Regulation of bud dormancy by manipulation of ABA in isolated buds of Rosa hybrida cultured in vitro

1999 ◽  
Vol 26 (3) ◽  
pp. 273 ◽  
Author(s):  
Manuel Le Bris ◽  
Nicole Michaux-Ferrière ◽  
Yves Jacob ◽  
Alain Poupet ◽  
Philippe Barthe ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Control Culture ◽  
Rosa Hybrida ◽  
Bud Dormancy ◽  
G2 Phase ◽  
Intense Activity

In vitro cultures showed that the proximal buds isolated from a rose (Rosa hybrida L. cv. Ruidriko Vivaldi®) stem were endodormant. Growth and a high percentage of bud break could be observed when cultures were treated with fluridone, an inhibitor of carotenoid synthesis. Flow cytometry determination of nuclear DNA content revealed that cell cycle activity of endodormant buds was arrested in the G 1 phase. Upon culture, the large decrease in bud ABA content was responsible for the progress from G1 to G2 phase whatever the culture medium. However, in control culture, neither cell division nor leaf primordium initiation could be observed and cells appeared stably arrested in G2 . By contrast, with fluridone, an additional ABA decrease was observed resulting from an inhibition of its synthesis inside the bud. New leaf primordia were initiated and many figures of mitosis could be observed, indicating that intense activity of cell division occurred after DNA replication. Therefore, the results indicate that, as long as ABA was synthesized inside the buds, cell cycle was arrested in G2 phase and buds remained dormant. Continued in situ ABA biosynthesis appears, therefore, to be required for the maintenance of bud dormancy.

The cell cycle and its relationship to development in Acanthamoeba castellanii

1987 ◽  
Vol 88 (5) ◽  
pp. 579-590
Author(s):  
MICHAEL STÖHR ◽  
KURT BOMMERT ◽  
INGRID SCHULZE ◽  
HELGA JANTZEN
Keyword(s):  
Cell Cycle ◽  
Stationary Phase ◽  
Nuclear Dna ◽  
Acanthamoeba Castellanii ◽  
Nuclear Dna Content ◽  
Defined Medium ◽  
G2 Phase ◽  
D Cells ◽  
High Degree ◽  
The Relationship

The cell cycle and the relationship between particular cell cycle phases and the differentiation of trophozoites into cysts were reinvestigated in Acanthamoeba castellanii using flow fluorometric measurements of nuclear DNA content and synthesis and synchronization of cells by release from the stationary phase. The investigation was performed with cultures growing in non-defined medium (ND cells) showing a high degree of encystation in response to starvation and with subcultures growing in chemically defined nutrient medium (D cells) exhibiting a very low encystation competence. In both cultures the cell cycle starts with a short S phase taking place simultaneously with cytokinesis followed by a long G2 phase. A G1 phase seems to be either absent or very short. Synchronization experiments reveal that in ND cells encystation is initiated from a particular position of late G2. The high encystation competence of stationary phase ND cells seems to be due to arrest of cells at this particular cell cycle position. The lack of encystation competence of stationary phase D cells correlates with the loss of accumulation of cells at this particular stage of the cell cycle. This change of the property of cells is related to the growth condition and not to an irreversible loss of encystation competence of D cells.

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 Cell cycle arrest of cdc mutants and specificity of the RAD9 checkpoint.

Genetics ◽  
1993 ◽  
Vol 134 (1) ◽  
pp. 63-80 ◽  
Author(s):  
T A Weinert ◽  
L H Hartwell
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Control ◽  
Dna Lesions ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
A Cell ◽  
G2 Phase ◽  
Rad Mutants

Abstract In eucaryotes a cell cycle control called a checkpoint ensures that mitosis occurs only after chromosomes are completely replicated and any damage is repaired. The function of this checkpoint in budding yeast requires the RAD9 gene. Here we examine the role of the RAD9 gene in the arrest of the 12 cell division cycle (cdc) mutants, temperature-sensitive lethal mutants that arrest in specific phases of the cell cycle at a restrictive temperature. We found that in four cdc mutants the cdc rad9 cells failed to arrest after a shift to the restrictive temperature, rather they continued cell division and died rapidly, whereas the cdc RAD cells arrested and remained viable. The cell cycle and genetic phenotypes of the 12 cdc RAD mutants indicate the function of the RAD9 checkpoint is phase-specific and signal-specific. First, the four cdc RAD mutants that required RAD9 each arrested in the late S/G2 phase after a shift to the restrictive temperature when DNA replication was complete or nearly complete, and second, each leaves DNA lesions when the CDC gene product is limiting for cell division. Three of the four CDC genes are known to encode DNA replication enzymes. We found that the RAD17 gene is also essential for the function of the RAD9 checkpoint because it is required for phase-specific arrest of the same four cdc mutants. We also show that both X- or UV-irradiated cells require the RAD9 and RAD17 genes for delay in the G2 phase. Together, these results indicate that the RAD9 checkpoint is apparently activated only by DNA lesions and arrests cell division only in the late S/G2 phase.

