The Effect of Trifluralin on the Ultrastructure of Dividing Cells of the Root Meristem of Cotton (Gossypium Hirsutum L. ‘ACALA 4-42’)

1974 ◽  
Vol 15 (2) ◽  
pp. 429-441
Author(s):  
D. HESS ◽  
D. BAYER
Keyword(s):  
Cell Division ◽  
Gossypium Hirsutum ◽  
Lateral Root ◽  
Root Meristem ◽  
Metaphase Plate ◽  
Threshold Concentration ◽  
Gossypium Hirsutum L ◽  
Ultrastructural Studies ◽  
Cell Divisions ◽  
Dividing Cells

Ultrastructural studies of trifluralin-treated cells in lateral root meristems of cotton (Gossypium hirsutum L.) revealed that mitotic disruptions were due to the absence of microtubules. The extent of disruption varied between individual roots and correlated with the presence or absence of microtubules. Where microtubules were absent, cells began division with a normal prophase chromosome cycle. The chromosomes did not line up along a metaphase plate, but coalesced in the cell. If cell division had begun prior to microtubule disappearance the mitotic process was arrested at the stage that had been reached when the disappearance occurred. In some cell divisions randomly oriented microtubules were noted, with mitosis apparently arrested at those stages. Nuclear envelope reformation yielded cells that were polyploid, polymorphonucleate, binucleate, or occasionally multinucleate. If microtubules were present and if their orientation were normal, all stages of mitosis occurred. The range of mitotic disruption observed can be explained by the threshold concentration for microtubule disappearance being very near aqueous saturation of trifluralin.

discordia mutations specifically misorient asymmetric cell divisions during development of the maize leaf epidermis

Development ◽  
1999 ◽  
Vol 126 (20) ◽  
pp. 4623-4633 ◽  
Author(s):  
K. Gallagher ◽  
L.G. Smith
Keyword(s):  
Cell Division ◽  
Preprophase Band ◽  
Cytochalasin D ◽  
Leaf Epidermis ◽  
Asymmetric Cell Divisions ◽  
Maize Leaf ◽  
Cell Divisions ◽  
Cytoskeletal Structure ◽  
Dividing Cells ◽  
Preprophase Bands

In plant cells, cytokinesis depends on a cytoskeletal structure called a phragmoplast, which directs the formation of a new cell wall between daughter nuclei after mitosis. The orientation of cell division depends on guidance of the phragmoplast during cytokinesis to a cortical site marked throughout prophase by another cytoskeletal structure called a preprophase band. Asymmetrically dividing cells become polarized and form asymmetric preprophase bands prior to mitosis; phragmoplasts are subsequently guided to these asymmetric cortical sites to form daughter cells of different shapes and/or sizes. Here we describe two new recessive mutations, discordia1 (dcd1) and discordia2 (dcd2), which disrupt the spatial regulation of cytokinesis during asymmetric cell divisions. Both mutations disrupt four classes of asymmetric cell divisions during the development of the maize leaf epidermis, without affecting the symmetric divisions through which most epidermal cells arise. The effects of dcd mutations on asymmetric cell division can be mimicked by cytochalasin D treatment, and divisions affected by dcd1 are hypersensitive to the effects of cytochalasin D. Analysis of actin and microtubule organization in these mutants showed no effect of either mutation on cell polarity, or on formation and localization of preprophase bands and spindles. In mutant cells, phragmoplasts in asymmetrically dividing cells are structurally normal and are initiated in the correct location, but often fail to move to the position formerly occupied by the preprophase band. We propose that dcd mutations disrupt an actin-dependent process necessary for the guidance of phragmoplasts during cytokinesis in asymmetrically dividing cells.

scholarly journals Emerging mechanisms of asymmetric stem cell division

2018 ◽  
Vol 217 (11) ◽  
pp. 3785-3795 ◽  
Author(s):  
Zsolt G. Venkei ◽  
Yukiko M. Yamashita
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Division ◽  
Asymmetric Cell Division ◽  
Binary Outcomes ◽  
Cellular Mechanisms ◽  
Asymmetric Cell Divisions ◽  
Cell Divisions ◽  
Dividing Cells ◽  
Stem Cell Division

The asymmetric cell division of stem cells, which produces one stem cell and one differentiating cell, has emerged as a mechanism to balance stem cell self-renewal and differentiation. Elaborate cellular mechanisms that orchestrate the processes required for asymmetric cell divisions are often shared between stem cells and other asymmetrically dividing cells. During asymmetric cell division, cells must establish asymmetry/polarity, which is guided by varying degrees of intrinsic versus extrinsic cues, and use intracellular machineries to divide in a desired orientation in the context of the asymmetry/polarity. Recent studies have expanded our knowledge on the mechanisms of asymmetric cell divisions, revealing the previously unappreciated complexity in setting up the cellular and/or environmental asymmetry, ensuring binary outcomes of the fate determination. In this review, we summarize recent progress in understanding the mechanisms and regulations of asymmetric stem cell division.

scholarly journals Transcriptome profiling of the elongating internode of cotton (Gossypium hirsutum L.) seedlings in response to mepiquat chloride

