Ultrastructure of laticifers in redifferentiated organs on callus from Papaver somniferum (Papaveraceae)

1979 ◽  
Vol 57 (6) ◽  
pp. 675-685 ◽  
Author(s):  
Craig L. Nessler ◽  
Paul G. Mahlberg
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Cross Section ◽  
Papaver Somniferum ◽  
Reticulum Cell ◽  
Central Vacuole ◽  
Conspicuous Feature ◽  
Intact Plants ◽  
Meristematic Region ◽  
Large Central Vacuole

Callus was initiated from seedling hypocotyls and mature stems of Papaver somniferum and maintained in culture. The ultrastructure of callus cells resembled parenchyma of intact plants, their most conspicuous feature being a large central vacuole. Meristemoids were formed at random on the surface of calli transferred to the appropriate medium. In cross section, meristemoids appeared as an inner meristematic region surrounded by several layers of concentrically arranged cells. Cells of meristemoids were smaller, more densely cytoplasmic, and more compactly arranged compared with callus. Roots and shoots induced to form from callus possessed cells that were morphologically and developmentally similar to laticifers in intact plants. Laticifers in redifferentiated organs, like those in intact plants, contained numerous capped vesicles that are apparently derived from stacked endoplasmic reticulum. Cell wall perforations between adjacent laticifer elements in redifferentiated organs developed by the gradual, simultaneous thinning of walls at the perforation sites.

scholarly journals Trafficking and Sequestration of Anthocyanins

2008 ◽  
Vol 3 (8) ◽  
pp. 1934578X0800300 ◽  
Author(s):  
Erich Grotewold ◽  
Kevin Davies
Keyword(s):  
Endoplasmic Reticulum ◽  
Central Vacuole ◽  
Cytoplasmic Surface ◽  
Large Central Vacuole ◽  
Frequent Localization

Flavonoids are synthesized on the cytoplasmic surface of the endoplasmic reticulum (ER). As is the case for several other phytochemicals, anthocyanins and other products of the pathway often accumulate in the large central vacuole. This review summarizes recent findings on the possible mechanisms by which flavonoids traffic between the ER and the vacuole, and discusses the frequent localization of anthocyanins in sub-vacuolar structures with variable characteristics.

scholarly journals The Endoplasmic Reticulum and the Golgi Structures in Maize Root Cells

1959 ◽  
Vol 5 (3) ◽  
pp. 501-506 ◽  
Author(s):  
W. Gordon Whaley ◽  
Hilton H. Mollenhauer ◽  
Joyce E. Kephart
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Electron Microscope ◽  
Nuclear Envelope ◽  
Epoxy Resin ◽  
Maize Root ◽  
Root Tips ◽  
Animal Cells ◽  
Root Cells ◽  
Vesicular Structure

Maize root tips were fixed in potassium permanganate, embedded in epoxy resin, sectioned to show silver interference color, and studied with the electron microscope. All the cells were seen to contain an endoplasmic reticulum and apparently independent Golgi structures. The endoplasmic reticulum is demonstrated as a membrane-bounded, vesicular structure comparable in many aspects to that of several types of animal cells. With the treatment used here the membranes appear smooth surfaced. The endoplasmic reticulum is continuous with the nuclear envelope and, by contact at least, with structures passing through the cell wall. The nuclear envelope is characterized by discontinuities, as previously reported for animal cells. The reticula of adjacent cells seem to be in contact at or through the plasmodesmata. Because of these contacts the endoplasmic reticulum of a given cell appears to be part of an intercellular system. The Golgi structures appear as stacks of platelet-vesicles which apparently may, under certain conditions, produce small vesicles around their edges. Their form changes markedly with development of the cell.

