Ultrastructure and development of urediospore ornamentation in Melampsora lini

1971 ◽  
Vol 49 (12) ◽  
pp. 2067-2073 ◽  
Author(s):  
L. J. Littlefield ◽  
C. E. Bracker
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Outer Surface ◽  
Spore Wall ◽  
Wall Material ◽  
Wild Type ◽  
Melampsora Lini ◽  
Inner Surface ◽  
External Position ◽  
Basal Portion

The urediospores of Melampsora lini (Ehrenb.) Lev. are echinulate, with spines ca. 1 μ long over their surface. The spines are electron-transparent, conical projections, with their basal portion embedded in the electron-dense spore wall. The entire spore, including the spines, is covered by a wrinkled pellicle ca. 150–200 Å thick. The spore wall consists of three recognizable layers in addition to the pellicle. Spines form initially as small deposits at the inner surface of the spore wall adjacent to the plasma membrane. Endoplasmic reticulum occurs close to the plasma membrane in localized areas near the base of spines. During development, the spore wall thickens, and the spines increase in size. Centripetal growth of the wall encases the spines in the wall material. The spines progressively assume a more external position in the spore wall and finally reside at the outer surface of the wall. A mutant strain with finely verrucose spores was compared to the wild type. The warts on the surface of the mutant spores are rounded, electron-dense structures ca. 0.2–0.4 μ high, in contrast to spines of the wild type. Their initiation near the inner surface of the spore wall and their eventual placement on the outer surface of the spore are similar to that of spines. The wall is thinner in mutant spores than in wild-type spores.

scholarly journals Retention of adenovirus E19 glycoprotein in the endoplasmic reticulum is essential to its ability to block antigen presentation.

1991 ◽  
Vol 174 (6) ◽  
pp. 1629-1637 ◽  
Author(s):  
J H Cox ◽  
J R Bennink ◽  
J W Yewdell
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Antigen Presentation ◽  
Viral Proteins ◽  
Genetically Engineered ◽  
Class I ◽  
Wild Type ◽  
Histocompatibility Complex ◽  
Infected Cells ◽  
Lumenal Domain

The E3/19K glycoprotein of adenovirus functions to diminish recognition of adenovirus-infected cells by major histocompatibility complex class I-restricted cytotoxic T lymphocytes (CTLs) by binding intracellular class I molecules and preventing them from reaching the plasma membrane. In the present study we have characterized the nature of the interaction between E3/19K and the H-2Kd (Kd) molecule. An E3/19K molecule genetically engineered to terminate six residues from its normal COOH terminus (delta E19), was found to associate with Kd in a manner indistinguishable from wild-type E3/19K. Unlike E3/19K, however, delta E19 was transported through the Golgi complex to the plasma membrane, where it could be detected biochemically and immunocytochemically using a monoclonal antibody specific for the lumenal domain of E3/19K. Importantly, delta E19 also differed from E3/19K in being unable to prevent the presentation of Kd-restricted viral proteins to CTLs. This is unlikely to be due to delta E19 having a lower avidity for Kd than E3/19K, since delta E19 was able to compete with E3/19K for Kd binding, both physically, and functionally in nullifying the E3/19K blockade of antigen presentation. These findings indicate that the ability of E3/19K to block antigen presentation is due solely to its ability to retain newly synthesized class I molecules in the endoplasmic reticulum.

Defective targeting of hemojuvelin to plasma membrane is a common pathogenetic mechanism in juvenile hemochromatosis

Blood ◽  
2007 ◽  
Vol 109 (10) ◽  
pp. 4503-4510 ◽  
Author(s):  
Laura Silvestri ◽  
Alessia Pagani ◽  
Claudia Fazi ◽  
Gianmario Gerardi ◽  
Sonia Levi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Iron Supplementation ◽  
Proteolytic Processing ◽  
Dual Function ◽  
Wild Type ◽  
Pathogenetic Mechanism ◽  
Gpi Anchor ◽  
Juvenile Hemochromatosis ◽  
Deficient Mice

Abstract Hemojuvelin (HJV) positively modulates the iron regulator hepcidin, and its mutations are the major cause of juvenile hemochromatosis (JH), a recessive disease leading to iron overload. Defective HJV reduces hepcidin up-regulation both in humans and in Hjv-deficient mice. To investigate the JH pathogenesis and the functional properties of human HJV we studied the biosynthesis and maturation of 6 HJV pathogenic mutants in HeLa and HepG2 cells. We show that proteolytic processing is defective in mutants F170S, W191C, and G320V, but not in G99V and C119F. Moreover, we show that mutants G99V and C119F are targeted to the cell surface, while F170S, W191C, G320V, and R326X (lacking the glycosilphosphatidylinositol [GPI] anchor) are mainly retained in the endoplasmic reticulum, although all mutants are released as soluble forms (s-HJV) in a proportion that is modulated by iron supplementation. Membrane HJV (m-HJV) is mainly composed of the cleaved protein, and its level is increased by iron in wild-type (WT) mice but not in the mutants. Altogether, the data demonstrate that the loss of HJV membrane export is central to the pathogenesis of JH, and that HJV cleavage is essential for the export. The results support a dual function for s- and m-HJV in iron deficiency and overload, respectively.

