Evolution and Design of Invertebrate Circadian Clocks

2017 ◽  
pp. 594-614 ◽  
Author(s):  
Vu H. Lam ◽  
Joanna C. Chiu
Keyword(s):  
Circadian Clock ◽  
Neuronal Network ◽  
External Environment ◽  
Circadian Clocks ◽  
Daily Activities ◽  
Endogenous Timing ◽  
Diverse Group ◽  
Temporal Cues ◽  
Wide Range ◽  
Timing System

Invertebrates are an incredibly diverse group of animals that come in all shapes and sizes, and live in a wide range of habitats. In order for all these organisms to perform optimally, they need to organize their daily activities and physiology around the perpetuating day-night cycles that exist on Earth. The circadian clock is the endogenous timing system that enables organisms to anticipate daily environmental cycles and governs these roughly 24-hour cellular and overt rhythms. Given its importance to organismal performance and coordination with external environment, it is not surprising that the circadian clock is believed to be ubiquitous in invertebrates. This chapter will discuss the evolution and molecular designs of the invertebrate circadian clocks and describe our current understanding of the circadian clock neuronal network responsible for interpreting external temporal cues and coordinating cellular and physiological rhythms.

scholarly journals Independence of Circadian Timing from Cell Division in Cyanobacteria

2001 ◽  
Vol 183 (8) ◽  
pp. 2439-2444 ◽  
Author(s):  
Tetsuya Mori ◽  
Carl Hirschie Johnson
Keyword(s):  
Gene Expression ◽  
Cell Division ◽  
Circadian Clock ◽  
Clock Gene ◽  
Circadian Clock Gene ◽  
Circadian Timing ◽  
Wide Range ◽  
Timing System ◽  
Circadian Timing System ◽  
Cell Division Timing

ABSTRACT In the cyanobacterium Synechococcus elongatus, cell division is regulated by a circadian clock. Deletion of the circadian clock gene, kaiC, abolishes rhythms of gene expression and cell division timing. Overexpression of the ftsZ gene halted cell division but not growth, causing cells to grow as filaments without dividing. The nondividing filamentous cells still exhibited robust circadian rhythms of gene expression. This result indicates that the circadian timing system is independent of rhythmic cell division and, together with other results, suggests that the cyanobacterial circadian system is stable and well sustained under a wide range of intracellular conditions.

scholarly journals A Circadian Clock in Antarctic Krill: An Endogenous Timing System Governs Metabolic Output Rhythms in the Euphausid Species Euphausia superba

PLoS ONE ◽  
2011 ◽  
Vol 6 (10) ◽  
pp. e26090 ◽  
Author(s):  
Mathias Teschke ◽  
Sabrina Wendt ◽  
So Kawaguchi ◽  
Achim Kramer ◽  
Bettina Meyer
Keyword(s):  
Circadian Clock ◽  
Antarctic Krill ◽  
Euphausia Superba ◽  
Endogenous Timing ◽  
Timing System ◽  
Metabolic Output

scholarly journals Epigenetic Regulation of Circadian Clocks and Its Involvement in Drug Addiction

Genes ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1263
Author(s):  
Lamis Saad ◽  
Jean Zwiller ◽  
Andries Kalsbeek ◽  
Patrick Anglard
Keyword(s):  
Circadian Clock ◽  
Drug Addiction ◽  
Epigenetic Regulation ◽  
Molecular Mechanisms ◽  
Feedback System ◽  
Circadian Clocks ◽  
Shift Workers ◽  
Timing System ◽  
Small Regulatory Rnas ◽  
Circadian Timing System

