The Plant Circadian Clock: From a Simple Timekeeper to a Complex Developmental Manager

Sanchez, Sabrina E.; Kay, Steve A.

doi:10.1101/cshperspect.a027748

Cited by 169 publications

(158 citation statements)

References 124 publications

(173 reference statements)

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“…These oscillators have strong influences on other physiological processes by regulating gene expression according to the time of day. The circadian clock in plants maintains a strong influence on growth, reproductive development, and metabolism (reviewed in depth in Hsu & Harmer ; McClung ; Sanchez & Kay ). The clock allows the plant to anticipate daily changes in the environment, such as dawn and dusk, and regulates gene expression programmes based on time of day.…”

Section: Hello Darkness My Old Friendmentioning

confidence: 99%

“…Internal cross-regulation of clock gene transcripts is indicated by arrowheads (positive regulation) or bars (negative regulation). For detailed description of clock function and input mechanisms, we direct the reader to Hsu & Harmer (2014); Jones (2009); McClung (2011) and Sanchez & Kay (2016).ELF, early flowering. plants occurs with severely limited environmental light input and thus damped external rhythmic stimulus.…”

Section: Evolution Of the Etiolated Body Plan: In The Beginning Was mentioning

confidence: 99%

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Dancing in the dark: darkness as a signal in plants

Seluzicki

Burko

Chory

2017

Plant Cell & Environment

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Daily cycles of light and dark provide an organizing principle and temporal constraints under which life on Earth evolved. While light is often the focus of plant studies, it is only half the story. Plants continuously adjust to their surroundings, taking both dawn and dusk as cues to organize their growth, development and metabolism to appropriate times of day. In this review, we examine the effects of darkness on plant physiology and growth. We describe the similarities and differences between seedlings grown in the dark versus those grown in light–dark cycles, and the evolution of etiolated growth. We discuss the integration of the circadian clock into other processes, looking carefully at the points of contact between clock genes and growth-promoting gene-regulatory networks in temporal gating of growth. We also examine daily starch accumulation and degradation, and the possible contribution of dark-specific metabolic controls in regulating energy and growth. Examining these studies together reveals a complex and continuous balancing act, with many signals, dark included, contributing information and guiding the plant through its life cycle. The extraordinary interconnection between light and dark is manifest during cycles of day and night and during seedling emergence above versus below the soil surface.

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Section: Hello Darkness My Old Friendmentioning

confidence: 99%

Section: Evolution Of the Etiolated Body Plan: In The Beginning Was mentioning

confidence: 99%

Dancing in the dark: darkness as a signal in plants

Seluzicki

Burko

Chory

2017

Plant Cell & Environment

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“…Light is usually the dominant stimulus for entrainment of the clock in natural as well as controlled environment conditions, with entrainment being affected by both the level and spectral quality of the light (Millar, 2016;Sanchez and Kay, 2016). Light perception and signaling via phytochromes is a major input, although other direct light signaling systems (e.g.…”

Section: Metabolite Controlmentioning

confidence: 99%

Transitory Starch Metabolism in Guard Cells: Unique Features for a Unique Function

Santelia

Lunn

2017

Plant Physiol.

