Freezing

2017 ◽  
Author(s):  
Andrew Clarke
Keyword(s):  
Thermal Hysteresis ◽  
Higher Plants ◽  
Terrestrial Environment ◽  
Cold Temperatures ◽  
Cellular Dehydration ◽  
A Cell ◽  
Unicellular Organisms ◽  
Cell Cytosol ◽  
Freezing Temperatures ◽  
Multicellular Organisms

Freezing is a widespread ecological challenge, affecting organisms in over half the terrestrial environment as well as both polar seas. With very few exceptions, if a cell freezes internally, it dies. Polar teleost fish in shallow waters avoid freezing by synthesising a range of protein or glycoprotein antifreezes. Terrestrial organisms are faced with a far greater thermal challenge, and exhibit a more complex array of responses. Unicellular organisms survive freezing temperatures by preventing ice nucleating within the cytosol, and tolerating the cellular dehydration and membrane disruption that follows from ice forming in the external environment. Multicellular organisms survive freezing temperatures by manipulating the composition of the extracellular body fluids. Terrestrial organisms may freeze at high subzero temperatures, often promoted by ice nucleating proteins, and small molecular mass cryoprotectants (often sugars and polyols) moderate the osmotic stress on cells. A range of chaperone proteins (dehydrins, LEA proteins) help maintain the integrity of membranes and macromolecules. Thermal hysteresis (antifreeze) proteins prevent damaging recrystallisation of ice. In some cases arthropods and higher plants prevent freezing in their extracellular fluids and survive by supercooling. Vitrification of extracellular water, or of the cell cytosol, may be a more widespread response to very cold temperatures than recognised to date.

scholarly journals Phagocytosis: a repertoire of receptors and Ca2+ as a key second messenger

2008 ◽  
Vol 28 (5) ◽  
pp. 287-298 ◽  
Author(s):  
Alirio J. Melendez ◽  
Hwee Kee Tay
Keyword(s):  
Phagosome Maturation ◽  
Physiological Event ◽  
Signalling Molecules ◽  
Complex Process ◽  
Large Particles ◽  
A Cell ◽  
Unicellular Organisms ◽  
Multicellular Organisms ◽  
Innate Defence

Receptor-mediated phagocytosis is a complex process that mediates the internalization, by a cell, of other cells and large particles; this is an important physiological event not only in mammals, but in a wide diversity of organisms. Of simple unicellular organisms that use phagocytosis to extract nutrients, to complex metazoans in which phagocytosis is essential for the innate defence system, as a first line of defence against invading pathogens, as well as for the clearance of damaged, dying or dead cells. Evolution has armed multicellular organisms with a range of receptors expressed on many cells that serve as the molecular basis to bring about phagocytosis, regardless of the organism or the specific physiological event concerned. Key to all phagocytic processes is the finely controlled rearrangement of the actin cytoskeleton, in which Ca2+ signals play a major role. Ca2+ is involved in cytoskeletal changes by affecting the actions of a number of contractile proteins, as well as being a cofactor for the activation of a number of intracellular signalling molecules, which are known to play important roles during the initiation, progression and resolution of the phagocytic process. In mammals, the requirement of Ca2+ for the initial steps in phagocytosis, and the subsequent phagosome maturation, can be quite different depending on the type of cell and on the type of receptor that is driving phagocytosis. In this review we discuss the different receptors that mediate professional and non-professional phagocytosis, and discuss the role of Ca2+ in the different steps of this complex process.

scholarly journals ‘Bacterial Programmed Cell Death’: cellular altruism or genetic selfism?

