Behaviour of the nucleolar fibrillar centres in reproducing plant cells

1978 ◽  
Vol 36 (2) ◽  
pp. 210-211
Author(s):  
F. J. Medina ◽  
M.I. Rodrlguez-Garcia ◽  
M.C. Risueño
Keyword(s):  
Plant Cells ◽  
Pollen Grains ◽  
Constant Component ◽  
Plant Tissues ◽  
Reproductive Tissue ◽  
Animal Cells ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nucleolar Organizing Region ◽  
Nucleolar Component

The nucleolar fibrillar centres have been described recently in animal cells and in meristematic plant cells, as a constant component of the nucleolus, corresponding to the nucleolar organizing region (NOR).In order to find out if the nucleolar fibrillar centres represent a general nucleolar component, we have studied the nucleolus in several reproducing plant tissues (megasporocytes and megaspore from Pissum sativum and mono and bicellulate pollen grains from Allium cepa and Scilla non-scripta). In these cells the fibrillar centres have a different morphological behaviour during their development.Female reproductive tissueImmediately before the meiosis, the megasporocyte nucleolus has a compact and rounded aspect. The fibrillar part occupies the centre and the granular part the periphery. Inside the fibrillar part, there are clear areas containing in some cases, a dark core immersed in a grey fibrillar material (Fig. 1). A similar structure was described recently in meristematic cells. In the pachytene stage, when the nucleolus is joined to the nuclear envelope, the fibrillar centres are made up of a homogeneous fibrillar material with a medium electron density.

Ultrastructural association of the chromatin-containing lacunar spaces with the vacuolar component of the interphase nucleolus in Allium cepa

1982 ◽  
Vol 60 (12) ◽  
pp. 2624-2628 ◽  
Author(s):  
L. A. Chouinard
Keyword(s):  
Granular Material ◽  
Allium Cepa ◽  
Ultrastructural Level ◽  
Observational Evidence ◽  
The Other ◽  
Active Chromatin ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nucleolar Organizing Region ◽  
Root Meristematic Cells

At the ultrastructural level, some of the chromatin-containing lacunar spaces of the interphase nucleolus in root meristematic cells of Allium cepa are seen to be walled off, on one side, by dense-fibrillar material and to be contiguous, on the other side, to electron-transparent areas, of variable sizes and shapes, bordered by dense-granular material continuous with and indistinguishable from the dense-granular component of the nucleolar mass. These electron-transparent areas associated with the lacunar spaces are equated with nucleolar vacuoles since they contain scattered preribosomal-like granules and fibrils and are rimmed by dense-granular material. The relevant observational evidence would be consistent with the view that loops of transcriptionnally active chromatin emanating from the nucleolar organizing region project radially into either only the dense-fibrillar or both the dense-fibrillar and the interior of the electron-transparent vacuolar areas seen to be contiguous to the lacunar spaces in question. In relation to this problem, it is of interest to note that the vacuolar spaces of the interphase nucleolus in Allium cepa occasionally display within their confines discrete masses of fibrillar material, possibly chromatinic in character, and in various states of condensation and configuration.

Ultrastructural distribution of a MAP kinase and transcripts in quiescent and cycling plant cells and pollen grains

1999 ◽  
Vol 112 (7) ◽  
pp. 1065-1076
Author(s):  
G. Prestamo ◽  
P.S. Testillano ◽  
O. Vicente ◽  
P. Gonzalez-Melendi ◽  
M.J. Coronado ◽  
...  
Keyword(s):  
Catalytic Domain ◽  
Polyclonal Antibodies ◽  
Plant Cells ◽  
Pollen Grains ◽  
Cell Types ◽  
Protein Distribution ◽  
Animal Cells ◽  
Proliferating Cells ◽  
Quiescent Cells

Mitogen-activated protein kinases (MAPKs) are components of a kinase module that plays a central role in the transduction of diverse extracellular stimuli, including mitogens, specific differentiation and developmental signals and stress treatments. This shows that reversible protein phosphorylation cascades play a pivotal role in signal transduction in animal cells and yeast, particularly the entry into mitosis of arrested cells. Homologues of MAPKs have been found and cloned in various plant species, but there have been no data about their in situ localization at the subcellular level and their expression in plant cells so far. In the present paper we report the first data on the ultrastructural in situ localization of MAPK and their mRNAs in various plant cells. Proliferating and quiescent meristematic plant cells were studied to evaluate whether changes in MAPK presence, distribution and expression accompany the entry into proliferation of dormant cells. Moreover, MAPK localization was analyzed in vacuolate microspores. Polyclonal antibodies against the deduced MAPK from the tobacco Ntf6 clone were able to recognize homologue epitopes by immunocytochemical techniques in the cell types studied. The pattern of protein distribution is similar in all the cases studied: it is localized in the cytoplasm and in the nucleus, mainly in the interchromatin region. The quantitative study of the density showed that MAPK labelling is more abundant in cycling than in quiescent cells, also suggesting that, in plants, MAPK pathways might play a role in cell proliferation. RNA probes for conserved regions of the catalytic domain of plant MAPK homologue genes were used to study MAPK expression in those plant cells. In situ hybridization (ISH) showed the presence of MAPK transcripts in the three plant cell types studied, but levels were very low in quiescent cells compared to those in cycling cells. The quantification of labelling density of ISH signals strongly suggests a higher level of MAPK expression in proliferating cells, but also some basal messenger presence and/or expression in the quiescent ones. Immunogold and ISH results show the presence and distribution of MAPK proteins and mRNAs in vacuolate microspores. This represents a very dynamic stage during pollen development in which the cell nucleus is being prepared for an asymmetrical mitotic division, giving rise to both the generative and the vegetative nuclei of the bicellular pollen grain. Taken together, the data indicate a role played by MAPK in the re-entry into proliferation in plant cells.

