scholarly journals Light-mediated circuit switching in the Drosophila neuronal clock network

2019 ◽  
Author(s):  
M Schlichting ◽  
P Weidner ◽  
M Diaz ◽  
P Menegazzi ◽  
E Dalla-Benetta ◽  
...  
Keyword(s):  
Visual System ◽  
Circadian Clock ◽  
Molecular Mechanism ◽  
Essential Feature ◽  
Constant Darkness ◽  
Circuit Switching ◽  
Light Entrainment ◽  
Long Day ◽  
External Cues ◽  
A Cell

SummaryThe circadian clock is a timekeeper but also helps adapt physiology to the outside world. This is because an essential feature of clocks is their ability to adjust (entrain) to the environment, with light being the most important signal. Whereas Cryptochrome-mediated entrainment is well understood in Drosophila, integration of light information via the visual system lacks a neuronal or molecular mechanism. Here we show that a single photoreceptor sub-type is essential for long day adaptation. These cells activate key circadian neurons, namely the lLNvs, which release the neuropeptide PDF. Using a cell-specific CRISPR/Cas9 assay, we show that PDF directly interacts with neurons important for evening (E) activity timing. Interestingly, this pathway is specific for light entrainment and appears to be dispensable in constant darkness (DD). The results therefore indicate that external cues cause a rearrangement of neuronal hierarchy, which is a novel form of plasticity.

scholarly journals Entrainment of the Drosophila clock by the visual system

2020 ◽  
Vol 15 ◽  
pp. 263310552090370
Author(s):  
Matthias Schlichting
Keyword(s):  
Drosophila Melanogaster ◽  
Visual System ◽  
Clock Synchronization ◽  
Fruit Fly ◽  
Circadian Clocks ◽  
Cyclic Change ◽  
Animal Physiology ◽  
Light Entrainment ◽  
Physiological Evidence ◽  
External Cues

Circadian clocks evolved as an adaptation to the cyclic change of day and night. To precisely adapt to this environment, the endogenous period has to be adjusted every day to exactly 24 hours by a process called entrainment. Organisms can use several external cues, called zeitgebers, to adapt. These include changes in temperature, humidity, or light. The latter is the most powerful signal to synchronize the clock in animals. Research shows that a complex visual system and circadian photoreceptors work together to adjust animal physiology to the outside world. This review will focus on the importance of the visual system for clock synchronization in the fruit fly Drosophila melanogaster. It will cover behavioral and physiological evidence that supports the importance of the visual system in light entrainment.

scholarly journals The Importance of Stochastic Effects for Explaining Entrainment in the Zebrafish Circadian Clock

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Raphaela Heussen ◽  
David Whitmore
Keyword(s):  
Light Intensity ◽  
Circadian Clock ◽  
Light Exposure ◽  
Essential Feature ◽  
Strong Component ◽  
Stochastic Effects ◽  
Signal Decay ◽  
Physiological Processes ◽  
External Cues

The circadian clock plays a pivotal role in modulating physiological processes and has been implicated, either directly or indirectly, in a range of pathological states including cancer. Here we investigate how the circadian clock is entrained by external cues such as light. Working with zebrafish cell lines and combining light pulse experiments with simulation efforts focused on the role of synchronization effects, we find that even very modest doses of light exposure are sufficient to trigger some entrainment, whereby a higher light intensity or duration correlates with strength of the circadian signal. Moreover, we observe in the simulations that stochastic effects may be considered an essential feature of the circadian clock in order to explain the circadian signal decay in prolonged darkness, as well as light initiated resynchronization as a strong component of entrainment.

Circadian organization of chitin in some insect skeletons

1965 ◽  
Vol s3-106 (76) ◽  
pp. 315-325
Author(s):  
A. C. NEVILLE
Keyword(s):  
Circadian Clock ◽  
General Feature ◽  
Periplaneta Americana ◽  
Constant Darkness ◽  
Actual Rate ◽  
Rate Of Increase ◽  
Parallel Fibres ◽  
Astronomical Clock ◽  
Circadian Organization ◽  
Water Bugs