The yeast KRE5 gene encodes a probable endoplasmic reticulum protein required for (1----6)-beta-D-glucan synthesis and normal cell growth

1990 ◽  
Vol 10 (6) ◽  
pp. 3013-3019
Author(s):  
P Meaden ◽  
K Hill ◽  
J Wagner ◽  
D Slipetz ◽  
S S Sommer ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Cell Growth ◽  
Normal Cell ◽  
Secretory Pathway ◽  
Endoplasmic Reticulum Retention Signal ◽  
Endoplasmic Reticulum Protein ◽  
Glucan Synthesis ◽  
Retention Signal ◽  
Sequential Assembly

Yeast kre mutants define a pathway of cell wall (1----6)-beta-D-glucan synthesis, and mutants in genes KRE5 and KRE6 appear to interact early in such a pathway. We have cloned KRE5, and the sequence predicts the product to be a large, hydrophilic, secretory glycoprotein which contains the COOH-terminal endoplasmic reticulum retention signal, HDEL. Deletion of the KRE5 gene resulted in cells with aberrant morphology and extremely compromised growth. Suppressors to the KRE5 deletions arose at a frequency of 1 in 10(7) to 1 in 10(8) and permitted an analysis of deletions which were found to contain no alkali-insoluble (1----6)-beta-D-glucan. These results indicate a role for (1----6)-beta-D-glucan in normal cell growth and suggest a model for sequential assembly of (1----6)-beta-D-glucan in the yeast secretory pathway.

Ultrastructural Observations of Cell Wall Regeneration Around Isolated Tobacco Protoplasts

1974 ◽  
Vol 14 (2) ◽  
pp. 439-449
Author(s):  
J. BURGESS ◽  
E. N. FLEMING
Keyword(s):  
Electron Microscopy ◽  
Heavy Metal ◽  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Cell Wall Regeneration ◽  
Membrane Systems ◽  
Tobacco Protoplasts ◽  
Wall Formation ◽  
Wall Regeneration ◽  
Wall Growth

The process of cell wall regeneration around cultured protoplasts isolated from tobacco mesophyll has been examined by electron microscopy. The initially formed wall contains 2 components which stain with conventional heavy metal stains. The first consists of un-branched fibres, at first oriented at right angles to the plasmalemma surface. As wall growth proceeds the fibres lengthen and assume an orientation parallel to the plasmalemma. It seems probable that this component is cellulose. The second component of the wall is more amorphous and more densely stained. It is most frequently seen in situations where leaching of materials into the medium would be expected to be minimal. The endoplasmic reticulum and the plasmalemma are the only membrane systems which appear to contribute towards wall formation. No pattern of structure has been detected to explain the orientation or method of synthesis of the microfibrillar part of the wall.

ULTRASTRUCTURE OF THE HYPHAE AND HAUSTORIA OF PHYTOPHTHORA INFESTANS AND HYPHAE OF P. PARASITICA

1966 ◽  
Vol 44 (11) ◽  
pp. 1495-1503 ◽  
Author(s):  
Mary A. Ehrlich ◽  
Howard G. Ehrlich
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Phytophthora Infestans ◽  
Current Literature ◽  
Lipid Bodies ◽  
Potato Varieties ◽  
Parasitic Fungi ◽  
Obligate Parasites ◽  
Tubular Endoplasmic Reticulum ◽  
Cytoplasmic Continuity

The ultrastructure of the mycelium of both Phytophthora infestans and P. parasitica is consistent with that reported for other Oomycetes. A distinct plasmalemma, porate nuclei, tubular endoplasmic reticulum, mitochondria with tubular cristae, Golgi dictyosomes, and lipid bodies are present within the protoplast. The haustoria produced by P. infestans in the leaves of susceptible potato varieties consist of an expanded haustorial head surrounded by a fungus wall which is continuous with the wall of the intercellular mycelium. The haustorium lacks the long narrow stalk or neck often associated with this organ, and there is considerable cytoplasmic continuity between the haustorium and the intercellular mycelium. All P. infestans haustoria observed were anucleate and generally contained only a few mitochondria and sparse endoplasmic reticulum. The haustorium is enclosed in an encapsulation surrounded by a membrane which is continuous with the host plasmalemma. There is no evidence, around any portion of the haustorium, of a sheath originating from the cell wall of the host. A survey of the current literature on the ultrastructure of the Eumycotinia shows that the parasitic fungi exhibit no unique cytoplasmic features when compared with non-parasitic fungi, and the ultrastructure of the haustoria-producing facultative saprophyte is similar to that of the obligate parasites.

