scholarly journals Mutant with heat-sensitive capacity for phagocytosis in tetrahymena: isolation and genetic characterization

1975 ◽  
Vol 26 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Gary B. Silberstein ◽  
Eduardo Orias ◽  
Nina A. Pollock
Keyword(s):  
Cell Division ◽  
Vegetative Propagation ◽  
Genetic Characterization ◽  
Mutant Phenotype ◽  
Cellular Functions ◽  
Enrichment Procedure

SUMMARYA mutant of Tetrahymena with heat-sensitive phagocytosis was obtained using a tantalum-particle enrichment procedure. The mutant phenotype is most likely determined by a somatic (macronuclear) mutation(s). The inability of the mutant to sustain cell division and to phagocytize at 37 °C are most likely determined by the same mutation. The phenotype of the mutant is stably inherited under vegetative propagation at 30 °C. At 37 °C, the mutation affects the development of the oral apparatus, the phagocytotic organelle. This mutant has proven useful for the study of cellular functions related to phagocytosis.

scholarly journals The 3D architecture and molecular foundations of de novo centriole assembly via bicentrioles

2020 ◽  
Author(s):  
Sónia Gomes Pereira ◽  
Ana Laura Sousa ◽  
Catarina Nabais ◽  
Tiago Paixão ◽  
Alexander. J. Holmes ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
De Novo ◽  
Cellular Functions ◽  
Spindle Poles ◽  
3D Architecture ◽  
Centriole Assembly ◽  
Work Supports ◽  
Wall Components

Abstract/SummaryCentrioles are structurally conserved organelles, composing both centrosomes and cilia. In animal cycling cells, centrioles often form through a highly characterized process termed canonical duplication. However, a large diversity of eukaryotes form centrioles de novo through uncharacterized pathways. This unexplored diversity is key to understanding centriole assembly mechanisms and how they evolved to assist specific cellular functions. Here, combining electron microscopy and tomography, we show that during spermatogenesis of the moss Physcomitrium patens, centrioles are born as a co-axially oriented centriole pair united by a cartwheel. We observe that microtubules emanate from those bicentrioles, which localize to the spindle poles during cell division. Thereafter, each bicentriole breaks apart, and the two resulting sister centrioles mature asymmetrically, elongating specific microtubule triplets and a naked cartwheel. Subsequently, two cilia are assembled which are capable of beating asynchronously. We further show that conserved cartwheel and centriole wall components, SAS6, BLD10 and POC1 are expressed during spermatogenesis and are required for this de novo biogenesis pathway. Our work supports a scenario where centriole biogenesis is more diverse than previously thought and that conserved molecular modules underlie diversification of this essential pathway.

An ultradian clock controls locomotor behaviour and cell division in isolated cells of Paramecium tetraurelia

1996 ◽  
Vol 109 (4) ◽  
pp. 867-873 ◽  
Author(s):  
F. Kippert
Keyword(s):  
Cell Division ◽  
Time Window ◽  
Phase Relationship ◽  
Paramecium Tetraurelia ◽  
Temporal Control ◽  
Cellular Functions ◽  
Isolated Cells ◽  
Optimum Growth Temperature ◽  
Locomotor Behaviour ◽  
Generation Times

An ultradian clock operates in fast growing cells of the large ciliate, Paramecium tetraurelia. The period of around 70 minutes is well temperature-compensated over the temperature range tested, i.e. between 18 degrees C and 33 degrees C. The Q10 between 18 degrees C and 27 degrees C is 1.08; above 27 degrees C there is a slight overcompensation. The investigation of individual cells has revealed that two different cellular functions are under temporal control by this ultradian clock. First, locomotor behaviour, which is an alternation between a phase of fast swimming with only infrequent turning, and a phase of slow swimming with frequent spontaneous changes of direction. In addition, the ultradian clock is involved in the timing of cell division. Generation times are not randomly distributed, but occur in well separated clusters. At all of the six temperatures tested, the clusters are separated by around 70 minutes which corresponds well to the period of the locomotor behaviour rhythm at the respective temperatures. Whereas the interdivision times were gradually lengthened both above and below the optimum growth temperature, the underlying periodicity remained unaffected. Also cells of different clonal age had identical periods, suggesting that neither the differences in DNA content, not other changes associated with ageing in Paramecium have an effect on the clock. A constant phase relationship was observed between the rhythm in locomotor behaviour and the time window for cell division; this strongly suggests that the same ultradian clock exerts temporal control over both processes.

