Epigenetic silencing is essential for regulating gene expression and cellular diversity in eukaryotes. While DNA and H3K9 methylation silence transposable elements (TEs), H3K27me3 marks deposited by the Polycomb repressive complex 2 (PRC2) silence varying proportions of TEs and genes across different lineages. Despite the major development role epigenetic silencing plays in multicellular eukaryotes, little is known about how epigenetic regulatory networks were shaped over evolutionary time. Here, we analyze epigenomes from diverse species across the green lineage to infer the chronological epigenetic recruitment of genes during land plant evolution. We first reveal the nature of plant heterochromatin in the unicellular chlorophyte microalga Chlorella sorokiniana and identify several genes marked with H3K27me3, highlighting the deep origin of PRC2-regulated genes in the green lineage. By incorporating genomic phylostratigraphy, we show how genes of differing evolutionary age occupy distinct epigenetic states in plants. While young genes tend to be silenced by H3K9 methylation, genes that emerged in land plants are preferentially marked with H3K27me3, some of which form part of a common network of PRC2-repressed genes across distantly related species. Finally, we analyze the potential recruitment of PRC2 to plant H3K27me3 domains and identify conserved DNA-binding sites of ancient transcription factor families known to interact with PRC2. Our findings shed light on the conservation and potential origin of epigenetic regulatory networks in the green lineage, while also providing insight into the evolutionary dynamics and molecular triggers that underlie the adaptation and elaboration of epigenetic regulation, laying the groundwork for its future consideration in other eukaryotic lineages.

• Klíčová slova
• epigenetics, gene regulation, green algae, plant evolution,
• MeSH
• biologická evoluce * MeSH
• epigeneze genetická * MeSH
• genové regulační sítě * MeSH
• histony metabolismus   MeSH
• metylace DNA MeSH
• molekulární evoluce * MeSH
• vyšší rostliny * genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• histony MeSH

The production of organic deuterated compounds in microalgal systems represents a cheaper and more versatile alternative to more complicated chemical synthesis. In the present study, we investigate the autotrophic growth of two microalgae, Chlamydomonas reinhardtii and Desmodesmus quadricauda, in medium containing high doses of deuterated water, D2O. The growth of such cultures was evaluated in the context of the intensity of incident light, since light is a critical factor in the management of autotrophic algal cultures. Deuteration increases the light sensitivity of both model organisms, resulting in increased levels of singlet oxygen and poorer photosynthetic performance. Our results also show a slowdown in growth and cell division processes with increasing D2O concentrations. At the same time, impaired cell division leads to cell enlargement and accumulation of highly deuterated compounds, especially energy-storing molecules. Thus, considering the specifics of highly deuterated cultures and using the growth conditions proposed in this study, it is possible to obtain highly deuterated algal biomass, which could be a valuable source of deuterated organic compounds.

• Klíčová slova
• cell division, deuterated compounds, deuterium, light intensity, microalgae, physical stress,
• Publikační typ
• časopisecké články MeSH

The structural challenges faced by eukaryotic cells through the cell cycle are key for understanding cell viability and proliferation. We tested the hypothesis that the biosynthesis of structural lipids is linked to the cell cycle. If true, this would suggest that the cell's structure is important for progress through and perhaps even control of the cell cycle. Lipidomics (31P NMR and MS), proteomics (Western immunoblotting) and transcriptomics (RT-qPCR) techniques were used to profile the lipid fraction and characterise aspects of its metabolism at seven stages of the cell cycle of the model eukaryote, Desmodesmus quadricauda. We found considerable, transient increases in the abundance of phosphatidylethanolamine during the G1 phase (+35%, ethanolamine phosphate cytidylyltransferase increased 2·5×) and phosphatidylglycerol (+100%, phosphatidylglycerol synthase increased 22×) over the G1/pre-replication phase boundary. The relative abundance of phosphatidylcholine fell by ~35% during the G1. N-Methyl transferases for the conversion of phosphatidylethanolamine into phosphatidylcholine were not found in the de novo transcriptome profile, though a choline phosphate transferase was found, suggesting that the Kennedy pathway is the principal route for the synthesis of PC. The fatty acid profiles of the four most abundant lipids suggested that these lipids were not generally converted between one another. This study shows for the first time that there are considerable changes in the biosynthesis of the three most abundant phospholipid classes in the normal cell cycle of D. quadricauda, by margins large enough to elicit changes to the physical properties of membranes.