scholarly journals Talin mechanosensitivity is modulated by a direct interaction with cyclin-dependent kinase-1

2021 ◽  
Author(s):  
Rosemarie E. Gough ◽  
Matthew C. Jones ◽  
Thomas Zacharchenko ◽  
Shimin Le ◽  
Miao Yu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Cell Adhesion ◽  
Cell Division ◽  
Mechanical Response ◽  
Direct Interaction ◽  
Cyclin Dependent Kinase ◽  
Cell Cycle Regulator ◽  
Direct Binding

AbstractTalin is a mechanosensitive component of adhesion complexes that directly couples integrins to the actin cytoskeleton. In response to force, talin undergoes switch-like behaviour of its multiple rod domains that modulate interactions with its binding partners. Cyclin-dependent kinase-1 (CDK1) is a key regulator of the cell cycle, exerting its effects through synchronised phosphorylation of a large number of protein targets. CDK1 activity also maintains adhesion during interphase, and its inhibition is a prerequisite for the tightly choreographed changes in cell shape and adhesiveness that are required for successful completion of mitosis. Using a combination of biochemical, structural and cell biological approaches, we demonstrate a direct interaction between talin and CDK1 that occurs at sites of integrin-mediated adhesion. Mutagenesis demonstrated that CDK1 contains a functional talin-binding LD motif, and the binding site within talin was pinpointed to helical bundle R8 through the use of recombinant fragments. Talin also contains a consensus CDK1 phosphorylation motif centred on S1589; a site that was phosphorylated by CDK1in vitro. A phosphomimetic mutant of this site within talin lowered the binding affinity of KANK and weakened the mechanical response of the region, potentially altering downstream mechanotransduction pathways. The direct binding of the master cell cycle regulator, CDK1, to the primary integrin effector, talin, therefore provides a primordial solution for coupling the cell proliferation and cell adhesion machineries, and thereby enables microenvironmental control of cell division in multicellular organisms.SummaryThe direct binding of the master cell cycle regulator, CDK1, to the primary integrin effector, talin, provides a primordial solution for coupling the cell proliferation and cell adhesion machineries, and thereby enables microenvironmental control of cell division.

Cytofluorimetric analysis of nuclear DNA during meiosis, fertilization and macronuclear development in the ciliate Tetrahymena pyriformis, syngen 1

1975 ◽  
Vol 17 (3) ◽  
pp. 471-493 ◽  
Author(s):  
F.P. Doerder ◽  
L.E. Debault
Keyword(s):  
Cell Division ◽  
Dna Synthesis ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Tetrahymena Pyriformis ◽  
Cell Cycles ◽  
Macronuclear Development ◽  
Sister Chromatids ◽  
Nuclear Development ◽  
S Period

Fluorescence cytophotometry was used to study nuclear DNA content and synthesis patterns during meiosis, fertilization and macronuclear development in the ciliated protozoon, Tetrahymena pyriformis, syngen 1. It was found that cells entered conjugation with a G1 (45C) macronucleus and a G2 (4C) micronucleus. During meiosis the micronucleus was reduced to 4 haploid nuclei, each with a 1C amount of DNA; each meiotic product then replicated to 2C, but only the nucleus next to the attachment membrane in each conjugant divided to form the two 1C gametic nuclei. The gametic nuclei replicated to 2C prior to fertilization; hence there was no S-period in the 4C fertilization nucleus (synkaryon). The first postzygotic division products immediately entered an S-period to become 4C, and at the second postzygotic division, each of the two 4C nuclei in each conjugant divided to form one 2C micronucleus and one 2C macronuclear Anlage. The macronuclear Anlagen began DNA synthesis immediately and were about 8C at the completion of conjugation; the micronuclei did not undergo rapid DNA doubling and measured between 2C and 3C when the conjugants separated. The old macronucleus did not participate in any S-period during conjugation and began to decompose after the second postzygotic division; it contained an average of 24C at the end of conjugation. From this sequence of nuclear divisions a pattern emerges that, unless a general cytoplasmic signal for DNA synthesis is suppressed, DNA synthesis always occurs in micronuclear division products immediately following separation of sister chromatids. Nuclear development continued in the first two cell cycles after conjugation. In exconjugants (the first cycle), macronuclear Anlagen underwent two rounds of DNA synthesis to become 32C and both micronuclei also underwent DNA synthesis. However, prior to the first cell division, one micronucleus and the old macronucleus completely disintegrated, and at the first cell division the remaining 4C micronucleus divided and one macronuclear Anlage was distributed to each resulting caryonide. At the end of the second cell cycle, the dividing macronucleus of each caryonide contained about 128C. These results relate to the question of ploidy of macronuclear subunits. It is argued that the G1 macronucleus contains 22 or 23 diploid subunits, each subunit being a copy of the diploid micronuclear genome. It is suggested that unequal macronuclear division relates to the question of subunit ploidy by playing a role in the phenomenon of macronuclear assortment.