scholarly journals Vimentin filaments interact with the actin cortex in mitosis allowing normal cell division

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Sofia Duarte ◽  
Álvaro Viedma-Poyatos ◽  
Elena Navarro-Carrasco ◽  
Alma E. Martínez ◽  
María A. Pajares ◽  
...  
Keyword(s):  
Cell Division ◽  
Cell Types ◽  
Hiv Protease ◽  
Cell Cortex ◽  
Tail Domain ◽  
Cellular Functions ◽  
Cortical Actin ◽  
Intrinsically Disordered ◽  
Actin Cortex ◽  
Vimentin Filaments

Abstract The vimentin network displays remarkable plasticity to support basic cellular functions and reorganizes during cell division. Here, we show that in several cell types vimentin filaments redistribute to the cell cortex during mitosis, forming a robust framework interwoven with cortical actin and affecting its organization. Importantly, the intrinsically disordered tail domain of vimentin is essential for this redistribution, which allows normal mitotic progression. A tailless vimentin mutant forms curly bundles, which remain entangled with dividing chromosomes leading to mitotic catastrophes or asymmetric partitions. Serial deletions of vimentin tail domain gradually impair cortical association and mitosis progression. Disruption of f-actin, but not of microtubules, causes vimentin bundling near the chromosomes. Pathophysiological stimuli, including HIV-protease and lipoxidation, induce similar alterations. Interestingly, full filament formation is dispensable for cortical association, which also occurs in vimentin particles. These results unveil implications of vimentin dynamics in cell division through its interplay with the actin cortex.

scholarly journals ON THE MECHANISM OF ADAPTATION TO PROTEIN SYNTHESIS INHIBITORS BY TETRAHYMENA

1974 ◽  
Vol 62 (3) ◽  
pp. 707-716 ◽  
Author(s):  
Charles T. Roberts ◽  
Eduardo Orias
Keyword(s):  
Protein Synthesis ◽  
Cell Division ◽  
Protein Synthesis Inhibitor ◽  
Protein Synthesis Inhibitors ◽  
Cellular Functions ◽  
Synthesis Inhibitor ◽  
Experimental Conditions ◽  
Cellular Machinery ◽  
Time Required ◽  
Sublethal Concentrations

Tetrahymena is able to adapt to the presence of sublethal concentrations of many drugs which inhibit a wide variety of cellular functions. In spite of the generality of this phenomenon in Tetrahymena, the mechanism of adaptation at the cellular and molecular levels is unknown. This study deals mainly with adaptation to the protein synthesis inhibitors, cycloheximide and emetine. The physiological response of Tetrahymena to sublethal concentrations of these drugs is an immediate cessation of cell division for a period of time dependent on the drug concentration, followed by an abrupt resumption of exponential growth at a constant rate. By measuring the length of the growth lags under a variety of experimental conditions, we have confirmed several observations made by Frankel and coworkers, and provide evidence for two new phenomena associated with adaptation to cycloheximide: (a) adaptation to cycloheximide also results in adaptation of cells to emetine, another protein synthesis inhibitor not closely related structurally to cycloheximide. We have termed this phenomenon cross adaptation, (b) exposure to concentrations of cycloheximide too low to cause any growth lags or inhibition of protein synthesis significantly shortens the time required by cells to adapt to higher concentrations of cycloheximide. We have termed this phenomenon facilitation. Facilitation shows some degree of specificity in that facilitation with cycloheximide has no effect on adaptation to emetine. From this, we infer the existence of two distinct systems involved in adaptation to cycloheximide, one of which shows a higher degree of specificity towards cycloheximide than the other. We also show that transfer of adapted or facilitated cells to drug-free medium results in a gradual but complete resensitization. The kinetics of resensitization suggest that the cellular machinery responsible for adaptation and facilitation does not leave the cell, but is simply diluted out during cell division.