• Klíčová slova
• Cell cycle, Cell division, Cell structure, Desmodesmus quadricauda, Green algae, Lipid composition, Lipid metabolism,
• MeSH
• buněčný cyklus * MeSH
• fosfatidylcholiny metabolismus   biosyntéza   MeSH
• fosfatidylethanolaminy metabolismus   biosyntéza   MeSH
• fosfolipidy * metabolismus   biosyntéza   MeSH
• lipidomika metody   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• fosfatidylcholiny MeSH
• fosfatidylethanolaminy MeSH
• fosfolipidy * MeSH
• phosphatidylethanolamine MeSH Prohlížeč

The aim of the study was to verify the hypothesis that a potential cause of the phytotoxicity of diclofenac (DCF, a non-steroidal anti-inflammatory drug) is an effect of cell cycle progression. This research was conducted using synchronous cultures of a model organism, green alga Chlamydomonas reinhardtii. The project examined DCF effects on selected parameters that characterize cell cycle progression, such as cell size, attainment of commitment points, DNA replication, number of nuclei formed during cells division and morphology of cells in consecutive stages of the cell cycle, together with the physiological and biochemical parameters of algae cells at different stages. We demonstrated that individual cell growth remained unaffected, whereas cell division was delayed in the DCF-treated groups grown in continuous light conditions, and the number of daughter cells from a single cell decreased. Thus, the cell cycle progression is a target affected by DCF, which has a similar anti-proliferative effect on mammalian cells.

• Klíčová slova
• Chlamydomonas reinhardtii, cell cycle, diclofenac, non-steroidal anti-inflammatory drug,
• MeSH
• antiflogistika nesteroidní toxicita   MeSH
• buněčné dělení účinky léků   MeSH
• buněčný cyklus účinky léků   MeSH
• Chlamydomonas reinhardtii účinky léků   genetika   růst a vývoj   MeSH
• diklofenak toxicita   MeSH
• DNA rostlinná biosyntéza   genetika   MeSH
• fotosyntéza účinky léků   MeSH
• replikace DNA účinky léků   MeSH
• velikost buňky účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antiflogistika nesteroidní MeSH
• diklofenak MeSH
• DNA rostlinná MeSH

The extremophilic unicellular red microalga Galdieria sulphuraria (Cyanidiophyceae) is able to grow autotrophically, or mixo- and heterotrophically with 1% glycerol as a carbon source. The alga divides by multiple fission into more than two cells within one cell cycle. The optimal conditions of light, temperature and pH (500 µmol photons m-2 s-1, 40 °C, and pH 3; respectively) for the strain Galdieria sulphuraria (Galdieri) Merola 002 were determined as a basis for synchronization experiments. For synchronization, the specific light/dark cycle, 16/8 h was identified as the precondition for investigating the cell cycle. The alga was successfully synchronized and the cell cycle was evaluated. G. sulphuraria attained two commitment points with midpoints at 10 and 13 h of the cell cycle, leading to two nuclear divisions, followed subsequently by division into four daughter cells. The daughter cells stayed in the mother cell wall until the beginning of the next light phase, when they were released. Accumulation of glycogen throughout the cell cycle was also described. The findings presented here bring a new contribution to our general understanding of the cell cycle in cyanidialean red algae, and specifically of the biotechnologically important species G. sulphuraria.

