scholarly journals Cell size controlled in plants using DNA content as an internal scale

Science ◽  
2021 ◽  
Vol 372 (6547) ◽  
pp. 1176-1181
Author(s):  
Marco D’Ario ◽  
Rafael Tavares ◽  
Katharina Schiessl ◽  
Bénédicte Desvoyes ◽  
Crisanto Gutierrez ◽  
...  
Keyword(s):  
Dna Synthesis ◽  
Cell Size ◽  
Dna Content ◽  
Growth Period ◽  
Mitotic Chromosomes ◽  
Daughter Cells ◽  
Asymmetric Divisions ◽  
A Cell ◽  
Size Variability ◽  
Cell Niche

How eukaryotic cells assess and maintain sizes specific for their species and cell type remains unclear. We show that in the Arabidopsis shoot stem cell niche, cell size variability caused by asymmetric divisions is corrected by adjusting the growth period before DNA synthesis. KIP-related protein 4 (KRP4) inhibits progression to DNA synthesis and associates with mitotic chromosomes. The F BOX-LIKE 17 (FBL17) protein removes excess KRP4. Consequently, daughter cells are born with comparable amounts of KRP4. Inhibitor dilution models predicted that KRP4 inherited through chromatin would robustly regulate size, whereas inheritance of excess free KRP4 would disrupt size homeostasis, as confirmed by mutant analyses. We propose that a cell cycle regulator, stabilized by association with mitotic chromosomes, reads DNA content as a cell size–independent scale.

Regulation of G2 by cell size contributes to maintaining cell size variability within certain limits in higher plants

1987 ◽  
Vol 87 (5) ◽  
pp. 635-641
Author(s):  
M.H. Navarrete ◽  
A. Cuadrado ◽  
M. Escalera ◽  
J.L. Canovas
Keyword(s):  
Steady State ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Surface Area ◽  
Cell Size ◽  
Coefficient Of Variation ◽  
Higher Plants ◽  
Cell Populations ◽  
Cell Area ◽  
Size Variability

The variability of (1) surface area projection (size) at which cells terminate DNA replication, (2) the area at which they initiate mitosis, (3) the area at which they divide, (4) the duration of G2, and (5) the duration of G2 plus mitosis (in fact, prophase + metaphase + anaphase) has been estimated in steady-state cell populations of Allium cepa root meristems. The coefficient of variation of cell area at termination of DNA synthesis was found to be 14% while the coefficient of variation of cell area at mitosis initiation was 13%. As there is also a substantial variability of G2 (the coefficient of variation was estimated to be 38%), the combination of these data indicates that cell size regulation of G2 contributes to maintaining cell size variability (and therefore DNA concentration) within certain limits. Mitosis also varies but less than G2 (the coefficient of variation of G2 + mitosis was found to be 31%). As the coefficient of variation of cell area at division (14%) is hardly larger than the coefficient of variation of cell area at initiation of mitosis, it can be suggested that coordination between cell size and mitosis duration helps to avoid a significant increase in the variability of cell size at the end of the division cycle.

The expected population size in a cell-size-dependent branching process

1981 ◽  
Vol 18 (01) ◽  
pp. 65-75 ◽  
Author(s):  
Aidan Sudbury
Keyword(s):  
Cell Size ◽  
Exponential Growth ◽  
Branching Process ◽  
Expected Number ◽  
Size Dependent ◽  
Daughter Cells ◽  
Rate Of Increase ◽  
A Cell ◽  
Dependent Growth ◽  
Number Of Cells

In cell-size-dependent growth the probabilistic rate of division of a cell into daughter-cells and the rate of increase of its size depend on its size. In this paper the expected number of cells in the population at time t is calculated for a variety of models, and it is shown that population growths slower and faster than exponential are both possible. When the cell sizes are bounded conditions are given for exponential growth.

