scholarly journals Characterization of Growth and Cell Cycle Events Affected by Light Intensity in the Green Alga Parachlorella kessleri: A New Model for Cell Cycle Research

Biomolecules ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 891
Author(s):  
Vilém Zachleder ◽  
Ivan N. Ivanov ◽  
Veronika Kselíková ◽  
Vitali Bialevich ◽  
Milada Vítová ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Light Intensity ◽  
Green Alga ◽  
Neutral Lipids ◽  
Growth Parameters ◽  
Daughter Cells ◽  
Light Intensities ◽  
Multiple Fission ◽  
Parachlorella Kessleri

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.

Cell cycle events in the green alga Chlamydomonas eugametos and their control by environmental factors

1992 ◽  
Vol 102 (3) ◽  
pp. 469-474
Author(s):  
V. ZACHLEDER ◽  
H. VAN DEN ENDE
Keyword(s):  
Cell Cycle ◽  
Light Intensity ◽  
Green Alga ◽  
External Energy ◽  
Endogenous Factors ◽  
Daughter Cells ◽  
Commitment Period ◽  
Light Intensities ◽  
Chlamydomonas Eugametos ◽  
Sufficient Energy

A procedure for routine synchronization of large amounts of the unicellular green alga Chlamydomonas eugametos in liquid culture by alternating light and dark periods is described. The synchronized populations were grown at various light intensities and temperatures. The effect of these variables on the lengths of parts of the cell cycle and the number of daughter cells per cell division was followed. The cell cycle of C. eugametos started with a period in which the cells increased in size only (precommitment period). The length of this period was dependent on both the light intensity and the temperature. At the end of this period, a key point of the cell cycle (called commitment point) was attained. From this point, the cell were committed to divide and cell reproduction was triggered. The following period (post-commitment period), during which daughter cells were formed, could be traversed without supply of external energy, and without further growth of the cells. However, if sufficient energy was supplied during this period, the cells were able to attain more commitment points, leading to a higher number of daughter cells. The postcommitment period was fairly constant within a certain range of light intensity. At light intensities leading to more commitment points, however, this period was prolonged. No evidence was found for circadian rhythms or endogenous factors of “Zeitgeber” type playing a role in the control of growth and reproductive sequences in the cell cycle of C. eugametos.

Wachstumsparameter in normalen und durch Actinomycin verlängerten Zellzyklen von Tetrahymena / Growth Parameters in Normal and Actinomycin-induced prolonged Cell Cycles of Tetrahymena

1969 ◽  
Vol 24 (12) ◽  
pp. 1624-1629 ◽  
Author(s):  
Günter Cleffmann
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Growth ◽  
Rna Synthesis ◽  
Growth Parameters ◽  
Average Duration ◽  
Cell Cycles ◽  
Growing Cell

Actinomycin in low concentration (0,2 μg/ml — 0,5 μg/ml) prolongs the average duration of the cell cycle of Tetrahymena considerably, but does not inhibit cell division completely. Some parameters of the growing cell have been tested in cell cycles extended in this way and compared to those of normally growing cells. The RNA synthesis of treated cells is reduced to such an extent that the RNA content per cell decreases during the prolonged cell cycle. Nevertheless cell growth, protein synthesis and DNA replication proceed at almost the same rate as in untreated cells. These findings indicate that the presence of actinomycin does not interfere with RNA fractions necessary for growth but reduce the synthesis of RNA fractions which are essential for cell division. Therefore a longer period is needed for their accumulation.

Periodic sensitivity of mechanisms of cytodifferentiation in cleaving eggs of Limnaea stagnalis

Development ◽  
1964 ◽  
Vol 12 (2) ◽  
pp. 183-195
Author(s):  
W. L. M. Geilenkirchen
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Cell Division ◽  
Dna Replication ◽  
Time Course ◽  
Chromosome Doubling ◽  
Daughter Cells ◽  
Morphogenetic Factors ◽  
Limnaea Stagnalis