• Klíčová slova
• Galdieria, cell cycle, cell division, growth, light intensity, red algae, synchronization, temperature, trophic regimes,
• MeSH
• buněčný cyklus fyziologie   MeSH
• heterotrofní procesy fyziologie   MeSH
• kultivované buňky MeSH
• mikrořasy cytologie   růst a vývoj   MeSH
• Rhodophyta cytologie   růst a vývoj   MeSH
• teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Multiple fission is a cell cycle variation leading to the production of more than two daughter cells. Here, we used synchronized cultures of the chlorococcal green alga Parachlorella kessleri to study its growth and pattern of cell division under varying light intensities. The time courses of DNA replication, nuclear and cellular division, cell size, total RNA, protein content, dry matter and accumulation of starch were observed at incident light intensities of 110, 250 and 500 µmol photons m-2s-1. Furthermore, we studied the effect of deuterated water on Parachlorella kessleri growth and division, to mimic the effect of stress. We describe a novel multiple fission cell cycle pattern characterized by multiple rounds of DNA replication leading to cell polyploidization. Once completed, multiple nuclear divisions were performed with each of them, immediately followed by protoplast fission, terminated by the formation of daughter cells. The multiple fission cell cycle was represented by several consecutive doublings of growth parameters, each leading to the start of a reproductive sequence. The number of growth doublings increased with increasing light intensity and led to division into more daughter cells. This study establishes the baseline for cell cycle research at the molecular level as well as for potential biotechnological applications, particularly directed synthesis of (deuterated) starch and/or neutral lipids as carbon and energy reserves.

• Klíčová slova
• Parachlorella kessleri, cell cycle pattern, deuterated lipid, deuterated starch, deuterium, energy reserves, growth processes, light intensity, reproduction events,
• MeSH
• buněčné kultury * MeSH
• buněčný cyklus * MeSH
• Chlorophyta růst a vývoj   MeSH
• světlo * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Extensive in vivo replacement of hydrogen by deuterium, a stable isotope of hydrogen, induces a distinct stress response, reduces cell growth and impairs cell division in various organisms. Microalgae, including Chlamydomonas reinhardtii, a well-established model organism in cell cycle studies, are no exception. Chlamydomonas reinhardtii, a green unicellular alga of the Chlorophyceae class, divides by multiple fission, grows autotrophically and can be synchronized by alternating light/dark regimes; this makes it a model of first choice to discriminate the effect of deuterium on growth and/or division. Here, we investigate the effects of high doses of deuterium on cell cycle progression in C. reinhardtii. Synchronous cultures of C. reinhardtii were cultivated in growth medium containing 70 or 90% D2O. We characterize specific deuterium-induced shifts in attainment of commitment points during growth and/or division of C. reinhardtii, contradicting the role of the "sizer" in regulating the cell cycle. Consequently, impaired cell cycle progression in deuterated cultures causes (over)accumulation of starch and lipids, suggesting a promising potential for microalgae to produce deuterated organic compounds.

• Klíčová slova
• Chlamydomonas reinhardtii, cell cycle, cell division, commitment point, deuterium, heavy water, multiple fission, stress,
• MeSH
• buněčné dělení účinky léků   MeSH
• buněčný cyklus účinky léků   MeSH
• Chlamydomonas reinhardtii růst a vývoj   metabolismus   MeSH
• deuterium škodlivé účinky   chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• deuterium MeSH

Photosynthetic energy conversion and the resulting photoautotrophic growth of green algae can only occur in daylight, but DNA replication, nuclear and cellular divisions occur often during the night. With such a light/dark regime, an algal culture becomes synchronized. In this study, using synchronized cultures of the green alga Desmodesmus quadricauda, the dynamics of starch, lipid, polyphosphate, and guanine pools were investigated during the cell cycle by two independent methodologies; conventional biochemical analyzes of cell suspensions and confocal Raman microscopy of single algal cells. Raman microscopy reports not only on mean concentrations, but also on the distribution of pools within cells. This is more sensitive in detecting lipids than biochemical analysis, but both methods-as well as conventional fluorescence microscopy-were comparable in detecting polyphosphates. Discrepancies in the detection of starch by Raman microscopy are discussed. The power of Raman microscopy was proven to be particularly valuable in the detection of guanine, which was traceable by its unique vibrational signature. Guanine microcrystals occurred specifically at around the time of DNA replication and prior to nuclear division. Interestingly, guanine crystals co-localized with polyphosphates in the vicinity of nuclei around the time of nuclear division.

