scholarly journals MINOR COMPONENTS OF THE DNA OF PHYSARUM POLYCEPHALUM

1969 ◽  
Vol 40 (2) ◽  
pp. 484-496 ◽  
Author(s):  
Charles E. Holt ◽  
Elizabeth G. Gurney
Keyword(s):  
Cell Cycle ◽  
Physarum Polycephalum ◽  
Nuclear Dna ◽  
Buoyant Density ◽  
Cell Fractionation ◽  
Minor Components ◽  
Variable Level ◽  
The Mean ◽  
S Period ◽  
Dna Components

DNA metabolism in the slime mold Physarum polycephalum was studied by centrifugation in CsCl of lysates of cultures labeled with radioactive thymidine at various times in the cell cycle. During the G2 (premitotic) phase of the cell cycle, two components of the DNA are labeled. One component is lighter (buoyant density 1.686 g/cc) than the mean of the principal DNA (1.700 g/cc), and one is heavier (approximately 1.706 g/cc). The labeled light DNA was identified chemically by its denaturability, its susceptibility to DNase, and the recovery of its radioactivity in thymine. Cell fractionation studies showed that the heavy and the principal DNA components are located in the nucleus and that the light DNA is in the cytoplasm. The light DNA comprises approximately 10% of the DNA. About ⅓–½ of the light DNA is synthesized during the S period, and the remainder is synthesized throughout G2 (there is no G1 in Physarum). The light DNA is metabolically stable. A low, variable level of incorporation of radioactive thymidine into the principal, nuclear DNA component was observed during G2.

Nuclear DNA content and minimum generation time in herbaceous plants

1972 ◽  
Vol 181 (1063) ◽  
pp. 109-135 ◽  
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Cycle Time ◽  
Generation Time ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Annual Species ◽  
Cell Cycle Time ◽  
Developmental Processes ◽  
The Mean

Many components of cell and nuclear size and mass are correlated with nuclear DNA content in plants, as also are the durations and rates of such developmental processes as mitosis and meiosis. It is suggested that the multiple effects of the mass of nuclear DNA which affect all cells and apply throughout the life of the plant can together determine the minimum generation time for each species. The durations of mitosis and of meiosis are both positively correlated with nuclear DNA content and, therefore, species with a short minimum generation time might be expected to have a shorter mean cell cycle time and mean meiotic duration, and a lower mean nuclear DNA content, than species with a long mean minimum generation time. In tests of this hypothesis, using data collated from the literature, it is shown that the mean cell cycle time and the mean meiotic duration in annual species is significantly shorter than in perennial species. Furthermore, the mean nuclear DNA content of annual species is significantly lower than for perennial species both in dicotyledons and monocotyledons. Ephemeral species have a significantly lower mean nuclear DNA content than annual species. Among perennial monocotyledons the mean nuclear DNA content of species which can complete a life cycle within one year (facultative perennials) is significantly lower than the mean nuclear DNA content of those which cannot (obligate perennials). However, the mean nuclear DNA content of facultative perennials does not differ significantly from the mean for annual species. It is suggested that the effects of nuclear DNA content on the duration of developmental processes are most obvious during its determinant stages, and that the largest effects of nuclear DNA mass are expressed at times when development is slowest, for instance, during meiosis or at low temperature. It has been suggested that DNA influences development in two ways, directly through its informational content, and indirectly by the physical-mechanical effects of its mass. The term 'nucleotype' is used to describe those conditions of the nucleus which effect the phenotype independently of the informational content of the DNA. It is suggested that cell cycle time, meiotic duration, and minimum generation time are determined by the nucleotype. In addition, it may be that satellite DNA is significant in its nucleotypic effects on developmental processes.

scholarly journals Kinetic complexity of chloroplastal deoxyribonucleic acid and mitochondrial deoxyribonucleic acid from higher plants

1969 ◽  
Vol 112 (5) ◽  
pp. 777-786 ◽  
Author(s):  
Richard Wells ◽  
Max Birnstiel
Keyword(s):  
Molecular Weight ◽  
Mitochondrial Dna ◽  
Gaussian Distribution ◽  
Deoxyribonucleic Acid ◽  
Nuclear Dna ◽  
Higher Plants ◽  
Buoyant Density ◽  
Cell Fractionation ◽  
Caesium Chloride ◽  
Cellular Dna

