Clock In Plants Research Articles

Decoding the plant clock: a review of mathematical models for the circadian regulatory network.

Most organisms have evolved specific mechanisms to respond to changes in environmental conditions such as light and temperature over the course of day. These periodic changes in the physiology and behaviour of organisms, referred to as circadian rhythms, are a consequence of intricate molecular mechanisms in the form of transcription and translational feedback loops. The plant circadian regulatory network is a complex web of interconnected feedback loops involving various transcription factors such as CCA1, LHY, PRRs, TOC1, LUX, ELF3, ELF4, RVE8, and more. This network enables plants to adapt and thrive in diverse environmental conditions. It responds to entrainment signals, including light, temperature, and nutrient concentrations and interacts with most of the physiological functions such as flowering, growth and stress response. Mathematical modelling of these gene regulatory networks enables a deeper understanding of not only the function but also the perturbations that may affect the plant growth and function with changing climate. Over the years, numerous mathematical models have been developed to understand the diverse aspects of plant circadian regulation. In this review, we have delved into the systematic development of these models, outlining the model components and refinements over time. We have also highlighted strengths and limitations of each of the models developed so far. Finally, we conclude the review by describing the prospects for investigation and advancement of these models for better understanding of plant circadian regulation.

Interference of skeleton photoperiod in circadian clock and photosynthetic efficiency of tea plant: in-depth analysis of mathematical model.

The circadian system of plants is a complex physiological mechanism, a biological process in which plants can adjust themselves according to the day and night cycle. To understand the effects of different photoperiods on the biological clock of tea plants, we analyzed the expression levels of core clock genes (CCA1, PRR9, TOC1, ELF4) and photosynthesis-related genes (Lhcb, RbcS, atpA) under normal light (light/dark = 12h/12h, 12L12D) and took the cost function defined by cycle and phase errors as the basic model parameter. In the continuous light environment (24h light, 24L), the peak activity and cycle of key genes that control the biological clock and photosynthesis were delayed by 1-2h. Under a skeleton photoperiod (6L6D, 3L3D), the expression profiles of clock genes and photosynthesis-related genes in tea plants were changed and stomatal opening showed a circadian rhythm. These observations suggest that a skeleton photoperiod may have an effect on the circadian rhythm, photosynthetic efficiency and stomatal regulation of tea plants. Our study and model analyzed the components of circadian rhythms under different photoperiodic pathways, and also revealed the underlying mechanisms of circadian regulation of photosynthesis in tea plants.

The Circadian Clock Gene PHYTOCLOCK1 Mediates the Diurnal Emission of the Anti-Insect Volatile Benzyl Nitrile from Damaged Tea (Camellia sinensis) Plants.

Benzyl nitrile from tea plants attacked by various pests displays a diurnal pattern, which may be closely regulated by the endogenous circadian clock. However, the molecular mechanism by the circadian clock of tea plants that regulates the biosynthesis and release of volatiles remains unclear. In this study, the circadian clock gene CsPCL1 can activate both the expression of the benzyl nitrile biosynthesis-related gene CsCYP79 and the jasmonic acid signaling-related transcription factor CsMYC2 involved in upregulating CsCYP79 gene, thereby resulting in the accumulation and release of benzyl nitrile. Therefore, the anti-insect function of benzyl nitrile was explored in the laboratory. The application of slow-release beads of benzyl nitrile in tea plantations significantly reduced the number of tea geometrids and had positive effects on the yield of fresh tea leaves. These findings reveal the potential utility of herbivore-induced plant volatiles for the green control of pests in tea plantations.

NAC transcription factor ATAF1 negatively modulates the PIF-regulated hypocotyl elongation under a short-day photoperiod.

Day length modulates hypocotyl elongation in seedlings to optimize their overall fitness. Variations in cell growth-associated genes are regulated by several transcription factors. However, the specific transcription factors through which the plant clock increases plant fitness are still being elucidated. In this study, we identified the no apical meristem, Arabidopsis thaliana-activating factor (ATAF-1/2), and cup-shaped cotyledon (NAC) family transcription factor ATAF1 as a novel repressor of hypocotyl elongation under a short-day (SD) photoperiod. Variations in day length profoundly affected the transcriptional and protein levels of ATAF1. ATAF1-deficient mutant exhibited increased hypocotyl length and cell growth-promoting gene expression under SD conditions. Moreover, ATAF1 directly targeted and repressed the expression of the cycling Dof factor 1/5 (CDF1/5), two key transcription factors involved in hypocotyl elongation under SD conditions. Additionally, ATAF1 interacted with and negatively modulated the effects of phytochrome-interacting factor (PIF), thus inhibiting PIF-promoted gene expression and hypocotyl elongation. Taken together, our results revealed ATAF1-PIF as a crucial pair modulating the expression of key transcription factors to facilitate plant growth during day/night cycles under fluctuating light conditions.