scholarly journals Not just a pretty cargo carrier: the other face of kinesins

2018 ◽  
Vol 40 (2) ◽  
pp. 22-25
Author(s):  
Claire Friel
Keyword(s):  
Cell Division ◽  
Large Family ◽  
The Other ◽  
Cellular Functions ◽  
Microtubule Motors ◽  
Kinesin Superfamily

If you've only ever heard of one kinesin, it's likely to be one that walks along microtubules and carries cargo around in the cell. However, this type of kinesin is only part of the kinesin story. The ‘kinesin superfamily’ is a large family of microtubule motors and members of the superfamily are critical to a variety of cellular functions. This article focuses on a class of kinesins that regulate the growth and shrinkage dynamics of microtubules. These kinesins orchestrate the construction and maintenance of microtubule structures required temporarily by cells, such as the apparatus that separates replicate chromosomes during cell division.

scholarly journals Mobility of filamentous actin in living cytoplasm.

1987 ◽  
Vol 105 (6) ◽  
pp. 2811-2816 ◽  
Author(s):  
Y L Wang
Keyword(s):  
Cell Division ◽  
Cultured Cells ◽  
Stress Fibers ◽  
Detectable Effect ◽  
Filamentous Actin ◽  
Cellular Functions ◽  
Contractile Ring ◽  
Rhodamine Phalloidin ◽  
Affinity Probe ◽  
Dividing Cells

Filamentous actin in living cultured cells was labeled by microinjecting trace amounts of rhodamine-phalloidin (rh-pha) as a specific, high-affinity probe. The microinjection caused no detectable effect on cell morphology or cell division. The distribution of rh-pha-labeled filaments was then examined in dividing cells using image-intensified fluorescence microscopy, and the exchangeability of labeled filaments along stress fibers was studied during interphase using fluorescence recovery after photobleaching. rh-pha showed a rapid concentration at the contractile ring during cell division. In addition, recovery of fluorescence after photobleaching occurred along stress fibers with a halftime as short as 8 min. These observations suggest that at least some actin filaments undergo continuous movement and reorganization in living cells. This dynamic process may play an important role in various cellular functions.

scholarly journals SUMOylation of human septins is critical for septin filament bundling and cytokinesis

2017 ◽  
Vol 216 (12) ◽  
pp. 4041-4052 ◽  
Author(s):  
David Ribet ◽  
Serena Boscaini ◽  
Clothilde Cauvin ◽  
Martin Siguier ◽  
Serge Mostowy ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Posttranslational Modification ◽  
Diffusion Barriers ◽  
Cytoskeletal Proteins ◽  
Cellular Functions ◽  
Terminal Domain ◽  
Subcellular Compartmentalization ◽  
Protein Recruitment ◽  
Septin Filament

Septins are cytoskeletal proteins that assemble into nonpolar filaments. They are critical in diverse cellular functions, acting as scaffolds for protein recruitment and as diffusion barriers for subcellular compartmentalization. Human septins are encoded by 13 different genes and are classified into four groups based on sequence homology (SEPT2, SEPT3, SEPT6, and SEPT7 groups). In yeast, septins were among the first proteins reported to be modified by SUMOylation, a ubiquitin-like posttranslational modification. However, whether human septins could be modified by small ubiquitin-like modifiers (SUMOs) and what roles this modification may have in septin function remains unknown. In this study, we first show that septins from all four human septin groups can be covalently modified by SUMOs. We show in particular that endogenous SEPT7 is constitutively SUMOylated during the cell cycle. We then map SUMOylation sites to the C-terminal domain of septins belonging to the SEPT6 and SEPT7 groups and to the N-terminal domain of septins from the SEPT3 group. We finally demonstrate that expression of non-SUMOylatable septin variants from the SEPT6 and SEPT7 groups leads to aberrant septin bundle formation and defects in cytokinesis after furrow ingression. Altogether, our results demonstrate a pivotal role for SUMOylation in septin filament bundling and cell division.

scholarly journals Dynein light intermediate chains maintain spindle bipolarity by functioning in centriole cohesion

