Are there multiple circadian clocks in plants?

Hotta, Carlos Takeshi; Xu, Xiaodong; Xie, Qiguang; Dodd, Antony N.; Johnson, Carl Hirschie; Webb, Alex

doi:10.4161/psb.3.5.5352

Cited by 7 publications

(8 citation statements)

References 29 publications

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“…This disconnection could result from the presence of multiple oscillators or tissue-specific differences in the expression of FKF1 and CAB2 (51,52). FKF1 is expressed in both vascular bundles and mesophyll cells whereas CAB2 is expressed in mesophyll cells and epidermal guard cells (53,54).…”

Section: Discussionmentioning

confidence: 99%

“…Both genes respond differently to temperature signals although the spatial expression patterns of CAB2 and CAT3 overlap in the mesophyll. The toc1-1 mutant has short period rhythms of CAB2 but has a wild-type period for cytosolic Ca 2+ oscillation whereas the toc1-2 mutant has a short period for both CAB2 and Ca 2+ rhythms, which suggests that different mechanisms regulate the rhythms of CAB2 and Ca 2+ (52). We contemplated the possibility that because CAB2 is involved in photosynthetic responses and may be exposed to ROS fluctuations, its rhythms are buffered from ROS responses by some mechanism-perhaps a second oscillator.…”

Section: Discussionmentioning

confidence: 99%

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CIRCADIAN CLOCK-ASSOCIATED 1 regulates ROS homeostasis and oxidative stress responses

Lai

Doherty

Mueller‐Roeber

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

322

316

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Organisms have evolved endogenous biological clocks as internal timekeepers to coordinate metabolic processes with the external environment. Here, we seek to understand the mechanism of synchrony between the oscillator and products of metabolism known as Reactive Oxygen Species (ROS) in Arabidopsis thaliana. ROS-responsive genes exhibit a time-of-day-specific phase of expression under diurnal and circadian conditions, implying a role of the circadian clock in transcriptional regulation of these genes. Hydrogen peroxide production and scavenging also display time-ofday phases. Mutations in the core-clock regulator, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), affect the transcriptional regulation of ROSresponsive genes, ROS homeostasis, and tolerance to oxidative stress. Mis-expression of EARLY FLOWERING 3, LUX ARRHYTHMO, and TIMING OF CAB EXPRESSION 1 affect ROS production and transcription, indicating a global effect of the clock on the ROS network. We propose CCA1 as a master regulator of ROS homeostasis through association with the Evening Element in promoters of ROS genes in vivo to coordinate time-dependent responses to oxidative stress. We also find that ROS functions as an input signal that affects the transcriptional output of the clock, revealing an important link between ROS signaling and circadian output. Temporal coordination of ROS signaling by CCA1 and the reciprocal control of circadian output by ROS reveal a mechanistic link that allows plants to master oxidative stress responses.redox homeostasis | transcriptional coordination

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

CIRCADIAN CLOCK-ASSOCIATED 1 regulates ROS homeostasis and oxidative stress responses

Lai

Doherty

Mueller‐Roeber

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

322

316

View full text Add to dashboard Cite

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“…, 2003). It has been suggested that these differences in circadian phenotypes of gene expression show that TOC1 might interact with different proteins in a cell‐type specific manner (Hotta et al. , 2008).…”

Section: Discussionmentioning

confidence: 99%

“…In the toc1-1 line, LHCB in red light and GLYCINE RICH RNA BINDING PROTEIN7 (ATGRP7/CCR2) in the dark are expressed with a shorter period, while under the same conditions the genes are arrhythmic in toc1-2 plants (Somers et al, 1998;Strayer et al, 2000;Mas et al, 2003). It has been suggested that these differences in circadian phenotypes of gene expression show that TOC1 might interact with different proteins in a cell-type specific manner (Hotta et al, 2008). However, the most compelling evidence for differences in molecular composition of oscillators in different cell/organ types comes from a report showing that in roots, unlike in shoots, oscillator function does not require rhythmic expression of key circadian genes such as TOC1 (James et al, 2008).…”

Section: Guard Cells Have Different Circadian Rhythmsmentioning

confidence: 99%

Cell autonomous and cell‐type specific circadian rhythms in Arabidopsis

et al. 2011

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SUMMARYThe circadian system of plants regulates a wide range of rhythmic physiological and cellular output processes with a period of about 24 h. The rhythms are generated by an oscillator mechanism that, in Arabidopsis, consists of interlocking feedback loops of several components including CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION 1 (TOC1) and CCA1 HIKING EXPEDITION (CHE). Over recent years, researchers have gained a detailed picture of the clock mechanism at the resolution of the whole plant and several tissue types, but little information is known about the specificities of the clock mechanism at the level of individual cells. In this paper we have addressed the question of cell-typespecific differences in circadian systems. Using transgenic Arabidopsis plants with fluorescence-tagged CCA1 to measure rhythmicity in individual leaf cells in intact living plants, we showed that stomatal guard cells have a different period from surrounding epidermal and mesophyll leaf cells. By comparing transcript levels in guard cells with whole plants, we identified differences in the expression of some oscillator genes that may underlie cell-specific differences in clock properties. In addition, we demonstrated that the oscillators of individual cells in the leaf are robust, but become partially desynchronized in constant conditions. Taken together our results suggest that, at the level of individual cells, there are differences in the canonical oscillator mechanism that has been described for plants.

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“…Furthermore, the molecular composition of circadian clocks can differ between various cell and organ types. Thus, PRR3 modulates TOC1 stability in vasculature cell types, but not in others; CCA1 and LHY are not able to inhibit TOC1 expression in dark-grown roots (further examples in Harmer 2010; Hotta et al 2008).…”

Section: Clock Mechanism and Clock-controlled Genesmentioning

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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Are there multiple circadian clocks in plants?

Cited by 7 publications

References 29 publications

CIRCADIAN CLOCK-ASSOCIATED 1 regulates ROS homeostasis and oxidative stress responses

CIRCADIAN CLOCK-ASSOCIATED 1 regulates ROS homeostasis and oxidative stress responses

Cell autonomous and cell‐type specific circadian rhythms in Arabidopsis

How Light Resets Circadian Clocks

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