Based on studies describing an increased prevalence of addictive behaviours in several rare sleep disorders and shift workers, a relationship between circadian rhythms and addiction has been hinted for more than a decade. Although circadian rhythm alterations and molecular mechanisms associated with neuropsychiatric conditions are an area of active investigation, success is limited so far, and further investigations are required. Thus, even though compelling evidence connects the circadian clock to addictive behaviour and vice-versa, yet the functional mechanism behind this interaction remains largely unknown. At the molecular level, multiple mechanisms have been proposed to link the circadian timing system to addiction. The molecular mechanism of the circadian clock consists of a transcriptional/translational feedback system, with several regulatory loops, that are also intricately regulated at the epigenetic level. Interestingly, the epigenetic landscape shows profound changes in the addictive brain, with significant alterations in histone modification, DNA methylation, and small regulatory RNAs. The combination of these two observations raises the possibility that epigenetic regulation is a common plot linking the circadian clocks with addiction, though very little evidence has been reported to date. This review provides an elaborate overview of the circadian system and its involvement in addiction, and we hypothesise a possible connection at the epigenetic level that could further link them. Therefore, we think this review may further improve our understanding of the etiology or/and pathology of psychiatric disorders related to drug addiction.

scholarly journals The regulation of circadian clocks by light in fruitflies and mice

2001 ◽  
Vol 356 (1415) ◽  
pp. 1779-1789 ◽  
Author(s):  
Russell G. Foster ◽  
Charlotte Helfrich-Forster
Keyword(s):  
Circadian Clock ◽  
Local Time ◽  
Spectral Composition ◽  
Circadian Clocks ◽  
Daily Activities ◽  
Time Signal ◽  
Biological Time ◽  
Direction Change ◽  
Degree Of Convergence ◽  
High Degree

A circadian clock has no survival value unless biological time is adjusted (entrained) to local time and, for most organisms, the profound changes in the light environment provide the local time signal ( zeitgeber ). Over 24 h, the amount of light, its spectral composition and its direction change in a systematic way. In theory, all of these features could be used for entrainment, but each would be subject to considerable variation or ‘noise’. Despite this high degree of environmental noise, entrained organisms show remarkable precision in their daily activities. Thus, the photosensory task of entrainment is likely to be very complex, but fundamentally similar for all organisms. To test this hypothesis we compare the photoreceptors that mediate entrainment in both flies and mice, and assess their degree of convergence. Although superficially different, both organisms use specialized (employing novel photopigments) and complex (using multiple photopigments) photoreceptor mechanisms. We conclude that this multiplicity of photic inputs, in highly divergent organisms, must relate to the complex sensory task of using light as a zeitgeber .

Synchronizing the Neurospora crassa circadian clock with the rhythmic environment

2005 ◽  
Vol 33 (5) ◽  
pp. 949-952 ◽  
Author(s):  
N. Price-Lloyd ◽  
M. Elvin ◽  
C. Heintzen
Keyword(s):  
Light Intensity ◽  
Circadian Clock ◽  
Neurospora Crassa ◽  
Model Organism ◽  
Circadian Clocks ◽  
Current Understanding ◽  
Signalling Pathways ◽  
Selection Pressures ◽  
The Earth ◽  
Natural Cycles

The metronomic predictability of the environment has elicited strong selection pressures for the evolution of endogenous circadian clocks. Circadian clocks drive molecular and behavioural rhythms that approximate the 24 h periodicity of our environment. Found almost ubiquitously among phyla, circadian clocks allow preadaptation to rhythms concomitant with the natural cycles of the Earth. Cycles in light intensity and temperature for example act as important cues that couple circadian clocks to the environment via a process called entrainment. This review summarizes our current understanding of the general and molecular principles of entrainment in the model organism Neurospora crassa, a simple eukaryote that has one of the best-studied circadian systems and light-signalling pathways.

scholarly journals Impact of clock-associated Arabidopsis pseudo-response regulators in metabolic coordination

2009 ◽  
Vol 106 (17) ◽  
pp. 7251-7256 ◽  
Author(s):  
Atsushi Fukushima ◽  
Miyako Kusano ◽  
Norihito Nakamichi ◽  
Makoto Kobayashi ◽  
Naomi Hayashi ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Stress Responses ◽  
Clock Genes ◽  
Higher Plants ◽  
Tricarboxylic Acid Cycle ◽  
Integrated Analysis ◽  
Response Regulators ◽  
Triple Mutant ◽  
Mitochondrial Functions ◽  
Wide Range

