scholarly journals Synchronized emergence under diatom sperm competition

2020 ◽  
Vol 287 (1936) ◽  
pp. 20201074
Author(s):  
Yuka Shirokawa ◽  
Masakazu Shimada
Keyword(s):  
Evolutionary Game ◽  
Cell Interaction ◽  
Mitotic Division ◽  
Substantial Part ◽  
Centric Diatom ◽  
Unicellular Eukaryotes ◽  
Cellular Decision Making ◽  
Dividing Cells ◽  
Unicellular Organisms ◽  
Mating Time

Appropriate timing of mating is crucial for the success of individuals. However, we know little about factors that explain variation in mating time in unicellular organisms. Unicellular eukaryotes often have facultative sexuality, that is, the less frequent sex is occasionally induced after long clonal reproduction. Thus, males originated from clonemates could be non-negligible mating rivals. Using a centric diatom whose clonal cells differentiate into either male or female, we analysed whether males (spermatogonium) compete or cooperate with each other. By analysing differentiation timing with hypotheses based on evolutionary game theory, we estimated that a substantial part of the variation in the mating timing of the diatom can be explained by results of optimization through interactions among selfish individuals rather than cooperation among clonemates. However, the competition is fiercer than expected owing to excessive synchronization, which was realized by adjustment of meiotic duration: cells completed mitotic division in the earlier mating phase took longer to enter into meiosis, whereas late-dividing cells entered into meiosis more quickly. Adjacent cells tended to synchronize, and model analyses suggest that cell–cell interaction can create a gap between the optimal and actual decisions. Our results provide insights into the evolution of cellular decision making and its restriction.

Morphogenesis in hydra

Development ◽  
1970 ◽  
Vol 24 (1) ◽  
pp. 21-32
Author(s):  
Sondra C. Corff ◽  
Allison L. Burnett
Keyword(s):  
Nervous System ◽  
Cell Division ◽  
Hydrostatic Pressure ◽  
Low Temperature ◽  
Low Temperatures ◽  
Mitotic Division ◽  
Basal Disc ◽  
Dividing Cells ◽  
Short Time ◽  
Disc Formation

When Hydra oligactis is excised below the tentacles and incubated for a short time in concentrations of colchicine that inhibit spindle formation in dividing cells, a peduncle and basal disc subsequently form at the cut distal end, where hypostome and tentacles normally form (Corff & Burnett, 1969). Since recent reports suggest a similarity in the action of colchicine and low temperature, in this study the effects of low temperatures on regenerating hydra were investigated. High hydrostatic pressure and low temperature have been shown to act synergistically with colchicine to inhibit the first mitotic division in sea urchin eggs (Marsland, 1968). Colchicine and cooling have also been shown to cause disintegration of the microtubule system in Actinosphaerium (Tilney, 1965). We have previously discussed peduncle and basal disc formation at the distal end in terms of colchicine inhibition of cell division and the possible action of colchicine on the nervous system (Corff & Burnett, 1969).

scholarly journals The molecular evolution of the vertebrate behavioural repertoire

2016 ◽  
Vol 371 (1685) ◽  
pp. 20150051 ◽  
Author(s):  
Seth G. N. Grant
Keyword(s):  
Molecular Mechanisms ◽  
Gene Mutations ◽  
Behavioural Disorders ◽  
Major Question ◽  
Unicellular Eukaryotes ◽  
General Importance ◽  
Duplication Events ◽  
Genomic Studies ◽  
Unicellular Organisms ◽  
Behavioural Repertoire

How the sophisticated vertebrate behavioural repertoire evolved remains a major question in biology. The behavioural repertoire encompasses the set of individual behavioural components that an organism uses when adapting and responding to changes in its external world. Although unicellular organisms, invertebrates and vertebrates share simple reflex responses, the fundamental mechanisms that resulted in the complexity and sophistication that is characteristic of vertebrate behaviours have only recently been examined. A series of behavioural genetic experiments in mice and humans support a theory that posited the importance of synapse proteome expansion in generating complexity in the behavioural repertoire. Genome duplication events, approximately 550 Ma, produced expansion in the synapse proteome that resulted in increased complexity in synapse signalling mechanisms that regulate components of the behavioural repertoire. The experiments demonstrate the importance to behaviour of the gene duplication events, the diversification of paralogues and sequence constraint. They also confirm the significance of comparative proteomic and genomic studies that identified the molecular origins of synapses in unicellular eukaryotes and the vertebrate expansion in proteome complexity. These molecular mechanisms have general importance for understanding the repertoire of behaviours in different species and for human behavioural disorders arising from synapse gene mutations.

