scholarly journals Correction to: Preprophase-band positioning in isolated tobacco BY-2 cells: evidence for a principal role of nucleus-cell cortex interaction in default division-plane selection

PROTOPLASMA ◽  
2019 ◽  
Vol 256 (3) ◽  
pp. 731-731 ◽  
Author(s):  
Tetsuhiro Asada
Keyword(s):  
Preprophase Band ◽  
Cell Cortex ◽  
Division Plane ◽  
Principal Role

Use of abnormal preprophase bands to decipher division plane determination

2001 ◽  
Vol 114 (3) ◽  
pp. 599-607 ◽  
Author(s):  
C. Granger ◽  
R. Cyr
Keyword(s):  
Actin Filaments ◽  
Fluorescent Protein ◽  
Dominant Role ◽  
Preprophase Band ◽  
Cell Cortex ◽  
Reporter Protein ◽  
Division Plane ◽  
Green Fluorescent ◽  
Vacuolated Cells ◽  
Preprophase Bands

Many premitotic plant cells possess a cortical preprophase band of microtubules and actin filaments that encircles the nucleus. In vacuolated cells, the preprophase band is visibly connected to the nucleus by a cytoplasmic raft of actin filaments and microtubules termed the phragmosome. Typically, the location of the preprophase band and phragmosome corresponds to, and thus is thought to influence, the location of the cell division plane. To better understand the function of the preprophase band and phragmosome in orienting division, we used a green fluorescent protein-based microtubule reporter protein to observe mitosis in living tobacco bright yellow 2 cells possessing unusual preprophase bands. Observations of mitosis in these unusual cells support the involvement of the preprophase band/phragmosome in properly positioning the preprophase nucleus, influencing spindle orientation such that the cytokinetic phragmoplast initially grows in an appropriate direction, and delineating a region in the cell cortex that attracts microtubules and directs later stages of phragmoplast growth. Thus, the preprophase band/phragmosome appears to perform several interrelated functions to orient the division plane. However, functional information associated with the preprophase band is not always used or needed and there appears to be an age or distance-dependent character to the information. Cells treated with the anti-actin drug, latrunculin B, are still able to position the preprophase nucleus suggesting that microtubules may play a dominant role in premitotic positioning. Furthermore, in treated cells, spindle location and phragmoplast insertion are frequently abnormal suggesting that actin plays a significant role in nuclear anchoring and phragmoplast guidance. Thus, the microtubule and actin components of the preprophase band/phragmosome execute complementary activities to ensure proper orientation of the division plane.

Relationship between preprophase band organization, F-actin and the division site in Allium

1990 ◽  
Vol 97 (2) ◽  
pp. 283-295
Author(s):  
Y. MINEYUKI ◽  
B. A. PALEVITZ
Keyword(s):  
Higher Plants ◽  
Preprophase Band ◽  
Cell Plate ◽  
Mitotic Apparatus ◽  
Division Plane ◽  
Division Site ◽  
Dividing Cells ◽  
G2 Phase

The preprophase band (PPB) of microtubules (Mts), which appears in the G2 phase of the cell cycle in higher plants but disappears well before the end of karyokinesis, is implicated in the determination of the division plane because its location marks the site at which the phragmoplast/cell plate will fuse with the parental plasmalemma during cytokinesis. The PPB first appears as a rather wide array, which progressively narrows before or during prophase. Actin-containing microfilaments (Mfs) have recently been reported in the PPB, but the role of these elements in PPB organization and/or function remains unclear. The present study employed fluorescence and pharmacological methods in symmetrically and asymmetrically dividing epidermal cells of Allium to probe this problem. Our results show that PPBs in cells treated with 2–200μM cytochalasin D (CD) are still transversely aligned but remain two to three times wider than mature bands in control cells. Treatment for 0.5 h at 20 μM is sufficient to make the PPBs abnormally widel Premitotic nuclear migration in asymmetrically dividing cells is also inhibited by CD, as is the positioning of the mitotic apparatus and the new cell plate. The plate is still transverse, however. Band-like arrays of cortical Mfs become evident in most interphase cells by prophase. The band remains quite wide compared to the final dimensions of the Mt PPB, and clearly encompasses it. Levels of CD as high as 200μM decrease the number of cells with transverse actin bands, although a majority still retain them. Other F-actin arrays are disrupted by the drug. Thus, while CD does not inhibit the formation of an initial, broad, transverse PPB in most cells, it does prevent the narrowing process that defines the precise division site. The role of actin in this effect is discussed.

