Microtubules and microfilaments in tip growth: evidence that microtubules impose polarity on protonemal growth in Physcomitrella patens

1988 ◽  
Vol 89 (4) ◽  
pp. 533-540 ◽  
Author(s):  
J. H. DOONAN ◽  
D. J. COVE ◽  
C. W. LLOYD
Keyword(s):  
Tip Growth ◽  
Physcomitrella Patens ◽  
Cytochalasin D ◽  
Immunofluorescence Study ◽  
Apical Dome ◽  
High Concentrations ◽  
Cytoskeletal Elements ◽  
Drug Studies ◽  
Tip Cells ◽  
Cytoskeletal Drugs

In this study we compare the contributions of Factin and microtubules to tip growth in filamentous cells of the moss Physcomitrella patens. In tip growth, expansion seems to be restricted to the hemispherical apical dome. Cytoskeletal elements have been suspected, from drug studies, to be involved in this but electron microscopy has generally not confirmed the presence of an apical cytoskeleton. However, in a previous immunofluorescence study we reported that microtubules could be seen to focus upon the apical dome in tip cells of the moss P. patens. In the present investigation F-actin has also been detected at the apices of these cells. Anti-cytoskeletal drugs were therefore used to differentiate between the roles of actin filaments and microtubules in tip growth. At high concentrations (30μM), the herbicide cremart de-polymerized microtubules and caused tip swelling. F-actin was still present under such conditions but its fragmentation by cytochalasin D suppressed this herbicide-induced swelling. On its own, cytochalasin D arrested tip growth without causing swollen tips. At lower concentrations, cremart disorganized microtubules rather than causing their complete depolymerization. Under these conditions, new but swollen growing points were initiated along the filament. The addition of taxol to cremart-treated filaments tended to reduce swelling and to re-polarize outgrowth. With particular combinations of these drugs, multiple lateral out-growths were initiated in the vicinity of the nucleus. It is concluded: (1) that F-actin is present at the tips of Physcomitrella caulonemal apical cells; (2) that unfragmented F-actin is necessary for outgrowth; (3) that even disorganized microtubules permit some degree of outgrowth but that an unperturbed distribution of axial microtubules, focussing upon an apex, is essential in order to impose tubular shape and directionality upon expansion.

scholarly journals Novel roles of Kinesin-13 and Kinesin-8 during cell growth and division in the moss Physcomitrella patens

2019 ◽  
Author(s):  
Shu Yao Leong ◽  
Tomoya Edzuka ◽  
Gohta Goshima ◽  
Moé Yamada
Keyword(s):  
Cell Growth ◽  
Mitotic Spindle ◽  
Tip Growth ◽  
Physcomitrella Patens ◽  
Microtubule Dynamics ◽  
Chromosome Movement ◽  
Spindle Formation ◽  
Tip Cells ◽  
Null Mutants

AbstractKinesin-13 and -8 are well-known microtubule (MT) depolymerases that regulate MT length and chromosome movement in animal mitosis. While much is unknown about plant Kinesin-8, Arabidopsis and rice Kinesin-13 have been shown to depolymerise MTs in vitro. However, mitotic function of both kinesins has yet to be understood in plants. Here, we generated the complete null mutants in plants of Kinesin-13 and -8 in the moss Physcomitrella patens. Both kinesins were found to be non-essential for viability, but the Kinesin-13 knockout (KO) line had increased mitotic duration and reduced spindle length, whereas the Kinesin-8 KO line did not display obvious mitotic defects. Surprisingly, spindle MT poleward flux, for which Kinesin-13 is responsible for in animals, was retained in the absence of Kinesin-13. Concurrently, MT depolymerase activity of either moss kinesins could not be observed, with MT catastrophe inducing (Kinesin-13) or MT gliding (Kinesin-8) activity observed in vitro. Interestingly, both KO lines showed waviness in their protonema filaments, which correlated with positional instability of the MT foci in their tip cells. Taken together, the results suggest that plant Kinesin-13 and -8 have diverged in both mitotic function and molecular activity, acquiring new roles in regulating MT foci positioning for directed tip-growth.One sentence summaryThis study uncovered the roles of Kinesin-13 and Kinesin-8 in regulating microtubule dynamics for mitotic spindle formation and straight tip cell growth in the moss Physcomitrella patens