Investigations on cellular reproduction have led to a highly resolved and integrated picture of the cell cycle in a morphological and physiological sense. The various preparations for division, doubling of components or syntheses, follow their own time course parallel to one another. It has become evident that the various factors involved in cell division are dissociable, for example chromosome doubling and reproduction of centrioles (Bucher & Mazia, 1960), DNA replication and protein synthesis (Zeuthen, 1961). The conditions for cell division in general are applicable to division of egg cells. However, in addition in egg cells there is a complicating system of morphogenetic factors acting, as must be postulated from the observation that in ‘mosaic’ eggs the fate of the blastomeres is fixed. In dividing eggs differences between daughter cells may be due to local differences established during oögenesis in the mother which are parcelled out during cleavages.

scholarly journals Ultradian Growth inProchlorococcus spp

1998 ◽  
Vol 64 (3) ◽  
pp. 1066-1069 ◽  
Author(s):  
Alexi Shalapyonok ◽  
Robert J. Olson ◽  
Ludmila S. Shalapyonok
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Light Intensity ◽  
Circadian Clock ◽  
Nutrient Limitation ◽  
Maximal Rate ◽  
Optimal Conditions ◽  
Dark Cycle

ABSTRACT Species of the widespread marine prokaryoteProchlorococcus exhibited ultradian growth (faster than 1 division per day) both in situ and in culture, even though cell division is strictly phased to the light-dark cycle. Under optimal conditions a second DNA replication and cell division closely followed, but did not overlap with, the first division. The timing of cell cycle events was not affected by light intensity or duration, suggesting control by a light-triggered timer or circadian clock rather than by completion of a light-dependent assimilation phase. This mode of ultradian growth has not been observed previously and poses new questions about the regulation of cellular rhythms in prokaryotes. In addition, it implies that conclusions regarding the lack of nutrient limitation of Prochlorococcus in the open ocean, which were based on the appearance that cells were growing at their maximal rate, need to be reconsidered.

scholarly journals DNA replication and mitotic entry: A brake model for cell cycle progression

2019 ◽  
Vol 218 (12) ◽  
pp. 3892-3902 ◽  
Author(s):  
Bennie Lemmens ◽  
Arne Lindqvist
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Cycle Model ◽  
Cycle Progression ◽  
Daughter Cells ◽  
Core Function ◽  
A Cell

The core function of the cell cycle is to duplicate the genome and divide the duplicated DNA into two daughter cells. These processes need to be carefully coordinated, as cell division before DNA replication is complete leads to genome instability and cell death. Recent observations show that DNA replication, far from being only a consequence of cell cycle progression, plays a key role in coordinating cell cycle activities. DNA replication, through checkpoint kinase signaling, restricts the activity of cyclin-dependent kinases (CDKs) that promote cell division. The S/G2 transition is therefore emerging as a crucial regulatory step to determine the timing of mitosis. Here we discuss recent observations that redefine the coupling between DNA replication and cell division and incorporate these insights into an updated cell cycle model for human cells. We propose a cell cycle model based on a single trigger and sequential releases of three molecular brakes that determine the kinetics of CDK activation.

scholarly journals Growth under Different Trophic Regimes and Synchronization of the Red Microalga Galdieria sulphuraria

Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 939
Author(s):  
Vít Náhlík ◽  
Vilém Zachleder ◽  
Mária Čížková ◽  
Kateřina Bišová ◽  
Anjali Singh ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Optimal Conditions ◽  
Galdieria Sulphuraria ◽  
Light Phase ◽  
Dark Cycle ◽  
Important Species ◽  
Daughter Cells ◽  
Multiple Fission ◽  
Red Microalga ◽  
Mother Cell Wall

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.

scholarly journals Light intensity and spectral composition drive reproductive success in the marine benthic diatom Seminavis robusta

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gust Bilcke ◽  
Lore Van Craenenbroeck ◽  
Alexandre Castagna ◽  
Cristina Maria Osuna-Cruz ◽  
Klaas Vandepoele ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Light Intensity ◽  
Sexual Reproduction ◽  
Current Model ◽  
Incident Light ◽  
Flow Cytometric Analysis ◽  
Spectral Composition ◽  
Benthic Diatom ◽  
Cycle Phase ◽  
Light Intensities