scholarly journals GROWTH INHIBITION OF MURINE TUMOR CELLS, IN VITRO, BY PUROMYCIN, [6N]O2'-DIBUTYRYL 3',5'-ADENOSINE MONOPHOSPHATE, OR ADENOSINE

1973 ◽  
Vol 57 (2) ◽  
pp. 397-405 ◽  
Author(s):  
D. B. Thomas ◽  
Gay Medley ◽  
C. A. Lingwood
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Cell Growth ◽  
Growth Inhibition ◽  
Tumor Cells ◽  
Growth Arrest ◽  
Adenosine Monophosphate ◽  
Synchronous Cultures ◽  
Murine Tumor Cells

The cytostatic effects of puromycm, [6N]O2'-dibutyryl 3',5'-adenosine monophosphate, and adenosine on asynchronous and synchronous cultures of the murine mastocytoma, P815Y, have been studied. Cell growth was arrested after a minimum of one further division. A model is proposed for the inhibition of cell division in which the periods of inhibition and growth arrest are separated in time by one cell cycle.

Localization of Hematopoietic Stem Cells in Coculture with Mesenchymal Stromal Cells Impacts on Phenotype and Cell Cycle Status

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 4774-4774
Author(s):  
Duohui Jing ◽  
Nael Alakel ◽  
Fernando Fierro ◽  
Katrin Mueller ◽  
Martin Bornhaeuser ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Cell Division ◽  
Stromal Cells ◽  
The Other ◽  
Cell Contact ◽  
Adherent Cells ◽  
Hematopoietic Stem ◽  
Cell Fractions

Abstract Hematopoietic stem cells (HSC) are defined by their capacity of self-renewal and differentiation. In recent years it became clear that cell to cell contact mediated communication between mesenchymal stromal cells (MSC) and HSC is important for homeostasis of hematopoiesis. MSC play a crucial role in the so called bone marrow niche giving rise to the majority of marrow stromal cell lineages. In vitro we investigated the impact of MSC on CD34 purified HSC expansion and differentiation demonstrating a promoting impact of MSC on adherent HSC in comparison to non adherent HSC in terms of phenotype, migration capacity and clonogenicity. Performing phase contrast microscopy and confocal microscopy we are able to distinguish HSC which are located on the surface of a MSC monolayer (phase-bright cells) and HSC which are covered by MSC monolayer (phase-dim cells). Both HSC fractions and the non-adherent cells were isolated separately by performing serial washing steps. All three fractions were analyzed at fixed time points during the first week of co-culture in term of cell cycle progression, proliferation, maturation and cell division accompanied differentiation. First we performed propidium iodide (PI) staining for cell cycle analysis revealing that the phase-bright cells contained the highest percentage of G2 cells in comparison to the non adherent cells and the phase-dim cells; 13.9 ±1.0% vs 1.3 ±1.2% vs 2.7 ±2.0%, p<0.001. The data indicate the facilitating impact of MSC on HSC in performing mitosis which is however depending on the location of interaction. When HSC are released into supernatant (non adherent cells) or covered by MSC, G2 phase was significantly down-regulated. Next we studied the proliferation capacity of the separate cell fractions. Consistent with the data of cell cycle, cell number of phase-bright faction increased much faster than the other two fractions during the first 4 days suggesting that the MSC surface in vitro is the predominant location of HSC proliferation. Next we investigated the phenotype of HSC. According to FACS analysis results (CD34+CD38-) phase-dim cells revealed a more immature phenotype in comparison to the non adherent cells and the phase-bright cells. During the first four days 80% of phase-dim cells remained CD34+CD38-, while cells of the phase-bright- and the non adherent fraction exhibited a significant more mature phenotype. Performing cell division tracking using CFSE we were able to show that over time number of divisions of phase-dim cells were significantly diminished in comparison to the other two cell fractions in co-cultures. In addition, phase-dim cells started to lose CD34 at the 7th generation, while non-adherent and phase-bright cells already lost CD34 at the 4th generation. These data suggest that “stemness” of HSC was rather preserved in the cell fraction which was covered by MSC monolayer than in the cell fraction on the surface of MSC. In conclusion we demonstrate HSC in distinct locations in vitro showing different behaviors in terms of phenotype and proliferation. It becomes evident that not only the cell to cell contact matters but also the localization of contact. Further experiments are needed to investigate NOD/SCID repopulation potential of the different cell fractions.