1. Chloroplasts and mitochondria were isolated by aqueous and non-aqueous cell-fractionation techniques. In a variety of higher plants the mitochondrial DNA bands in a caesium chloride gradient at 1·706g.cm.−3, whereas chloroplastal DNA has a buoyant density of 1·697g.cm.−3. 2. In total cellular DNA of moderate molecular weight, the chloroplastal DNA is found within the Gaussian distribution of the nuclear DNA and is not resolved as a satellite. 3. Both chloroplastal DNA and mitochondrial DNA from lettuce renature rapidly. 4. The kinetic complexity of mitochondrial DNA is > 108 daltons. 5. Chloroplastal DNA is made up from fast and slow renaturing sequences with kinetic complexities of 3×106 and 1·2×108 daltons respectively. 6. From the discrepancy between analytical and kinetic complexity it is concluded that chloroplastal DNA is extensively reiterated.

Cycle cellulaire et teneurs en ADN nucléaire de cellules en suspension de l’Acer pseudoplatanus en phase exponentielle de croissance. Hétérogénéité de la culture

1974 ◽  
Vol 52 (7) ◽  
pp. 1535-1543 ◽  
Author(s):  
Jacques Rembur
Keyword(s):  
Cell Cycle ◽  
Doubling Time ◽  
Nuclear Dna ◽  
Cell Suspension Cultures ◽  
The Other ◽  
Acer Pseudoplatanus ◽  
Heterogeneous Cell Population ◽  
Constant Rate ◽  
Cell Groups ◽  
The Mean

The mean doubling time of Acer pseudoplatanus L. cell suspension cultures is 66 h during log-phase growth.A constant rate of proliferation and a stable mitotic index show this population to be asynchronous with little variation in the duration of the cell cycle.The results of both continuous and brief labelling show that only 84% of the cells divide. The cell cycle lasts 58 h with G1, S, G2, and M periods of 29, 21, 5.3, and 2.7 h respectively. G1 predominates while G2 is reduced.Microspectrophotometric analysis of nuclear DNA indicates a heterogeneous cell population made up of two proliferating groups, one diploid and the other tetraploid.The formation of tetraploids by endoreduplication and the possible evolution of both cell groups are discussed.

Plastochrone, cycle cellulaire et teneurs en ADN nucléaire du méristème caulinaire de plants de Chrysanthemum segetum soumis à deux conditions lumineuses différentes, sous une photopériode de 16 heures

1990 ◽  
Vol 68 (11) ◽  
pp. 2389-2397 ◽  
Author(s):  
Arlette Nougarède ◽  
Maria Nicola Di Michele ◽  
Pierre Rondet ◽  
Robert Saint-Côme
Keyword(s):  
Cell Cycle ◽  
Doubling Time ◽  
Nuclear Dna ◽  
Cycle Duration ◽  
Axial Zone ◽  
Lateral Zone ◽  
Cell Doubling Time ◽  
Photon Fluence ◽  
The Mean ◽  
Chrysanthemum Segetum

Chrysanthemum segetum plants were grown from seeds under a 16-h photoperiod, at two different photon fluence rates (70 or 200 μmol m−2 s−1. At 200 μmol m−2 s−1, by comparison with 70 μmol m−2 s−1, phyllotaxy was not modified, but the plastochron decreased and the apical diameter increased by extension of the axial zone. The mean cell doubling time decreased 36.2% in the lateral zone, 29% in the axial zone, and only 13% in the rib meristem. In contrast, mitosis duration was constant. Under both light conditions, nuclei with a DNA content within the limits of the 2C range were always predominant, which means that the G1 phase of the cell cycle was the longest. At 200 μmol m−2 s−1, the shortening of the mean cell doubling time is accompanied by a reduction of the percentage of nuclei with DNA levels within the limits of the 2C range. The decrease of the latter was the most important in the axial zone and the least important in the rib meristem, showing that control of cell proliferation was obtained by means of the G1 phase of the cell cycle. Key words: Chrysanthemum segetum, cell cycle, duration of mitosis, plastochron, nuclear DNA levels, zonation.

scholarly journals IMAGE ANALYSIS OF CHROMATIN IN CELLS OF PREIMPLANTATION MOUSE EMBRYOS

