational regulation play important roles in circadian clocks in Drosophila and Neurospora (7-10). The oscillator can be entrained by input pathways from environmental cues such as light and temperature, and, in turn, regulates specific cellular events such as expression of clock-controlled genes (1-3).Until recently, little was known about the molecular mechanisms of circadian clocks in plants (11-13). In Arabidopsis thaliana, the toc1 mutation affects the period of many circadian rhythms (14,15). Although the corresponding gene has not yet been cloned, it is thought that TOC1 encodes a component of the oscillator. The ELF3 gene is proposed to act in the input pathway (16). Two Myb-related genes, circadian clock-associated 1 (CCA1) and late elongated hypocotyl (LHY), have also been identified as potential clock genes (17, 18), and CCA1 was found to act as a transcription factor for Lhcb gene expression (19). Expression of CCA1 and LHY oscillates with a circadian rhythm. Constitutive expression of CCA1 was shown to abolish several distinct circadian rhythms, suppress its own expression as well as that of LHY, and delay flowering substa...

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“…Endogenous oscillators (circadian clocks) control diurnal rhythmic phenomena in prokaryotic cyanobacteria and almost all eukaryotes (Sweeney, 1987;Kondo et al, 1993;Hall, 1995;Dunlap, 1996). In plants several biological processes, including enzyme activities, leaf movements, stomatal opening and closing, and the expression of a large number of genes, exhibit endogenous rhythms (Sweeney, 1987;Edmunds, 1988;McClung and Kay, 1994).…”

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confidence: 99%

Circadian-Regulated Transcription of thepsbD Light-Responsive Promoter in Wheat Chloroplasts

et al. 1998

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The level of mRNAs derived from the plastid-encoded psbD light-responsive promoter (LRP) is controlled by a circadian clock(s) in wheat (Triticum aestivum). The circadian oscillations in the psbD LRP mRNA level persisted for at least three cycles in continuous light and for one cycle in continuous dark, with maxima in subjective morning and minima in subjective early night. In vitro transcription in chloroplast extracts revealed that the circadian cycles in the psbD LRP mRNA level were dominantly attributed to the circadian-regulated transcription of the psbD LRP. The effects of various mutations introduced into the promoter region on the psbD LRP activity in vitro suggest the existence of two positive elements located between ؊54 and ؊36, which generally enhance the transcription activity, and an anomalous core promoter structure lacking the functional "؊35" element, which plays a crucial role in the circadian fluctuation and light dependency of psbD LRP transcription activity.

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Genetic and Molecular Analysis of Circadian Rhythms

Cited by 242 publications

References 104 publications

The phytochrome B encoded by the HLG locus of Nicotiana plumbaginifolia is required for detection of photoperiod: hlg mutants show altered regulation of flowering and circadian movement

The phytochrome B encoded by the HLG locus of Nicotiana plumbaginifolia is required for detection of photoperiod: hlg mutants show altered regulation of flowering and circadian movement

The protein kinase CK2 is involved in regulation of circadian rhythms in Arabidopsis

Circadian-Regulated Transcription of thepsbD Light-Responsive Promoter in Wheat Chloroplasts

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