The Organization of the Cytoskeleton During Meiosis in Eggplant (Solanum Melongena (L.)): Microtubules and F-Actin are Both Necessary for Coordinated Meiotic Division

1989 ◽  
Vol 92 (4) ◽  
pp. 541-550 ◽  
Author(s):  
J. A. TRAAS ◽  
S. BURGAIN ◽  
R. DUMAS DE VAULX
Keyword(s):  
Higher Plants ◽  
Solanum Melongena ◽  
Preprophase Band ◽  
Male Meiosis ◽  
Animal Cells ◽  
Division Plane ◽  
Nucleation Sites ◽  
Division Process ◽  
Spatial Programming

Address for reprints Because two division planes form at right angles, male meiosis in higher plants provides striking examples of both division control and spatial programming. To investigate these processes we have stained microtubules and actin filaments during male meiosis in the eggplant. Our results indicate the following. (1) That microtubules and their nucleation sites are involved in the establishment of polarity; this is supported by our observation that the drug CIPC affects spindle polarity.(2) That actin microfilaments are involved in spindle formation and integrity, but not in the establishment of polarity: cytochalasin B and D affect the organization of the spindle microtubules, but not their polarized distribution.(3) That microtubules radiating from the daughter nuclei at the cell poles during interkinesis probably establish the future division plane by concentrating actin in that plane (cf. the proposed role of asters in positioning the contractile ring in animal cells).(4) That this concentration of F-actin in the division plane may be involved in preparing the cytoplasm for cytokinesis and in memorizing the division plane (much as the preprophase band observed in polarized tissues does).(5) That phragmoplast formation is a two-step process. No phragmoplast forms after metaphase I, but a four-way phragmoplast forms after metaphase II, indicating that mitosis and cytokinesis are not obligatorily coupled. These studies demonstrate that actin and microtubules are jointly involved in the spatial coordination of the division process.

Centrosome Aurora A gradient ensures single polarity axis in C. elegans embryos

2020 ◽  
Vol 48 (3) ◽  
pp. 1243-1253 ◽  
Author(s):  
Sukriti Kapoor ◽  
Sachin Kotak
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Cell Cortex ◽  
Axis Formation ◽  
Aurora A Kinase ◽  
Aurora A ◽  
C Elegans ◽  
Cell Embryo ◽  
Polarity Establishment

Cellular asymmetries are vital for generating cell fate diversity during development and in stem cells. In the newly fertilized Caenorhabditis elegans embryo, centrosomes are responsible for polarity establishment, i.e. anterior–posterior body axis formation. The signal for polarity originates from the centrosomes and is transmitted to the cell cortex, where it disassembles the actomyosin network. This event leads to symmetry breaking and the establishment of distinct domains of evolutionarily conserved PAR proteins. However, the identity of an essential component that localizes to the centrosomes and promotes symmetry breaking was unknown. Recent work has uncovered that the loss of Aurora A kinase (AIR-1 in C. elegans and hereafter referred to as Aurora A) in the one-cell embryo disrupts stereotypical actomyosin-based cortical flows that occur at the time of polarity establishment. This misregulation of actomyosin flow dynamics results in the occurrence of two polarity axes. Notably, the role of Aurora A in ensuring a single polarity axis is independent of its well-established function in centrosome maturation. The mechanism by which Aurora A directs symmetry breaking is likely through direct regulation of Rho-dependent contractility. In this mini-review, we will discuss the unconventional role of Aurora A kinase in polarity establishment in C. elegans embryos and propose a refined model of centrosome-dependent symmetry breaking.