2020 ◽  
Vol 367 (16) ◽  
Author(s):  
Bhaskar Chandra Mohan Ramisetty ◽  
Pavithra Anantharaman Sudhakari
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Free Living ◽  
Selfish Genes ◽  
A Cell ◽  
Unicellular Organisms ◽  
Multicellular Organisms ◽  
Restriction Modification ◽  
Restriction Modification Systems ◽  
Selection Of

ABSTRACT Cell-dependent propagation of the ‘self’ is the driver of all species, organisms and even genes. Conceivably, elimination of these entities is caused by cellular death. Then, how can genes that cause the death of the same cell evolve? Programmed cell death (PCD) is the gene-dependent self-inflicted death. In multicellular organisms, PCD of a cell confers fitness to the surviving rest of the organism, which thereby allows the selection of genes responsible for PCD. However, PCD in free-living bacteria is intriguing; the death of the cell is the death of the organism. How can such PCD genes be selected in unicellular organisms? The bacterial PCD in a population is proposed to confer fitness to the surviving kin in the form of sporulation, nutrition, infection-containment and matrix materials. While the cell-centred view leading to propositions of ‘altruism’ is enticing, the gene-centred view of ‘selfism’ is neglected. In this opinion piece, we reconceptualize the PCD propositions as genetic selfism (death due to loss/mutation of selfish genes) rather than cellular altruism (death for the conferment of fitness to kin). Within the scope and the available evidence, we opine that some of the PCD-like observations in bacteria seem to be the manifestation of genetic selfism by Restriction–Modification systems and Toxin–Antitoxin systems.

scholarly journals Evidence for binding of gastrin to ligandin, a cell cytosol protein

FEBS Letters ◽  
1975 ◽  
Vol 52 (2) ◽  
pp. 300-303
Author(s):  
R.E. Kirsch ◽  
A.I. Vinik ◽  
L.O'C. Frith ◽  
B. Gordon ◽  
B.J. Grant ◽  
...  
Keyword(s):  
A Cell ◽  
Cell Cytosol

scholarly journals Autotoxin-mediated voluntary triage in starved yeast community

2020 ◽  
Author(s):  
Arisa H. Oda ◽  
Miki Tamura ◽  
Kunihiko Kaneko ◽  
Kunihiro Ohta ◽  
Tetsuhiro S. Hatakeyama
Keyword(s):  
Environmental Changes ◽  
Yeast Cells ◽  
Glucose Starvation ◽  
Uniform Stress ◽  
Universal System ◽  
Stressful Environment ◽  
Yeast Community ◽  
Unicellular Organisms ◽  
Multicellular Organisms ◽  
Cell Community

When organisms face crises, such as starvation, every individual should adapt to environmental changes (1, 2), or the community alters their behaviour (3–5). Because a stressful environment reduces the carrying capacity (6), the population size of unicellular organisms shrinks in such conditions (7, 8). However, the uniform stress response of the cell community may lead to overall extinction or severely damage their entire fitness. How microbial communities accommodate this dilemma remains poorly understood. Here, we demonstrate an elaborate strategy of the yeast community against glucose starvation, named the voluntary triage. During starvation, yeast cells release some autotoxins, such as leucic acid and L-2keto-3methylvalerate, which can even kill the cells producing them. Although it may look like mass suicide at first glance, cells use epigenetic “tags” to adapt to the autotoxin inheritably. If non-tagged latecomers, regardless of whether they are closely related, try to invade the habitat, autotoxins kill them and inhibit their growth, but the tagged cells can selectively survive. Phylogenetically distant fission and budding yeast (9) share this strategy using the same autotoxins, which implies that the universal system of voluntary triage may be relevant to the major evolutional transition from unicellular to multicellular organisms (10).

Calcium/Calmodulin Affects Microtubule Stability in Lysed Protoplasts

1991 ◽  
Vol 100 (2) ◽  
pp. 311-317
Author(s):  
RICHARD J. CYR
Keyword(s):  
Cell Cycle ◽  
Dynamic Behavior ◽  
Growth And Development ◽  
Higher Plants ◽  
Plant Cells ◽  
Microtubule Stability ◽  
A Cell ◽  
Cycle Dependent ◽  
Carrot Protoplasts

Microtubules (Mts) are found in four distinct arrays appearing sequentially in a cell-cycle-dependent fashion within the cells of higher plants. Additionally, the cortical Mts of non-cycling cells are spatially altered in a variety of differentiated states. Information regarding the molecular details underlying these Mt-reorientation events in plant cells is scarce. Moreover, it is unclear how cytoskeletal behavior integrates with the myriad of other cellular activities that are altered concomitantly in both differentiating and cycling cells. Data are presented herein to indicate that calcium, in the form of a Ca2+/calmodulin complex, can alter the behavior of Mts in lysed carrot protoplasts. Mechanistically, we show that Ca2+/calmodulin most likely interacts with Mts via associations with microtubule associated pro- teins (MAPS). These results are discussed with reference to how Ca2+ may alter the dynamic behavior of Mts during growth and development.

