scholarly journals Shedding Light on the Circadian Clock of the Threespine Stickleback

2021 ◽  
Author(s):  
Marie-Pier Brochu ◽  
Nadia Aubin-Horth
Keyword(s):  
Circadian Clock ◽  
Gasterosteus Aculeatus ◽  
Clock Genes ◽  
Activity Rhythm ◽  
Internal Clock ◽  
Interindividual Variation ◽  
Masking Effect ◽  
Constant Darkness ◽  
Natural Environments ◽  
Threespine Sticklebacks

The circadian clock is an internal timekeeping system shared by most organisms, and knowledge about its functional importance and evolution in natural environments is still needed. Here, we investigated the circadian clock of wild-caught threespine sticklebacks (Gasterosteus aculeatus) at the behavioural and molecular levels. While their behaviour, ecology, and evolution are well studied, information on their circadian rhythms are scarce. We quantified the daily locomotor activity rhythm under a light-dark cycle (LD) and under constant darkness (DD). Under LD, all fish exhibited significant daily rhythmicity, while under DD, only 18% of individuals remained rhythmic. This interindividual variation suggests that the circadian clock controls activity only in certain individuals. Moreover, under LD, some fish were almost exclusively nocturnal, while others were active around the clock. Furthermore, the most nocturnal fish were also the least active. These results suggest that light masks activity (i.e. suppresses activity without entraining the internal clock) more strongly in some individuals than others. Finally, we quantified the expression of five clock genes in the brain of sticklebacks under DD using qPCR. We did not detect circadian rhythmicity, which could either indicate that the clock molecular oscillator is highly light-dependent, or that there was an oscillation but that we were unable to detect it. Overall, our study suggests that a strong circadian control on behavioural rhythms may not necessarily be advantageous in a natural population of sticklebacks and that the daily phase of activity varies greatly between individuals because of a differential masking effect of light.

scholarly journals Shedding Light on the Threespine Stickleback Circadian Clock

2021 ◽  
Author(s):  
Marie-Pier Brochu ◽  
Nadia Aubin-Horth
Keyword(s):  
Circadian Clock ◽  
Gasterosteus Aculeatus ◽  
Clock Genes ◽  
Activity Rhythm ◽  
Interindividual Variation ◽  
Masking Effect ◽  
Constant Darkness ◽  
Natural Environments ◽  
Threespine Sticklebacks ◽  
Nocturnal Fish

The circadian clock is an internal timekeeping system shared by most organisms, and knowledge about its functional importance and evolution in natural environments is still needed. Here, we investigated the circadian clock of wild-caught threespine sticklebacks (Gasterosteus aculeatus) at the behavioural and molecular levels. While their behaviour, ecology, and evolution are well studied, information on their circadian rhythms are scarce. We quantified the daily locomotor activity rhythm under a light-dark cycle (LD) and under constant darkness (DD). Under LD, all fish exhibited significant daily rhythmicity, while under DD, only 18% of individuals remained rhythmic. This interindividual variation suggests that the circadian clock controls activity only in certain individuals. Moreover, under LD, some fish were almost exclusively nocturnal, while others were active around the clock. Furthermore, the most nocturnal fish were also the least active. These results suggest that light masks activity more strongly in some individuals than others. Finally, we quantified the expression of five clock genes in the brain of sticklebacks under DD using qPCR. We did not detect circadian rhythmicity, which could either indicate that the clock molecular oscillator is highly light-dependent, or that there was an oscillation but that we were unable to detect it. Overall, our study suggests that a strong circadian control on behavioural rhythms may not necessarily be advantageous in a natural population of sticklebacks and that the daily phase of activity varies greatly between individuals because of a differential masking effect of light.

Enhanced effect of daytime restricted feeding on the circadian rhythm of streptozotocin-induced type 2 diabetic rats

2012 ◽  
Vol 302 (9) ◽  
pp. E1027-E1035 ◽  
Author(s):  
Tao Wu ◽  
Fen ZhuGe ◽  
Lu Sun ◽  
Yinhua Ni ◽  
Ou Fu ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Pineal Gland ◽  
Circadian Clock ◽  
Clock Genes ◽  
Activity Rhythm ◽  
Diabetic Rats ◽  
Restricted Feeding ◽  
Behavioral Rhythm ◽  
Type 2 Diabetic

