scholarly journals Slaves to the rhythm: Oscillations, cycling and the pace of life

2004 ◽  
Vol 26 (1) ◽  
pp. 11-13 ◽  
Author(s):  
Fabian Rudolf ◽  
Franziska Wehrle ◽  
Dorothee Staiger
Keyword(s):  
Circadian Clock ◽  
Limited Availability ◽  
Important Resource ◽  
Physiological Processes ◽  
Pace Of Life ◽  
Environmental Light ◽  
Metabolic Reactions ◽  
Sessile Organisms

Plants, as sessile organisms, are forced to take advantage of the limited availability of sunlight, their most important resource. Not surprisingly, many aspects of physiology and development are therefore organized by an endogenous chronometer in plants. This so-called ‘circadian’ clock imposes a 24-hour rhythm on metabolic reactions and physiological processes to optimally align them with the environmental light-dark cycle1.

scholarly journals Cryptochromes and the Circadian Clock: The Story of a Very Complex Relationship in a Spinning World

Genes ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 672
Author(s):  
Loredana Lopez ◽  
Carlo Fasano ◽  
Giorgio Perrella ◽  
Paolo Facella
Keyword(s):  
Circadian Clock ◽  
Cell Cycle Regulation ◽  
Molecular Mechanisms ◽  
Chloroplast Development ◽  
Complex Relationship ◽  
Physiological Processes ◽  
Environmental Light ◽  
Daily Cycles ◽  
Chromatin Organisation ◽  
Cycle Regulation

Cryptochromes are flavin-containing blue light photoreceptors, present in most kingdoms, including archaea, bacteria, plants, animals and fungi. They are structurally similar to photolyases, a class of flavoproteins involved in light-dependent repair of UV-damaged DNA. Cryptochromes were first discovered in Arabidopsis thaliana in which they control many light-regulated physiological processes like seed germination, de-etiolation, photoperiodic control of the flowering time, cotyledon opening and expansion, anthocyanin accumulation, chloroplast development and root growth. They also regulate the entrainment of plant circadian clock to the phase of light–dark daily cycles. Here, we review the molecular mechanisms by which plant cryptochromes control the synchronisation of the clock with the environmental light. Furthermore, we summarise the circadian clock-mediated changes in cell cycle regulation and chromatin organisation and, finally, we discuss a putative role for plant cryptochromes in the epigenetic regulation of genes.

A succinct access to ω-hydroxylated jasmonates via olefin metathesis

2017 ◽  
Vol 72 (7-8) ◽  
pp. 285-292 ◽  
Author(s):  
Guillermo H. Jimenez-Aleman ◽  
Selina Seçinti ◽  
Wilhelm Boland
Keyword(s):  
Abiotic Stress ◽  
Olefin Metathesis ◽  
Higher Plants ◽  
Environmentally Friendly ◽  
Signaling Molecules ◽  
Synthetic Route ◽  
Limited Availability ◽  
Cross Metathesis ◽  
Physiological Processes

AbstractIn higher plants, jasmonates are lipid-derived signaling molecules that control many physiological processes, including responses to abiotic stress, defenses against insects and pathogens, and development. Among jasmonates, ω-oxidized compounds form an important subfamily. The biological roles of these ω-modified derivatives are not fully understood, largely due to their limited availability. Herein, a brief (two-step), simple and efficient (>80% yield), versatile, gram-scalable, and environmentally friendly synthetic route to ω-oxidized jasmonates is described. The approach utilizes olefin cross-metathesis as the key step employing inexpensive, commercially available substrates and catalysts.

scholarly journals Weathering the impacts of climate change

2020 ◽  
pp. 227-238
Author(s):  
Brian Helmuth
Keyword(s):  
Climate Change ◽  
Environmental Conditions ◽  
Quantitative Methods ◽  
Heat Waves ◽  
Heat Budget ◽  
Spatial Scales ◽  
Physiological Tolerance ◽  
Physiological Processes ◽  
Local Environments ◽  
Sessile Organisms