scholarly journals Modelling population dynamics in a unicellular social organism community using a minimal model and evolutionary game theory

Open Biology ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 200206
Author(s):  
Ravindra Garde ◽  
Jan Ewald ◽  
Ákos T. Kovács ◽  
Stefan Schuster
Keyword(s):  
Game Theory ◽  
Population Dynamics ◽  
Evolutionary Game Theory ◽  
Evolutionary Game ◽  
Minimal Models ◽  
Unicellular Organisms ◽  
Cyclic Dynamics ◽  
High Level ◽  
Complex Phenomena ◽  
Social Organism

Most unicellular organisms live in communities and express different phenotypes. Many efforts have been made to study the population dynamics of such complex communities of cells, coexisting as well-coordinated units. Minimal models based on ordinary differential equations are powerful tools that can help us understand complex phenomena. They represent an appropriate compromise between complexity and tractability; they allow a profound and comprehensive analysis, which is still easy to understand. Evolutionary game theory is another powerful tool that can help us understand the costs and benefits of the decision a particular cell of a unicellular social organism takes when faced with the challenges of the biotic and abiotic environment. This work is a binocular view at the population dynamics of such a community through the objectives of minimal modelling and evolutionary game theory. We test the behaviour of the community of a unicellular social organism at three levels of antibiotic stress. Even in the absence of the antibiotic, spikes in the fraction of resistant cells can be observed indicating the importance of bet hedging. At moderate level of antibiotic stress, we witness cyclic dynamics reminiscent of the renowned rock–paper–scissors game. At a very high level, the resistant type of strategy is the most favourable.

scholarly journals Lhr and Hmr are required for sister chromatid detachment during anaphase but not for centromere function

2017 ◽  
Author(s):  
Jacob A. Blum ◽  
Silvia Bonaccorsi ◽  
Marta Marzullo ◽  
Valeria Palumbo ◽  
Yukiko M. Yamashita ◽  
...  
Keyword(s):  
Metaphase Plate ◽  
Mitotic Division ◽  
Loss Of Function ◽  
Hybrid Lethality ◽  
Hybrid Male ◽  
Anaphase Bridges ◽  
Sister Chromatids ◽  
Chromosome Alignment ◽  
Dividing Cells ◽  
Lethal Hybrid

AbstractCrosses between Drosophila melanogaster females and Drosophila simulans males produce hybrid sons that die at the larval stage. This hybrid lethality is suppressed by loss-of-function mutations in the D. melanogaster Hybrid male rescue (Hmr) or in the D. simulans Lethal hybrid rescue (Lhr) genes. Previous studies have shown that Hmr and Lhr interact with heterochromatin proteins and suppress expression of transposable elements within D. melanogaster. It also has been proposed that Hmr and Lhr function at the centromere. We examined mitotic divisions in larval brains from Hmr and Lhr single mutants and Hmr; Lhr double mutants in D. melanogaster. In none of the mutants did we observe defects in metaphase chromosome alignment or hyperploid cells, which are hallmarks of centromere or kinetochore dysfunction. In addition, we found that Hmr-HA and Lhr-HA do not localize to centromeres either during interphase or mitotic division. However, all mutants displayed anaphase bridges and chromosome aberrations resulting from the breakage of these bridges, predominantly at the euchromatin-heterochromatin junction. The few dividing cells present in hybrid males showed irregularly condensed chromosomes with fuzzy and often closely apposed sister chromatids. Despite this defect in condensation, chromosomes in hybrids managed to align on the metaphase plate and undergo anaphase. We conclude that there is no evidence for a centromeric function of Hmr and Lhr within D. melanogaster nor for a centromere defect causing hybrid lethality. Instead we find that Hmr and Lhr are required in D. melanogaster for detachment of sister chromatids during anaphase.

