Proportional control of organelle position by a mechanism which similarly monitors cell size of wild type and conical form-mutant Tetrahymena

Development ◽  
1977 ◽  
Vol 42 (1) ◽  
pp. 261-274
Author(s):  
Denis H. Lynn
Keyword(s):  
Cell Size ◽  
Tetrahymena Thermophila ◽  
Cell Length ◽  
Basal Bodies ◽  
Wild Type ◽  
Cell Type ◽  
Cell Width ◽  
Dividing Cells ◽  
Conical Form

Distance between mouthparts of dividing cells of wild type and conical form-mutant Tetrahymena thermophila (formerly T. pyriformis syngen 1) is directly proportional to cell size. This distance is related to cell length in both wild type and conical cells although the proportionality is different in each cell type. However, for both wild type and conical cells the distance between mouthparts is directly and similarly proportional to the product of cell length and cell width which is an estimate of cell size. Evidence has been obtained which suggests that the new mouthparts are positioned with reference to the anterior mouthparts rather than to either pole of the cell. Determination of the site of the new mouthparts is not related to the number of basal bodies between the two sets of mouthparts.

scholarly journals Identification of mutants with increased variation in cell size at onset of mitosis in fission yeast

2021 ◽  
pp. jcs.251769
Author(s):  
Elizabeth Wood ◽  
Kazunori Kume ◽  
Francisco J. Navarro ◽  
Paul Nurse
Keyword(s):  
Fission Yeast ◽  
Cell Size ◽  
Wild Type Strain ◽  
Cell Length ◽  
Yeast Cells ◽  
Wild Type ◽  
Gene Deletions ◽  
Cytoplasmic Transport ◽  
Dividing Cells ◽  
The Mean

Fission yeast cells divide at a similar cell length with little variation about the mean. This is thought to be the result of a control mechanism that senses size and corrects for any deviations by advancing or delaying onset of mitosis. Gene deletions that advance cells into mitosis at a smaller size or delay cells entering mitosis, have identified genes potentially involved in this mechanism. However, the molecular basis of this control is still not understood. In this work, we have screened for genes, which when deleted, increase the variability in size of dividing cells. The strongest candidate of this screen was mga2. The mga2 deletion shows a greater variation in cell length at division, with a coefficient of variation (CV) of 15-24% while the wild type strain has a CV of 5-8%. Furthermore, unlike wild type cells, the mga2 deletion cells are unable to correct cell size deviations within one cell cycle. We show that the mga2 gene genetically interacts with nem1 and influences the nuclear membrane, and speculate that it may influence the nucleus/cytoplasmic transport of CDK regulators.

Cell size and proportional distance assessment during determination of organelle position in the cortex of the ciliate Tetrahymena

1976 ◽  
Vol 21 (1) ◽  
pp. 35-46 ◽  
Author(s):  
D.H. Lynn ◽  
J.B. Tucker
Keyword(s):  
Cell Division ◽  
Cell Size ◽  
Cell Length ◽  
Basal Bodies ◽  
Chemical Signalling

Developing oral organelles of dividing Tetrahymena corlissi appear to be positioned by mechanisms which assess distances as a proportion of the organism's overall dimensions. In some respects, the cortex of this protozoan obeys the ‘French flag’ rule formulated by Wolpert for describing regulation of spatial proportions during differentiation of metazoan embryos. Dividing Tetrahymena of markedly different sizes occur when division is synchronized by starvation and refeeding. At the start of cell division, the distance between old and new mouthparts varies proportionately with respect to cell length. In addition, determination of the site where new oral organelles will develop is apparently not directly related to the number of ciliated basal bodies which separate the 2 sets of mouthparts; the greater the distance between the old and developing sets of mouthparts, the greater the number of ciliated basal bodies in the rows between them. It is suggested that 2 distinct mechanisms are largely responsible for defining organelle position in ciliates. The new terms structural positioning and chemical signalling are defined to describe these mechanisms.