Ectothermic organisms experience their local environments in ways that humans can have difficulty conceptualizing. Physics-based (ecomechanical) approaches, for example heat budget models, can lend insights into how an organism’s very local environmental conditions (microclimate) can drive niche-level conditions such as body temperature; these in turn drive physiological processes. Quantitative methods also allow insights into the temporal and spatial scales that may ultimately determine responses to larger-scale environmental change. For example, for small, sessile organisms, microhabitats such as crevices in rocks may provide microrefugia that allow survival during heat waves. As a result, larger-scale recovery following heat waves (rescue effects) may ultimately be influenced by much smaller-scale processes. Ecomechanics techniques also facilitate the use of interventions such as shading that can maintain environmental conditions within physiological tolerance levels.

scholarly journals Circadian Clock Regulates Inflammation and the Development of Neurodegeneration

2021 ◽  
Vol 11 ◽  
Author(s):  
Xiao-Lan Wang ◽  
Lianjian Li
Keyword(s):  
Circadian Clock ◽  
Immune Cells ◽  
Brain Function ◽  
Cellular Tissue ◽  
Physiological Processes ◽  
Circadian Control ◽  
Prevention And Treatment ◽  
Potential Strategy ◽  
Peripheral Immune Cells

The circadian clock regulates numerous key physiological processes and maintains cellular, tissue, and systemic homeostasis. Disruption of circadian clock machinery influences key activities involved in immune response and brain function. Moreover, Immune activation has been closely linked to neurodegeneration. Here, we review the molecular clock machinery and the diurnal variation of immune activity. We summarize the circadian control of immunity in both central and peripheral immune cells, as well as the circadian regulation of brain cells that are implicated in neurodegeneration. We explore the important role of systemic inflammation on neurodegeneration. The circadian clock modulates cellular metabolism, which could be a mechanism underlying circadian control. We also discuss the circadian interventions implicated in inflammation and neurodegeneration. Targeting circadian clocks could be a potential strategy for the prevention and treatment of inflammation and neurodegenerative diseases.

scholarly journals EARLY FLOWERING 3 controls temperature responsiveness of the circadian clock

2020 ◽  
Author(s):  
Zihao Zhu ◽  
Marcel Quint ◽  
Muhammad Usman Anwer
Keyword(s):  
Circadian Clock ◽  
Biological Rhythms ◽  
Early Flowering ◽  
Climate Change Scenarios ◽  
Temperature Changes ◽  
Physiological Processes ◽  
Average Global Temperature ◽  
Clock Component ◽  
Rhythmic Growth

SummaryPredictable changes in light and temperature during a diurnal cycle are major entrainment cues that enable the circadian clock to generate internal biological rhythms that are synchronized with the external environment. With the average global temperature predicted to keep increasing, the intricate light-temperature coordination that is necessary for clock functionality is expected to be seriously affected. Hence, understanding how temperature signals are perceived by the circadian clock has become an important issue, especially in light of climate change scenarios. In Arabidopsis, the clock component EARLY FLOWERING 3 (ELF3) not only serves as an essential light Zeitnehmer, but also functions as a thermosensor participating in thermomorphogenesis. However, the role of ELF3 in temperature entrainment of the circadian clock is not fully understood. Here, we report that ELF3 is essential for delivering temperature input to the clock. We demonstrate that in the absence of ELF3, the oscillator was unable to properly respond to temperature changes, resulting in an impaired gating of thermoresponses. Consequently, clock-controlled physiological processes such as rhythmic growth and cotyledon movement were disturbed. Together, our results reveal that ELF3 is an essential Zeitnehmer for temperature sensing of the oscillator, and thereby for coordinating the rhythmic control of thermoresponsive physiological outputs.

Entrainment of circadian phase in developing gray short-tailed opossums: mother vs. environment.