A circadian clock is shown to be involved in the control of macromolecular orientation of chitin by cells secreting and organizing insect endocuticle. Daily organization of locust endocuticle into alternating lamellate and non-lamellate layers persists in constant temperature (36° C) and constant darkness for at least 2 weeks; the freerunning period is then about 23 h, so that after a number of days the circadian clock is 180° out of phase with the astronomical clock, with which it is normally phased. The rhythm is almost independent of temperature, with a Q10 of 1.04, as contrasted with a Q10 of 2.0 for the actual rate of increase of endocuticular thickness. Locust epidermal cells differ in response to specific imposed environmental conditions according to their location in the integument. In some cells, constant low temperature uncouples chitin lamellogenesis from the circadian clock, provided that illumination (light or dark) is constant also: the result is continuously lamellate endocuticle. In other cells constant light acts as an uncoupling factor, provided that temperature (high or low) is constant also: the result in this case is continuously non-lamellate endocuticle. The circadian rhythm of chitin lamellogenesis persists in a cave cricket (Dolichopoda linderi). A similar circadian lamellogenesis rhythm occurs in the endocuticle of nymphs and adults of the cockroach Periplaneta americana. A crossed-fibre multiple-ply endocuticle in the legs and wings of giant toe-biter water bugs (Belosto-matidae) also displays circadian organization, the chitin macromolecules in any one layer lying in parallel fibres, at an angle of approximately 6o° to those in the next layer. It is suggested that daily organization of the skeleton may be a general feature of arthropods. Examples include the phenomena of timing of chitin lamellogenesis; chitin crossed-fibrillar organization; degree of fluorescence of the rubber-like protein resilin; and mineralization of crayfish gastroliths.

scholarly journals PDF neuron firing phase-shifts key circadian activity neurons in Drosophila

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Fang Guo ◽  
Isadora Cerullo ◽  
Xiao Chen ◽  
Michael Rosbash
Keyword(s):  
Response Curve ◽  
Phase Response Curve ◽  
Receptor Expression ◽  
Phase Shifting ◽  
Constant Darkness ◽  
Behavioral Rhythms ◽  
Circadian Phase ◽  
Phase Adjustment ◽  
Drosophila Brain ◽  
A Cell

Our experiments address two long-standing models for the function of the Drosophila brain circadian network: a dual oscillator model, which emphasizes the primacy of PDF-containing neurons, and a cell-autonomous model for circadian phase adjustment. We identify five different circadian (E) neurons that are a major source of rhythmicity and locomotor activity. Brief firing of PDF cells at different times of day generates a phase response curve (PRC), which mimics a light-mediated PRC and requires PDF receptor expression in the five E neurons. Firing also resembles light by causing TIM degradation in downstream neurons. Unlike light however, firing-mediated phase-shifting is CRY-independent and exploits the E3 ligase component CUL-3 in the early night to degrade TIM. Our results suggest that PDF neurons integrate light information and then modulate the phase of E cell oscillations and behavioral rhythms. The results also explain how fly brain rhythms persist in constant darkness and without CRY.

scholarly journals Effect of Circadian Clock and Light–Dark Cycles in Onchidium reevesii: Possible Implications for Long-Term Memory

Genes ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 488
Author(s):  
Xu ◽  
Yang ◽  
Shen
Keyword(s):  
Circadian Clock ◽  
Intertidal Zone ◽  
Peak Level ◽  
Constant Darkness ◽  
Long Term Memory ◽  
Term Memory ◽  
Expression Levels ◽  
Peak Expression ◽  
Cry1 Gene

The sea slug Onchidium reevesii inhabits the intertidal zone, which is characterized by a changeable environment. Although the circadian modulation of long-term memory (LTM) is well documented, the interaction of the circadian clock with light–dark masking in LTM of intertidal animals is not well understood. We characterized the LTM of Onchidium and tested the expression levels of related genes under a light–dark (LD) cycle and constant darkness (i.e., dark–dark, or DD) cycle. Results indicated that both learning behavior and LTM show differences between circadian time (CT) 10 and zeitgeber time (ZT) 10. In LD, the cry1 gene expressed irregularly, and per2 expression displayed a daily pattern and a peak expression level at ZT 18. OnCREB1 (only in LD conditions) and per2 transcripts cycled in phase with each other. In DD, the cry1 gene had its peak expression at CT 10, and per2 expressed its peak level at CT 18. OnCREB1 had two peak expression levels at ZT 10 or ZT 18 which correspond to the time node of peaks in cry1 and per2, respectively. The obtained results provide an LTM pattern that is different from other model species of the intertidal zone. We conclude that the daily transcriptional oscillations of Onchidium for LTM were affected by circadian rhythms and LD cycle masking.

scholarly journals Synechocystis KaiC3 Displays Temperature- and KaiB-Dependent ATPase Activity and Is Important for Growth in Darkness

2019 ◽  
Vol 202 (4) ◽  
Author(s):  
Anika Wiegard ◽  
Christin Köbler ◽  
Katsuaki Oyama ◽  
Anja K. Dörrich ◽  
Chihiro Azai ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Circadian Clock ◽  
Atp Hydrolysis ◽  
Synechococcus Elongatus ◽  
Constant Darkness ◽  
Content Type ◽  
Clock Proteins ◽  
Pcc 7942 ◽  
Pcc 6803