Cytoskeleton-related structures in tetrahymena thermophila: microfilaments at the apical and division-furrow rings

1981 ◽  
Vol 51 (1) ◽  
pp. 241-253
Author(s):  
M. Jerka-Dziadosz
Keyword(s):  
Cell Membrane ◽  
Type Strain ◽  
Wild Type Strain ◽  
Tetrahymena Thermophila ◽  
Apical Region ◽  
Basal Bodies ◽  
Wild Type ◽  
Fixation Procedure ◽  
Contractile Ring ◽  
Dividing Cells

A ring consisting of microfilaments was found in the apical region of Tetrahymena thermophila wild-type strain B and janus mutant. This ring, about 0.4 micrometer wide and 0.2 micrometer thick, is located at the bases of the anterior, non-ciliated basal bodies of the apical ciliary couplets. The apical ring is made of fine filaments showing a banded pattern, the distance between bands depending on the fixation procedure and ranging from 30–200 nm. The bands are made of small beads fastened to the filaments. The microfilaments of the apical ring are attached to the bases of the basel bodies. No connection with the cell membrane was found. In dividing cells in the incipient furrow region of filamentous band originates from the epiplasmic fibrogranular meshwork. This contractile ring is about 0.4 micrometer wide and 0.8 micrometer thick. It is formed by circumferentially aligned microfibrils. During constriction the contractile ring remains associated with the epiplasmic layer, which in turn adheres to the inner alveolar membrane. The microfilaments of both the apical and the division-furrow rings have diameters ranging from about 3.8-7.I nm.

Growth in cell length in the fission yeast Schizosaccharomyces pombe

1985 ◽  
Vol 75 (1) ◽  
pp. 357-376 ◽  
Author(s):  
J.M. Mitchison ◽  
P. Nurse
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Cell Size ◽  
Single Cells ◽  
Temperature Shift ◽  
Time Lapse ◽  
Cell Length ◽  
Wild Type ◽  
Cycle Growth ◽  
A Cell ◽  
Mutant Cells

The cylindrical cells of Schizosaccharomyces pombe grow in length by extension at the ends and not the middle. At the beginning of the cell cycle, growth is restricted to the ‘old end’, which existed in the previous cycle. Later on, the ‘new end’, formed from the septum, starts to grow at a point in the cycle that we have called NETO (‘new end take-off’). Fluorescence microscopy on cells stained with Calcofluor has been used to study NETO in size mutants, in blocked cdc mutants and with different growth temperatures and media. In wild-type cells (strain 972) NETO happens at 0.34 of the cycle with a cell length of 9.5 microns. With size mutants that are smaller at division, NETO takes place at the same size (9.0-9.5 microns) but this is not achieved until later in the cycle. Another control operates in larger size mutants since NETO occurs at the same stage of the cycle (about 0.32) as in wild type but at a larger cell size. This control is probably a requirement to have completed an event in early G2, since most cdc mutant cells blocked before this point in the cycle do not show NETO whereas most of those blocked in late G2 do show it. We conclude that NETO only happens if: (1) the cell length is greater than a critical value of 9.0-9.5 microns; and (2) the cell has traversed the first 0.3-0.35 of the cycle and passed early G2. NETO is delayed in poor media, in which cell size is also reduced. Temperature has little effect on NETO under steady-state conditions, but there is a transient delay for some hours after a temperature shift. NETO is later in another wild-type strain, 132. Time-lapse photomicrography was used to follow the rates of length growth in single cells. Wild-type cells showed two linear segments during the first 75% of the cycle. There was a rate-change point (RCP), coincident with NETO, where the rate of total length extension increased by 35%. This increase was not due simply to the start of new-end growth, since old-end growth slowed down in some cells at the RCP. cdc 11.123 is a mutant in which septation and division is blocked at 35 degrees C but nuclear division continues.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals Basal bodies and associated structures are not required for normal flagellar motion or phototaxis in the green alga Chlorogonium elongatum.

1985 ◽  
Vol 100 (1) ◽  
pp. 297-309 ◽  
Author(s):  
H J Hoops ◽  
G B Witman
Keyword(s):  
Green Alga ◽  
High Speed ◽  
Beat Frequency ◽  
Flagellar Apparatus ◽  
Cell Types ◽  
Basal Bodies ◽  
Daughter Cells ◽  
Flagellar Beat ◽  
Dividing Cells

