scholarly journals The Cell Division Cycle of Euglena gracilis Indicates That the Level of Circadian Plasticity to the External Light Regime Changes in Prolonged-Stationary Cultures

Plants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1475
Author(s):  
Shota Kato ◽  
Hong Gil Nam
Keyword(s):  
Cell Division ◽  
Circadian Rhythms ◽  
Euglena Gracilis ◽  
Cell Cycle Progression ◽  
Light Signal ◽  
Cell Division Cycle ◽  
Regime Changes ◽  
Fitness Advantage ◽  
Subjective Night ◽  
Free Running

In unicellular photosynthetic organisms, circadian rhythm is tightly linked to gating of cell cycle progression, and is entrained by light signal. As several organisms obtain a fitness advantage when the external light/dark cycle matches their endogenous period, and aging alters circadian rhythms, senescence phenotypes of the microalga Euglena gracilis of different culture ages were characterized with respect to the cell division cycle. We report here the effects of prolonged-stationary-phase conditions on the cell division cycles of E. gracilis under non-24-h light/dark cycles (T-cycles). Under T-cycles, cells established from 1-month-old and 2-month-old cultures produced lower cell concentrations after cultivation in the fresh medium than cells from 1-week-old culture. This decrease was not due to higher concentrations of dead cells in the populations, suggesting that cells of different culture ages differ in their capacity for cell division. Cells from 1-week-old cultures had a shorter circadian period of their cell division cycle under shortened T-cycles than aged cells. When algae were transferred to free-running conditions after entrainment to shortened T-cycles, the young cells showed the peak growth rate at a time corresponding to the first subjective night, but the aged cells did not. This suggests that circadian rhythms are more plastic in younger E. gracilis cells.

Circadian changes in cyclic AMP levels in synchronously dividing and stationary-phase cultures of the achlorophyllous ZC mutant of Euglena gracilis

1989 ◽  
Vol 94 (2) ◽  
pp. 267-272
Author(s):  
ISABELLE A. CARRÉ ◽  
DANIELLE L. LAVAL-MARTIN ◽  
LELAND N. EDMUNDS
Keyword(s):  
Cell Division ◽  
Cyclic Amp ◽  
Euglena Gracilis ◽  
Phase Response Curve ◽  
Circadian Variation ◽  
Light Signal ◽  
Circadian Oscillator ◽  
Circadian Oscillation ◽  
Continuous Darkness ◽  
Free Running

Oscillations in adenosine 3′,5′-cyclic monophosphate (cyclic AMP) level have been proposed to be part of the biochemical feed-back loop(s), or ‘clock(8)’, believed to underlie circadian rhythmicity. This possibility has been examined for a cellular circadian oscillator in synchronously dividing (or nondividing) cultures of the photosynthesis- deficient ZC mutant of the alga Euglena gracilis Klebs (Z). We have demonstrated a bimodal, autonomously oscillating, circadian variation of cyclic AMP content in this unicell. Rhythmic changes of the cyclic AMP level, which may reflect the transition of the cell population through the different phases of the cell division cycle (CDC) in division-phased cultures, also persisted after the culture medium had become limiting and the cells had stopped dividing. We have also shown that the free-running, circadian oscillation of cyclic AMP content displayed by nondividing cells in continuous darkness could be phase-shifted by a light signal (a property inherent to most circadian systems), in a manner that could be predicted from the phase-response curve previously obtained for the cell division rhythm in the ZC mutant. These results suggest a possible role for cyclic AMP, either as an element of the coupling pathway for the control of the CDC by the circadian oscillator, or as a ‘gear’ of the clock itself.

scholarly journals Dissociating the Centrosomal Matrix Protein AKAP450 from Centrioles Impairs Centriole Duplication and Cell Cycle Progression

2003 ◽  
Vol 14 (6) ◽  
pp. 2436-2446 ◽  
Author(s):  
Guy Keryer ◽  
Oliwia Witczak ◽  
Annie Delouvée ◽  
Wolfram A. Kemmner ◽  
Danielle Rouillard ◽  
...  
Keyword(s):  
Cell Division ◽  
Hela Cells ◽  
Cellular Localization ◽  
Cell Cycle Progression ◽  
Matrix Protein ◽  
Coiled Coil ◽  
Cell Division Cycle ◽  
Scaffolding Protein ◽  
Centriole Duplication ◽  
C Terminus

Centrosomes provide docking sites for regulatory molecules involved in the control of the cell division cycle. The centrosomal matrix contains several proteins, which anchor kinases and phosphatases. The large A-Kinase Anchoring Protein AKAP450 is acting as a scaffolding protein for other components of the cell signaling machinery. We selectively perturbed the centrosome by modifying the cellular localization of AKAP450. We report that the expression in HeLa cells of the C terminus of AKAP450, which contains the centrosome-targeting domain of AKAP450 but not its coiled-coil domains or binding sites for signaling molecules, leads to the displacement of the endogenous centrosomal AKAP450 without removing centriolar or pericentrosomal components such as centrin, γ-tubulin, or pericentrin. The centrosomal protein kinase A type II α was delocalized. We further show that this expression impairs cytokinesis and increases ploidy in HeLa cells, whereas it arrests diploid RPE1 fibroblasts in G1, thus further establishing a role of the centrosome in the regulation of the cell division cycle. Moreover, centriole duplication is interrupted. Our data show that the association between centrioles and the centrosomal matrix protein AKAP450 is critical for the integrity of the centrosome and for its reproduction.

scholarly journals Regulation of cell division cycle progression by bcl-2 expression: a potential mechanism for inhibition of programmed cell death.