The circadian clock and thermal regulation in plants: novel insights into the role of positive circadian clock regulators in temperature responses.

The impact of rising global temperatures on crop yields is a serious concern, and the development of heat-resistant crop varieties is crucial for mitigating the effects of climate change on agriculture. To achieve this, a better understanding of the molecular basis of the thermal responses of plants is necessary. The circadian clock plays a central role in modulating plant biology in synchrony with environmental changes, including temperature fluctuations. Recent studies have uncovered the role of transcriptional activators of the core circadian network in plant temperature responses. This expert view highlights key novel findings regarding the role of the RVE and LNK gene families in controlling gene expression patterns and plant growth under different temperature conditions, ranging from regular diurnal oscillations to extreme stress temperatures. These findings reinforce the essential role of the circadian clock in plant adaptation to changing temperatures and provide a basis for future studies on crop improvement.

Circadian rhythms and circadian clock gene homologs of complex alga Chromera velia.

Most organisms on Earth are affected by periodic changes in their environment. The circadian clock is an endogenous device that synchronizes behavior, physiology, or biochemical processes to an approximately 24-hour cycle, allowing organisms to anticipate the periodic changes of day and night. Although circadian clocks are widespread in organisms, the actual molecular components differ remarkably among the clocks of plants, animals, fungi, and prokaryotes. Chromera velia is the closest known photosynthetic relative of apicomplexan parasites. Formation of its motile stage, zoospores, has been described as associated with the light part of the day. We examined the effects on the periodic release of the zoospores under different light conditions and investigated the influence of the spectral composition on zoosporogenesis. We performed a genomic search for homologs of known circadian clock genes. Our results demonstrate the presence of an almost 24-hour free-running cycle of zoosporogenesis. We also identified the blue light spectra as the essential compound for zoosporogenesis. Further, we developed a new and effective method for zoospore separation from the culture and estimated the average motility speed and lifespan of the C. velia zoospores. Our genomic search identified six cryptochrome-like genes, two genes possibly related to Arabidopsis thaliana CCA/LHY, whereas no homolog of an animal, cyanobacterial, or fungal circadian clock gene was found. Our results suggest that C. velia has a functional circadian clock, probably based mainly on a yet undefined mechanism.

An evolutionary epigenetic clock in plants.

Molecular clocks are the basis for dating the divergence between lineages over macroevolutionary timescales (~105 to 108 years). However, classical DNA-based clocks tick too slowly to inform us about the recent past. Here, we demonstrate that stochastic DNA methylation changes at a subset of cytosines in plant genomes display a clocklike behavior. This "epimutation clock" is orders of magnitude faster than DNA-based clocks and enables phylogenetic explorations on a scale of years to centuries. We show experimentally that epimutation clocks recapitulate known topologies and branching times of intraspecies phylogenetic trees in the self-fertilizing plant Arabidopsis thaliana and the clonal seagrass Zostera marina, which represent two major modes of plant reproduction. This discovery will open new possibilities for high-resolution temporal studies of plant biodiversity.

An epigenetic clock in plants.

DNA methylation can identify evolutionary relationships among close plant lineages.

A Small-Molecule Modulator Affecting the Clock-Associated PSEUDO-RESPONSE REGULATOR 7 Amount.

Circadian clocks are biological timekeeping systems that coordinate genetic, metabolic and physiological behaviors with the external day-night cycle. The clock in plants relies on the transcriptional-translational feedback loops transcription-translation feedback loop (TTFL), consisting of transcription factors including PSUEDO-RESPONSE REGULATOR (PRR) proteins, plant lineage-specific transcriptional repressors. Here, we report that a novel synthetic small-molecule modulator, 5-(3,4-dichlorophenyl)-1-phenyl-1,7-dihydro-4H-pyrazolo[3,4-d] pyrimidine-4,6(5H)-dione (TU-892), affects the PRR7 protein amount. A clock reporter line of Arabidopsis was screened against the 10,000 small molecules in the Maybridge Hitfinder 10K chemical library. This screening identified TU-892 as a period-lengthening molecule. Gene expression analyses showed that TU-892 treatment upregulates CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) mRNA expression. TU-892 treatment reduced the amount of PRR7 protein, a transcriptional repressor of CCA1. Other PRR proteins including TIMING OF CAB EXPRESSION 1 were altered less by TU-892 treatment. TU-892-dependent CCA1 upregulation was attenuated in mutants impaired in PRR7. Collectively, TU-892 is a novel type of clock modulator that reduces the levels of PRR7 protein.