The interphase flagellar apparatus of the green alga Chlorogonium elongatum resembles that of Chlamydomonas reinhardtii in the possession of microtubular rootlets and striated fibers. However, Chlorogonium, unlike Chlamydomonas, retains functional flagella during cell division. In dividing cells, the basal bodies and associated structures are no longer present at the flagellar bases, but have apparently detached and migrated towards the cell equator before the first mitosis. The transition regions remain with the flagella, which are now attached to a large apical mitochondrion by cross-striated filamentous components. Both dividing and nondividing cells of Chlorogonium propagate asymmetrical ciliary-type waveforms during forward swimming and symmetrical flagellar-type waveforms during reverse swimming. High-speed cinephotomicrographic analysis indicates that waveforms, beat frequency, and flagellar coordination are similar in both cell types. This indicates that basal bodies, striated fibers, and microtubular rootlets are not required for the initiation of flagellar beat, coordination of the two flagella, or determination of flagellar waveform. Dividing cells display a strong net negative phototaxis comparable to that of nondividing cells; hence, none of these structures are required for the transmission or processing of the signals involved in phototaxis, or for the changes in flagellar beat that lead to phototactic turning. Therefore, all of the machinery directly involved in the control of flagellar motion is contained within the axoneme and/or transition region. The timing of formation and the positioning of the newly formed basal structures in each of the daughter cells suggests that they play a significant role in cellular morphogenesis.

scholarly journals Evaluation of wild-type MIC distributions as a tool for determination of clinical breakpoints for Mycobacterium tuberculosis

2009 ◽  
Vol 64 (4) ◽  
pp. 786-793 ◽  
Author(s):  
T. Schon ◽  
P. Jureen ◽  
C. G. Giske ◽  
E. Chryssanthou ◽  
E. Sturegard ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Wild Type ◽  
Clinical Breakpoints

scholarly journals Expression Level of Mature miR172 in Wild Type and StSUT4-Silenced Plants of Solanum tuberosum Is Sucrose-Dependent

2021 ◽  
Vol 22 (3) ◽  
pp. 1455
Author(s):  
Varsha Garg ◽  
Aleksandra Hackel ◽  
Christina Kühn
Keyword(s):  
Solanum Tuberosum ◽  
Wild Type ◽  
Potato Plants ◽  
Mature Leaves ◽  
In Vitro Plantlets ◽  
Long Time ◽  
Short Time ◽  
Cut Leaves

In potato plants, the phloem-mobile miR172 is involved in the sugar-dependent transmission of flower and tuber inducing signal transduction pathways and a clear link between solute transport and the induction of flowering and tuberization was demonstrated. The sucrose transporter StSUT4 seems to play an important role in the photoperiod-dependent triggering of both developmental processes, flowering and tuberization, and the phenotype of StSUT4-inhibited potato plants is reminiscent to miR172 overexpressing plants. The first aim of this study was the determination of the level of miR172 in sink and source leaves of StSUT4-silenced as well as StSUT4-overexpressing plants in comparison to Solanum tuberosum ssp. Andigena wild type plants. The second aim was to investigate the effect of sugars on the level of miRNA172 in whole cut leaves, as well as in whole in vitro plantlets that were supplemented with exogenous sugars. Experiments clearly show a sucrose-dependent induction of the level of mature miR172 in short time as well as long time experiments. A sucrose-dependent accumulation of miR172 was also measured in mature leaves of StSUT4-silenced plants where sucrose export is delayed and sucrose accumulates at the end of the light period.

scholarly journals Gating Competence of Constitutively Open CLC-0 Mutants Revealed by the Interaction with a Small Organic Inhibitor

2003 ◽  
Vol 122 (3) ◽  
pp. 295-306 ◽  
Author(s):  
Sonia Traverso ◽  
Laura Elia ◽  
Michael Pusch
Keyword(s):  
Chloride Channels ◽  
Bound State ◽  
Side Chain ◽  
Pore Channel ◽  
Kinetic Properties ◽  
Wild Type ◽  
High Affinity ◽  
Critical Residue ◽  
Fast Gating