The effect of cytochalasin D on preprophase band organization in root tip cells of Allium

1992 ◽  
Vol 103 (4) ◽  
pp. 989-998 ◽  
Author(s):  
E.P. Eleftheriou ◽  
B.A. Palevitz
Keyword(s):  
Preprophase Band ◽  
Cytochalasin D ◽  
Root Tip ◽  
Average Width ◽  
Exact Position ◽  
The Relationship ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Control Samples

The relationship between microfilaments (Mfs) and microtubules (Mts) in the organization of the preprophase band (PPB) was investigated in Allium root tip cells subjected to treatment with cytochalasin D (CD). Mts and Mfs were visualized by indirect immunofluorescence and various parameters such as PPB width were analyzed quantitatively. In control samples, the PPB first appears as a wide Mt band that progressively narrows to an average width of 4 micrometre in mid-prophase. Randomly oriented Mfs are present throughout the cytoplasm of most interphase control cells. Preprophase and prophase cells, however, contain cortical Mfs arranged parallel to the PPB. The Mfs initially occupy much of the cortex but in most cells they progressively become restricted to an area wider than the PPB. In the presence of CD, the PPB fails to narrow and remains at least two-fold wider than in control cells. PPB width expressed as a percentage of nuclear or cell length also increases compared to controls. Widening is concentration dependent, and the effect of 10 micromolar CD is near maximal only 15 min after application of the drug. This rapid response suggests that a rebroadening of already condensed PPBs takes place. After as little as 15 min in CD, Mfs are replaced by many small specks and rods. Dual localizations of both Mts and Mfs show that prophase cells contain broad PPBs without Mfs. The rapid disorganization of Mfs, by CD, therefore coincides with the rebroadening of PPBs. CD-treated cells in metaphase, anaphase and telophase contain larger actin aggregates at the poles, as previously reported. The results indicate that Mfs play an important role in the narrowing of the PPB, which in turn is essential for determination of the exact position of the plane of division. They also indicate that movement of intact Mts is important in PPB organization.

scholarly journals Regulation of CD18 expression in human neutrophils as related to shape changes

1993 ◽  
Vol 106 (2) ◽  
pp. 493-501
Author(s):  
A. Volz
Keyword(s):  
Phorbol Myristate Acetate ◽  
Surface Expression ◽  
Cytochalasin D ◽  
Human Neutrophils ◽  
Chemotactic Peptide ◽  
Myristate Acetate ◽  
Surface Distribution ◽  
Quantitative Expression ◽  
High Concentrations ◽  
Shape Changes

The study analyses the distribution and quantitative expression of surface CD18 of neutrophils exposed to distinct stimuli that produce different types of continuous shape changes, including types that are associated with locomotion and others that are not. The chemotactic peptide N-formyl-L-norleucyl-L-leucyl-L-phenylalanine, colchicine and nocodazole were used to induce a polarized locomotor morphology, phorbol myristate acetate, 1,2-dioctanoylglycerol and 1-oleoyl-2-acetyl-glycerol to induce non-polar motile cells ruffling all over the surface and 2H2O to induce non-polar cells performing circus movements as have been previously described. Except for colchicine and nocodazole, these stimuli increased surface expression of CD18. Thus, stimulated shape changes are frequently, though not always, associated with increased surface expression of CD18. High concentrations (10(−7) to 10(−5) M) of phorbol myristate acetate but not of chemotactic peptide induced down-regulation of surface CD18. Cytochalasin D (10(−4) M) stimulated CD18 expression even though it inhibited shape changes. The surface distribution of CD18 determined by light microscopy was uniform in unstimulated cells or in various forms of stimulation except for cells treated with 10(−5) M cytochalasin D. Cytochalasin D (10(−5) M) produced CD18 accumulation at the pole opposite the F-actin cap. Experiments with colchicine, nocodazole, 2H2O and cytochalasin D suggest that microtubules as well as microfilaments modulate surface expression of CD18. The results suggest that protein kinase C and phosphatases play a role in regulating surface expression of CD18 in neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Systematic survey of the function of ROP regulators and effectors during tip growth in the moss Physcomitrella patens