In higher plants, the circadian clock controls a wide range of cellular processes such as photosynthesis and stress responses. Understanding metabolic changes in arrhythmic plants and determining output-related function of clock genes would help in elucidating circadian-clock mechanisms underlying plant growth and development. In this work, we investigated physiological relevance of PSEUDO-RESPONSE REGULATORS (PRR 9, 7, and 5) in Arabidopsis thaliana by transcriptomic and metabolomic analyses. Metabolite profiling using gas chromatography–time-of-flight mass spectrometry demonstrated well-differentiated metabolite phenotypes of seven mutants, including two arrhythmic plants with similar morphology, a PRR 9, 7, and 5 triple mutant and a CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1)-overexpressor line. Despite different light and time conditions, the triple mutant exhibited a dramatic increase in intermediates in the tricarboxylic acid cycle. This suggests that proteins PRR 9, 7, and 5 are involved in maintaining mitochondrial homeostasis. Integrated analysis of transcriptomics and metabolomics revealed that PRR 9, 7, and 5 negatively regulate the biosynthetic pathways of chlorophyll, carotenoid and abscisic acid, and α-tocopherol, highlighting them as additional outputs of pseudo-response regulators. These findings indicated that mitochondrial functions are coupled with the circadian system in plants.

scholarly journals Interaction between photoperiod and variation in circadian rhythms in tomato

2022 ◽  
Author(s):  
Yanli Xiang ◽  
Thomas Sapir ◽  
Pauline Rouillard ◽  
Marina Ferrand ◽  
Jose M Jimenez-Gomez
Keyword(s):  
Seasonal Variation ◽  
Circadian Rhythms ◽  
Phase Shift ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Circadian Clocks ◽  
Biological Processes ◽  
Near Isogenic Lines ◽  
Transcriptomic Profiling ◽  
Isogenic Lines

Many biological processes follow circadian rhythmicity and are controlled by the circadian clock. Predictable environmental changes such as seasonal variation in photoperiod can modulate circadian rhythms, allowing organisms to adjust to the time of the year. Modification of circadian clocks is especially relevant in crops to enhance their cultivability in specific regions by changing their sensibility to photoperiod. In tomato, the appearance of mutations in EMPFINDLICHER IM DUNKELROTEN LICHT 1 (EID1, Solyc09g075080) and NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED GENE 2 (LNK2, Solyc01g068560) during domestication delayed its circadian rhythms, and allowed its expansion outside its equatorial origin. Here we study how variation in circadian rhythms in tomato affects its perception of photoperiod. To do this, we create near isogenic lines carrying combinations of wild alleles of EID1 and LNK2 and perform transcriptomic profiling under two different photoperiods. We observe that EID1, but not LNK2, has a large effect on the tomato transcriptome and its response to photoperiod. This large effect of EID1 is likely a consequence of the global phase shift elicited by this gene in tomato's circadian rhythms.

scholarly journals Peripheral Sensory Organs Contribute to Temperature Synchronization of the Circadian Clock in Drosophila melanogaster

2021 ◽  
Vol 12 ◽  
Author(s):  
Rebekah George ◽  
Ralf Stanewsky
Keyword(s):  
Gene Expression ◽  
Drosophila Melanogaster ◽  
Circadian Clock ◽  
Temperature Fluctuations ◽  
Fruit Fly ◽  
Circadian Clocks ◽  
Sensory Cells ◽  
Clock Gene Expression ◽  
External Time ◽  
Peripheral Sensory