scholarly journals eIF4E and Interactors from Unicellular Eukaryotes

2020 ◽  
Vol 21 (6) ◽  
pp. 2170
Author(s):  
Daniela Ross-Kaschitza ◽  
Michael Altmann
Keyword(s):  
Leishmania Major ◽  
Yeast Species ◽  
Life Cycle Stage ◽  
Initiation Factor ◽  
Marine Microorganisms ◽  
Protozoan Parasites ◽  
Interacting Protein ◽  
Unicellular Eukaryotes ◽  
Unicellular Organisms ◽  
And Function

eIF4E, the mRNA cap-binding protein, is well known as a general initiation factor allowing for mRNA-ribosome interaction and cap-dependent translation in eukaryotic cells. In this review we focus on eIF4E and its interactors in unicellular organisms such as yeasts and protozoan eukaryotes. In a first part, we describe eIF4Es from yeast species such as Saccharomyces cerevisiae, Candida albicans, and Schizosaccharomyces pombe. In the second part, we will address eIF4E and interactors from parasite unicellular species—trypanosomatids and marine microorganisms—dinoflagellates. We propose that different strategies have evolved during evolution to accommodate cap-dependent translation to differing requirements. These evolutive “adjustments” involve various forms of eIF4E that are not encountered in all microorganismic species. In yeasts, eIF4E interactors, particularly p20 and Eap1 are found exclusively in Saccharomycotina species such as S. cerevisiae and C. albicans. For protozoan parasites of the Trypanosomatidae family beside a unique cap4-structure located at the 5′UTR of all mRNAs, different eIF4Es and eIF4Gs are active depending on the life cycle stage of the parasite. Additionally, an eIF4E-interacting protein has been identified in Leishmania major which is important for switching from promastigote to amastigote stages. For dinoflagellates, little is known about the structure and function of the multiple and diverse eIF4Es that have been identified thanks to widespread sequencing in recent years.

RELATION BETWEEN CELL CYCLE AND YIELD OF ABERRATIONS OBSERVED IN IRRADIATED HUMAN LYMPHOCYTES

1979 ◽  
Vol 21 (4) ◽  
pp. 473-478 ◽  
Author(s):  
A. Leonard ◽  
G. Decat
Keyword(s):  
Cell Cycle ◽  
Cell Kinetics ◽  
Human Lymphocytes ◽  
Mitotic Division ◽  
Fixation Time ◽  
X Rays ◽  
Mitotic Delay ◽  
Dividing Cells ◽  
Ionizing Radiations ◽  
Pha Stimulation

The bromodeoxyuridine-Giemsa technique has been used to study systematically the incidence of cells in first or subsequent mitoses at different fixation times of human lymphocyte control cultures as well as the influence of ionizing radiations on cell kinetics. Second divisions appear (3%) in cultures harvested 48 h after initiation. In 72 h cultures 40% of the dividing cells are in second and 33% in third division. Administration of 200 rads of X-rays before PHA stimulation results in a mitotic delay but does not increase the incidence of SCE. The yield of dicentrics after an exposure to 200 rads was the same for all cells in first mitosis regardless of fixation time. These results demonstrate that there is no evidence for the existence of sensitive subpopulations that could be distinguished by the time of the first mitotic division following stimulation.

Do growth and cell division rates determine cell size in multicellular organisms?

2000 ◽  
Vol 113 (17) ◽  
pp. 2927-2934 ◽  
Author(s):  
C.M. Coelho ◽  
S.J. Leevers
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Imaginal Disc ◽  
Minimum Size ◽  
Organ Growth ◽  
Unicellular Eukaryotes ◽  
Genes Encoding ◽  
Dividing Cells ◽  
Phosphoinositide 3 Kinase ◽  
Multicellular Organisms

Studies in yeast have provided some clues to how cell size might be determined in unicellular eukaryotes; yet little attention has been paid to this issue in multicellular organisms. Reproducible cell sizes might be achieved in the dividing cells of multicellular organisms by the coordination of growth with cell division. Recently, mutations in genes encoding homologues of components of the mammalian insulin/phosphoinositide 3-kinase signalling pathway have been shown to affect organ growth and cell size during Drosophila melanogaster imaginal disc development. The data suggest that signalling through this pathway alters cell size because it primarily affects the growth of these organs (i.e. their increase in mass) and does not have a proportional impact on cell division. These observations are in keeping with the hypothesis that growth and cell division are regulated independently, and that cell size is just a consequence of the rate at which tissues grow and the cells within them divide. However, signalling through this pathway can affect cell cycle phasing and at least influence cell division. These interactions may provide a means of coordinating growth and cell division, such that cells divide only when they are above a minimum size.