2014 ◽  
Vol 207 (4) ◽  
pp. 499-516 ◽  
Author(s):  
Laura A. Jones ◽  
Cécile Villemant ◽  
Toby Starborg ◽  
Anna Salter ◽  
Georgina Goddard ◽  
...  
Keyword(s):  
Cell Division ◽  
Cytoplasmic Dynein ◽  
Small Interfering Rnas ◽  
Cellular Functions ◽  
Multipolar Spindles ◽  
Early Embryos ◽  
Microtubule Motor ◽  
Morpholino Oligonucleotides ◽  
Dynein Light Intermediate Chains ◽  
Intermediate Chains

Cytoplasmic dynein 1 (dynein) is a minus end–directed microtubule motor protein with many cellular functions, including during cell division. The role of the light intermediate chains (LICs; DYNC1LI1 and 2) within the complex is poorly understood. In this paper, we have used small interfering RNAs or morpholino oligonucleotides to deplete the LICs in human cell lines and Xenopus laevis early embryos to dissect the LICs’ role in cell division. We show that although dynein lacking LICs drives microtubule gliding at normal rates, the LICs are required for the formation and maintenance of a bipolar spindle. Multipolar spindles with poles that contain single centrioles were formed in cells lacking LICs, indicating that they are needed for maintaining centrosome integrity. The formation of multipolar spindles via centrosome splitting after LIC depletion could be rescued by inhibiting Eg5. This suggests a novel role for the dynein complex, counteracted by Eg5, in the maintenance of centriole cohesion during mitosis.

scholarly journals Navigating the plant cell: intracellular transport logistics in the green kingdom

2015 ◽  
Vol 26 (19) ◽  
pp. 3373-3378 ◽  
Author(s):  
Anja Geitmann ◽  
Andreas Nebenführ
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Plant Cell ◽  
Cytoplasmic Streaming ◽  
Intracellular Transport ◽  
Plant Cells ◽  
Cellular Functions ◽  
Cell Organelles ◽  
Myosin Xi ◽  
Transport Logistics

Intracellular transport in plant cells occurs on microtubular and actin arrays. Cytoplasmic streaming, the rapid motion of plant cell organelles, is mostly driven by an actin–myosin mechanism, whereas specialized functions, such as the transport of large cargo or the assembly of a new cell wall during cell division, are performed by the microtubules. Different modes of transport are used, fast and slow, to either haul cargo over long distances or ascertain high-precision targeting, respectively. Various forms of the actin-specific motor protein myosin XI exist in plant cells and might be involved in different cellular functions.

scholarly journals Role of the α-Glucanase Agn1p in Fission-Yeast Cell Separation

2004 ◽  
Vol 15 (8) ◽  
pp. 3903-3914 ◽  
Author(s):  
Nick Dekker ◽  
Dave Speijer ◽  
Christian H. Grün ◽  
Marlene van den Berg ◽  
Annett de Haan ◽  
...  
Keyword(s):  
Cell Division ◽  
Fission Yeast ◽  
Cell Separation ◽  
Wall Material ◽  
Dependent Manner ◽  
Cellular Functions ◽  
Daughter Cells ◽  
Primary Septum ◽  
Cycle Dependent ◽  
Division Cell

Cell division in the fission yeast Schizosaccharomyces pombe yields two equal-sized daughter cells. Medial fission is achieved by deposition of a primary septum flanked by two secondary septa within the dividing cell. During the final step of cell division, cell separation, the primary septum is hydrolyzed by an endo-(1,3)-β-glucanase, Eng1p. We reasoned that the cell wall material surrounding the septum, referred to here as the septum edging, also must be hydrolyzed before full separation of the daughter cells can occur. Because the septum edging contains (1,3)-α-glucan, we investigated the cellular functions of the putative (1,3)-α-glucanases Agn1p and Agn2p. Whereas agn2 deletion results in a defect in endolysis of the ascus wall, deletion of agn1 leads to clumped cells that remained attached to each other by septum-edging material. Purified Agn1p hydrolyzes (1,3)-α-glucan predominantly into pentasaccharides, indicating an endo-catalytic mode of hydrolysis. Furthermore, we show that the transcription factors Sep1p and Ace2p regulate both eng1 and agn1 expression in a cell cycle-dependent manner. We propose that Agn1p acts in concert with Eng1p to achieve efficient cell separation, thereby exposing the secondary septa as the new ends of the daughter cells.

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