scholarly journals DNA CONTENT OF PLACENTAL NUCLEI

1962 ◽  
Vol 13 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Michael Galton
Keyword(s):  
Cell Proliferation ◽  
Dna Synthesis ◽  
Mitotic Activity ◽  
Dna Content ◽  
Reproductive Capacity ◽  
Interphase Nuclei ◽  
Daughter Cells ◽  
Reproductive Ability ◽  
Dna Values ◽  
Rapid Accumulation

The DNA content of individual nuclei in four immature human placentas was determined by microspectrophotometric analysis of Feulgen-stained sections. The absence of mitosis in the syncytiotrophoblast, taken together with the finding of a diploid unimodal distribution, at a time of rapid placental growth, indicated that the syncytiotrophoblast possessed little or no intrinsic reproductive capacity. In contrast, the cytotrophoblast displayed considerable mitotic activity and was found to contain a high proportion of nuclei with DNA values in excess of the diploid amount, corresponding to DNA synthesis in interphase nuclei preparatory to division. From the complementary behavior of the two layers of trophoblast, with respect to evidence of reproductive ability, it is concluded that the rapid accumulation of nuclei in the syncytiotrophoblast, during the early development of the placenta, is accounted for by cell proliferation within the cytotrophoblast followed by alignment and coalescence of some daughter cells in the syncytiotrophoblast.

scholarly journals The solution to the cytological paradox of isomorphy.

1987 ◽  
Vol 104 (3) ◽  
pp. 739-748 ◽  
Author(s):  
L J Goff ◽  
A W Coleman
Keyword(s):  
Cell Size ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Plastid Dna ◽  
Diploid Cell ◽  
Red Alga ◽  
Haploid Nucleus ◽  
Two Generations ◽  
A Cell

Cells with polyploid nuclei are generally larger than cells of the same organism or species with nonpolyploid nuclei. However, no such change of cell size with ploidy level is observed in those red algae which alternate isomorphic haploid with diploid generations. The results of this investigation reveal the explanation. Nuclear DNA content and other parameters were measured in cells of the filamentous red alga Griffithsia pacifica. Nuclei of the diploid generation contain twice the DNA content of those of the haploid generation. However, all cells except newly formed reproductive cells are multinucleate. The nuclei are arranged in a nearly perfect hexagonal array just beneath the cell surface. When homologous cells of the two generations are compared, although the cell size is nearly identical, each nucleus of the diploid cell is surrounded by a region of cytoplasm (a "domain") nearly twice that surrounding a haploid nucleus. Cytoplasmic domains associated with a diploid nucleus contain twice the number of plastids, and consequently twice the amount of plastid DNA, than is associated with the domain of a haploid nucleus. Thus, doubling of ploidy is reflected in doubling of the size and organelle content of the domain associated with each nucleus. However, cell size does not differ between homologous cells of the two generations, because total nuclear DNA (sum of the DNA in all nuclei in a cell) per cell does not differ. This is the solution to the cytological paradox of isomorphy.

scholarly journals Cell size regulation in bacteria

2014 ◽  
Author(s):  
Ariel Amir
Keyword(s):  
Cell Size ◽  
Narrow Range ◽  
Size Control ◽  
Exponential Dependence ◽  
Model Parameters ◽  
E Coli ◽  
Daughter Cells ◽  
Mother And Daughter ◽  
A Cell ◽  
Initiation Of Dna Replication

Various bacteria such as the canonical gram negative Escherichia coli or the well-studied gram positive Bacillus subtilis divide symmetrically after they approximately double their volume. Their size at division is not constant, but is typically distributed over a narrow range. Here, we propose an analytically tractable model for cell size control, and calculate the cell size and inter-division time distributions, and the correlations between these variables. We suggest ways of extracting the model parameters from experimental data, and show that existing data for E. coli supports partial size control, and a particular explanation: a cell attempts to add a constant volume from the time of initiation of DNA replication to the next initiation event. This hypothesis accounts for the experimentally observed correlations between mother and daughter cells as well as the exponential dependence of size on growth rate.