Programmed development in the mouse embryo

Development ◽  
1984 ◽  
Vol 83 (Supplement) ◽  
pp. 197-231
Author(s):  
M. H. Johnson ◽  
J. McConnell ◽  
J. Van Blerkom
Keyword(s):  
Single Cell ◽  
Mouse Embryo ◽  
Positional Information ◽  
Cell Interaction ◽  
Mitotic Division ◽  
Target Cells ◽  
Founder Population ◽  
Developmental Systems ◽  
Cell Position ◽  
Molecular Nature

The programmed development of the embryo involves the specification of cells in space and in time. Specification of cells according to their location is evidently achieved by a process of cell interaction and the recognition of relative cell position. Some positional cues function by setting up within a single cell asymmetries of organization that result in intercellular differences after mitotic division. Others operate within a founder population of homogeneous precursor cells, generating variety via inductive or graded diffusional signals of various sorts (reviewed for various species by Slack, 1983; Johnson & Pratt, 1983). The molecular nature of the cues that convey positional information is known for few, if any, developmental systems, but the available evidence suggests that the cues themselves are unlikely to be highly specific informational molecules. Rather, specificity is achieved through the interaction of positional signals with target cells ‘primed’ to respond to them.

scholarly journals Unusual Order of Chromosome Arrangement Location in Late Prophase - Early Prometaphase of Mitosis in Haploid Maize Plant Obtained With the Use of Mutation ig

2021 ◽  
Vol 7 (1) ◽  
pp. 10-18
Author(s):  
R. Yudina ◽  
E. Levites
Keyword(s):  
Higher Plants ◽  
Mitotic Division ◽  
Maize Plant ◽  
Late Prophase ◽  
Simple Method ◽  
Ploidy Levels ◽  
Dividing Cells ◽  
Maize Plants ◽  
Lower Plants ◽  
Plant Forms

Despite the huge amount of works devoted to the study of mitotic division, there is still a lot of unclear in its mechanisms. For example, insufficient attention has been paid to the processes of cell division in plant forms of different ploidy levels. The literature contains only fragmentary data on haploids in lower plants. This does not allow making any generalizations regarding mitosis in haploids of higher plants. This article presents the results of a cytological study of mitotically dividing cells of haploid maize plants. The article demonstrates the effectiveness of the well-known Chase method, based on the use of genetic markers and the ig mutation (indeterminate gametophyte) for obtaining and detecting haploids. An effective modification of a simple method of acetocarmine staining of cytological preparations is described. An essential result obtained is, in our opinion, the detection of a very brief moment in the state of chromosomes in a dividing cell of a haploid maize plant. This moment is characterized by the fact that the chromatids have already separated and turned into independent chromosomes, but have not yet begun their movement under the action of kinetochore microtubules. It is this feature that made it possible to designate this state as late prophase – early prometaphase of mitosis. An equally important feature of the detected moment is the unusual ordered arrangement of chromosomes, which lie parallel to each other close to each other along their entire length with the centromeres located on one line, which can be considered the equator of the fission spindle. The revealed fact allows us to assume that an essential role in the formation of such an arrangement of chromosomes is played by the bond of chromosomes with the equator of the nuclear membrane and their subsequent connection with the equator of the fission spindle.

scholarly journals Estimation the porosity of the valves of centric diatom Minidiscus vodyanitskiyi Lyakh & Bedoshvili using SEM images

2019 ◽  
Author(s):  
Anton M. Lyakh ◽  
Yekaterina D. Bedoshvili ◽  
Olga V. Shikhat
Keyword(s):  
Surface Area ◽  
Total Surface Area ◽  
Centric Diatom ◽  
Relative Area ◽  
Diatom Species ◽  
Sem Images ◽  
Material Resources ◽  
Unicellular Organisms ◽  
Diatom Valve ◽  
Outer Environment

AbstractThe diatoms interact with the outer environment through the siliceous walls of a frustule. Because of that the surface area of the frustule determines the ability of diatoms to absorb and excrete material resources. Such as unicellular organisms exchange matter only through the pores in their cell wall, to find relationships between characteristics of material fluxes and surface area of microorganism cover that is penetrable for substance, it is necessary to estimate the total surface area of pores or a porosity – relative area of pores perforated frustule. In the paper we describe a method of estimating the porosity of a diatom valve using SEM images. The method is tested on SEM images of the valves of centric diatom Minidiscus vodyanitskiyi recently described from the Sea of Azov. The results show that the valves porosity is less than 5 % of the total valves area. This value is consistent with the relative perforation of land plants leaves, which is less than 3%. We hypothesize that such value of diatom valves porosity is usual for many other diatom species. To verify this hypothesis additional researches are necessary.

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