OsTOC1 plays dual roles in the regulation of plant circadian clock by functioning as a direct transcription activator or repressor

Plant clock function relies on precise timing of gene expression through complex regulatory networks consisting of activators and repressors at the core of oscillators. Although TIMING OF CAB EXPRESSION 1 (TOC1) has been recognized as a repressor involved in shaping oscillations and regulating clock-driven processes, its potential to directly activate gene expression remains unclear. In this study, we find that OsTOC1 primarily acts as a transcriptional repressor for core clock components, including OsLHY and OsGI. Here, we show that OsTOC1 possesses the ability to directly activate the expression of circadian target genes. Through binding to the promoters of OsTGAL3a/b, transient activation of OsTOC1 induces the expression of OsTGAL3a/b, indicating its role as an activator contributing to pathogen resistance. Moreover, TOC1 participates in regulating multiple yield-related traits in rice. These findings suggest that TOC1's function as a transcriptional repressor is not inherent, providing flexibility to circadian regulations, particularly in outputs.

Rhizosphere microbial community composition shifts diurnally and in response to natural variation in host clock phenotype.

Plant-associated microbial assemblages are known to shift at time scales aligned with plant phenology, as influenced by the changes in plant-derived nutrient concentrations and abiotic conditions observed over a growing season. But these same factors can change dramatically in a sub-24-hour period, and it is poorly understood how such diel cycling may influence plant-associated microbiomes. Plants respond to the change from day to night via mechanisms collectively referred to as the internal "clock," and clock phenotypes are associated with shifts in rhizosphere exudates and other changes that we hypothesize could affect rhizosphere microbes. The mustard Boechera stricta has wild populations that contain multiple clock phenotypes of either a 21- or a 24-hour cycle. We grew plants of both phenotypes (two genotypes per phenotype) in incubators that simulated natural diel cycling or that maintained constant light and temperature. Under both cycling and constant conditions, the extracted DNA concentration and the composition of rhizosphere microbial assemblages differed between time points, with daytime DNA concentrations often triple what were observed at night and microbial community composition differing by, for instance, up to 17%. While we found that plants of different genotypes were associated with variation in rhizosphere assemblages, we did not see an effect on soil conditioned by a particular host plant circadian phenotype on subsequent generations of plants. Our results suggest that rhizosphere microbiomes are dynamic at sub-24-hour periods, and those dynamics are shaped by diel cycling in host plant phenotype. IMPORTANCE We find that the rhizosphere microbiome shifts in composition and extractable DNA concentration in sub-24-hour periods as influenced by the plant host's internal clock. These results suggest that host plant clock phenotypes could be an important determinant of variation in rhizosphere microbiomes.

Plant domestication: setting biological clocks.

Through domestication of wild species, humans have induced large changes in the developmental and circadian clocks of plants. As a result of these changes, modern crops are more productive and adaptive to contrasting environments from the center of origin of their wild ancestors, albeit with low genetic variability and abiotic stress tolerance. Likewise, a complete restructuring of plant metabolic timekeeping probably occurred during crop domestication. Here, we highlight that contrasting timings among organs in wild relatives of crops allowed them to recognize environmental adversities faster. We further propose that connections among biological clocks, which were established during plant domestication, may represent a fundamental source of genetic variation to improve crop resilience and yield.

Current Insights into m6A RNA Methylation and Its Emerging Role in Plant Circadian Clock.