Inhibition of Cell Division by High External NaCl Concentrations in Synchronized Cultures of Chlorella emersonii

1982 ◽  
Vol 9 (2) ◽  
pp. 179 ◽  
Author(s):  
T.L Setter ◽  
H Greenway ◽  
J Kuo
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
Dna Synthesis ◽  
Dna Content ◽  
Cell Cycles ◽  
Daughter Cells ◽  
Specific Effects ◽  
Rna And Dna ◽  
Synchronized Cultures ◽  
In Cells

Effects of high external NaCl concentrations on growth were examined in the unicellular freshwater alga Cldorella emevsonii during different phases of cell development, using synchronized cultures obtained by alternating light-dark cycles. Growth of cultures synchronized at 1 mM NaCl [external osmotic pressure (next=) 0.08 MPa] was compared with (i) cultures synchronized at 200 mM NaCl (n,,, = 1.01 MPa) and (ii) cultures synchronized at 1 mM NaCl from which the daughter cells were suddenly transferred to 100, 150 or 200 mM NaCl. The effects of these two treatments on synthesis of protein, RNA and DNA during cell cycles were similar, and are attributed to the high nexta nd not to specific effects of Na+ and C1-. Growth inhibitions in cells at 200 mM NaCl relative to 1 mM NaCl occurred mainly via effects on cell division; this was confirmed by electron microscopy. There was a lag before net DNA synthesis commenced, and there were reductions in rates of net DNA synthesis in cells at 200 mM NaCl relative to 1 mM NaC1. Rates of increase in cell volume and in protein and RNA content per cell were little affected by high external NaCl concentrations. Consequently, daughter cells at 200 mM NaCl were approximately twice the volume and contained twice as much protein and RNA as daughter cells at 1 mM NaCl, while DNA content was equal in daughter cells at 1 and 200 mM NaCl.

scholarly journals Downward regulation of cell size in Paramecium tetraurelia: effects of increased cell size, with or without increased DNA content, on the cell cycle

1982 ◽  
Vol 57 (1) ◽  
pp. 315-329
Author(s):  
C.D. Rasmussen ◽  
J.D. Berger
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Dna Synthesis ◽  
Cell Size ◽  
Dna Content ◽  
Cell Mass ◽  
Cycle Duration ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Rates Of Growth

Two temperature-sensitive cell-cycle mutants were used to generate abnormally large cells (size estimated by protein content) with either normal or increased DNA contents. The first mutant, cc1, blocks DNA synthesis, but allows cell growth at the restrictive temperature. The cells do not progress through the cell cycle while at the restrictive temperature, but do recover and complete the cell cycle when returned to permissive conditions. The progeny have increased cell size and normal DNA content. Downward regulation of cell size occurs during the ensuing cell cycle at permissive temperature. Two processes are involved. First, the G1 period is reduced or eliminated. As initial cell size increases there is a progressive shortening of the cell cycle to 75% of normal. This limit cell-cycle duration is reached when the initial mass of the cell is equal to or greater than that of normal cells at the time of DNA synthesis initiation (0.25 of a cell cycle). Cells with the limit cell cycle begin macronuclear DNA synthesis immediately after fission. The durations of the S period and fission are normal. Second, the rate of cell growth is unaffected by the increase in cell size, and results in the partitioning of excess cell mass between the daughter cells at the next fission. The second mutant, cc2, blocks cell division, but allows DNA synthesis to occur at a reduced rate so that cells with up to about 140% of the normal initial DNA content and twice the normal cell mass can be produced. The pattern of cell-cycle shortening is the same as in ccl. The rates of growth and both the rate and amount of DNA synthesis are proportional to the initial DNA content. This suggests that the rates of growth and DNA synthesis are limited by the transcriptional activity of the macronucleus in both cc1 and cc2 cells when they begin the cell cycle with experimentally increased cell mass. Increases in both cell size and initial DNA content are required to bring about increases in the rates of growth and DNA accumulation.