Development in simple organisms

1997 ◽  
Author(s):  
John Maynard Smith ◽  
Eors Szathmary
Keyword(s):  
Higher Plants ◽  
Molecular Data ◽  
Alternative Interpretation ◽  
Cambrian Explosion ◽  
Differentiated Cells ◽  
Worldwide Distribution ◽  
Cell Layers ◽  
Sudden Appearance ◽  
Multicellular Organisms ◽  
Ediacaran Fauna

Complex multicellular organisms, whose bodies consist of differentiated cells of many kinds, have evolved independently on three occasions—animals, higher plants and fungi. In addition, multicellular organisms with a lesser degree of cellular differentiation have evolved on a number of occasions. For example, the algae have given rise to ‘seaweeds’ several times. In this and the next three chapters, we discuss the origin and subsequent evolution of such organisms. Some 540 million years ago, at the beginning of the Cambrian, there appeared an array of multicellular marine animals, including the major phyla that exist today—coelenterates, platyhelminths, annelids, arthropods, molluscs, echinoderms and others. Chordates are also present in the Cambrian: they are not known from the earliest deposits, in which only hard parts are preserved, but are present in the slightly later Burgess Shale, in which soft-bodied forms are preserved. Forty years ago, this sudden appearance of metazoan fossils was not only a puzzle but something of an embarassment: the absence of any known fossils from earlier rocks was a weapon widely used by creationists. Today, the fossil evidence for prokaryotes goes back 3000 million years, and for protists some 1000 million years. The Cambrian explosion remains a puzzle, however, which has been only fitfully illuminated by the discovery of the enigmatic soft-bodied Ediacaran fauna, which had a worldwide distribution between 580 and 560 million years ago. There are still doubts about how these fossils should be interpreted (Conway Morris, 1993). The orthodox, and more plausible, view is that the fauna is dominated by coelenterates, with some specimens identified as echinoderms and annelids. An alternative interpretation (Seilacher, 1992) is that they belong to an extinct clade of multicellular eukaryotes, the ventobionts, probably lacking an alimentary canal, muscles and nervous system. Although such organisms may have existed, at least some of the Ediacaran fauna have been successfully compared to recent metazoans. If the interpretation of most of these fossils as coelenterates proves to be correct, it would fit in well with the morphological and molecular evidence. The molecular data suggest that coelenterates arose early, but probably not independently of other metazoans. Morphologically they are simple in being diploblastic (formed from two cell layers), in contrast to the triploblastic animals that predominate in the Cambrian.

Cyclization of 2,3-oxidosqualene to cycloartenol in a cell-free system from higher plants

1968 ◽  
Vol 9 (6) ◽  
pp. 723-725 ◽  
Author(s):  
H.H. Rees ◽  
L.J. Goad ◽  
T.W. Goodwin
Keyword(s):  
Higher Plants ◽  
Free System ◽  
Cell Free System ◽  
A Cell

scholarly journals Leaf Trichome Distribution Pattern in Arabidopsis Reveals Gene Expression Variation Associated with Environmental Adaptation

Plants ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 909
Author(s):  
Shotaro Okamoto ◽  
Kohei Negishi ◽  
Yuko Toyama ◽  
Takeo Ushijima ◽  
Kengo Morohashi
Keyword(s):  
Gene Expression ◽  
Distribution Pattern ◽  
Higher Plants ◽  
Reaction Diffusion ◽  
Distribution Patterns ◽  
Environmental Adaptation ◽  
Stochastic Variation ◽  
Biological Relevance ◽  
Homogeneous Cell ◽  
Multicellular Organisms

