Circadian clocks in changing weather and seasons: Lessons from the picoalga <i>Ostreococcus tauri</i>

Pfeuty, Benjamin; Thommen, Quentin; Corellou, Florence; Djouani-Tahri, El Batoul; Bouget, François‐Yves; Lefranc, Marc

doi:10.1002/bies.201200012

Cited by 27 publications

(32 citation statements)

References 76 publications

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“…We know from the dead zone in the experimental PRC that the fly clock is insensitive to light during most of the day, possibly because there is a gate that prevents light from increasing the degradation rate of TIM during that time. We also know that for entrainment to be robust, the deadzone is critical (Pfeuty et al, 2011, 2012). However, if a model accurately captures all clock processes affected by light, and is merely missing a gate, then it should be possible to entrain it with a light/dark cycle that itself gates the light, as in the work of Thommen et al (2010).…”

Section: Resultsmentioning

confidence: 99%

Velocity response curves demonstrate the complexity of modeling entrainable clocks

Taylor

Cheever

Harmon

2014

Journal of Theoretical Biology

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Circadian clocks are biological oscillators that regulate daily behaviors in organisms across the kingdoms of life. Their rhythms are generated by complex systems, generally involving interlocked regulatory feedback loops. These rhythms are entrained by the daily light/dark cycle, ensuring that the internal clock time is coordinated with the environment. Mathematical models play an important role in understanding how the components work together to function as a clock which can be entrained by light. For a clock to entrain, it must be possible for it to be sped up or slowed down at appropriate times. To understand how biophysical processes affect the speed of the clock, one can compute velocity response curves (VRCs). Here, in a case study involving the fruit fly clock, we demonstrate that VRC analysis provides insight into a clock’s response to light. We also show that biochemical mechanisms and parameters together determine a model’s ability to respond realistically to light. The implication is that, if one is developing a model and its current form has an unrealistic response to light, then one must reexamine one’s model structure, because searching for better parameter values is unlikely to lead to a realistic response to light.

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Section: Resultsmentioning

confidence: 99%

Velocity response curves demonstrate the complexity of modeling entrainable clocks

Taylor

Cheever

Harmon

2014

Journal of Theoretical Biology

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“…The circadian clock is a simplified Arabidopsis clock possessing only two of its clock gene types (see Sect. 8.4 and Thommen et al 2010;Djouani-Tahri et al 2010;Corellou et al 2009) and has been modeled (Dixon et al 2014;Pfeuty et al 2012;Troein et al 2011) using only one feedback loop (see Fig. 8.1).…”

Section: Ostreococcus Taurimentioning

confidence: 97%

“…There is furthermore a feedback (arrows) from the TTFL to the photoreceptors. After Pfeuty et al (2012), McClung (2011a and Troein et al (2011) Light receptors in Ostreococcus tauri are a histidine kinase LOV-HK, which absorbs blue light, and a histidine kinase, Rhodopsin-HK (Rhod-HK), which senses longer wavelengths . Using long-and short-wavelength photoreceptors (see Fig.…”

Section: Ostreococcus Taurimentioning

confidence: 99%

Photoperiodism: The Calendar of Plants

Engelmann

2015

Rhythms in Plants

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The daylength varies with the time of the year and can thus be used by plants-and other organisms-to react photoperiodically in developmental steps and morphological features such as cyst formation, germination of zygospores and cell division in certain algae, succulence of stems and leaves, formation of storage organs, and flower induction. The functioning and molecular bases of circadian clocks of plants are mentioned and shown how they are entrained to the day, and whether they are involved in photoperiodic timing. Seasonal aspects for various crops and the evolution of photoperiodism are briefly touched upon.

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“…18.5). Models with only one feedback loop were proposed by Pfeuty et al (2012) and Troein et al (2011) to describe the Ostreococcus clock (see Fig. 18.4).…”

Section: Algal Clocks: From Simple To Complexmentioning

confidence: 99%

How Light Resets Circadian Clocks

2014

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The daily revolutions of the earth around its axis are responsible for day and night and its annual orbit around the sun for the seasons with their fluctuations in day length. Most organisms have adapted to these diurnal and annual cycles. The strategies and mechanisms used are quite delicate and complicated.It came as a surprise that photosynthesis and many other processes are, however, additionally controlled by internal clocks. Thus, photosynthesis fluctuates not only during the daily light-dark cycle (=LD; see the List of Abbreviations and http://www.circadian.org/dictionary.html) but also when the plants are kept under LL and constant temperature (Hennessey and Field 1991). However, the period length (period for short) of this rhythmic event then deviates from exactly 24 h and is therefore called circadian (from Latin circa, about, and dies, day). If in the absence of LD and temperature cycles other 24 h time cues (also called zeitgeber, German for time giver) would control the rhythm, it should show an exact 24 h rhythm. This is not the case, demonstrating the endogenous nature of a clock that is locked to light signals (see Fig. 18.1). Spectrum of RhythmsEndogenous rhythms of organisms are not only tuned to the daily cycle of 24 h. The range of rhythms found in organisms covers ultradian (with periods of several hours to very short ones), circadian, and annual (with periods of about a year) rhythms. Other rhythms such as tidal, 14-day, and monthly ones cope with influences of the moon on the earth, mainly on the water movements of the oceans, and they are therefore found in organisms at the coasts and in the sea. Annual rhythms interact with the day-length changes during the year (see below). There are furthermore rhythms with periods covering several years. The following discussion of a "biological clock" is restricted to circadian rhythms. Even they are often not just composed of one clock type but form a "circadian system" consisting of two or more clocks with different prop- Function of Circadian ClocksThe term "clock" usually implies a time-measuring device or function. For instance, the day length (or night length) can be determined by an organism. Since day length is a function of the time of the year (long days in summer, short days in winter), it can be used to time certain events such as flowering or tuber formation of a plant or breeding of birds and mammals during the most appropriate season. These processes are denoted photoperiodism (see Chap. 19).However, a clock can also be used to set a certain temporal order. For instance, the circadian control of our sleepwake cycle ensures that we rise in the morning and fall asleep in the evening at a preferred time. Food intake and digestion are likewise controlled by this clock and gated to certain times of the day (Silver et al. 2011;Duguay and Cermakian 2009;Forsgren 1935). The circadian clock will time these events also under constant conditions. Furthermore, circadian clocks can serve as alarm clocks.

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Circadian clocks in changing weather and seasons: Lessons from the picoalga Ostreococcus tauri

Cited by 27 publications

References 76 publications

Velocity response curves demonstrate the complexity of modeling entrainable clocks

Velocity response curves demonstrate the complexity of modeling entrainable clocks

Photoperiodism: The Calendar of Plants

How Light Resets Circadian Clocks

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