1990 ◽  
Vol 259 (3) ◽  
pp. E384
Author(s):  
S A Rivkees ◽  
S M Reppert
Keyword(s):  
Circadian Clock ◽  
Metabolic Activity ◽  
Biological Clock ◽  
Monodelphis Domestica ◽  
Dark Cycle ◽  
Circadian Phase ◽  
Environmental Light ◽  
Circadian Time ◽  
Retinohypothalamic Tract ◽  
Marsupial Species

In a marsupial species, the gray short-tailed opossum (Monodelphis domestica), the suprachiasmatic nuclei (SCN), the site of a circadian clock, are formed postnatally and begin oscillating as a circadian clock on day 20. In this study, we examined how the timing (phase) of the SCN clock in the developing opossum is coordinated to the environmental light-dark cycle. When pups were reared from birth in darkness by intact dams, the circadian phases in SCN metabolic activity (monitored by 2-deoxy-D-[14C]glucose autoradiography) in 27-day-old pups were desynchronized. When pups were reared in a light-dark cycle that was 12 h out of phase with the circadian time of blinded dams, the pattern of SCN metabolic activity on day 20 was rhythmic and in phase with the light-dark cycle but out of phase with the circadian time of the dam. On day 20, retina-mediated light activation of SCN metabolic activity was also demonstrated, and anterograde tract-tracing studies revealed the presence of the retinohypothalamic tract within the SCN. These results show there is no influence of the opossum dam on the timing of the pup's biological clock. Instead, from the inception of the daily rhythm in SCN metabolic activity, its timing is regulated by retina-mediated light-dark entrainment.

Achilles-Mediated and Sex-Specific Regulation of Circadian mRNA Rhythms in Drosophila

2019 ◽  
Vol 34 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Jiajia Li ◽  
Renee Yin Yu ◽  
Farida Emran ◽  
Brian E. Chen ◽  
Michael E. Hughes
Keyword(s):  
Circadian Clock ◽  
Molecular Mechanisms ◽  
Rna Binding ◽  
Clock Genes ◽  
Peripheral Tissues ◽  
Knock Down ◽  
Rhythmic Expression ◽  
The Core ◽  
Physiological Processes ◽  
Specific Regulation

The circadian clock is an evolutionarily conserved mechanism that generates the rhythmic expression of downstream genes. The core circadian clock drives the expression of clock-controlled genes, which in turn play critical roles in carrying out many rhythmic physiological processes. Nevertheless, the molecular mechanisms by which clock output genes orchestrate rhythmic signals from the brain to peripheral tissues are largely unknown. Here we explored the role of one rhythmic gene, Achilles, in regulating the rhythmic transcriptome in the fly head. Achilles is a clock-controlled gene in Drosophila that encodes a putative RNA-binding protein. Achilles expression is found in neurons throughout the fly brain using fluorescence in situ hybridization (FISH), and legacy data suggest it is not expressed in core clock neurons. Together, these observations argue against a role for Achilles in regulating the core clock. To assess its impact on circadian mRNA rhythms, we performed RNA sequencing (RNAseq) to compare the rhythmic transcriptomes of control flies and those with diminished Achilles expression in all neurons. Consistent with previous studies, we observe dramatic upregulation of immune response genes upon knock-down of Achilles. Furthermore, many circadian mRNAs lose their rhythmicity in Achilles knock-down flies, suggesting that a subset of the rhythmic transcriptome is regulated either directly or indirectly by Achilles. These Achilles-mediated rhythms are observed in genes involved in immune function and in neuronal signaling, including Prosap, Nemy and Jhl-21. A comparison of RNAseq data from control flies reveals that only 42.7% of clock-controlled genes in the fly brain are rhythmic in both males and females. As mRNA rhythms of core clock genes are largely invariant between the sexes, this observation suggests that sex-specific mechanisms are an important, and heretofore under-appreciated, regulator of the rhythmic transcriptome.

scholarly journals It is not the parts, but how they interact that determines the behaviour of circadian rhythms across scales and organisms

2014 ◽  
Vol 4 (3) ◽  
pp. 20130076 ◽  
Author(s):  
Daniel DeWoskin ◽  
Weihua Geng ◽  
Adam R. Stinchcombe ◽  
Daniel B. Forger
Keyword(s):  
Experimental Data ◽  
Mathematical Models ◽  
Circadian Clock ◽  
Feedback Loop ◽  
Biological Rhythms ◽  
Proper Function ◽  
Detailed Model ◽  
Physiological Processes ◽  
Drastic Effect ◽  
Different Levels