2018 ◽  
Vol 70 (2) ◽  
pp. 447-457 ◽  
Author(s):  
Carlisle Bascom ◽  
Graham M Burkart ◽  
Darren R Mallett ◽  
Jacquelyn E O’Sullivan ◽  
Alexis J Tomaszewski ◽  
...  
Keyword(s):  
Tip Growth ◽  
Physcomitrella Patens ◽  
Systematic Survey

Correlation between protonema morphogenesis and the development of the microtubule system in Funaria spore germination under normal conditions and at high auxin concentrations: an immunofluorescence study

1989 ◽  
Vol 67 (8) ◽  
pp. 2227-2234 ◽  
Author(s):  
N. Ljubešić ◽  
H. Quader ◽  
E. Schnepf
Keyword(s):  
Cell Division ◽  
Spore Germination ◽  
Germ Tube ◽  
Immunofluorescence Study ◽  
Cell Morphogenesis ◽  
Antimicrotubule Agents ◽  
High Concentrations ◽  
High Auxin

Ungerminated spores of Funaria do not contain distinct microtubules but show diffuse antitubulin antibody fluorescence. The microtubules arise when, 24–48 h after sowing, the spores are swollen and the first germ tube begins to protrude. Initially, diffuse fluorescence and microtubules are concentrated around the nucleus. Treatment with auxin at high concentrations (5 × 10−5 – 10−4 M) retards germination and cell division. Like antimicrotubule agents, such as colchicine and chloroisopropyl-N-phenylcarbamate, high auxin concentrations affect the formation of microtubules; either short, irregularly shaped microtubules and fluorescent spots arise, or there is no evidence of microtubules. The auxin effects on growth and microtubules can be reversed in less than 1 day. There is a correlation between the formation of the microtubule system and cell morphogenesis.

scholarly journals Actin disassembly by cofilin, coronin, and Aip1 occurs in bursts and is inhibited by barbed-end cappers

2008 ◽  
Vol 182 (2) ◽  
pp. 341-353 ◽  
Author(s):  
Hao Yuan Kueh ◽  
Guillaume T. Charras ◽  
Timothy J. Mitchison ◽  
William M. Brieher
Keyword(s):  
Actin Filaments ◽  
Mammalian Cells ◽  
Cytochalasin D ◽  
Reaction Intermediates ◽  
Latrunculin B ◽  
Interacting Protein ◽  
Physiological Relevance ◽  
High Concentrations ◽  
End Capping ◽  
In Cells

Turnover of actin filaments in cells requires rapid actin disassembly in a cytoplasmic environment that thermodynamically favors assembly because of high concentrations of polymerizable monomers. We here image the disassembly of single actin filaments by cofilin, coronin, and actin-interacting protein 1, a purified protein system that reconstitutes rapid, monomer-insensitive disassembly (Brieher, W.M., H.Y. Kueh, B.A. Ballif, and T.J. Mitchison. 2006. J. Cell Biol. 175:315–324). In this three-component system, filaments disassemble in abrupt bursts that initiate preferentially, but not exclusively, from both filament ends. Bursting disassembly generates unstable reaction intermediates with lowered affinity for CapZ at barbed ends. CapZ and cytochalasin D (CytoD), a barbed-end capping drug, strongly inhibit bursting disassembly. CytoD also inhibits actin disassembly in mammalian cells, whereas latrunculin B, a monomer sequestering drug, does not. We propose that bursts of disassembly arise from cooperative separation of the two filament strands near an end. The differential effects of drugs in cells argue for physiological relevance of this new disassembly pathway and potentially explain discordant results previously found with these drugs.