scholarly journals Structural Insight into the Mechanism of N-Linked Glycosylation by Oligosaccharyltransferase

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 624 ◽  
Author(s):  
Smita Mohanty ◽  
Bharat P Chaudhary ◽  
David Zoetewey
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Modification ◽  
Cell Communication ◽  
Reticulum Cell ◽  
Enzyme Complex ◽  
Single Polypeptide Chain ◽  
Domains Of Life ◽  
And Function ◽  
Insight Into

Asparagine-linked glycosylation, also known as N-linked glycosylation is an essential and highly conserved post-translational protein modification that occurs in all three domains of life. This modification is essential for specific molecular recognition, protein folding, sorting in the endoplasmic reticulum, cell–cell communication, and stability. Defects in N-linked glycosylation results in a class of inherited diseases known as congenital disorders of glycosylation (CDG). N-linked glycosylation occurs in the endoplasmic reticulum (ER) lumen by a membrane associated enzyme complex called the oligosaccharyltransferase (OST). In the central step of this reaction, an oligosaccharide group is transferred from a lipid-linked dolichol pyrophosphate donor to the acceptor substrate, the side chain of a specific asparagine residue of a newly synthesized protein. The prokaryotic OST enzyme consists of a single polypeptide chain, also known as single subunit OST or ssOST. In contrast, the eukaryotic OST is a complex of multiple non-identical subunits. In this review, we will discuss the biochemical and structural characterization of the prokaryotic, yeast, and mammalian OST enzymes. This review explains the most recent high-resolution structures of OST determined thus far and the mechanistic implication of N-linked glycosylation throughout all domains of life. It has been shown that the ssOST enzyme, AglB protein of the archaeon Archaeoglobus fulgidus, and the PglB protein of the bacterium Campylobactor lari are structurally and functionally similar to the catalytic Stt3 subunit of the eukaryotic OST enzyme complex. Yeast OST enzyme complex contains a single Stt3 subunit, whereas the human OST complex is formed with either STT3A or STT3B, two paralogues of Stt3. Both human OST complexes, OST-A (with STT3A) and OST-B (containing STT3B), are involved in the N-linked glycosylation of proteins in the ER. The cryo-EM structures of both human OST-A and OST-B complexes were reported recently. An acceptor peptide and a donor substrate (dolichylphosphate) were observed to be bound to the OST-B complex whereas only dolichylphosphate was bound to the OST-A complex suggesting disparate affinities of two OST complexes for the acceptor substrates. However, we still lack an understanding of the independent role of each eukaryotic OST subunit in N-linked glycosylation or in the stabilization of the enzyme complex. Discerning the role of each subunit through structure and function studies will potentially reveal the mechanistic details of N-linked glycosylation in higher organisms. Thus, getting an insight into the requirement of multiple non-identical subunits in the N-linked glycosylation process in eukaryotes poses an important future goal.

THE ORGANIZATION OF CYTOPLASMIC COMPONENTS DURING THE PHASE OF CELL WALL THICKENING IN DIFFERENTIATING CAMBIAL DERIVATIVES OF ACER RUBRUM

1965 ◽  
Vol 43 (11) ◽  
pp. 1401-1407 ◽  
Author(s):  
James Cronshaw
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Plasma Membrane ◽  
Osmium Tetroxide ◽  
Acer Rubrum ◽  
Middle Layer ◽  
Wall Thickening ◽  
Cytoplasmic Microtubules ◽  
Derivatives Of ◽  
Peripheral Cytoplasm