Biological rhythms, generated by feedback loops containing interacting genes, proteins and/or cells, time physiological processes in many organisms. While many of the components of the systems that generate biological rhythms have been identified, much less is known about the details of their interactions. Using examples from the circadian (daily) clock in three organisms, Neurospora , Drosophila and mouse, we show, with mathematical models of varying complexity, how interactions among (i) promoter sites, (ii) proteins forming complexes, and (iii) cells can have a drastic effect on timekeeping. Inspired by the identification of many transcription factors, for example as involved in the Neurospora circadian clock, that can both activate and repress, we show how these multiple actions can cause complex oscillatory patterns in a transcription–translation feedback loop (TTFL). Inspired by the timekeeping complex formed by the NMO–PER–TIM–SGG complex that regulates the negative TTFL in the Drosophila circadian clock, we show how the mechanism of complex formation can determine the prevalence of oscillations in a TTFL. Finally, we note that most mathematical models of intracellular clocks model a single cell, but compare with experimental data from collections of cells. We find that refitting the most detailed model of the mammalian circadian clock, so that the coupling between cells matches experimental data, yields different dynamics and makes an interesting prediction that also matches experimental data: individual cells are bistable, and network coupling removes this bistability and causes the network to be more robust to external perturbations. Taken together, we propose that the interactions between components in biological timekeeping systems are carefully tuned towards proper function. We also show how timekeeping can be controlled by novel mechanisms at different levels of organization.

scholarly journals Roles of Neuropeptides, VIP and AVP, in the Mammalian Central Circadian Clock

2021 ◽  
Vol 15 ◽  
Author(s):  
Daisuke Ono ◽  
Ken-ichi Honma ◽  
Sato Honma
Keyword(s):  
Transcription Factors ◽  
Circadian Rhythms ◽  
Circadian Clock ◽  
Cellular Networks ◽  
Clock Genes ◽  
Circadian System ◽  
Developmental Changes ◽  
Circadian Period ◽  
Functional Roles ◽  
Environmental Light

In mammals, the central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Individual SCN cells exhibit intrinsic oscillations, and their circadian period and robustness are different cell by cell in the absence of cellular coupling, indicating that cellular coupling is important for coherent circadian rhythms in the SCN. Several neuropeptides such as arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) are expressed in the SCN, where these neuropeptides function as synchronizers and are important for entrainment to environmental light and for determining the circadian period. These neuropeptides are also related to developmental changes of the circadian system of the SCN. Transcription factors are required for the formation of neuropeptide-related neuronal networks. Although VIP is critical for synchrony of circadian rhythms in the neonatal SCN, it is not required for synchrony in the embryonic SCN. During postnatal development, the clock genes cryptochrome (Cry)1 and Cry2 are involved in the maturation of cellular networks, and AVP is involved in SCN networks. This mini-review focuses on the functional roles of neuropeptides in the SCN based on recent findings in the literature.

scholarly journals GIGANTEA gates gibberellin signaling through stabilization of the DELLA proteins in Arabidopsis

2019 ◽  
Vol 116 (43) ◽  
pp. 21893-21899 ◽  
Author(s):  
Maria A. Nohales ◽  
Steve A. Kay
Keyword(s):  
Circadian Clock ◽  
Signaling Pathways ◽  
Hormone Signaling ◽  
The Core ◽  
Della Proteins ◽  
Physiological Processes ◽  
Ga Signaling ◽  
Clock Component ◽  
Mechanistic Understanding ◽  
Gibberellin Signaling

Circadian clock circuitry intersects with a plethora of signaling pathways to adequately time physiological processes to occur at the most appropriate time of the day and year. However, our mechanistic understanding of how the clockwork is wired to its output is limited. Here we uncover mechanistic connections between the core clock component GIGANTEA (GI) and hormone signaling through the modulation of key components of the transduction pathways. Specifically, we show how GI modulates gibberellin (GA) signaling through the stabilization of the DELLA proteins, which act as negative components in the signaling of this hormone. GI function within the GA pathway is required to precisely time the permissive gating of GA sensitivity, thereby determining the phase of GA-regulated physiological outputs.

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