Gene expression varies stochastically even in both heterogenous and homogeneous cell populations. This variation is not simply useless noise; rather, it is important for many biological processes. Unicellular organisms or cultured cell lines are useful for analyzing the variation in gene expression between cells; however, owing to technical challenges, the biological relevance of this variation in multicellular organisms such as higher plants remain unclear. Here, we addressed the biological relevance of this variation between cells by examining the genetic basis of trichome distribution patterns in Arabidopsis thaliana. The distribution pattern of a trichome on a leaf is stochastic and can be mathematically represented using Turing’s reaction-diffusion (RD) model. We analyzed simulations based on the RD model and found that the variability in the trichome distribution pattern increased with the increase in stochastic variation in a particular gene expression. Moreover, differences in heat-dependent variability of the trichome distribution pattern between the accessions showed a strong correlation with environmental factors to which each accession was adapted. Taken together, we successfully visualized variations in gene expression by quantifying the variability in the Arabidopsis trichome distribution pattern. Thus, our data provide evidence for the biological importance of variations in gene expression for environmental adaptation.

scholarly journals Antimicrobial peptides and bacteriocins: alternatives to traditional antibiotics

2008 ◽  
Vol 9 (2) ◽  
pp. 227-235 ◽  
Author(s):  
Yongming Sang ◽  
Frank Blecha
Keyword(s):  
Antimicrobial Peptides ◽  
Membrane Integrity ◽  
Principal Component ◽  
Protective Response ◽  
Antimicrobial Drugs ◽  
Induce Resistance ◽  
Unicellular Organisms ◽  
Conventional Antibiotics ◽  
Multicellular Organisms ◽  
Recent Attention

AbstractAntimicrobial peptides (AMPs) are ubiquitous, gene-encoded natural antibiotics that have gained recent attention in the search for new antimicrobials to combat infectious disease. In multicellular organisms, AMPs, such as defensins and cathelicidins, provide a coordinated protective response against infection and are a principal component of innate immunity in vertebrates. In unicellular organisms, AMPs, such as bacteriocins, function to suppress competitor species. Because many AMPs kill bacteria by disruption of membrane integrity and are thus thought to be less likely to induce resistance, AMPs are being extensively evaluated as novel antimicrobial drugs. This review summarizes and discusses the antibiotic properties of AMPs highlighting their potential as alternatives to conventional antibiotics.

scholarly journals Cell-specific expression buffering promotes cell survival and cancer robustness

2021 ◽  
Author(s):  
Hao-Kuen Lin ◽  
Jen-Hao Cheng ◽  
Chia-Chou Wu ◽  
Feng-Shu Hsieh ◽  
Carolyn A Dunlap ◽  
...  
Keyword(s):  
Cell Survival ◽  
Rna Seq ◽  
Specific Expression ◽  
Tissue Specific ◽  
Gene Pairs ◽  
Genome Wide ◽  
A Cell ◽  
Physiological Homeostasis ◽  
Multicellular Organisms ◽  
Score Index

Functional buffering ensures biological robustness critical for cell survival and physiological homeostasis in response to environmental challenges. However, in multicellular organisms, the mechanism underlying cell- and tissue-specific buffering and its implications for cancer development remain elusive. Here, we propose a Cell-specific Expression-BUffering (CEBU) mechanism, whereby a gene's function is buffered by cell-specific expression of a buffering gene, to describe functional buffering in humans. The likelihood of CEBU between gene pairs is quantified using a C-score index. By computing C-scores using genome-wide CRISPR screens and transcriptomic RNA-seq of 684 human cell lines, we report that C-score-identified putative buffering gene pairs are enriched for members of the same pathway, protein complex and duplicated gene family. Furthermore, these buffering gene pairs contribute to cell-specific genetic interactions and are indicative of tissue-specific robustness. C-score derived buffering capacities can help predict patient survival in multiple cancers. Our results reveal CEBU as a critical mechanism of functional buffering contributing to cell survival and cancer robustness in humans.

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