N6-adenosine methylation (m6A) is a prevalent form of RNA modification found in the expressed transcripts of many eukaryotic organisms. Moreover, m6A methylation is a dynamic and reversible process that requires the functioning of various proteins and their complexes that are evolutionarily conserved between species and include methylases, demethylases, and m6A-binding proteins. Over the past decade, the m6A methylation process in plants has been extensively studied and the understanding thereof has drastically increased, although the regulatory function of some components relies on information derived from animal systems. Notably, m6A has been found to be involved in a variety of factors in RNA processing, such as RNA stability, alternative polyadenylation, and miRNA regulation. The circadian clock in plants is a molecular timekeeping system that regulates the daily and rhythmic activity of many cellular and physiological processes in response to environmental changes such as the day-night cycle. The circadian clock regulates the rhythmic expression of genes through post-transcriptional regulation of mRNA. Recently, m6A methylation has emerged as an additional layer of post-transcriptional regulation that is necessary for the proper functioning of the plant circadian clock. In this review, we have compiled and summarized recent insights into the molecular mechanisms behind m6A modification and its various roles in the regulation of RNA. We discuss the potential role of m6A modification in regulating the plant circadian clock and outline potential future directions for the study of mRNA methylation in plants. A deeper understanding of the mechanism of m6A RNA regulation and its role in plant circadian clocks will contribute to a greater understanding of the plant circadian clock.

Biochemical Society Science Communication Prize 2022

For the past 11 years, the Biochemical Society has looked to identify and celebrate outstanding science communication by bioscience students with an annual Science Communication Prize. This year, the competition was open for creative and engaging entries aimed at the general public, in both written and media categories.We would like to congratulate all the entrants and winners on their fantastic pieces submitted for the Science Communication Prize this year. The Biochemical Society was delighted with the entries, which came from across the globe and covered a broad range of diverse topics, from the microbiome to HIV. The winners were selected by a panel of five judges with knowledge and expertise across the science communication sector: Agnese Abrusci (Media Editor at Nature), Dr Emma Yhnell (Senior Lecturer in Neuroscience at Cardiff University and Science Communicator), Dr Heather Doran (Public Engagement Manager, Leverhulme Centre for Forensic Science at University of Dundee; Science Editor, The Biochemist), Nikolaus Muldal (Education and Public Outreach Manager for the UK Atomic Energy Authority) and Dr Güneş Taylor (Postdoctoral Training Fellow at The Francis Crick Institute and freelance science communicator). Güneş said:The winners of each category received a cash prize – £300 for the first prize, £200 for the second prize and £100 for the third prize. The winning article entries in the written category also win the opportunity for their piece to be published in The Biochemist. Competition judge Emma Yhnell said:This year, the written category saw a range of entries on the molecular aspects of cancer, alcohol, love and the wonder of plants, to name a few. The first prize went to Zuzana Osifová (Charles University, Czech Republic), for a powerful and thought-provoking article on anorexia nervosa, titled ‘Meanwhile in an anorexic mind’. Zuzana is currently studying for a PhD in NMR spectroscopy, and when asked why she chose to write about anorexia nervosa, Zuzana said:Zuzana also generously donated half of her cash prize to a charity in Czech Republic that helps eating disorder sufferers.The judges were impressed with Natural Sciences undergraduate Natalie Bicknell’s (University of Leeds, UK) truly original and engaging newspaper entry on the fascinating internal clock of plants, titled ‘Breaking news: plants can tell the time!’ When asked about her chosen topic, Natalie said:We strongly encourage readers to view Natalie’s piece in the supplemental material to this article, where it can be seen in full.Undergraduate microbiology student Iris Floria (University of Glasgow, UK) submitted an eye-opening (and sometimes horrifying!) piece on cannibalistic microbes and the fight against antibiotic resistance, titled ‘Microbial predators: an unlikely ally?’ When asked why she chose to enter the competition, Iris said:For Iris, participation certainly paid off as she was awarded third prize in the written category.The media category of the competition allows entrants to explore a variety of creative visual techniques to communicate their chosen topic. This year’s entries certainly delivered.The first prize in the media category went to Biomedical Sciences undergraduate Rosanna Culver (University of Edinburgh, UK), for her inventive video using a roll of toilet paper to describe how vaccines work, titled ‘Rolling out vaccines: the fight against COVID-19’. When asked about entering the Science Communication Prize, Rosanna said:Recent PhD graduate Leonardo Feletto (University of Leicester, UK) received the second prize for his timely video on ‘How COVID-19 spiked the interest for structural biology’, using animations and special effects to highlight the key role that structural biology has on combating the COVID-19 pandemic. Leonardo said:The third prize in the media category went to PhD student Martyna Kasprzyk (University of Edinburgh, UK), for her animated video on ‘Deciphering the code of protein folding’. Of opting to enter the media category, Martyna said;Congratulations again to the six winners, and don’t forget to visit our website to watch and read the outstanding winning entries in full: Science Communication Prize – Biochemical Society.