Ascospore development in the fission yeasts Schizosaccharomyces pombe and S. japonicus

1982 ◽  
Vol 56 (1) ◽  
pp. 263-279 ◽  
Author(s):  
K. Tanaka ◽  
A. Hirata
Keyword(s):  
Plasma Membrane ◽  
Schizosaccharomyces Pombe ◽  
Periodic Acid ◽  
Staining Technique ◽  
Membrane System ◽  
Spore Wall ◽  
Wall Material ◽  
Dense Granules ◽  
Thin Sectioning ◽  
Ascospore Development

The fine structure of ascospore formation in the fission yeasts Schizosaccharomyces pombe and Schizosaccharomyces japonicus var. japonicus was studied by serial thin-sectioning and electron microscopy. The morphogenetic events were almost the same in both species. Ascospore development was initiated by the formation of the forespore membrane on the cytoplasmic side of the differentiated nucleus-associated organelle (NAO) in the interval between meiosis I and II in S. pombe, or during the post-meiotic nuclear division in S. japonicus, and the process proceeded almost synchronously through the two or four nuclei in the ascus. The forespore membrane developed by fusion of the cytoplasmic vesicles and this was clearly demonstrated in S. japonicus where the behaviour of vesicles involved in the forespore membrane development could be traced as they were marked by the presence of electron-dense granules. The staining technique, by phosphotungustic acid—chromic acid (PTA-CA) after treatment with periodic acid, was used to attempt to elucidate the origin and the nature of the forespore membrane. The method specific to plasmalemma-type membranes stained both ascus and ascospore plasmalemmas; the forespore membrane was not stained at first but developed the same affinity for stain as the plasma membrane in the course of ascospore development. The results suggest that the forespore membrane did not come directly from the ascus plasma membrane, but from another membrane system such as the endoplasmic reticulum. Spore wall material was deposited in the space between the inner and outer leaflets of the forespore membrane.

scholarly journals Subcellular localization of cellulases in auxin-treated pea.

1976 ◽  
Vol 69 (1) ◽  
pp. 97-105 ◽  
Author(s):  
A K Bal ◽  
D P Verma ◽  
H Byrne ◽  
G A Maclachlan
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Plasma Membrane ◽  
Major Part ◽  
Osmium Tetroxide ◽  
Close Association ◽  
Cellulase Activity ◽  
Cytochemical Localization ◽  
Tissue Sections ◽  
Inner Surface

Two forms of cellulase, buffer soluble (BS) and buffer insoluble (BI), are induced as a result of auxin treatment of dark-grown pea epicotyls. These two cellulases have been purified to homogeneity. Antibodies raised against the purified cellulases were conjugated with ferritin and were used to localize the two cellulases. Tissue sections were fixed in cold paraformaldehyde-glutaraldehyde and incubated for 1 h in the ferritin conjugates. The sections were washed with continuous shaking for 18 h and subsequently postfixed in osmium tetroxide. Tissue incubated in unconjugated ferritin was used as a control. A major part of BI cellulase is localized at the inner surface of the cell wall in close association with microfibrils. BS cellulase is localized mainly within the distended endoplasmic reticulum. Gogli complex and plasma membrane appear to be completely devoid of any cellulase activity. These observations are consistent with cytochemical localization and biochemical data on the distribution of these two cellulases among various cell and membrane fractions.

scholarly journals A 3D analysis of yeast ER structure reveals how ER domains are organized by membrane curvature

2011 ◽  
Vol 193 (2) ◽  
pp. 333-346 ◽  
Author(s):  
Matt West ◽  
Nesia Zurek ◽  
Andreas Hoenger ◽  
Gia K. Voeltz
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Membrane Curvature ◽  
3D Analysis ◽  
Wild Type ◽  
Nanometer Resolution ◽  
Ribosome Density ◽  
Multiple Stages

We analyzed the structure of yeast endoplasmic reticulum (ER) during six sequential stages of budding by electron tomography to reveal a three-dimensional portrait of ER organization during inheritance at a nanometer resolution. We have determined the distribution, dimensions, and ribosome densities of structurally distinct but continuous ER domains during multiple stages of budding with and without the tubule-shaping proteins, reticulons (Rtns) and Yop1. In wild-type cells, the peripheral ER contains cytoplasmic cisternae, many tubules, and a large plasma membrane (PM)–associated ER domain that consists of both tubules and fenestrated cisternae. In the absence of Rtn/Yop1, all three domains lose membrane curvature, ER ribosome density changes, and the amount of PM-associated ER increases dramatically. Deletion of Rtns/Yop1 does not, however, prevent bloated ER tubules from being pulled from the mother cisterna into the bud and strongly suggests that Rtns/Yop1 stabilize/maintain rather than generate membrane curvature at all peripheral ER domains in yeast.