2019 ◽  
Author(s):  
Li Wang ◽  
Ying Yin ◽  
Li-Feng Wang ◽  
Menglei Wang ◽  
Miao Zhao ◽  
...  
Keyword(s):  
Cell Division ◽  
Gossypium Hirsutum ◽  
Molecular Mechanism ◽  
Transcriptome Profiling ◽  
Internode Elongation ◽  
Gossypium Hirsutum L ◽  
Mepiquat Chloride ◽  
Downstream Signaling ◽  
Aba Metabolism ◽  
Expression Of Genes

Abstract Background The plant growth retardant mepiquat chloride (MC) has been extensively used to produce compact plant canopies and increase yield in cotton (Gossypium hirsutum L.). Previous studies mainly focused on the role of gibberellins (GA) in MC-induced growth inhibition of cotton. However, the molecular mechanism underlying MC-induced growth retardation has remained largely unknown. Results In the present study, we conducted histological, transcriptomic, and phytohormone analyses of the second elongating internodes of cotton seedlings treated with MC. Histological analysis revealed that the MC-mediated shortening of internodes was caused by the suppression of cell division and decrease in cell length; this phenotype was confirmed by transcriptome profiling. Many genes related to cell growth were significantly downregulated in MC-treated internodes, such as cell cycle, cell wall biosynthesis and modification, and transport protein aquaporins. Furthermore, the expression of genes related to secondary metabolism, especially lignin and flavonoid, was down-regulated by MC treatment. The expression of genes related to GA, auxin, brassinosteroid (BR), and ethylene metabolism and signaling was remarkably suppressed, whereas that of genes related to cytokinin (CK) and abscisic acid (ABA) metabolism was induced by MC. Consistent with RNA-Seq analysis, significant decrease in endogenous GA, auxin, and BR content, but an increase in CK content, was observed in cotton internodes after MC treatment. In addition, many transcription factors (TFs) such as bHLH, AP2-EREBP, Orphans, MYB, GRF, and TCP were differentially regulated by MC; these TFs are associated with cell division and expansion, phytohormone signaling, and circadian rhythm. Conclusions This study provides novel insights into the molecular mechanism underlying the MC-mediated inhibition of internode elongation in cotton seedlings. MC reduces internode elongation by suppressing the biosynthesis and downstream signaling cascades of GA, auxin, and BR; altering the expression of many TFs; and further reducing cell division and expansion.

scholarly journals Week-long imaging of cell divisions in the Arabidopsis root meristem

2018 ◽  
Author(s):  
Ramin Rahni ◽  
Kenneth D. Birnbaum
Keyword(s):  
Stem Cell ◽  
Cell Division ◽  
Stem Cell Niche ◽  
Root Meristem ◽  
Imaging Method ◽  
Fluorescent Reporters ◽  
Cell Divisions ◽  
4D Imaging ◽  
Root Stem Cell ◽  
Cell Niche

AbstractCharacterizing the behaviors of dynamic systems requires capturing them with high temporal and spatial resolution. Owing to its transparency and genetic tractability, theArabidopsis thalianaroot lends itself well to live imaging when combined with cell and tissue-specific fluorescent reporters. We developed a novel 4D imaging method that utilizes simple confocal microscopy and readily available components to track cell divisions in the root stem cell niche and surrounding region for up to one week. This new setup allows us to finely analyze meristematic cell division rates that lead to patterning. Using this method, we performed a direct measurement of cell division intervals within and around the root stem cell niche. The results reveal a short, steep gradient of cell division in proximal stem cells, with progressively more rapid cell division rates from QC, to cells in direct contact with the QC (initials), to their immediate daughters, after which division rates appear to become more homogeneous. These results provide a baseline to study how perturbations in signaling could affect cell division patterns in the root meristem.

scholarly journals The expa1-1 mutant reveals a new biophysical lateral root organogenesis checkpoint

2018 ◽  
Author(s):  
Priya Ramakrishna ◽  
Graham A Rance ◽  
Lam Dai Vu ◽  
Evan Murphy ◽  
Kamal Swarup ◽  
...  
Keyword(s):  
Cell Division ◽  
Root System ◽  
Lateral Root ◽  
Root Formation ◽  
Lateral Roots ◽  
Lateral Root Formation ◽  
Asymmetric Cell Divisions ◽  
Cell Divisions ◽  
Root Organogenesis ◽  
Pericycle Cells

ABSTRACTIn plants, post-embryonic formation of new organs helps shape the adult organism. This requires the tight regulation of when and where a new organ is formed, and a coordination of the underlying cell divisions. To build a root system, new lateral roots are continuously developing, and this process requires asymmetric cell division in adjacent pericycle cells. Characterization of an expansin a1 (expa1) mutant has revealed a novel checkpoint during lateral root formation. Specifically, a minimal pericycle width was found to be necessary and sufficient to trigger asymmetric pericycle cell divisions during auxin-driven lateral root formation. We conclude that a localized radial expansion of adjacent pericycle cells is required to position the asymmetric cell divisions and generate a core of small daughter cells, which is a prerequisite for lateral root organogenesis.SIGNFICANCE STATEMENTOrgan formation is an essential process in plants and animals, driven by cell division and cell identity establishment. Root branching, where lateral roots form along the primary root axis, increases the root system and aids capture of water and nutrients. We have discovered that tight control of cell width is necessary to co-ordinate asymmetric cell divisions in cells that give rise to a new lateral root organ. While biomechanical processes have been shown to play a role in plant organogenesis, including lateral root formation, our data give new mechanistic insights into the cell size checkpoint during lateral root initiation.