Red Light Resets the Expression Pattern, Phase, and Period of the Circadian Clock in Plants: A Computational Approach.

Simple SummaryProgress in computational biology has provided a comprehensive understanding of the dynamics of the plant circadian clock. Previously proposed models of the plant circadian clock have intended to model its entrainment using white-light/dark cycles. However, these models have failed to take into account the effect of light quality on circadian rhythms, which has been experimentally observed. In this work, we developed a computational approach to characterizing the effects of light quality on plant circadian rhythms. The results demonstrated that red light can reset the expression patterns, phases, and periods of clock component genes. The circadian period, amplitude, and phase can be co-optimized for high-quality and efficient breeding.Recent research in the fields of biochemistry and molecular biology has shown that different light qualities have extremely different effects on plant development, and optimizing light quality conditions can speed up plant growth. Clock-regulated red-light signaling, can enhance hypocotyl elongation, and increase seedling height and flower and fruit productivity. In order to investigate the effect of red light on circadian clocks in plants, a novel computational model was established. The expression profiles of the circadian element CCA1 from previous related studies were used to fit the model. The simulation results were validated by the expression patterns of CCA1 in Arabidopsis, including wild types and mutants, and by the phase shifts of CCA1 after red-light pulse. The model was used to further explore the complex responses to various photoperiods, such as the natural white-light/dark cycles, red/white/dark cycles, and extreme 24 h photoperiods. These results demonstrated that red light can reset the expression pattern, period, and phase of the circadian clock. Finally, we identified the dependence of phase shifts on the length of red-light pulse and the minimum red-light pulse length required for producing an observable phase shift. This work provides a promising computational approach to investigating the response of the circadian clock to other light qualities.

Calcium signaling in coordinating plant development, circadian oscillations and environmental stress responses in plants

Calcium (Ca 2+ ) is an intracellular second messenger involved in many signal transduction pathways in plants. The perception of environmental and internal cues leads to alterations in the cytosolic Ca 2+ signatures which translate into changes in gene expression and cellular functions. Herein, we review the novel roles of Ca 2+ signalling in coordinating plant stem cell niche homeostasis for root and shoot development. We also summarize the regulatory networks between Ca 2+ signalling and other plant signalling pathways which commence into activation or repression of genes involved in regulating vegetative to reproductive phase transition and light-mediated plant growth responses. The possible functions of Ca 2+ in the input pathway as a second messenger, external stimuli and the output of the clock regulating the rhythmicity of the plant circadian system are being reviewed. Additionally, we have also highlighted the new insights into the roles of Ca 2+ signalling components in the perception and regulation of abiotic/ biotic stress responses in plants. • Ca 2+ signalling integrates several signalling pathways in response to various environmental stimuli in plants. • Nuclear Ca 2+ signalling correlates cell activity, plant development, developmental phase transition, and hormonal homeostasis. • Ca 2+ signalling plays crucial roles in coordinating phosphorylation-mediated photoacclimation processes in plants. • Cytosolic-free Ca 2+ oscillations regulate circadian clocks in plants through Ca 2+ dependent calcium binding proteins. • Spatiotemporal regulation of Ca 2+ binding proteins couple biotic/abiotic stress responses contributing towards plant adaptation.

Development of DNA methylation-based epigenetic age predictors in loblolly pine (Pinus taeda).

Biological ageing is connected to life history variation across ecological scales and informs a basic understanding of age-related declines in organismal function. Altered DNA methylation dynamics are a conserved aspect of biological ageing and have recently been modelled to predict chronological age among vertebrate species. In addition to their utility in estimating individual age, differences between chronological and predicted ages arise due to acceleration or deceleration of epigenetic ageing, and these discrepancies are linked to disease risk and multiple life history traits. Although evidence suggests that patterns of DNA methylation can describe ageing in plants, predictions with epigenetic clocks have yet to be performed. Here, we resolve the DNA methylome across CpG, CHG, and CHH-methylation contexts in the loblolly pine tree (Pinus taeda) and construct epigenetic clocks capable of predicting ages in this species within 6% of its maximum lifespan. Although patterns of CHH-methylation showed little association with age, both CpG and CHG-methylation contexts were strongly associated with ageing, largely becoming hypomethylated with age. Among age-associated loci were those in close proximity to malate dehydrogenase, NADH dehydrogenase, and 18S and 26S ribosomal RNA genes. This study reports one of the first epigenetic clocks in plants and demonstrates the universality of age-associated DNA methylation dynamics which can inform conservation and management practices, as well as our ecological and evolutionary understanding of biological ageing in plants.