Cambial derivatives of Acer rubrum have been examined at stages of their differentiation following fixation in 3% or 6% glutaraldehyde with a post fixation in osmium tetroxide. At early stages of development numerous free ribosomes are present in the cytoplasm, and elements of the endoplasmic reticulum tend to align themselves parallel to the cell surfaces. The plasma membrane is closely applied to the cell walls. During differentiation a complex system of cytoplasmic microtubules develops in the peripheral cytoplasm. These microtubules are oriented, mirroring the orientation of the most recently deposited microfibrils of the cell wall. The microtubules form a steep helix in the peripheral cytoplasm at the time of deposition of the middle layer of the secondary wall. During differentiation the free ribosomes disappear from the cytoplasm and numerous elements of rough endoplasmic reticulum with associated polyribosomes become more evident. In many cases the endoplasmic reticulum is associated with the cell surface. During the later stages of differentiation there are numerous inclusions between the cell wall and the plasma membrane.

A light and electron microscope investigation of the transfer cell region of maize caryopses

1990 ◽  
Vol 68 (3) ◽  
pp. 471-479 ◽  
Author(s):  
Ronald W. Davis ◽  
J. D. Smith ◽  
B. Greg Cobb
Keyword(s):  
Cell Wall ◽  
Cross Section ◽  
Close Association ◽  
Transfer Cells ◽  
Transfer Cell ◽  
Cell Region ◽  
Maternal Tissue ◽  
X Ray ◽  
Numerous Cell ◽  
Electron Microscopes

The transfer cell zones from 23-day postpollination corn caryopses were examined using light and electron microscopes and X-ray elemental analysis. The transfer cells were sectioned in cross and longitudinal planes and were characterized by having numerous cell-wall extensions in the form of anastomosing lamellae. The most basal transfer cells had more cell-wall extensions than those that were successively deeper in the endosperm. Cytoplasm, rich with mitochondria, filled the interstices of cell-wall extensions, and many vesiculate areas could be found along the plasma membrane. Some transfer cells contained crystals within plastids. The crystals were composed of magnesium, phosphorus, calcium, and zinc. Other cells had large aggregations of endoplasmic reticulum that were often in close association with mitochondria or unidentified, single membrane bounded organelles. When viewed in cross section, the cell-wall extensions of contiguous cells tended to originate from common loci. Plasmodesmata were absent in the bottom parts of the basal transfer cells where they contacted the maternal tissue but were abundant in the upper parts of these cells and in the transfer cells found deeper in the endosperm. The plasmodesmata were found in clusters and alternated with the wall extension areas.

scholarly journals Different polarisome components play distinct roles in Slt2p-regulated cortical ER inheritance in Saccharomyces cerevisiae

2013 ◽  
Vol 24 (19) ◽  
pp. 3145-3154 ◽  
Author(s):  
Xia Li ◽  
Susan Ferro-Novick ◽  
Peter Novick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Protein Kinase ◽  
Protein Phosphatase ◽  
Mitogen Activated Protein Kinase ◽  
Common Mechanism ◽  
Late Step ◽  
Mitogen Activated Protein ◽  
Cortical Endoplasmic Reticulum

Ptc1p, a type 2C protein phosphatase, is required for a late step in cortical endoplasmic reticulum (cER) inheritance in Saccharomyces cerevisiae. In ptc1Δ cells, ER tubules migrate from the mother cell and contact the bud tip, yet fail to spread around the bud cortex. This defect results from the failure to inactivate a bud tip–associated pool of the cell wall integrity mitogen-activated protein kinase, Slt2p. Here we report that the polarisome complex affects cER inheritance through its effects on Slt2p, with different components playing distinct roles: Spa2p and Pea2p are required for Slt2p retention at the bud tip, whereas Bni1p, Bud6p, and Sph1p affect the level of Slt2p activation. Depolymerization of actin relieves the ptc1Δ cER inheritance defect, suggesting that in this mutant the ER becomes trapped on the cytoskeleton. Loss of Sec3p also blocks ER inheritance, and, as in ptc1Δ cells, this block is accompanied by activation of Slt2p and is reversed by depolymerization of actin. Our results point to a common mechanism for the regulation of ER inheritance in which Slt2p activity at the bud tip controls the association of the ER with the actin-based cytoskeleton.

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