Action Spectrum for Resetting the Circadian Phototaxis Rhythm in the CW15 Strain of <i>Chlamydomonas</i>

Johnson, Carl Hirschie; Kondo, Takao; Hastings, J. Woodland

doi:10.1104/pp.97.3.1122

Cited by 49 publications

(26 citation statements)

References 17 publications

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“…In the eukaryotic alga Lingulodinium polyedrum (formerly Gonyaulax polyedra), a sublethal concentration of DCMU shortens the FRP (30). DCMU also inhibits phase shifting in response to a light pulse in L. polyedrum (19) and in Chlamydomonas reinhardtii (18). Thus, a connection between photosynthetic electron transport and light input pathways of the circadian system is a common characteristic among some phototropic organisms.…”

Section: Discussionmentioning

confidence: 99%

ldpA Encodes an Iron-Sulfur Protein Involved in Light-Dependent Modulation of the Circadian Period in the Cyanobacterium Synechococcus elongatus PCC 7942

et al. 2003

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We generated random transposon insertion mutants to identify genes involved in light input pathways to the circadian clock of the cyanobacterium Synechococcus elongatus PCC 7942. Two mutants, AMC408-M1 and AMC408-M2, were isolated that responded to a 5-h dark pulse differently from the wild-type strain. The two mutants carried independent transposon insertions in an open reading frame here named ldpA (for lightdependent period). Although the mutants were isolated by a phase shift screening protocol, the actual defect is a conditional alteration in the circadian period. The mutants retain the wild-type ability to phase shift the circadian gene expression (bioluminescent reporter) rhythm if the timing of administration of the dark pulse is corrected for a 1-h shortening of the circadian period in the mutant. Further analysis indicated that the conditional short-period mutant phenotype results from insensitivity to light gradients that normally modulate the circadian period in S. elongatus, lengthening the period at low light intensities. The ldpA gene encodes a polypeptide that predicts a 7Fe-8S cluster-binding motif expected to be involved in redox reactions. We suggest that the LdpA protein modulates the circadian clock as an indirect function of light intensity by sensing changes in cellular physiology.

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Section: Discussionmentioning

confidence: 99%

ldpA Encodes an Iron-Sulfur Protein Involved in Light-Dependent Modulation of the Circadian Period in the Cyanobacterium Synechococcus elongatus PCC 7942

et al. 2003

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“…Like Arabidopsis for higher plants, Chlamydomonas is a model for green algae because its genome has been sequenced and correctly annotated (Merchant et al, 2007), genetics are feasible (Rochaix, 1995), and sexual and vegetative growing conditions are versatile and optimal for scientific research (Harris, 1989). Some of the most important physiological processes of the green microalga C. reinhardtii are under circadian and/or photoperiod control, including phototaxia (Johnson et al, 1991), starch accumulation (Ral et al, 2006), and the synchronicity of cell cycle and growth that happens under specific conditions (Lien and Knutsen, 1976). Nevertheless, there is no model describing how the photoperiod response may work in algae.…”

Section: The Photoperiod Response In Algaementioning

confidence: 99%

CONSTANS and the evolutionary origin of photoperiodic timing of flowering

Valverde

2011

Journal of Experimental Botany

172

146

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A network of promoting and inhibiting pathways that respond to environmental and internal signals controls the flowering transition. The outcome of this regulatory network establishes, for any particular plant, the correct time of the year to flower. The photoperiod pathway channels inputs from light, day length, and the circadian clock to promote the floral transition. CONSTANS (CO) is a central regulator of this pathway, triggering the production of the mobile florigen hormone FT (FLOWERING LOCUS T) that induces flower differentiation. Because plant reproductive fitness is directly related to its capacity to flower at a precise time, the photoperiod pathway is present in all known plant species. Recent findings have stretched the evolutionary span of this photophase signal to unicellular algae, which show unexpected conserved characteristics with modern plant photoperiodic responses. In this review, a comparative description of the photoperiodic systems in algae and plants will be presented and a general role for the CO family of transcriptional activators proposed.

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“…One of the major cues for resetting the circadian clock is light. In C. reinhardtii, it has been demonstrated that the action spectrum for the phase resetting of the circadian clock shows two peaks around green (520 nm) and red (660 nm) light in dark-adapted cells or around blue (450-480 nm) and red (650-670 nm) light in illuminated cells (15,16). However, the underlying molecular mechanisms remain largely unknown.…”

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confidence: 99%

Phase-resetting mechanism of the circadian clock in Chlamydomonas reinhardtii

Niwa

Matsuo

Onai

et al. 2013

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

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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.LUCnc | light pulse | phase shift C ircadian rhythms, observed ubiquitously in organisms from prokaryotic cyanobacteria to humans, are generated by the circadian clock, which is thought to rely on transcriptional/translational feedback loops and posttranslational biochemical oscillations of some genes and their protein products called clock genes/proteins (1-4). Clock genes/proteins have been identified in several organisms, including mammals, insects, fungi, land plants, cyanobacteria, and, recently, green algae (1, 2, 5-8). Except for general kinases and phosphatases (9), most of the components of circadian clocks are not conserved among evolutionarily divergent organisms. On the other hand, the components are conserved to some extent between organisms that are relatively close evolutionarily (i.e., mammals and insects, land plants and green algae) (6-8, 10).The clock components in algae were first identified in the model green alga Chlamydomonas reinhardtii. There are the RNAbinding protein complex CHLAMY1 (11), a casein kinase (12), and RHYTHM OF CHLOROPLAST (ROC) proteins, including putative DNA-binding proteins (ROC15, ROC40, ROC66, and ROC75), an F-box protein (ROC114), and a leucine-rich repeat protein (ROC55) (13). The DNA-binding motifs of ROC proteins are homologous to those of Arabidopsis thaliana proteins associated with the circadian clock and photoperiodic flowering (13)...

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Action Spectrum for Resetting the Circadian Phototaxis Rhythm in the CW15 Strain of Chlamydomonas

Cited by 49 publications

References 17 publications

ldpA Encodes an Iron-Sulfur Protein Involved in Light-Dependent Modulation of the Circadian Period in the Cyanobacterium Synechococcus elongatus PCC 7942

ldpA Encodes an Iron-Sulfur Protein Involved in Light-Dependent Modulation of the Circadian Period in the Cyanobacterium Synechococcus elongatus PCC 7942

CONSTANS and the evolutionary origin of photoperiodic timing of flowering

Phase-resetting mechanism of the circadian clock in Chlamydomonas reinhardtii

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