ABSTRACT Cyanobacteria form a heterogeneous bacterial group with diverse lifestyles, acclimation strategies, and differences in the presence of circadian clock proteins. In Synechococcus elongatus PCC 7942, a unique posttranslational KaiABC oscillator drives circadian rhythms. ATPase activity of KaiC correlates with the period of the clock and mediates temperature compensation. Synechocystis sp. strain PCC 6803 expresses additional Kai proteins, of which KaiB3 and KaiC3 proteins were suggested to fine-tune the standard KaiAB1C1 oscillator. In the present study, we therefore characterized the enzymatic activity of KaiC3 as a representative of nonstandard KaiC homologs in vitro. KaiC3 displayed ATPase activity lower than that of the Synechococcus elongatus PCC 7942 KaiC protein. ATP hydrolysis was temperature dependent. Hence, KaiC3 is missing a defining feature of the model cyanobacterial circadian oscillator. Yeast two-hybrid analysis showed that KaiC3 interacts with KaiB3, KaiC1, and KaiB1. Further, KaiB3 and KaiB1 reduced in vitro ATP hydrolysis by KaiC3. Spot assays showed that chemoheterotrophic growth in constant darkness is completely abolished after deletion of ΔkaiAB1C1 and reduced in the absence of kaiC3. We therefore suggest a role for adaptation to darkness for KaiC3 as well as a cross talk between the KaiC1- and KaiC3-based systems. IMPORTANCE The circadian clock influences the cyanobacterial metabolism, and deeper understanding of its regulation will be important for metabolic optimizations in the context of industrial applications. Due to the heterogeneity of cyanobacteria, characterization of clock systems in organisms apart from the circadian model Synechococcus elongatus PCC 7942 is required. Synechocystis sp. strain PCC 6803 represents a major cyanobacterial model organism and harbors phylogenetically diverged homologs of the clock proteins, which are present in various other noncyanobacterial prokaryotes. By our in vitro studies we unravel the interplay of the multiple Synechocystis Kai proteins and characterize enzymatic activities of the nonstandard clock homolog KaiC3. We show that the deletion of kaiC3 affects growth in constant darkness, suggesting its involvement in the regulation of nonphotosynthetic metabolic pathways.

scholarly journals Inhibition of Transferrin Recycling and Endosome Tubulation by Phospholipase A2Antagonists

2001 ◽  
Vol 276 (50) ◽  
pp. 47361-47370 ◽  
Author(s):  
Paul de Figueiredo ◽  
Anne Doody ◽  
Renée S. Polizotto ◽  
Daniel Drecktrah ◽  
Salli Wood ◽  
...  
Keyword(s):  
Cell Surface ◽  
Molecular Mechanism ◽  
Golgi Complex ◽  
Broad Spectrum ◽  
Tubule Formation ◽  
Recycling Endosomes ◽  
Low Concentrations ◽  
A Cell ◽  
Recycling Pathway ◽  
Lines Of Evidence

We report here that a broad spectrum of phospholipase A2(PLA2) antagonists produce a concentration-dependent, differential block in the endocytic recycling pathway of transferrin (Tf) and Tf receptors (TfRs) but have no acute affect on Tf uptake from the cell surface. At low concentrations of antagonists (∼1 μm), Tf and TfR accumulated in centrally located recycling endosomes, whereas at higher concentrations (∼10 μm), Tf-TfR accumulated in peripheral sorting endosomes. Several independent lines of evidence suggest that this inhibition of recycling may result from the inhibition of tubule formation. First, BFA-stimulated endosome tubule formation was similarly inhibited by PLA2antagonists. Second, endocytosed tracers were found in larger spherical endosomes in the presence of PLA2antagonists. And third, endosome tubule formation in a cell-free, cytosol-dependent reconstitution system was equally sensitive PLA2antagonists. These results are consistent with the conclusion that endosome membrane tubules are formed by the action of a cytoplasmic PLA2and that PLA2-dependent tubules are involved in intracellular recycling of Tf and TfR. When taken together with previous studies on the Golgi complex, these results also indicate that an intracellular PLA2activity provides a novel molecular mechanism for inducing tubule formation from multiple organelles.

scholarly journals Conserved Expression Profiles of Circadian Clock-related Genes in Two Lemna Species Showing Long-day and Short-day Photoperiodic Flowering Responses

2006 ◽  
Vol 47 (5) ◽  
pp. 601-612 ◽  
Author(s):  
Kumiko Miwa ◽  
Masayuki Serikawa ◽  
Sayaka Suzuki ◽  
Takao Kondo ◽  
Tokitaka Oyama
Keyword(s):  
Circadian Clock ◽  
Expression Profiles ◽  
Short Day ◽  
Photoperiodic Flowering ◽  
Long Day
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