1974 ◽  
Vol 63 (1) ◽  
pp. 227-233 ◽  
Author(s):  
Wojciech Sawicki ◽  
Jan Rowínski ◽  
Jan Abramczuk
Keyword(s):  
Cell Cycle ◽  
Image Analysis ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Mouse Embryos ◽  
Stage Of Development ◽  
Preimplantation Mouse Embryos ◽  
Preimplantation Mouse ◽  
The Mean

Mouse two-celled embryos and blastulae were Feulgen stained and the DNA content of their nuclei was measured with an integrating microdensitometer. The cells considered on the basis of their nuclear DNA content to be in G1, S, and G2 phases of the cell cycle were selected and their total chromatin area and chromatin areas at different gray levels were measured by the image analyzing computer, Quantimet. The measurements were aimed at quantitation of several features of the chromatin morphology of cells in different functional states. The total area of chromatin was found to increase, and the mean density of chromatin to decrease, from the G1 to the G2 phase of the cell cycle in both two-celled embryos and blastulae. The area of chromatin decreased, and the mean density of chromatin increased, as embryos developed from two-celled to blastula stage. It was concluded that nuclear morphology in preimplantation mouse embryos depends on both the phase of the cell cycle and the stage of development. The method of image analysis described was found to be useful for quantitation of changes in chromatin morphology.

scholarly journals Pattern of DNA increase in macronuclear anlagen of Tetrahymena

1986 ◽  
Vol 83 (1) ◽  
pp. 155-164
Author(s):  
J. Roth ◽  
G. Cleffmann
Keyword(s):  
Cell Cycle ◽  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
S Phase ◽  
The Mean

By combining cytophotometry with autoradiography, five stages of macronuclear anlagen can be discriminated by their DNA content until the end of the first cell cycle after conjugation in Tetrahymena. DNA increases from 2C to about 32C. Each S-phase is followed by a non-synthetic period. Comparing the mean nuclear DNA content after and before each S-phase revealed that 16C anlagen contain significantly less DNA than twice the amount of 8C anlagen. This is unlike the situation in other S-phases during which the amount of DNA is precisely doubled. In the second cell cycle after conjugation some of the cells increase their macronuclear G2 DNA content beyond the 64C stage, while the majority show a mean G2 content of about 64C.

scholarly journals AUTORADIOGRAPHIC EVIDENCE FOR MANY SEGREGATING DNA MOLECULES IN THE CHLOROPLAST OF OCHROMONAS DANICA

1973 ◽  
Vol 59 (2) ◽  
pp. 318-328 ◽  
Author(s):  
Sarah P. Gibbs ◽  
Ronald J. Poole
Keyword(s):  
Cell Cycle ◽  
Chloroplast Dna ◽  
Exponential Growth ◽  
Light Microscope ◽  
Nuclear Dna ◽  
Serial Sections ◽  
Dna Molecules ◽  
Ochromonas Danica ◽  
Microscope Autoradiography ◽  
S Period

Light-grown cells of Ochromonas danica, which contain a single chloroplast per cell, were labeled with [methyl-3H]thymidine for 3 h (0.36 generations) and the distribution of labeled DNA among the progeny chloroplasts was followed during exponential growth in unlabeled medium for a further 3.3 generations using light microscope autoradiography of serial sections of entire chloroplasts. Thymidine was specifically incorporated into DNA in both nuclei and chloroplasts. Essentially all the chloroplasts incorporated label in the 3-h labeling period, indicating that chloroplast DNA is synthesized throughout the cell cycle. Nuclear DNA has a more limited S period. Both chloroplast DNA and nuclear DNA are conserved during 3.3 generations. After 3.3 generations in unlabeled medium, grains per chloroplast followed a Poisson distribution indicating essentially equal labeling of all progeny chloroplasts. It is concluded that the average chloroplast in cells of Ochromonas growing exponentially in the light contains at least 10 segregating DNA molecules.

scholarly journals Cell cycle dependent change in the endogenous phosphorylation of nucleolar proteins of Physarum polycephalum

FEBS Letters ◽  
1981 ◽  
Vol 124 (1) ◽  
pp. 53-56 ◽  
Author(s):  
Toshiko Shibayama ◽  
Shouzou Sawai ◽  
Kazuyasu Nakaya ◽  
Yasuharu Nakamura
Keyword(s):  
Cell Cycle ◽  
Physarum Polycephalum ◽  
Nucleolar Proteins ◽  
Dependent Change ◽  
Cycle Dependent
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