Modulation of in vitro proliferation kinetics and primitive hematopoietic potential of individual human CD34+CD38–/lo cells in G0

Blood ◽  
2005 ◽  
Vol 105 (8) ◽  
pp. 3109-3116 ◽  
Author(s):  
Edward F. Srour ◽  
Xia Tong ◽  
Ki Woong Sung ◽  
P. Artur Plett ◽  
Susan Rice ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Severe Combined Immunodeficiency ◽  
Extrinsic Factors ◽  
In Vitro Proliferation ◽  
Cell Divisions ◽  
Human Cd34 ◽  
Cytokine Stimulation ◽  
Kinetics Of

AbstractWhether cytokines can modulate the fate of primitive hematopoietic progenitor cells (HPCs) through successive in vitro cell divisions has not been established. Single human marrow CD34+CD38–/lo cells in the G0 phase of cell cycle were cultured under 7 different cytokine combinations, monitored for proliferation on days 3, 5, and 7, then assayed for long-term culture-initiating cell (LTC-IC) function on day 7. LTC-IC function was then retrospectively correlated with prior number of in vitro cell divisions to determine whether maintenance of LTC-IC function after in vitro cell division is dependent on cytokine exposure. In the presence of proliferation progression signals, initial cell division was independent of cytokine stimulation, suggesting that entry of primitive HPCs into the cell cycle is a stochastic property. However, kinetics of proliferation beyond day 3 and maintenance of LTC-IC function were sensitive to cytokine stimulation, such that LTC-IC underwent an initial long cell cycle, followed by more synchronized shorter cycles varying in length depending on the cytokine combination. Nonobese diabetic/severe combined immunodeficiency (NOD/SCID) transplantation studies revealed analogous results to those obtained with LTC-ICs. These data suggest that although exit from quiescence and commitment to proliferation might be stochastic, kinetics of proliferation, and possibly fate of primitive HPCs, might be modulated by extrinsic factors.

Assessment of the cellular DNA content of whole mounted mouse and human oocytes and of blastomeres containing single or multiple nuclei

Zygote ◽  
1993 ◽  
Vol 1 (1) ◽  
pp. 17-25 ◽  
Author(s):  
Nicola J. Winston ◽  
Martin H. Johnson ◽  
Peter R. Braude
Keyword(s):  
Dna Content ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Structural Features ◽  
Chromosomal Dna ◽  
Individual Values ◽  
Mean Values ◽  
Mouse Oocytes ◽  
Cellular Dna

SummaryThe nuclear DNA content of intact, live or fixed, human and mouse oocytes and blastomeres has been measured rapidly and reliably. Chromosomal DNA has been stained with DAPI, the fluorescent emission from which has been measured photocytometrically.In vitrofertilised mouse oocytes and embryos at various stages of development were assessed for their DNA content. The mean values of 1C, 2C and 4C DNA content were clearly different, and it was possible to assign correctly individual values for DNA content to each class with 92%, 61% and 81% confidence respectively. Maintaining the cells as whole mounts allowed other morphological and structural features to be examined. When formation of multiple micronuclei was induced in mouse oocytes by their insemination in the presence of nocodazole, the additive signal from all the micronuclei in one zygote was equivalent to the expected DNA content. Application to early human blastomeres of this photocytometric technique for measurement of the total cellular DNA content revealed that multinucleated blastomeres contained 2C to 4C DNA levels, consistent with a diploid DNA content.

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