• Klíčová slova
• Desmodesmus quadricauda, cell cycle, confocal Raman microscopy, guanine, lipids, microalgae, polyphosphate, starch,
• MeSH
• buněčná stěna chemie   MeSH
• buněčný cyklus * MeSH
• časové faktory MeSH
• Chlorophyta cytologie   růst a vývoj   MeSH
• guanin analýza   MeSH
• lipidová tělíska metabolismus   MeSH
• lipidy analýza   MeSH
• mikroskopie * MeSH
• polyfosfáty analýza   MeSH
• Ramanova spektroskopie * MeSH
• škrob analýza   MeSH
• velikost buňky MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• guanin MeSH
• lipidy MeSH
• polyfosfáty MeSH
• škrob MeSH

Temperature is one of the key factors affecting growth and division of algal cells. High temperature inhibits the cell cycle in Chlamydomonas reinhardtii. At 39 °C, nuclear and cellular divisions in synchronized cultures were blocked completely, while DNA replication was partly affected. In contrast, growth (cell volume, dry matter, total protein, and RNA) remained unaffected, and starch accumulated at very high levels. The cell cycle arrest could be removed by transfer to 30 °C, but a full recovery occurred only in cultures cultivated up to 14 h at 39 °C. Thereafter, individual cell cycle processes began to be affected in sequence; daughter cell release, cell division, and DNA replication. Cell cycle arrest was accompanied by high mitotic cyclindependent kinase activity that decreased after completion of nuclear and cellular division following transfer to 30 °C. Cell cycle arrest was, therefore, not caused by a lack of cyclin-dependent kinase activity but rather a blockage in downstream processes.

• Klíčová slova
• Chlamydomonas reinhardtii, DNA replication, cell cycle arrest, cell size, cyclin-dependent kinase, starch accumulation, supraoptimal temperature, synchronized cultures,
• MeSH
• bílkoviny řas metabolismus   MeSH
• buněčné kultury metody   MeSH
• Chlamydomonas reinhardtii cytologie   fyziologie   MeSH
• cyklin-dependentní kinasy metabolismus   MeSH
• down regulace MeSH
• fyziologický stres MeSH
• kontrolní body buněčného cyklu * MeSH
• regulace genové exprese u rostlin MeSH
• vysoká teplota MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bílkoviny řas MeSH
• cyklin-dependentní kinasy MeSH

DNA damage is a ubiquitous threat endangering DNA integrity in all living organisms. Responses to DNA damage include, among others, induction of DNA repair and blocking of cell cycle progression in order to prevent transmission of damaged DNA to daughter cells. Here, we tested the effect of the antibiotic zeocin, inducing double stranded DNA breaks, on the cell cycle of synchronized cultures of the green alga Chlamydomonas reinhardtii. After zeocin application, DNA replication partially occurred but nuclear and cellular divisions were completely blocked. Application of zeocin combined with caffeine, known to alleviate DNA checkpoints, decreased cell viability significantly. This was probably caused by a partial overcoming of the cell cycle progression block in such cells, leading to aberrant cell divisions. The cell cycle block was accompanied by high steady state levels of mitotic cyclin-dependent kinase activity. The data indicate that DNA damage response in C. reinhardtii is connected to the cell cycle block, accompanied by increased and stabilized mitotic cyclin-dependent kinase activity.

• Klíčová slova
• Chlamydomonas reinhardtii, DNA damage, caffeine, cell cycle, cyclin-dependent kinase, double-stranded break, zeocin,
• MeSH
• bleomycin toxicita   MeSH
• Chlamydomonas reinhardtii účinky léků   genetika   MeSH
• cyklin-dependentní kinasy metabolismus   MeSH
• cytostatické látky toxicita   MeSH
• DNA rostlinná účinky léků   MeSH
• dvouřetězcové zlomy DNA MeSH
• kofein farmakologie   MeSH
• kontrolní body buněčného cyklu MeSH
• mutageny toxicita   MeSH
• replikace DNA MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• bleomycin MeSH
• cyklin-dependentní kinasy MeSH
• cytostatické látky MeSH
• DNA rostlinná MeSH
• kofein MeSH
• mutageny MeSH
• Zeocin MeSH Prohlížeč