There is increasing awareness of the link between impaired circadian clocks and multiple metabolic diseases. However, the impairment of the circadian clock by type 2 diabetes has not been fully elucidated. To understand whether and how the function of circadian clock is impaired under the diabetic condition, we examined not only the expression of circadian genes in the heart and pineal gland but also the behavioral rhythm of type 2 diabetic and control rats in both the nighttime restricted feeding (NRF) and daytime restricted feeding (DRF) conditions. In the NRF condition, the circadian expression of clock genes in the heart and pineal gland was conserved in the diabetic rats, being similar to that in the control rats. DRF shifted the circadian phases of peripheral clock genes more efficiently in the diabetic rats than those in the control rats. Moreover, the activity rhythm of rats in the diabetic group was completely shifted from the dark phase to the light phase after 5 days of DRF treatment, whereas the activity rhythm of rats in the control group was still under the control of the suprachiasmatic nucleus (SCN) after the same DRF treatment. Furthermore, the serum glucose rhythm of type 2 diabetic rats was also shifted and controlled by the external feeding schedule, ignoring the SCN rhythm. Therefore, DRF shows stronger effect on the reentrainment of circadian rhythm in the type 2 diabetic rats, suggesting that the circadian system in diabetes is unstable and more easily shifted by feeding stimuli.

scholarly journals Deep sequencing analysis of the circadian transcriptome of the jewel wasp Nasonia vitripennis

2016 ◽  
Author(s):  
Nathaniel J. Davies ◽  
Eran Tauber
Keyword(s):  
Circadian Clock ◽  
Deep Sequencing ◽  
Clock Genes ◽  
Model System ◽  
Model Organisms ◽  
Constant Darkness ◽  
Sequencing Analysis ◽  
Rna Seq ◽  
Nasonia Vitripennis ◽  
Deep Sequencing Analysis

AbstractThe study of the circadian clock has benefited greatly from using Drosophila as a model system. Yet, accumulating evidence suggests that the fly might not be the canonical insect model. Here, we have analysed the circadian transcriptome of the Jewl wasp Nasonia vitripennis by using RNA-seq in both constant darkness (DD) and constant light (LL, the wasps are rhythmic in LL with period shortening). At a relatively stringent FDR (q < 0.1), we identified 1,057 cycling transcripts in DD and 929 in LL (fraction of 6.7% and 5.9% of all transcripts analysed in DD and LL respectively). Although there was little similarity between cycling genes in Drosophila and Nasonia, the functions fulfilled by cycling transcripts were similar in both species. Of the known Drosophila core clock genes, only pdp1e, shaggy and Clok showed a significant cycling in Nasonia, underscoring the importance of studying the clock in non-model organisms.

scholarly journals The Circadian Clock Is Sustained in the Thyroid Gland of VIP Receptor 2 Deficient Mice

2021 ◽  
Vol 12 ◽  
Author(s):  
Birgitte Georg ◽  
Jan Fahrenkrug ◽  
Henrik L. Jørgensen ◽  
Jens Hannibal
Keyword(s):  
Circadian Clock ◽  
Clock Genes ◽  
Hormone Secretion ◽  
Heart Rhythm ◽  
Thyroid Stimulating Hormone ◽  
Constant Darkness ◽  
Receptor Signaling ◽  
Knockout Animals ◽  
The Impact ◽  
Deficient Mice

VIP/VPAC2-receptor signaling is crucial for functioning of the circadian clock in the suprachiasmatic nucleus (SCN) since the lack results in disrupted synchrony between SCN cells and altered locomotor activity, body temperature, hormone secretion and heart rhythm. Endocrine glands, including the thyroid, show daily oscillations in clock gene expression and hormone secretion, and SCN projections target neurosecretory hypothalamic thyroid-stimulating hormone (TSH)-releasing hormone cells. The aim of the study was to gain knowledge of mechanisms important for regulation of the thyroid clock by evaluating the impact of VIP/VPAC2-receptor signaling. Quantifications of mRNAs of three clock genes (Per1, Per2 and Bmal1) in thyroids of wild type (WT) and VPAC2-receptor deficient mice were done by qPCR. Tissues were taken every 4th h during 24-h 12:12 light-dark (LD) and constant darkness (DD) periods, both genders were used. PER1 immunoreactivity was visualized on sections of both WT and VPAC2 lacking mice during a LD cycle. Finally, TSH and the thyroid hormone T4 levels were measured in the sera by commercial ELISAs. During LD, rhythmic expression of all three mRNA was found in both the WT and knockout animals. In VPAC2-receptor knockout animals, the amplitudes were approximately halved compared to the ones in the WT mice. In the WT, Per1 mRNA peaked around “sunset”, Per2 mRNA followed with approximately 2 h, while Bmal1 mRNA was in antiphase with Per1. In the VPAC2 knockout mice, the phases of the mRNAs were advanced approximately 5 h compared to the WT. During DD, the phases of all the mRNAs were identical to the ones found during LD in both groups of mice. PER1 immunoreactivity was delayed compared to its mRNA and peaked during the night in follicular cells of both the thyroid and parathyroid glands in the WT animals. In WT animals, TSH was high around the transition to darkness compared to light-on, while T4 did not change during the 24 h cycle. In conclusion, sustained and identical rhythms (phases and amplitudes) of three clock genes were found in VPAC2 deficient mice during LD and DD suggesting high degree of independence of the thyroid clock from the master SCN clock.