PIF-independent regulation of growth by an evening complex in the liverwort Marchantia polymorpha.

Previous studies in the liverwort Marchantia polymorpha have shown that the putative evening complex (EC) genes LUX ARRHYTHMO (LUX) and ELF4-LIKE (EFL) have a function in the liverwort circadian clock. Here, we studied the growth phenotypes of MpLUX and MpEFL loss-of-function mutants, to establish if PHYTOCHROME-INTERACTING FACTOR (PIF) and auxin act downstream of the M. polymorpha EC in a growth-related pathway similar to the one described for the flowering plant Arabidopsis. We examined growth rates and cell properties of loss-of-function mutants, analyzed protein-protein interactions and performed gene expression studies using reporter genes. Obtained data indicate that an EC can form in M. polymorpha and that this EC regulates growth of the thallus. Altered auxin levels in Mplux mutants could explain some of the phenotypes related to an increased thallus surface area. However, because MpPIF is not regulated by the EC, and because Mppif mutants do not show reduced growth, the growth phenotype of EC-mutants is likely not mediated via MpPIF. In Arabidopsis, the circadian clock regulates elongation growth via PIF and auxin, but this is likely not an evolutionarily conserved growth mechanism in land plants. Previous inventories of orthologs to Arabidopsis clock genes in various plant lineages showed that there is high levels of structural differences between clocks of different plant lineages. Here, we conclude that there is also variation in the output pathways used by the different plant clocks to control growth and development.

UBP12 and UBP13 deubiquitinases destabilize the CRY2 blue light receptor to regulate Arabidopsis growth

Light is a crucial exogenous signal sensed by cryptochrome (CRY) blue light receptors to modulate growth and the circadian clock in plants and animals. However, how CRYs interpret light quantity to regulate growth in plants remains poorly understood. Furthermore, CRY2 protein levels and activity are tightly regulated in light to fine-tune hypocotyl growth; however, details of the mechanisms that explain precise control of CRY2 levels are not fully understood. We show that in Arabidopsis, UBP12 and UBP13 deubiquitinases physically interact with CRY2 in light. UBP12/13 negatively regulates CRY2 by promoting its ubiquitination and turnover to modulate hypocotyl growth. Growth and development were explicitly affected in blue light when UBP12/13 were disrupted or overexpressed, indicating their role alongside CRY2. UBP12/13 also interacted with and stabilized COP1, which is partially required for CRY2 turnover. Our combined genetic and molecular data support a mechanistic model in which UBP12/13 interact with CRY2 and COP1, leading to the stabilization of COP1. Stabilized COP1 then promotes the ubiquitination and degradation of CRY2 under blue light. Despite decades of studies on deubiquitinases, the knowledge of how their activity is regulated is limited. Our study provides insight into how exogenous signals and ligands, along with their receptors, regulate deubiquitinase activity by protein-protein interaction. Collectively, our results provide a framework of cryptochromes and deubiquitinases to detect and interpret light signals to control plant growth at the most appropriate time.

Circadian and diel regulation of photosynthesis in the bryophyte Marchantia polymorpha.

Circadian rhythms are 24‐h biological cycles that align metabolism, physiology, and development with daily environmental fluctuations. Photosynthetic processes are governed by the circadian clock in both flowering plants and some cyanobacteria, but it is unclear how extensively this is conserved throughout the green lineage. We investigated the contribution of circadian regulation to aspects of photosynthesis in Marchantia polymorpha, a liverwort that diverged from flowering plants early in the evolution of land plants. First, we identified in M. polymorpha the circadian regulation of photosynthetic biochemistry, measured using two approaches (delayed fluorescence, pulse amplitude modulation fluorescence). Second, we identified that light‐dark cycles synchronize the phase of 24 h cycles of photosynthesis in M. polymorpha, whereas the phases of different thalli desynchronize under free‐running conditions. This might also be due to the masking of the underlying circadian rhythms of photosynthesis by light‐dark cycles. Finally, we used a pharmacological approach to identify that chloroplast translation might be necessary for clock control of light‐harvesting in M. polymorpha. We infer that the circadian regulation of photosynthesis is well‐conserved amongst terrestrial plants.