Opening of CLC chloride channels is coupled to the translocation of the permeant anion. From the recent structure determination of bacterial CLC proteins in the closed and open configuration, a glutamate residue was hypothesized to form part of the Cl−-sensitive gate. The negatively charged side-chain of the glutamate was suggested to occlude the permeation pathway in the closed state, while opening of a single protopore of the double-pore channel would reflect mainly a movement of this side-chain toward the extracellular pore vestibule, with little rearrangement of the rest of the channel. Here we show that mutating this critical residue (Glu166) in the prototype Torpedo CLC-0 to alanine, serine, or lysine leads to constitutively open channels, whereas a mutation to aspartate strongly slowed down opening. Furthermore, we investigated the interaction of the small organic channel blocker p-chlorophenoxy-acetic acid (CPA) with the mutants E166A and E166S. Both mutants were strongly inhibited by CPA at negative voltages with a >200-fold larger affinity than for wild-type CLC-0 (apparent KD at −140 mV ∼4 μM). A three-state linear model with an open state, a low-affinity and a high-affinity CPA-bound state can quantitatively describe steady-state and kinetic properties of the CPA block. The parameters of the model and additional mutagenesis suggest that the high-affinity CPA-bound state is similar to the closed configuration of the protopore gate of wild-type CLC-0. In the E166A mutant the glutamate side chain that occludes the permeation pathway is absent. Thus, if gating consists only in movement of this side-chain the mutant E166A should not be able to assume a closed conformation. It may thus be that fast gating in CLC-0 is more complex than anticipated from the bacterial structures.

scholarly journals Replication of an rRNA gene origin plasmid in the Tetrahymena thermophila macronucleus is prevented by transcription through the origin from an RNA polymerase I promoter.

1995 ◽  
Vol 15 (6) ◽  
pp. 3372-3381 ◽  
Author(s):  
W J Pan ◽  
R C Gallagher ◽  
E H Blackburn
Keyword(s):  
Rna Polymerase ◽  
Tetrahymena Thermophila ◽  
Rna Polymerase I ◽  
Rrna Gene ◽  
Wild Type ◽  
Independent Evidence ◽  
Origin Region ◽  
Origin Function ◽  
Polymerase I ◽  
Wild Type Promoter

In the somatic macronucleus of the ciliate Tetrahymena thermophila, the palindromic rRNA gene (rDNA) minichromosome is replicated from an origin near the center of the molecule in the 5' nontranscribed spacer. The replication of this rDNA minichromosome is under both cell cycle and copy number control. We addressed the effect on origin function of transcription through this origin region. A construct containing a pair of 1.9-kb tandem direct repeats of the rDNA origin region, containing the origin plus a mutated (+G), but not a wild type, rRNA promoter, is initially maintained in macronuclei as an episome. Late, linear and circular replicons with long arrays of tandem repeats accumulate (W.-J. Pan and E. H. Blackburn, Nucleic Acids Res, in press). We present direct evidence that the +G mutation inactivates this rRNA promoter. It lacks the footprint seen on the wild-type promoter and produces no detectable in vivo transcript. Independent evidence that the failure to maintain wild-type 1.9-kb repeats was caused by transcription through the origin came from placing a short DNA segment containing the rRNA gene transcriptional termination region immediately downstream of the wild-type rRNA promoter. Insertion of this terminator sequence in the correct, but not the inverted, orientation restored plasmid maintenance. Hence, origin function was restored by inactivating the rRNA promoter through the +G mutation or causing termination before transcripts from a wild-type promoter reached the origin region. We propose that transcription by RNA polymerase I through the rDNA origin inhibits replication by preventing replication factors from assembling at the origin.

scholarly journals Characterization of recombinant-derived granulocyte-colony stimulating factor (G-CSF)

1988 ◽  
Vol 256 (1) ◽  
pp. 213-218 ◽  
Author(s):  
P Wingfield ◽  
R Benedict ◽  
G Turcatti ◽  
B Allet ◽  
J J Mermod ◽  
...  
Keyword(s):  
Coli Strain ◽  
Granulocyte Colony Stimulating Factor ◽  
Colony Stimulating Factor ◽  
Wild Type ◽  
Disulphide Bonds ◽  
Disulphide Bond Formation ◽  
Stimulating Factor ◽  
Factor G

Human granulocyte colony-stimulating factor (G-CSF), and a mutant having a Ser for Cys substitution at residue 18 were produced in Escherichia coli strain W3110. About 60 mg of pure protein was obtained from 50 g of wet cells with a recovery of about 20%. The proteins were characterized physically and chemically, including determination of disulphide bonds, which were found to exist between residues 37-43 and 65-75. Cys-18 is not involved in disulphide bond formation and was substituted by Ser with no effects on gross protein conformation or biological activity. Both the wild-type and the mutant recombinant-derived proteins, although not glycosylated, possess colony-stimulating activities. In a bioassay using the murine myelomonocytic leukaemic cell line WEH1 3B D+, activities were obtained which were similar to those of natural G-CSF and of a glycosylated recombinant-derived human G-CSF produced in monkey cells.

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