1996 ◽  
Vol 183 (5) ◽  
pp. 2219-2226 ◽  
Author(s):  
S Mazel ◽  
D Burtrum ◽  
H T Petrie
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cell Division ◽  
Programmed Cell Death ◽  
Cell Cycle Progression ◽  
Control Point ◽  
Cell Division Cycle ◽  
Cell Cycle Distribution ◽  
Cycle Progression ◽  
Critical Control Point

Expression of the bcl-2 gene has been shown to effectively confer resistance to programmed cell death under a variety of circumstances. However, despite a wealth of literature describing this phenomenon, very little is known about the mechanism of resistance. In the experiments described here, we show that bcl-2 gene expression can result in an inhibition of cell division cycle progression. These findings are based upon the analysis of cell cycle distribution, cell cycle kinetics, and relative phosphorylation of the retinoblastoma tumor suppressor protein, using primary tissues in vivo, ex vivo, and in vitro, as well as continuous cell lines. The effects of bcl-2 expression on cell cycle progression appear to be focused at the G1 to S phase transition, which is a critical control point in the decision between continued cell cycle progression or the induction programmed cell death. In all systems tested, bcl-2 expression resulted in a substantial 30-60% increase in the length of G1 phase; such an increase is very substantial in the context of other regulators of cell cycle progression. Based upon our findings, and the related findings of others, we propose a mechanism by which bcl-2 expression might exert its well known inhibition of programmed cell death by regulating the kinetics of cell cycle progression at a critical control point.

scholarly journals Is the cell division cycle gated by a circadian clock? The case of Chlamydomonas reinhardtii.

1995 ◽  
Vol 129 (4) ◽  
pp. 1061-1069 ◽  
Author(s):  
K Goto ◽  
C H Johnson
Keyword(s):  
Cell Division ◽  
Circadian Clock ◽  
Chlamydomonas Reinhardtii ◽  
Cell Division Cycle ◽  
Circadian Rhythmicity ◽  
Circadian Period ◽  
Circadian Oscillators ◽  
A Cell ◽  
Free Running

Circadian oscillators are known to regulate the timing of cell division in many organisms. In the case of Chlamydomonas reinhardtii, however, this conclusion has been challenged by several investigators. We have reexamined this issue and find that the division behavior of Chlamydomonas meets all the criteria for circadian rhythmicity: persistence of a cell division rhythm (a) with a period of approximately 24 h under free-running conditions, (b) that is temperature compensated, and (c) which can entrain to light/dark signals. In addition, a mutation that lengthens the circadian period of the phototactic rhythm similarly affects the cell division rhythm. We conclude that a circadian mechanism determines the timing of cell division in Chlamydomonas reinhardtii.

scholarly journals Multiple layers of phospho-regulation coordinate metabolism and the cell cycle in budding yeast

2019 ◽  
Author(s):  
Lichao Zhang ◽  
Sebastian Winkler ◽  
Fabian Schlottmann ◽  
Oliver Kohlbacher ◽  
Josh E. Elias ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Progression ◽  
Budding Yeast ◽  
Cell Metabolism ◽  
Acid Synthesis ◽  
Metabolic Enzymes ◽  
Cell Division Cycle ◽  
Amino Acid Synthesis ◽  
Metabolic Fluxes

AbstractThe coordination of metabolism and growth with cell division is crucial for proliferation. While it has long been known that cell metabolism regulates the cell division cycle, it is becoming increasingly clear that the cell division cycle also regulates metabolism. In budding yeast, we previously showed that over half of all measured metabolites change concentration through the cell cycle indicating that metabolic fluxes are extensively regulated during cell cycle progression. However, how this regulation is achieved still remains poorly understood. Since both the cell cycle and metabolism are regulated to a large extent by protein phosphorylation, we here decided to measure the phosphoproteome through the budding yeast cell cycle. Specifically, we chose a cell cycle synchronisation strategy that avoids stress and nutrient-related perturbations of metabolism, and we grew the yeast on ethanol minimal medium to force cells to utilize their full biosynthetic repertoire. Using a tandem-mass-tagging approach, we found over 200 sites on metabolic enzymes and transporters to be phospho-regulated. These sites were distributed among many pathways including carbohydrate catabolism, lipid metabolism and amino acid synthesis and therefore likely contribute to changing metabolic fluxes through the cell cycle. Among all one thousand sites whose phosphorylation increases through the cell cycle, the CDK consensus motif and an arginine-directed motif were highly enriched. This arginine-directed R-R-x-S motif is associated with protein-kinase A, which regulates metabolism and promotes growth. Finally, we also found over one thousand sites that are dephosphorylated through the G1/S transition. We speculate that the phosphatase Glc7/ PP1, known to regulate both the cell cycle and carbon metabolism, may play an important role because its regulatory subunits are phospho-regulated in our data. In summary, our results identify extensive cell cycle dependent phosphorylation and dephosphorylation of metabolic enzymes and suggest multiple mechanisms through which the cell division cycle regulates metabolic signalling pathways to temporally coordinate biosynthesis with distinct phases of the cell division cycle.

