Molecular Components of a Model Circadian Clock

1998 ◽  
Author(s):  
Paul Hardin ◽  
Amita Sehgal
Keyword(s):  
Circadian Clock ◽  
Molecular Components

scholarly journals A Functional Connection between the Circadian Clock and Hormonal Timing in Arabidopsis

Genes ◽  
2018 ◽  
Vol 9 (12) ◽  
pp. 567 ◽  
Author(s):  
Manjul Singh ◽  
Paloma Mas
Keyword(s):  
Circadian Clock ◽  
Biological Significance ◽  
Feedback Regulation ◽  
Environmental Cues ◽  
Hormone Signaling ◽  
Functional Connection ◽  
The Earth ◽  
Exogenous Cues ◽  
Rotation Of The Earth ◽  
Molecular Components

The rotation of the Earth entails changes in environmental conditions that pervasively influence an organism’s physiology and metabolism. An internal cellular mechanism known as the circadian clock acts as an internal timekeeper that is able to perceive the changes in environmental cues to generate 24-h rhythms in synchronization with daily and seasonal fluctuations. In plants, the circadian clock function is particularly important and regulates nearly every aspect of plant growth and development as well as proper responses to stresses. The circadian clock does not function in isolation but rather interconnects with an intricate network of different pathways, including those of phytohormones. Here, we describe the interplay of the circadian clock with a subset of hormones in Arabidopsis. The molecular components directly connecting the circadian and hormone pathways are described, highlighting the biological significance of such connections in the control of growth, development, fitness, and survival. We focus on the overlapping as well as contrasting circadian and hormonal functions that together provide a glimpse on how the Arabidopsis circadian system regulates hormone function in response to endogenous and exogenous cues. Examples of feedback regulation from hormone signaling to the clock are also discussed.

scholarly journals Molecular components of the mammalian circadian clock

2006 ◽  
Vol 15 (suppl_2) ◽  
pp. R271-R277 ◽  
Author(s):  
Caroline H. Ko ◽  
Joseph S. Takahashi
Keyword(s):  
Circadian Clock ◽  
Molecular Components

scholarly journals Pressed for time: the circadian clock and hypertension

2009 ◽  
Vol 107 (4) ◽  
pp. 1328-1338 ◽  
Author(s):  
R. Daniel Rudic ◽  
David J. Fulton
Keyword(s):  
Blood Pressure ◽  
Cardiovascular Disease ◽  
Risk Factor ◽  
Locomotor Activity ◽  
Circadian Clock ◽  
Animal Studies ◽  
Organ Damage ◽  
Control Fluid ◽  
Molecular Components ◽  
Over Time

Hypertension is a major risk factor for cardiovascular disease and death. The “silent” rise of blood pressure that occurs over time is largely asymptomatic. However, its impact is deafening—causing and exacerbating cardiovascular disease, end-organ damage, and death. The present article addresses recent observations from human and animal studies that provide new insights into how the circadian clock regulates blood pressure, contributes to hypertension, and ultimately evolves vascular disease. Further, the molecular components of the circadian clock and their relationship with locomotor activity, metabolic control, fluid balance, and vascular resistance are discussed with an emphasis on how these novel, circadian clock-controlled mechanisms contribute to hypertension.

scholarly journals Regulatory principles and experimental approaches to the circadian control of starch turnover

2014 ◽  
Vol 11 (91) ◽  
pp. 20130979 ◽  
Author(s):  
Daniel D. Seaton ◽  
Oliver Ebenhöh ◽  
Andrew J. Millar ◽  
Alexandra Pokhilko
Keyword(s):  
Circadian Clock ◽  
Starch Synthesis ◽  
Starch Degradation ◽  
Dynamic Adjustment ◽  
Carbohydrate Starvation ◽  
Circadian Control ◽  
Experimental Approaches ◽  
Downstream Processes ◽  
Molecular Components ◽  
Dependent Interaction

In many plants, starch is synthesized during the day and degraded during the night to avoid carbohydrate starvation in darkness. The circadian clock participates in a dynamic adjustment of starch turnover to changing environmental condition through unknown mechanisms. We used mathematical modelling to explore the possible scenarios for the control of starch turnover by the molecular components of the plant circadian clock. Several classes of plausible models were capable of describing the starch dynamics observed in a range of clock mutant plants and light conditions, including discriminating circadian protocols. Three example models of these classes are studied in detail, differing in several important ways. First, the clock components directly responsible for regulating starch degradation are different in each model. Second, the intermediate species in the pathway may play either an activating or inhibiting role on starch degradation. Third, the system may include a light-dependent interaction between the clock and downstream processes. Finally, the clock may be involved in the regulation of starch synthesis. We discuss the differences among the models’ predictions for diel starch profiles and the properties of the circadian regulators. These suggest additional experiments to elucidate the pathway structure, avoid confounding results and identify the molecular components involved.

scholarly journals The role of the circadian clock system in nutrition and metabolism

2012 ◽  
Vol 108 (3) ◽  
pp. 381-392 ◽  
Author(s):  
Felino R. Cagampang ◽  
Kimberley D. Bruce
Keyword(s):  
Circadian Clock ◽  
Well Being ◽  
Internal Clock ◽  
Feedback Mechanism ◽  
Hypothalamic Region ◽  
Peripheral Tissues ◽  
Clock System ◽  
Physiological Processes ◽  
Liver And Pancreas ◽  
Molecular Components

Mammals have an endogenous timing system in the suprachiasmatic nuclei (SCN) of the hypothalamic region of the brain. This internal clock system is composed of an intracellular feedback loop that drives the expression of molecular components and their constitutive protein products to oscillate over a period of about 24 h (hence the term ‘circadian’). These circadian oscillations bring about rhythmic changes in downstream molecular pathways and physiological processes such as those involved in nutrition and metabolism. It is now emerging that the molecular components of the clock system are also found within the cells of peripheral tissues, including the gastrointestinal tract, liver and pancreas. The present review examines their role in regulating nutritional and metabolic processes. In turn, metabolic status and feeding cycles are able to feed back onto the circadian clock in the SCN and in peripheral tissues. This feedback mechanism maintains the integrity and temporal coordination between various components of the circadian clock system. Thus, alterations in environmental cues could disrupt normal clock function, which may have profound effects on the health and well-being of an individual.

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