A ‘Dynamic Adder Model’ For Cell Size Homeostasis in Dictyostelium Cells

2021 ◽  
Author(s):  
Masahito Tanaka ◽  
Shigehiko Yumura
Keyword(s):  
Cell Surface ◽  
Surface Area ◽  
Cell Size ◽  
Surface Membrane ◽  
Total Cell ◽  
Membrane Turnover ◽  
Cell Surface Area ◽  
Daughter Cells ◽  
A Cell ◽  
Original Size

Abstract After a cell divides into two daughter cells, the total cell surface area of the daughtercells should increase to the original size to maintain cell size homeostasis in a single cellcycle. Previously, three models have been proposed to explain the regulation of cell sizehomeostasis: sizer, timer, and adder models. Here, we precisely measured the total cellsurface area of Dictyostelium cells in a whole cell cycle by using the agar-overlaymethod, which eliminated the influence of surface membrane reservoirs, such asmicrovilli and membrane winkles. The total cell surface area linearly increased duringinterphase, slightly decreased at the metaphase, and then increased by approximately20% during cytokinesis. From the analysis of the added surface area, we concluded thatthe cell size was regulated by the near-adder model in interphase and by the timer modelin the mitotic phase. The adder model in the interphase is not caused by a simple cellmembrane addition, but is more dynamic due to the rapid cell membrane turnover. Wepropose a ‘dynamic adder model’ to explain cell size homeostasis in the interphase.

The expected population size in a cell-size-dependent branching process

1981 ◽  
Vol 18 (1) ◽  
pp. 65-75 ◽  
Author(s):  
Aidan Sudbury
Keyword(s):  
Cell Size ◽  
Exponential Growth ◽  
Branching Process ◽  
Expected Number ◽  
Size Dependent ◽  
Daughter Cells ◽  
Rate Of Increase ◽  
A Cell ◽  
Dependent Growth ◽  
Number Of Cells

In cell-size-dependent growth the probabilistic rate of division of a cell into daughter-cells and the rate of increase of its size depend on its size. In this paper the expected number of cells in the population at time t is calculated for a variety of models, and it is shown that population growths slower and faster than exponential are both possible. When the cell sizes are bounded conditions are given for exponential growth.

scholarly journals Mitochondrial growth and DNA synthesis occur in the absence of nuclear DNA replication in fission yeast

1990 ◽  
Vol 97 (3) ◽  
pp. 509-516 ◽  
Author(s):  
S. Sazer ◽  
S.W. Sherwood
Keyword(s):  
Mitochondrial Dna ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Fission Yeast ◽  
Dna Content ◽  
Nuclear Dna ◽  
Equal Distribution ◽  
Daughter Cells ◽  
Mitochondrial Dna Content ◽  
Mitochondrial Volume

Cell growth and division require the doubling of cellular constituents followed by their equal distribution to the two daughter cells. Within a growing population, the ratio of mitochondrial to cellular volume is maintained, as is the number of mitochondrial genomes per cell. The mechanisms responsible for coordinating nuclear and mitochondrial DNA synthesis, and for balancing increases in cell and mitochondrial size are not well understood. In studies of the fission yeast Schizosaccharomyces pombe we quantified cellular and mitochondrial DNA content by both Southern blot analysis and flow cytometry of cells stained with a variety of DNA-binding fluorochromes, which we show are able to detect nuclear and mitochondrial DNA with different efficiencies. In the conditional cell division cycle mutant cdc10, which is unable to initiate nuclear DNA synthesis, we found that there was an increase in the mitochondrial DNA content in the absence of nuclear DNA replication. This demonstrates that mitochondrial and nuclear DNA synthesis are not obligately linked. We also show that mitochondrial DNA replication is not required for the increase in mitochondrial size that occurs as cells elongate, although this results in a decrease in the ratio of mitochondrial DNA to mitochondrial volume.

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