scholarly journals Short Neuropeptide F regulates the starvation mediated enhanced locomotor Activity in Drosophila

2019 ◽  
Author(s):  
Anna Geo ◽  
Himani Pathak ◽  
Anamika Elizabeth Kujur ◽  
Sreesha R Sudhakar ◽  
Nisha N Kannan
Keyword(s):  
Locomotor Activity ◽  
Circadian Clock ◽  
Internal Energy ◽  
Nutrient Availability ◽  
Activity Rhythm ◽  
Transcript Level ◽  
Constant Darkness ◽  
Starvation Resistance ◽  
Neuropeptide F

AbstractThe circadian clock regulates various behavioral, metabolic and physiological processes to occur at the most suitable time of the day. Internal energy stores and nutrient availability modulates the most apparent circadian clock mediated locmotor activity rhythm in Drosophila. Although previous studies unraveled the role of circadian clock in metabolism and activity rest rhythm, the precise pathway through which the circadian neuropeptidergic signaling regulates internal energy storage and the starvation-mediated increase in activity resembling foraging remains largely unclear. This study was aimed to elucidate the role of circadian neuropeptide, short neuropeptide F (sNPF) in triglyceride metabolism, starvation resistance and starvation-mediated increased locomotor activity in Drosophila. The results showed that snpf transcripts exhibits significant rhythmicity in wild type flies under 12:12 hour light-dark cycles (LD) and constant darkness (DD) whereas snpf transcript level in period null flies did not exhibit any significant rhythmicity under LD. Knockdown of sNPF in circadian clock neurons reduced the triglyceride level, starvation resistance and increased the starvation-mediated hyperactivity response after 24 hour of starvation. Further studies showed that knock down of sNPF receptors (sNPFR) expressed in insulin producing cells (IPC) increased the starvation resistance and reduced starvation-induced hyperactivity response after 24 hour of starvation. Collectively, our results suggest that transcriptional oscillation of snpf mRNA is endogenously controlled by the circadian clock and elucidate the role of sNPF in modulating locomotor activity in accordance with the nutrient availability in Drosophila.

scholarly journals Transcriptional Structure of Petunia Clock in Leaves and Petals

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 860 ◽  
Author(s):  
Marta I. Terry ◽  
Marta Carrera-Alesina ◽  
Julia Weiss ◽  
Marcos Egea-Cortines
Keyword(s):  
Circadian Clock ◽  
Clock Genes ◽  
Time Of Day ◽  
Constant Darkness ◽  
Petunia X Hybrida ◽  
Environmental Signals ◽  
Expression Variability ◽  
Rhythmic Expression ◽  
Free Running ◽  
Maximum Expression

The plant circadian clock coordinates environmental signals with internal processes including secondary metabolism, growth, flowering, and volatile emission. Plant tissues are specialized in different functions, and petals conceal the sexual organs while attracting pollinators. Here we analyzed the transcriptional structure of the petunia (Petunia x hybrida) circadian clock in leaves and petals. We recorded the expression of 13 clock genes in petunia under light:dark (LD) and constant darkness (DD). Under light:dark conditions, clock genes reached maximum expression during the light phase in leaves and the dark period in petals. Under free running conditions of constant darkness, maximum expression was delayed, especially in petals. Interestingly, the rhythmic expression pattern of PhLHY persisted in leaves and petals in LD and DD. Gene expression variability differed among leaves and petals, time of day and photoperiod. The transcriptional noise was higher especially in leaves under constant darkness. We found that PhPRR7, PhPRR5, and PhGI paralogs showed changes in gene structure including exon number and deletions of CCT domain of the PRR family. Our results revealed that petunia petals presented a specialized clock.

scholarly journals Differential impacts of the head onPlatynereis dumeriliiperipheral circadian rhythms