scholarly journals Ultrastructure and Differentiation in Chara Sp. II. Mitosis

1967 ◽  
Vol 20 (5) ◽  
pp. 883 ◽  
Author(s):  
JD Pickett-Heaps
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Division ◽  
Asymmetric Cell Division ◽  
Metaphase Plate ◽  
Early Prophase ◽  
Cell Organelles ◽  
Vegetative Cells ◽  
Nucleolar Material ◽  
Dividing Cells ◽  
Late Telophase

The ultrastructure of some dividing cells of Chara are described. No centrioles have ever been detected in vegetative cells. Asymmetric cell division, forming a predetermined pattern of cells, was apparently not preceded by any characteristic grouping of cell organelles. The nucleoli became dispersed during pre-prophase, and most of the nucleolar material appeared intimately associated with the chromosomes throughout division, although some seemed excluded from the nucleus at late telophase. Polar zones of endoplasmic reticulum were formed in early prophase, and attachment of microtubules to daughter chromosomes slightly preceded the formation of a very precisely aligned metaphase plate. The chromosome arms were also apparently all aligned in the plane of this plate.

scholarly journals PLETHORA transcription factors orchestrate de novo organ patterning during Arabidopsis lateral root outgrowth

2017 ◽  
Vol 114 (44) ◽  
pp. 11709-11714 ◽  
Author(s):  
Yujuan Du ◽  
Ben Scheres
Keyword(s):  
Transcription Factors ◽  
Lateral Root ◽  
De Novo ◽  
Stage Ii ◽  
Lateral Root Primordia ◽  
Growth Axis ◽  
Cell Divisions ◽  
Dividing Cells ◽  
Response Gradient

Plant development is characterized by repeated initiation of meristems, regions of dividing cells that give rise to new organs. During lateral root (LR) formation, new LR meristems are specified to support the outgrowth of LRs along a new axis. The determination of the sequential events required to form this new growth axis has been hampered by redundant activities of key transcription factors. Here, we characterize the effects of three PLETHORA (PLT) transcription factors, PLT3, PLT5, and PLT7, during LR outgrowth. In plt3plt5plt7 triple mutants, the morphology of lateral root primordia (LRP), the auxin response gradient, and the expression of meristem/tissue identity markers are impaired from the “symmetry-breaking” periclinal cell divisions during the transition between stage I and stage II, wherein cells first acquire different identities in the proximodistal and radial axes. Particularly, PLT1, PLT2, and PLT4 genes that are typically expressed later than PLT3, PLT5, and PLT7 during LR outgrowth are not induced in the mutant primordia, rendering “PLT-null” LRP. Reintroduction of any PLT clade member in the mutant primordia completely restores layer identities at stage II and rescues mutant defects in meristem and tissue establishment. Therefore, all PLT genes can activate the formative cell divisions that lead to de novo meristem establishment and tissue patterning associated with a new growth axis.

scholarly journals Establishing the Initial Embryonic Axis

2007 ◽  
Vol 15 (6) ◽  
pp. 3-5
Author(s):  
Stephen W. Carmichael ◽  
Gary C. Schoenwolf
Keyword(s):  
Cell Division ◽  
Mouse Model ◽  
Inner Cell Mass ◽  
Molecular Genetic ◽  
Cell Mass ◽  
Embryonic Axis ◽  
The Other ◽  
Mammalian Embryo ◽  
Cell Divisions ◽  
Dividing Cells

In the mammalian embryo, the first axis to appear is at the time of the fifth cell division when the inner cell mass (ICM) becomes visible. The localization of the ICM on one side of a cavity formed within the cluster of dividing cells marks the embryonic-abembryonic (E-Ab) axis. This name derives from the fact the most of the embryo will develop from the ICM, whereas other tissues (the placenta, etc.) will develop from the other cells. There has been a long-standing controversy as to what determines the mammalian E-Ab axis; is the information inherently in the zygote, or is it determined after several cell divisions? In an elegant series of studies whereby dividing cells were labeled using new molecular genetic tools and then carefully followed during development, Yoko Kurotaki, Kohei Hatta, Kazuki Nakao, Yo-ichi Nabeshima, and Toshihiko Fujimori have provided an answer in a mouse model.

Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

1970 ◽  
Vol 28 ◽  
pp. 186-187
Author(s):  
Krishan Awtar
Keyword(s):  
Cell Division ◽  
Normal Cell ◽  
Virus Production ◽  
Multinucleate Cells ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Nuclear Membranes ◽  
Division 2 ◽  
Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

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