scholarly journals Physcomitrella patens: a model to investigate the role of RAC/ROP GTPase signalling in tip growth

2010 ◽  
Vol 61 (7) ◽  
pp. 1917-1937 ◽  
Author(s):  
D. Magnus Eklund ◽  
Emma M. Svensson ◽  
Benedikt Kost
Keyword(s):  
Tip Growth ◽  
Physcomitrella Patens ◽  
Rop Gtpase

Ultrastructural analysis of hyphal tip cell growth in fungi: Spitzenkorper, cytoskeleton and endomembranes after freeze-substitution

1981 ◽  
Vol 48 (1) ◽  
pp. 89-103
Author(s):  
R.J. Howard
Keyword(s):  
Freeze Substitution ◽  
Hyphal Growth ◽  
Coated Vesicle ◽  
Fusarium Acuminatum ◽  
Tip Cell ◽  
Transmission Electron ◽  
Cytoplasmic Vesicles ◽  
Cytoskeletal Elements ◽  
Tip Cells ◽  
Hyphal Tip

The ultrastructure of freeze-substituted tip cells of Fusarium acuminatum was analysed by conventional and high-voltage transmission electron microscopy (HVEM). At least 2 morphologically distinct types of Golgi-like endomembrane cisternae were observed, each existing as single, fenestrated sheets and tubular elements that were often very closely associated with mitochondria. From HVEM observations of thick (0.25 and 0.5 micron) sections, the Spitzenkorper appeared to correspond to an apical mass of vesicles. A network of microfilaments was identified among component vesicles of the Spitzenkorper and adjacent to developing septa. Microtubules were oriented primarily parallel to the direction of hyphal growth and were located in all areas of the cytoplasm, including the tip cell apex. Cytoplasmic vesicles were closely associated with these microtubules. From these observations it is suggested that cytoskeletal elements play important roles in localized cell wall formation. The filasome, a previously unreported type of coated vesicle in fungi, might also be involved in wall synthesis.

scholarly journals Myosin XI Is Essential for Tip Growth in Physcomitrella patens

2010 ◽  
Vol 22 (6) ◽  
pp. 1868-1882 ◽  
Author(s):  
Luis Vidali ◽  
Graham M. Burkart ◽  
Robert C. Augustine ◽  
Erin Kerdavid ◽  
Erkan Tüzel ◽  
...  
Keyword(s):  
Tip Growth ◽  
Physcomitrella Patens ◽  
Myosin Xi

scholarly journals Cytochalasin releases mRNA from the cytoskeletal framework and inhibits protein synthesis.

1986 ◽  
Vol 6 (5) ◽  
pp. 1650-1662 ◽  
Author(s):  
D A Ornelles ◽  
E G Fey ◽  
S Penman
Keyword(s):  
Protein Synthesis ◽  
Hela Cells ◽  
Cell Structure ◽  
Cytochalasin D ◽  
Reversible Inhibitor ◽  
Dependent Manner ◽  
Inhibitor Of Protein Synthesis ◽  
Cytoskeletal Elements ◽  
Mrna Binding

Cytochalasin D was shown to be a reversible inhibitor of protein synthesis in HeLa cells. The inhibition was detectable at drug levels typically used to perturb cell structure and increased in a dose-dependent manner. The drug also released mRNA from the cytoskeletal framework in direct proportion to the inhibition of protein synthesis. The released mRNA was unaltered in its translatability as measured in vitro but was no longer translated in the cytochalasin-treated HeLa cells. The residual protein synthesis occurred on polyribosomes that were reduced in amount but displayed a normal sedimentation distribution. The results support the hypothesis that mRNA binding to the cytoskeletal framework is necessary although not sufficient for translation. Analysis of the cytoskeletal framework, which binds the polyribosomes, revealed no alterations in composition or amount of protein as a result of treatment with cytochalasin D. Electron microscopy with embedment-free sections shows the framework in great detail. The micrographs revealed the profound reorganization effected by the drug but did not indicate substantial disaggregation of the cytoskeletal elements.

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