scholarly journals Clock-in, clock-out: circadian timekeeping between tissues

2020 ◽  
Vol 42 (2) ◽  
pp. 6-10
Author(s):  
Jacob G. Smith ◽  
Paolo Sassone-Corsi
Keyword(s):  
Circadian Clock ◽  
Daily Activity ◽  
Biological Processes ◽  
Stored Energy ◽  
Conscious Thought ◽  
Complex Organism ◽  
The Earth ◽  
Daily Cycles ◽  
Rotation Of The Earth ◽  
Time Information

Life evolved in the presence of alternating periods of light and dark that accompany the daily rotation of the Earth on its axis. This offered an advantage for organisms able to regulate their physiology to anticipate these daily cycles. In each light-sensitive organism studied, spanning single-celled bacteria to complex mammals, there exist timekeeping mechanisms able to control physiology over the course of 24 hours. Endowed with internal timekeeping, organisms can put their previously stored energy to the most efficient use, selectively ramping up biological processes at specific times of day or night according to when they will be needed. Humans have evolved to be more active during the day (diurnal), likely due to the increased opportunities for foraging or hunting in our evolutionary past, and this daily activity is accompanied by an up-regulation of genes involved in metabolism to increase the energy available for such behaviours. Remarkably, this happens without conscious thought—due to a complex organism-wide signalling apparatus known as the circadian clock network, which conveys time information between cells and tissues.

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 How to Live on Mars With a Proper Circadian Clock?

2022 ◽  
Vol 8 ◽  
Author(s):  
Rujia Luo ◽  
Yutao Huang ◽  
Huan Ma ◽  
Jinhu Guo
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
The Self ◽  
Circadian Clocks ◽  
Environmental Cues ◽  
Circadian Misalignment ◽  
The Earth ◽  
Adaptive Challenges ◽  
Rotation Of The Earth ◽  
And Behavior

Intrinsic circadian clocks generate circadian rhythms of physiology and behavior, which provide the capabilities to adapt to cycling environmental cues that result from the self-rotation of the Earth. Circadian misalignment leads to deleterious impacts on adaptation and health in different organisms. The environmental cues on the interplanetary journey to and on Mars dramatically differ from those on Earth. These differences impose numerous adaptive challenges, including challenges for humans’ circadian clock. Thus, adaptation of circadian rhythms to the Martian environment is a prerequisite for future landing and dwelling on Mars. Here, we review the progress of studies associated with the influence of the Martian environment on circadian rhythms and propose directions for further study and potential strategies to improve the adaptation of the circadian clock for future Mars missions.

scholarly journals Why Lungs Keep Time: Circadian Rhythms and Lung Immunity

2020 ◽  
Vol 82 (1) ◽  
pp. 391-412 ◽  
Author(s):  
Charles Nosal ◽  
Anna Ehlers ◽  
Jeffrey A. Haspel
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Respiratory System ◽  
Lung Diseases ◽  
Environmental Changes ◽  
Biological Processes ◽  
General Introduction ◽  
Daily Cycles ◽  
Ancient Times ◽  
Lung Immunity

Circadian rhythms are daily cycles in biological function that are ubiquitous in nature. Understood as a means for organisms to anticipate daily environmental changes, circadian rhythms are also important for orchestrating complex biological processes such as immunity. Nowhere is this more evident than in the respiratory system, where circadian rhythms in inflammatory lung disease have been appreciated since ancient times. In this focused review we examine how emerging research on circadian rhythms is being applied to the study of fundamental lung biology and respiratory disease. We begin with a general introduction to circadian rhythms and the molecular circadian clock that underpins them. We then focus on emerging data tying circadian clock function to immunologic activities within the respiratory system. We conclude by considering outstanding questions about biological timing in the lung and how a better command of chronobiology could inform our understanding of complex lung diseases.

scholarly journals Plants signal the time

2020 ◽  
Vol 42 (2) ◽  
pp. 28-31 ◽  
Author(s):  
Zeenat B Noordally ◽  
Antony N Dodd
Keyword(s):  
Circadian Clock ◽  
Environmental Conditions ◽  
Food Production ◽  
Plant Traits ◽  
Crucial Importance ◽  
The Earth ◽  
Model Plant Arabidopsis Thaliana ◽  
Rotation Of The Earth ◽  
Agricultural Food ◽  
Plant Arabidopsis Thaliana

Plants are generally sessile photosynthetic autotrophs; they depend on light for their existence and cannot move to escape challenging environmental conditions. This means that the lives of plants are intimately linked to daily fluctuations in environmental conditions caused by the rotation of the Earth on its axis. As a result, circadian regulation has an incredibly pervasive influence upon plant physiology, metabolism and development. For example, around 30% of the transcriptome of the model plant Arabidopsis thaliana is circadian regulated. In plants, the circadian clock influences processes of crucial importance such as photosynthesis, opening of the stomatal pores that allow gas exchange with the atmosphere, plant growth rates and organ position. It also contributes to the seasonal regulation of flowering. Taken together, this means that the circadian clock influences plant traits that are crucial to agricultural food production.

The Terrestrial Coordinate System and International Earth-rotation Services

1985 ◽  
Vol 38 (02) ◽  
pp. 216-217
Author(s):  
G. A. Wilkins
Keyword(s):  
Coordinate System ◽  
Earth Rotation ◽  
Reference System ◽  
New Techniques ◽  
Crustal Movements ◽  
Earth Observations ◽  
The Earth ◽  
External Reference ◽  
External Objects ◽  
Rotation Of The Earth

New techniques of measurement make it possible in 1984 to determine positions on the surface of the Earth to a much higher precision than was possible in 1884. If we look beyond the requirements of navigation we can see useful applications of global geodetic positioning to centimetric accuracy for such purposes as the control of mapping and the study of crustal movements. These new techniques depend upon observations of external objects, such as satellites or quasars rather than stars, and they require that the positions of these objects and the orientation of the surface of the Earth are both known with respect to an appropriate external reference system that is ‘fixed’ in space. We need networks of observing stations and analysis centres that monitor the motions of the external objects and the rotation of the Earth. Observations of stars by a transit circle are no longer adequate for this purpose.

Sensing the rotation of the Earth

1992 ◽  
Vol 30 (2) ◽  
pp. 111-111
Author(s):  
H. Richard Crane
Keyword(s):  
The Earth ◽  
Rotation Of The Earth

scholarly journals Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016 ◽  
Vol 34 (11) ◽  
pp. 961-974 ◽  
Author(s):  
Lukas Maes ◽  
Romain Maggiolo ◽  
Johan De Keyser
Keyword(s):  
Seasonal Variations ◽  
Solar Zenith Angle ◽  
The Sun ◽  
Polar Ionosphere ◽  
Polar Cap ◽  
Polar Wind ◽  
Simple Set ◽  
The Earth ◽  
Rotation Of The Earth ◽  
Set Up

Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90°. The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

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.

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