2019 ◽  
Author(s):  
Enrique Arboleda ◽  
Martin Zurl ◽  
Kristin Tessmar-Raible
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Clock Genes ◽  
Functional Model ◽  
Circadian Clocks ◽  
Constant Darkness ◽  
Dark Cycle ◽  
Peripheral Tissues ◽  
Platynereis Dumerilii ◽  
Strong Control

AbstractBackgroundThe marine bristle wormPlatynereis dumeriliiis a useful functional model system for the study of the circadian clock and its interplay with others, e.g. circalunar clocks. The focus has so far been on the worm’s head. However, behavioral and physiological cycles in other animals typically arise from the coordination of circadian clocks located in the brain and in peripheral tissues. Here we focus on peripheral circadian rhythms and clocks, revisit and expand classical circadian work on the worm’s chromatophores, investigate locomotion as read-out and include molecular analyses.ResultsWe establish that different pieces of the trunk exhibit synchronized, robust oscillations of core circadian clock genes. These circadian core clock transcripts are under strong control of the light-dark cycle, quickly losing synchronized oscillation under constant darkness, irrespective of the absence or presence of heads. Different wavelengths are differently effective in controlling the peripheral molecular synchronization. We have previously shown that locomotor activity is under circadian clock control. Here we show that upon decapitation it still follows the light-dark cycle, but does not free-run under constant darkness. We also observe the rhythmicity of pigments in the worm’s individual chromatophores, confirming that chromatophore size changes follow a circadian pattern. These size changes continue under constant darkness, but cannot be re-entrained by light upon decapitation.ConclusionsHere we provide the first basic characterization of the peripheral circadian clock ofPlatynereis dumerilii. In the absence of the head, light is essential as a major synchronization cue for peripheral molecular and locomotor circadian rhythms. Circadian changes in chromatophore size can however continue for several days in the absence of light/dark changes and the head. Thus, the dependence on the head depends on the type of peripheral rhythm studied. These data show that peripheral circadian rhythms and clocks should be considered when investigating the interactions of clocks with different period lengths, a notion likely also true for other organisms with circadian and non-circadian clocks.

scholarly journals The role of clockwork orange in the circadian clock of the cricket Gryllus bimaculatus

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Yasuaki Tomiyama ◽  
Tsugumichi Shinohara ◽  
Mirai Matsuka ◽  
Tetsuya Bando ◽  
Taro Mito ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Clock Genes ◽  
Clock Cycle ◽  
Constant Darkness ◽  
Mrna Levels ◽  
Gryllus Bimaculatus ◽  
Locomotor Rhythm ◽  
Rhythmic Expression ◽  
Cryptochrome 2

Abstract The circadian clock generates rhythms of approximately 24 h through periodic expression of the clock genes. In insects, the major clock genes period (per) and timeless (tim) are rhythmically expressed upon their transactivation by CLOCK/CYCLE, with peak levels in the early night. In Drosophila, clockwork orange (cwo) is known to inhibit the transcription of per and tim during the daytime to enhance the amplitude of the rhythm, but its function in other insects is largely unknown. In this study, we investigated the role of cwo in the clock mechanism of the cricket Gryllus bimaculatus. The results of quantitative RT-PCR showed that under a light/dark (LD) cycle, cwo is rhythmically expressed in the optic lobe (lamina-medulla complex) and peaks during the night. When cwo was knocked down via RNA interference (RNAi), some crickets lost their locomotor rhythm, while others maintained a rhythm but exhibited a longer free-running period under constant darkness (DD). In cwoRNAi crickets, all clock genes except for cryptochrome 2 (cry2) showed arrhythmic expression under DD; under LD, some of the clock genes showed higher mRNA levels, and tim showed rhythmic expression with a delayed phase. Based on these results, we propose that cwo plays an important role in the cricket circadian clock.

scholarly journals Constant Light in Critical Postnatal Days Affects Circadian Rhythms in Locomotion and Gene Expression in the Suprachiasmatic Nucleus, Retina, and Pineal Gland Later in Life

Biomedicines ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 579
Author(s):  
Aneta Kubištová ◽  
Veronika Spišská ◽  
Lucie Petrželková ◽  
Leona Hrubcová ◽  
Simona Moravcová ◽  
...  
Keyword(s):  
Gene Expression ◽  
Locomotor Activity ◽  
Circadian Clock ◽  
Clock Genes ◽  
Activity Rhythm ◽  
Brain Structures ◽  
Constant Light ◽  
Postnatal Exposure ◽  
Endogenous Rhythms ◽  
Locomotor Activity Rhythm