An Ultrastructural and Radio-Autographic Study of the Evolution of the Interphase Nucleus in Plant Meristematic Cells (Allium Porrum)

1974 ◽  
Vol 14 (2) ◽  
pp. 263-287
Author(s):  
J. G. LAFONTAINE ◽  
A. LORD
Keyword(s):  
Interphase Nucleus ◽  
Structural Changes ◽  
Tritiated Thymidine ◽  
Light And Electron Microscopy ◽  
Allium Porrum ◽  
Meristematic Cells ◽  
Fibrillar Material ◽  
Nuclear Structures ◽  
S Period ◽  
Dense Chromatin

Radioautography under both light and electron microscopy was exploited to investigate the structural changes of the chromatin reticulum which characterizes the interphase nucleus of a number of plants. Allium porrum meristematic plant cells were used for this purpose. In this species, the telophase chromosomes uncoil into dense strands which, during the G1 period, gradually give rise to a coarse reticulum. There then follows an extensive unravelling of portions of these strands, and high-resolution radioautography reveals that labelling with tritiated thymidine predominantly occurs over zones of the nucleus consisting of diffuse fine fibrillar material. As the S-period progresses, a chromatin reticulum reappears throughout the nuclear cavity, the tortuous strands being approximately 0.25 µm in diameter. Most of the radioautographic grains still remain over the light nucleoplasmic areas but a number of these are now located on the outermost portion of the dense chromatin profiles. By the end of the S-period, the chromatin strands are slightly thicker (ca. 0.3 µm) and form a looser reticulum. Labelling has decreased noticeably in nuclei of that period, the radioautographic grains being grouped into clusters resting over more or less spherical regions of the chromatin reticulum. Judging from their localization at the surface of the nucleolus or close to the nuclear envelope, these structures correspond to chromocentres. The additional interesting finding that such nuclear structures appear much less compactly organized strongly suggests that chromocentres undergo important conformational modifications during duplication of their DNA.

Experimental Investigation of Effects of Extrusion Pressure on Cell Growth of Bioprinted Algae Cells in Green Bioprinting

2020 ◽  
Author(s):  
Laura Jerpseth ◽  
Ketan Thakare ◽  
Zhijian Pei ◽  
Hongmin Qin
Keyword(s):  
Cell Growth ◽  
Cell Count ◽  
Plant Cells ◽  
Extrusion Pressure ◽  
Layer By Layer ◽  
Animal Cells ◽  
Physical Damage ◽  
The Third ◽  
Cell Counts ◽  
The Difference

Abstract In bioprinting, biomaterials are deposited layer-by-layer to fabricate structures. Bioprinting has many potential applications in drug screening, tissue engineering, and regenerative medicine. Both animal cells and plant cells can be used to synthesize bioinks. Green bioprinting uses bioinks that have been synthesized using plant cells. Constructs fabricated via green bioprinting contain immobilized plant cells, with these cells arranged at desired locations. The constructs provide scaffolds for cell growth. Printing parameters affecting the growth of cells in green bioprinted constructs include print speed, needle diameter, extrusion temperature, and extrusion pressure. This paper reports a study to examine effects of extrusion pressure on cell growth (measured by cell count) in bioprinted constructs, using bioink containing Chlamydomonas reinhardtii algae cells. Three levels of extrusion pressure were used: 3, 5, and 7 bar. Cell counts in the bioprinted constructs were measured on the third and sixth days after bioprinting. It was found that, as extrusion pressure increased, cell count decreased on both the third and sixth days after bioprinting. Furthermore, the difference in cell counts between the third and the sixth days decreased as extrusion pressure increased. These trends suggest that increasing extrusion pressure during green bioprinting negatively affects cell growth. A possible reason for these trends is physical damage to or death of cells in the bioprinted constructs when extrusion pressure became higher.