Asymmetric cell division in fucoid algae: a role for cortical adhesions in alignment of the mitotic apparatus

2001 ◽  
Vol 114 (23) ◽  
pp. 4319-4328
Author(s):  
Sherryl R. Bisgrove ◽  
Darryl L. Kropf
Keyword(s):  
Cell Division ◽  
Asymmetric Cell Division ◽  
Cell Cortex ◽  
Mitotic Apparatus ◽  
Pharmacological Agents ◽  
Division Plane ◽  
Adhesion Sites ◽  
Spindle Poles ◽  
Pelvetia Compressa ◽  
Two Phases

The first cell division in zygotes of the fucoid brown alga Pelvetia compressa is asymmetric and we are interested in the mechanism controlling the alignment of this division. Since the division plane bisects the mitotic apparatus, we investigated the timing and mechanism of spindle alignments. Centrosomes, which give rise to spindle poles, aligned with the growth axis in two phases – a premetaphase rotation of the nucleus and centrosomes followed by a postmetaphase alignment that coincided with the separation of the mitotic spindle poles during anaphase and telophase. The roles of the cytoskeleton and cell cortex in the two phases of alignment were analyzed by treatment with pharmacological agents. Treatments that disrupted cytoskeleton or perturbed cortical adhesions inhibited pre-metaphase alignment and we propose that this rotational alignment is effected by microtubules anchored at cortical adhesion sites. Postmetaphase alignment was not affected by any of the treatments tested, and may be dependent on asymmetric cell morphology.

scholarly journals Cell Cycle-Specific Disruption of the Preprophase Band of Microtubules in Fern Protonemata: Effects of Displacement of the Endoplasm by Centrifugation

1992 ◽  
Vol 101 (1) ◽  
pp. 93-98 ◽  
Author(s):  
TAKASHI MURATA ◽  
MASAMITSU WADA
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Plant Cells ◽  
Preprophase Band ◽  
Higher Plant ◽  
The Future ◽  
Prophase Nucleus ◽  
Original Region ◽  
Fern Protonemata

The preprophase band (PPB) of microtubules (MTs), which appears at the future site of cytokinesis prior to cell division in higher plant cells, disappears by metaphase. Recent studies have shown that displacement of the endoplasm from the PPB region by centrifugation delays the disappearance of the PPB. To study the role of the endoplasm in the cell cycle-specific disruption of the PPB, the filamentous protonemal cells of the fern Adiantum capilius-veneris L. were centrifuged twice so that the first centrifugation displaced the endoplasm from the site of the PPB and the second returned it to its original location. The endoplasm, including the nucleus of various stages of mitosis, could be returned by the second centrifugation to the original region of the PPB, which persists during mitosis in the centrifuged cells. When endoplasm with a prophase nucleus was returned to its original location, the PPB was not disrupted. When endoplasm with a prometa-phase telophase nucleus was similarly returned, the PPB was disrupted within 10 min of termination of centrifugation. In protonemal cells of Adiantum, a second PPB is often formed near the displaced nucleus after the first centrifugation. In cells in which the endoplasm was considered to have been returned to its original location at the prophase/prometaphase transition, the second PPB did not disappear even though the initial PPB was disrupted by the endoplasm. These results suggest that cell cycle-specific disruption of the PPB is regulated by some factor(s) in the endoplasm, which appears at prometaphase, i.e. the stage at which the PPB is disrupted in non-centrifuged cells.

scholarly journals A Study of Facts and Generating Factors of “Dislike for Exercise” and “Dislike for Physical Education”