The circadian clock regulates bodily rhythms by time cues that result from the integration of genetically encoded endogenous rhythms with external cycles, most potently with the light/dark cycle. Chronic exposure to constant light in adulthood disrupts circadian system function and can induce behavioral and physiological arrhythmicity with potential clinical consequences. Since the developing nervous system is particularly vulnerable to experiences during the critical period, we hypothesized that early-life circadian disruption would negatively impact the development of the circadian clock and its adult function. Newborn rats were subjected to a constant light of 16 lux from the day of birth through until postnatal day 20, and then they were housed in conditions of L12 h (16 lux): D12 h (darkness). The circadian period was measured by locomotor activity rhythm at postnatal day 60, and the rhythmic expressions of clock genes and tissue-specific genes were detected in the suprachiasmatic nuclei, retinas, and pineal glands at postnatal days 30 and 90. Our data show that early postnatal exposure to constant light leads to a prolonged endogenous period of locomotor activity rhythm and affects the rhythmic gene expression in all studied brain structures later in life.

scholarly journals Homologues of key circadian clock genes present in Verticillium dahliae do not direct circadian programs of development or mRNA abundance

2019 ◽  
Author(s):  
Emma Cascant-Lopez ◽  
Susan K. Crosthwaite ◽  
Louise J. Johnson ◽  
Richard J. Harrison
Keyword(s):  
Gene Expression ◽  
Circadian Clock ◽  
Verticillium Dahliae ◽  
Plant Pathogen ◽  
Environmental Conditions ◽  
Clock Genes ◽  
Circadian Clocks ◽  
Constant Darkness ◽  
Clock Proteins ◽  
Central Clock

AbstractMany organisms harbour circadian clocks that promote their adaptation to the rhythmic environment. While a broad knowledge of the molecular mechanism of circadian clocks has been gained through the fungal model Neurospora crassa, little is known about circadian clocks in other fungi. N. crassa belongs to the same class as many important plant pathogens including the vascular wilt fungus Verticillium dahliae. We identified homologues of N. crassa clock proteins in V. dahliae, which showed high conservation in key protein domains. However, no evidence for an endogenous, free-running and entrainable rhythm was observed in the daily formation of conidia and microsclerotia. In N. crassa the frequency (frq) gene encodes a central clock protein expressed rhythmically and in response to light. In contrast, expression of Vdfrq is not light-regulated. Temporal gene expression profiling over 48 hours in constant darkness and temperature revealed no circadian expression of key clock genes. Furthermore, RNA-seq over a 24 h time-course revealed no robust oscillations of RNA in constant darkness. Comparison of gene expression between wild-type V. dahliae and a ΔVdfrq mutant showed that genes involved in metabolism, transport and redox processes are mis-regulated in the absence of Vdfrq. In addition, VdΔfrq mutants display growth defects and reduced pathogenicity in a strain dependent manner. Our data indicate that if a circadian clock exists in Verticillium, it is based on alternative mechanisms such as post-transcriptional interactions of VdFRQ and the WC proteins or the components of a FRQ-less oscillator. Alternatively, it could be that whilst the original functions of the clock proteins have been maintained, in this species the interactions that generate rhythmicity have been lost or are only triggered when specific environmental conditions are met. The presence of conserved clock genes in genomes should not be taken as definitive evidence of circadian function.Author summaryCircadian clocks are used by organisms to orchestrate the activity of cellular processes such that they occur at an optimal time of day. Research carried out in the filamentous fungus Neurospora crassa has revealed a huge amount of information about the components its circadian clock, its interactions with the environment and how it drives cellular biochemistry and physiology. Although homologues of the Neurospora clock genes are present in a number of fungi, functional clocks have been demonstrated in a just a handful. Importantly, a link between the circadian clock of the plant pathogen Botrytis cinerea and virulence has recently been reported. We report that another significant plant pathogen, Verticillium dahliae, contains well-conserved homologues of all key clock genes. We find that diurnal development of conidia and microsclerotia is not influenced by a circadian clock. Furthermore, in a constant environment we find no evidence of rhythmic transcript accumulation. However, deletion of the central clock component results in altered growth and reduced virulence. This led us to question the role of clock genes in Verticillium. We are forced to consider that in this species the interactions that generate rhythmicity have been lost, are generated purely via post-transcriptional modification of clock proteins, are only triggered when specific environmental conditions are met or never evolved.

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