AbstractThe properties of incident light play a crucial role in the mating process of diatoms, a group of ecologically important microalgae. While species-specific requirements for light intensity and photoperiod have been observed in several diatom species, little is known about the light spectrum that allows sexual reproduction. Here, we study the effects of spectral properties and light intensity on the initiation and progression of sexual reproduction in the model benthic diatom Seminavis robusta. We found that distinct stages of the mating process have different requirements for light. Vigorous mating pair formation occurred under a broad range of light intensities, ranging from 10 to 81 µE m−2 s−1, while gametogenesis and subsequent stages were strongly affected by moderate light intensities of 27 µE m−2 s−1 and up. In addition, light of blue or blue–green wavelengths was required for the formation of mating pairs. Combining flow cytometric analysis with expression profiling of the diatom-specific cyclin dsCyc2 suggests that progression through a blue light-dependent checkpoint in the G1 cell cycle phase is essential for induction of sexual reproduction. Taken together, we expand the current model of mating in benthic pennate diatoms, which relies on the interplay between light, cell cycle and sex pheromone signaling.

scholarly journals Supra-Optimal Temperature: An Efficient Approach for Overaccumulation of Starch in the Green Alga Parachlorella kessleri

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1806
Author(s):  
Vilém Zachleder ◽  
Veronika Kselíková ◽  
Ivan N. Ivanov ◽  
Vitali Bialevich ◽  
Milada Vítová ◽  
...  
Keyword(s):  
Green Alga ◽  
Time Course ◽  
Neutral Lipids ◽  
Incident Light ◽  
Energy Reserves ◽  
Optimal Temperature ◽  
Algal Biotechnology ◽  
Cell Reproduction ◽  
Parachlorella Kessleri ◽  
Synchronized Cultures

Green algae are fast-growing microorganisms that are considered promising for the production of starch and neutral lipids, and the chlorococcal green alga Parachlorella kessleri is a favorable model, as it can produce both starch and neutral lipids. P. kessleri commonly divides into more than two daughter cells by a specific mechanism—multiple fission. Here, we used synchronized cultures of the alga to study the effects of supra-optimal temperature. Synchronized cultures were grown at optimal (30 °C) and supra-optimal (40 °C) temperatures and incident light intensities of 110 and 500 μmol photons m−2 s−1. The time course of cell reproduction (DNA replication, cellular division), growth (total RNA, protein, cell dry matter, cell size), and synthesis of energy reserves (net starch, neutral lipid) was studied. At 40 °C, cell reproduction was arrested, but growth and accumulation of energy reserves continued; this led to the production of giant cells enriched in protein, starch, and neutral lipids. Furthermore, we examined whether the increased temperature could alleviate the effects of deuterated water on Parachlorella kessleri growth and division; results show that supra-optimal temperature can be used in algal biotechnology for the production of protein, (deuterated) starch, and neutral lipids.

scholarly journals CcrZ is a pneumococcal spatiotemporal cell cycle regulator that interacts with FtsZ and controls DNA replication by modulating the activity of DnaA

2021 ◽  
Author(s):  
Clement Gallay ◽  
Stefano Sanselicio ◽  
Mary E. Anderson ◽  
Young Min Soh ◽  
Xue Liu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Daughter Cells ◽  
Cell Cycle Regulator ◽  
Regulator Protein ◽  
Cytoskeleton Protein ◽  
Initiation Of Dna Replication ◽  
Bacterial Cell Cycle ◽  
The Right

AbstractMost bacteria replicate and segregate their DNA concomitantly while growing, before cell division takes place. How bacteria synchronize these different cell cycle events to ensure faithful chromosome inheritance by daughter cells is poorly understood. Here, we identify Cell Cycle Regulator protein interacting with FtsZ (CcrZ) as a conserved and essential protein in pneumococci and related Firmicutes such as Bacillus subtilis and Staphylococcus aureus. CcrZ couples cell division with DNA replication by controlling the activity of the master initiator of DNA replication, DnaA. The absence of CcrZ causes mis-timed and reduced initiation of DNA replication, which subsequently results in aberrant cell division. We show that CcrZ from Streptococcus pneumoniae interacts directly with the cytoskeleton protein FtsZ, which places CcrZ in the middle of the newborn cell where the DnaA-bound origin is positioned. This work uncovers a mechanism for control of the bacterial cell cycle in which CcrZ controls DnaA activity to ensure that the chromosome is replicated at the right time during the cell cycle.

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