System Analysis of the Circadian Rhythm of Euglena gracilis, II: Masking Effects and Mutual Interactions of Light and Temperature Responses

1984 ◽  
Vol 39 (7-8) ◽  
pp. 801-811 ◽  
Author(s):  
T. Kreuels ◽  
R. Joerres ◽  
W. Martin ◽  
K. Brinkmann
Keyword(s):  
Circadian Rhythms ◽  
Euglena Gracilis ◽  
System Analysis ◽  
Limited Range ◽  
Circadian System ◽  
System A ◽  
Input Signals ◽  
Free Running ◽  
Single Input ◽  
White Mutant

Abstract Motility of Euglena gracilis shows free running circadian rhythms. The circadian system is sensitive to light and temperature signals, but it is always masked by direct responses of motility to light (photokinesis) and temperature (thermokinesis). By means of a compartimental model which defines the interrelations between the pathways of thermokinesis, photokinesis and the circadian system a unifying view of effects of temperature and light input signals is outlined. According to the model, and using double sine input signals the dynamics of thermokinesis is described by a differential amplifier with constant gain. Although thermokinesis heavily masks circadian responses to temperature signals, the limited range of circadian entrainment is indirectly demonstrated by a limited reappearance of free running circadian oscillations after stopping the temperature program. Free running circadian oscillations do reappear only after pretreatment with temperature periods near the circadian eigenperiod.A white mutant lacking photosynthesis is used to investigate the role of photosynthesis in the signal processing. Although light synchronizes the circadian rhythms of the white mutant if applied as single input, it does not affect the motility if applied together with temperature inputs near the circadian eigenperiod. These results indicate frequency dependent mutual interactions between the model compartments.

Modelling the controls of the eukaryotic cell cycle

2003 ◽  
Vol 31 (6) ◽  
pp. 1526-1529 ◽  
Author(s):  
B. Novák ◽  
J.J. Tyson
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Mathematical Modelling ◽  
Dynamic Characteristics ◽  
Cell Cycle Progression ◽  
Eukaryotic Cell ◽  
Cell Division Cycle ◽  
Comprehensive Model ◽  
Cycle Progression

The eukaryotic cell-division cycle is regulated by three modules that control G1/S, G2/M and meta/anaphase transitions. By using mathematical modelling, we show the dynamic characteristics of these individual modules and we also assemble them together into a comprehensive model of the eukaryotic cell-division cycle. With this comprehensive model, we also discuss the mechanisms by which different checkpoint pathways stabilize different cell-cycle states and inhibit the transitions that drive cell-cycle progression.

scholarly journals Identification of circadian rhythms in Nannochloropsis species using bioluminescence reporter lines

2019 ◽  
Author(s):  
Eric Poliner ◽  
Cameron Cummings ◽  
Linsey Newton ◽  
Eva M. Farré
Keyword(s):  
Cell Division ◽  
Circadian Rhythms ◽  
Molecular Mechanisms ◽  
Environmental Changes ◽  
Firefly Luciferase ◽  
Constant Light ◽  
Future Studies ◽  
Circadian Oscillators ◽  
Free Running

SummaryCircadian clocks allow organisms to predict environmental changes caused by the rotation of the Earth. Although circadian rhythms are widespread among different taxa, the core components of circadian oscillators are not conserved and differ between bacteria, plants, animals and fungi. Stramenopiles are a large group of organisms in which circadian rhythms have been only poorly characterized and no clock components have been identified. We have investigated cell division and molecular rhythms in Nannochloropsis species. In the four strains tested, cell division occurred principally during the night period under diel conditions, however, rhythms dampened within 2-3 days after transfer to constant light. We developed firefly luciferase reporters for long-term monitoring of in vivo transcriptional rhythms in two Nannochlropsis species, N. oceanica CCMP1779 and N. salina CCMP537. The reporter lines express free-running bioluminescence rhythms with periods of ~21-31 h that dampen within ~3-4 days under constant light. Using different entrainment regimes, we demonstrate that these rhythms are regulated by a circadian-type oscillator. In addition, the phase of free-running luminescence rhythms can be modulated pharmacologically using a CK1 ε/δ inhibitor, suggesting a role of this kinase in the Nannochloropsis clock. Together with the molecular and genomic tools available for Nannochloropsis species, these reporter lines represent an excellent system for future studies on the molecular mechanisms of stramenopile circadian oscillators.Significance statementStramenopiles are a large and diverse line of eukaryotes in which circadian rhythms have been only poorly characterized and no clock components have been identified. We have developed bioluminescence reporter lines in Nannochloropsis species and provide evidence for the presence of a circadian oscillator in stramenopiles; these lines will serve as tools for future studies to uncover the molecular mechanisms of circadian oscillations in these species.

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