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This update focuses on the starch that accumulates in the guard cells that control stomatal pore size and thus the exchange of water vapor, CO 2 , and O 2 between the leaf and the atmosphere. Transitory starch in these cells plays a key role in determining the velocity of stomatal opening in the light. This significantly differs from the transitory starch in the mesophyll leaves, which acts primarily as a carbohydrate reserve to sustain plant metabolism during the night. We discuss how the unique function of transitory starch in guard cells is reflected in the timing of its deposition and mobilization, along with differences from mesophyll cells in the pathways and regulation of starch metabolism.Starch is a nonstructural polysaccharide synthesized inside plastids of plants and algae. It consists of two types of a-1,4-linked glucan polymers-amylose and amylopectin-that differ in chain length and frequency of a-1,6-branches. These polymers adopt complex secondary and tertiary structures that organize into insoluble, semicrystalline granules to store energy in a dense, osmotically inert form (Pfister and Zeeman, 2016).Starch is a vital substance for plants, both for shortand long-term storage of carbohydrates. In heterotrophic organs, such as potato tubers, cassava roots, cereal seed endosperm, and the stems of woody perennials, starch is synthesized in specialized amylopasts from imported sucrose (Suc) and stored over the seasons, or even for many years. Remobilization of this long-term storage starch takes place during seed germination, tuber sprouting, or regrowth, when photosynthesis has either not yet resumed or is insufficient to meet the demand for energy and carbon skeletons (Lloyd and Kossmann, 2015). In photosynthetic tissues, starch is synthesized in the chloroplasts of mesophyll cells during the day and remobilized at night to provide carbon and energy for maintenance and growth (Stitt and Zeeman, 2012). These short-term reserves, known as transitory starch, are formed directly from intermediates of the Calvin-Benson cycle in the light and when broken down at night provide substrates for respiration in the leaf and synthesis of Suc that can be exported to growing sink organs. Within the leaf epidermis, transitory starch is also present in the chloroplasts of the guard cells that surround the stomatal pore.

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“…The circadian clock is a time‐keeping mechanism that enables organisms to adaptively match many transcriptomic, physiological, developmental, and biochemical processes to natural diurnal cycles (McClung, ; Resco de Dios & Gessler, ; Sanchez & Kay, ; Yerushalmi & Green, ). By comparing the phenotypes of wild‐type plants to mutant genotypes with altered clock function, several studies have demonstrated that diverse ecophysiological traits (e.g., total CO 2 assimilation rates, sugar status, and photosynthetic operating efficiency) are affected by the circadian clock (Dodd et al, ; Graf, Schlereth, Stitt, & Smith, ; Jones, ; Litthauer, Battle, Lawson, & Jones, ).…”

Section: Introductionmentioning

confidence: 99%

Circadian rhythms are associated with variation in photosystem II function and photoprotective mechanisms

Yarkhunova

Rubin

Davis

et al. 2018

Plant Cell & Environment

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The circadian clock regulates many aspects of leaf gas supply and biochemical demand for CO , and is hypothesized to improve plant performance. Yet the extent to which the clock may regulate the efficiency of photosystem II (PSII) and photoprotective mechanisms such as heat dissipation is less explored. Based on measurements of chlorophyll a fluorescence, we estimated the maximum efficiency of PSII in light (Fv'/Fm') and heat dissipation by nonphotochemical quenching (NPQ). We further dissected total NPQ into its main components, qE (pH-dependent quenching), qT (state-transition quenching), and qI (quenching related to photoinhibition), in clock mutant genotypes of Arabidopsis thaliana, the cognate wild-type genotypes, and a panel of recombinant inbred lines expressing quantitative variation in clock period. Compared with mutants with altered clock function, we observed that wild-type genotypes with clock period lengths of approximately 24 hr had both higher levels of Fv'/Fm', indicative of improved PSII function, and reduced NPQ, suggestive of lower stress on PSII light harvesting complexes. In the recombinant inbred lines, genetic variances were significant for Fv'/Fm' and all 3 components of NPQ, with qE explaining the greatest proportion of NPQ. Bivariate tests of association and structural equation models of hierarchical trait relationships showed that quantitative clock variation was empirically associated with Fv'/Fm' and NPQ, with qE mediating the relationship with gas exchange. The results demonstrate significant segregating variation for all photoprotective components, and suggest the adaptive significance of the clock may partly derive from its regulation of the light reactions of photosynthesis and of photoprotective mechanisms.

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The Plant Circadian Clock: From a Simple Timekeeper to a Complex Developmental Manager

Cited by 169 publications

References 124 publications

Dancing in the dark: darkness as a signal in plants

Dancing in the dark: darkness as a signal in plants

Transitory Starch Metabolism in Guard Cells: Unique Features for a Unique Function

Circadian rhythms are associated with variation in photosystem II function and photoprotective mechanisms

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