The pH of Plant Cells The pH of Animal Cells

1955 ◽  
Author(s):  
James Small ◽  
Floyd J. Wiercinski
Keyword(s):  
Plant Cells ◽  
Animal Cells

scholarly journals An Improved HRPE-Based Transcriptional Output Reporter to Detect Hypoxia and Anoxia in Plant Tissue

Biosensors ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 197
Author(s):  
Gabriele Panicucci ◽  
Sergio Iacopino ◽  
Elisa De Meo ◽  
Pierdomenico Perata ◽  
Daan A. Weits
Keyword(s):  
Fluorescent Protein ◽  
Narrow Range ◽  
Oxygen Deficiency ◽  
Plant Cells ◽  
Untranslated Regions ◽  
Plant Tissues ◽  
Reporter Activity ◽  
Hypoxic Conditions ◽  
Environmental Availability ◽  
Transcriptional Output

Oxygen levels in plant tissues may vary, depending on metabolism, diffusion barriers, and environmental availability. Current techniques to assess the oxic status of plant cells rely primarily on invasive microoptodes or Clark-type electrodes, which are not optimally suited for experiments that require high spatial and temporal resolution. In this case, a genetically encoded oxygen biosensor is required instead. This article reports the design, test, and optimization of a hypoxia-signaling reporter, based on five-time repeated hypoxia-responsive promoter elements (HRPE) driving the expression of different reporter proteins. Specifically, this study aimed to improve its performance as a reporter of hypoxic conditions by testing the effect of different untranslated regions (UTRs) at the 5′ end of the reporter coding sequence. Next, we characterized an optimized version of the HRPE promoter (HRPE-Ω) in terms of hypoxia sensitivity and time responsiveness. We also observed that severe oxygen deficiency counteracted the reporter activity due to inhibition of GFP maturation, which requires molecular oxygen. To overcome this limitation, we therefore employed an oxygen-independent UnaG fluorescent protein-coupled to an O2-dependent mCherry fluorophore under the control of the optimized HRPE-Ω promoter. Remarkably, this sensor, provided a different mCherry/UnaG ratiometric output depending on the externally imposed oxygen concentration, providing a solution to distinguish between different degrees of tissue hypoxia. Moreover, a ubiquitously expressed UnaG-mCherry fusion could be used to image oxygen concentrations directly, albeit at a narrow range. The luminescent and fluorescent hypoxia-reporters described here can readily be used to conduct studies that involve anaerobiosis in plants.

The Cell's Biological Rods and Ropes

MRS Bulletin ◽  
1999 ◽  
Vol 24 (10) ◽  
pp. 27-31 ◽  
Author(s):  
David Boal
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Chemical Composition ◽  
Intermediate Filaments ◽  
Plant Cells ◽  
Cell Type ◽  
Animal Cells ◽  
Limited Variation ◽  
A Cell ◽  
Mechanical Elements

Despite a variety of shapes and sizes, the generic mechanical structure of cells is remarkably similar from one cell type to the next. All cells are bounded by a plasma membrane, a fluid sheet that controls the passage of materials into and out of the cell. Plant cells and bacteria reinforce this membrane with a cell wall, permitting the cell to operate at an elevated osmotic pressure. Simple cells, such as the bacterium shown in Figure 1a, possess a fairly homogeneous interior containing the cell's genetic blueprint and protein workhorses, but no mechanical elements. In contrast, as can be seen in Figure 1b, plant and animal cells contain internal compartments and a filamentous cytoskeleton—a network of biological ropes, cables, and poles that helps maintain the cell's shape and organize its contents.Four principal types of filaments are found in the cytoskeleton: spectrin, actin, microtubules, and a family of intermediate filaments. Not all filaments are present in all cells. The chemical composition of the filaments shows only limited variation from one cell to another, even in organisms as diverse as humans and yeasts. Membranes have a more variable composition, consisting of a bi-layer of dual-chain lipid molecules in which are embedded various proteins and frequently a moderate concentration of cholesterol. The similarity of the cell's mechanical elements in chemical composition and physical characteristics encourages us to search for universal strategies that have developed in nature for the engineering specifications of the cell. In this article, we concentrate on the cytoskeleton and its filaments.

scholarly journals Dynamic continuity of cytoplasmic and membrane compartments between plant cells.

1988 ◽  
Vol 106 (3) ◽  
pp. 715-721 ◽  
Author(s):  
O Baron-Epel ◽  
D Hernandez ◽  
L W Jiang ◽  
S Meiners ◽  
M Schindler
Keyword(s):  
Cell Communication ◽  
Plant Cells ◽  
Tumor Promoter ◽  
Ionophore A23187 ◽  
Animal Cells ◽  
Root Cells ◽  
Dynamic Membrane ◽  
Membrane Compartments ◽  
Intercellular Movement ◽  
Soybean Cell

Fluorescence photobleaching was employed to examine the intercellular movement of fluorescein and carboxyfluorescein between contiguous soybean root cells (SB-1 cell line) growing in tissue culture. Results of these experiments demonstrated movement of these fluorescent probes between cytoplasmic (symplastic) compartments. This symplastic transport was inhibited with Ca2+ in the presence of ionophore A23187, and also with the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Both of these agents have previously been demonstrated to inhibit gap junction-mediated cell-cell communication in animal cells. In a companion experiment, a fluorescent phospholipid analogue, N-4-nitrobenzo-2-oxa-1,3-diazole phosphatidylcholine (NBD-PC), was incorporated into soybean cell membranes to examine whether dynamic membrane continuity existed between contacting cells, a transport route not existing between animal cells. Photobleaching single soybean cells growing in a filamentous strand demonstrated that phospholipid did exchange between contiguous cells.

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