2021 ◽  
Vol 10 (1) ◽  
pp. 1-7
Author(s):  
B.Chuluun- Erdene ◽  
D. Azjargal
Keyword(s):  
Physical Education ◽  
Physical Fitness ◽  
Negative Attitude ◽  
Policy Recommendations ◽  
Health And Physical Education ◽  
Principal Role ◽  
Lack Of Exercise ◽  
Governmental Institutions ◽  
Course Of Study

Recently, a decline in children’s fitness and lack of exercise has become a serious issue in Japan. Consequently, various governmental institutions have repeatedly taken up this problem and a number of policy recommendations have been made that aim to remedy the situation. Following these recommendations, the new Course of Study has proposed measures such as increasing the number of teaching hours for health and Physical Education (hereinafter abbreviated as “PE”) and reforming the PE curriculum within 12 years. By doing so, it has further emphasized the need “to develop the capacity and skills to engage in exercise throughout life, to realize an enriching sports life, and to improve physical fitness.” Despite these measures, the polarization between those children who actively engage in exercise and those who do not, as well as children who have an unfavorable or negative attitude toward exercise and PE lessons “Dislike for Exercise (hereinafter abbreviated as “DE”)” and “Dislike for Physical Education (hereinafter abbreviated as “DPE”)” still persist. The principal role of PE lessons at school is to introduce children to the joy and excitement of exercise. Within this context, emphasis should be placed on “PE” education that forms the basis of life-long engagement with sports. However, “DE” and “DPE” attitudes inhibit PE in school from achieving its goals.

Division Plane Establishment and Cytokinesis

2019 ◽  
Vol 70 (1) ◽  
pp. 239-267 ◽  
Author(s):  
Pantelis Livanos ◽  
Sabine Müller
Keyword(s):  
Secretory Pathway ◽  
Preprophase Band ◽  
Cell Plate ◽  
Division Plane ◽  
Spatial Reference ◽  
Division Site ◽  
Eukaryotic Proteins ◽  
Plate Formation ◽  
Membrane Compartment ◽  
Cytoplasmic Content

Plant cells divide their cytoplasmic content by forming a new membrane compartment, the cell plate, via a rerouting of the secretory pathway toward the division plane aided by a dynamic cytoskeletal apparatus known as the phragmoplast. The phragmoplast expands centrifugally and directs the cell plate to the preselected division site at the plasma membrane to fuse with the parental wall. The division site is transiently decorated by the cytoskeletal preprophase band in preprophase and prophase, whereas a number of proteins discovered over the last decade reside continuously at the division site and provide a lasting spatial reference for phragmoplast guidance. Recent studies of membrane fusion at the cell plate have revealed the contribution of functionally conserved eukaryotic proteins to distinct stages of cell plate biogenesis and emphasize the coupling of cell plate formation with phragmoplast expansion. Together with novel findings concerning preprophase band function and the setup of the division site, cytokinesis and its spatial control remain an open-ended field with outstanding and challenging questions to resolve.

U.S. Regulatory Environment

1988 ◽  
Vol 6 (4-5) ◽  
pp. 369-377
Author(s):  
Susan J. Court
Keyword(s):  
Natural Gas ◽  
Environmental Impact ◽  
End Users ◽  
Regulatory Environment ◽  
Principal Role ◽  
The Third ◽  
Natural Gas Prices ◽  
New Construction ◽  
Rate Design

Decontrol of natural gas prices created more competition at the wellhead and the need for greater flexibility in the transportation rules to allow sales directly to end users and distribution without middlemen. In 1987, the Commission issued Order No. 500 which would end the disputes that had arisen by addressing three concerns: take-or-pay, contract demand adjustments, and ‘grand fathering’. The first and the most important was dealt with by a flexible crediting mechanism, the second eliminated and the third of insufficient importance to change the rules. Other issues about natural gas trade of concern to the Commission include: Marketing affiliates which threatened monopolistic practices that have required procedures to eliminate prohibitive practices and to deal with complaints: Rate design, which is the principal role of the Commissions that is treated on an individual basis; Certificate Proceedings for new construction that involve solving issues of rates and environmental impact.

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