Circadian clocks are cell-autonomous endogenous oscillators, generated and maintained by self-sustained 24-h rhythms of clock gene expression. In the fruit fly Drosophila melanogaster, these daily rhythms of gene expression regulate the activity of approximately 150 clock neurons in the fly brain, which are responsible for driving the daily rest/activity cycles of these insects. Despite their endogenous character, circadian clocks communicate with the environment in order to synchronize their self-sustained molecular oscillations and neuronal activity rhythms (internal time) with the daily changes of light and temperature dictated by the Earth’s rotation around its axis (external time). Light and temperature changes are reliable time cues (Zeitgeber) used by many organisms to synchronize their circadian clock to the external time. In Drosophila, both light and temperature fluctuations robustly synchronize the circadian clock in the absence of the other Zeitgeber. The complex mechanisms for synchronization to the daily light–dark cycles are understood with impressive detail. In contrast, our knowledge about how the daily temperature fluctuations synchronize the fly clock is rather limited. Whereas light synchronization relies on peripheral and clock-cell autonomous photoreceptors, temperature input to the clock appears to rely mainly on sensory cells located in the peripheral nervous system of the fly. Recent studies suggest that sensory structures located in body and head appendages are able to detect temperature fluctuations and to signal this information to the brain clock. This review will summarize these studies and their implications about the mechanisms underlying temperature synchronization.

scholarly journals The Circadian Clock, the Brain, and COVID-19: The Cases of Olfaction and the Timing of Sleep

2021 ◽  
pp. 074873042110312
Author(s):  
Rachel S. Herz ◽  
Erik D. Herzog ◽  
Martha Merrow ◽  
Sara B. Noya
Keyword(s):  
Ischemic Stroke ◽  
Cognitive Function ◽  
Human Brain ◽  
Circadian Clock ◽  
Clinical Data ◽  
Circadian Clocks ◽  
Olfactory Sensitivity ◽  
Daily Rhythms ◽  
Sense Of Smell ◽  
The Brain

Daily rhythms of behavior and neurophysiology are integral to the circadian clocks of all animals. Examples of circadian clock regulation in the human brain include daily rhythms in sleep-wake, cognitive function, olfactory sensitivity, and risk for ischemic stroke, all of which overlap with symptoms displayed by many COVID-19 patients. Motivated by the relatively unexplored, yet pervasive, overlap between circadian functions and COVID-19 neurological symptoms, this perspective piece uses daily variations in the sense of smell and the timing of sleep and wakefulness as illustrative examples. We propose that time-stamping clinical data and testing may expand and refine diagnosis and treatment of COVID-19.

Who Was “Hitler” Before Hitler? Historical Analogies and the Struggle to Understand Nazism, 1930–1945

2018 ◽  
Vol 51 (2) ◽  
pp. 249-281
Author(s):  
Gavriel D. Rosenfeld
Keyword(s):  
World War Ii ◽  
Postwar Period ◽  
Diverse Group ◽  
Turn Of The Millennium ◽  
World War ◽  
Ongoing Debate ◽  
Wide Range ◽  
The World ◽  
Historical Analogy ◽  
Nazi Era

AbstractSince the turn of the millennium, major political figures around the world have been routinely compared to Adolf Hitler. These comparisons have increasingly been investigated by scholars, who have sought to explain their origins and assess their legitimacy. This article sheds light on this ongoing debate by examining an earlier, but strikingly similar, discussion that transpired during the Nazi era itself. Whereas commentators today argue about whether Hitler should be used as a historical analogy, observers in the 1930s and 1940s debated which historical analogies should be used to explain Hitler. During this period, Anglophone and German writers identified a diverse group of historical villains who, they believed, explained the Nazi threat. The figures spanned a wide range of tyrants, revolutionaries, and conquerors. But, by the end of World War II, the revelation of the Nazis' unprecedented crimes exposed these analogies as insufficient and led many commentators to flee from secular history to religious mythology. In the process, they identified Hitler as Western civilization's new archetype of evil and turned him into a hegemonic analogy for the postwar period. By explaining how earlier analogies struggled to make sense of Hitler, we can better understand whether Hitler analogies today are helping or hindering our effort to understand contemporary political challenges.

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