scholarly journals STRUCTURAL FEATURES OF MESOSOMES (CHONDRIOIDS) OF BACILLUS SUBTILIS AFTER FREEZE-ETCHING

1968 ◽  
Vol 39 (2) ◽  
pp. 251-263 ◽  
Author(s):  
N. Nanninga
Keyword(s):  
Cell Wall ◽  
Bacillus Subtilis ◽  
Plasma Membrane ◽  
Outer Surface ◽  
Osmium Tetroxide ◽  
Close Association ◽  
Membrane Surface ◽  
Bacterial Membranes ◽  
Inner Surface ◽  
Freeze Etching

Freeze-etched cells of Bacillus subtilis have been studied with the electron microscope. The outer surface of the plasma membrane, i.e. the side facing the cell wall, is covered with numerous granules and short strands, each measuring approximately 50 A in diameter. These strands are occasionally seen to enter the cell wall. The inner surface of the plasma membrane, i.e. the side facing the cytoplasm, appears to be sparsely dotted with small particles measuring about 50 A. The envelope of mesosomes differs from the plasma membrane. Blunt protrusions arise from its outer surface; the inner surface appears smooth. Stalked particles, as described by other investigators after negative staining with phosphotungstic acid, were not observed on any membrane surface in our material. Preparations were also made of specimens prefixed in osmium tetroxide prior to freeze-etching. Under these conditions the bacterial membranes appeared to be surprisingly well preserved. In contrast to directly frozen, unfixed cells, some osmium tetroxide-fixed preparations showed a differentiation in cytoplasm and nucleoplasm, which made it possible to observe the close association of the mesosome with the latter.

scholarly journals Cytochrome P-450 3A13 and endothelin jointly mediate ductus arteriosus constriction to oxygen in mice

2011 ◽  
Vol 300 (3) ◽  
pp. H892-H901 ◽  
Author(s):  
Barbara Baragatti ◽  
Enrica Ciofini ◽  
Francesca Scebba ◽  
Debora Angeloni ◽  
Daria Sodini ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Immunofluorescence Microscopy ◽  
Oxygen Sensing ◽  
Ductus Arteriosus ◽  
Wild Type ◽  
Phasic Response ◽  
Sensing System ◽  
Cytochrome P 450

The fetal ductus arteriosus (DA) contracts to oxygen, and this feature, maturing through gestation, is considered important for its closure at birth. We have previously obtained evidence of the involvement of cytochrome P-450, possibly of the 3A subfamily (CYP3A), in oxygen sensing and have also identified endothelin (ET)-1 as the attendant effector for the contraction. Here, we examined comparatively wild-type (WT) and CYP3A-null ( Cyp3a−/−) mice for direct validation of this concept. We found that the CYP3A subfamily is represented only by CYP3A13 in the WT DA. CYP3A13 was also detected in the DA by immunofluorescence microscopy, being primarily colocalized with the endoplasmic reticulum in both endothelial and muscle cells. However, a distinct signal was also evident in the plasma membrane. Isolated DAs from term WT animals developed a sustained contraction to oxygen with transient contractions superimposed. Conversely, no tonic response occurred in Cyp3a−/− DAs, whereas the phasic response persisted unabated. Oxygen did not contract the preterm WT DA but caused a full-fledged contraction after retinoic acid (RA) treatment. RA also promoted an oxygen contraction in the Cyp3a −/− DA. However, responses of RA-treated WT and Cyp3a−/− mice differed in that only the former abated with ET-1 suppression. This implies the existence of an alternative target for RA responsible for the oxygen-induced contraction in the absence of CYP3A13. In vivo, the DA was constricted in WT and Cyp3a−/− newborns, although with a tendency to be less narrowed in the mutant. We conclude that oxygen acts primarily through the complex CYP3A13 (sensor)/ET-1 (effector) and, in an accessory way, directly onto ET-1. However, even in the absence of CYP3A13, the DA may close postnatally thanks to the contribution of ET-1 and the likely involvement of compensating mechanism(s) identifiable with an alternative oxygen-sensing system and/or the withdrawal of relaxing influence(s) operating prenatally.

An NH2-terminal deleted plasma membrane H+-ATPase is a dominant negative mutant and is sequestered in endoplasmic reticulum derived structures

2000 ◽  
Vol 78 (1) ◽  
pp. 51-58 ◽  
Author(s):  
Claudio Akio Masuda ◽  
Mónica Montero-Lomelí
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Immunofluorescence Microscopy ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Wild Type ◽  
Internal Peptide ◽  
Limited Trypsinolysis ◽  
Wild Type Yeast ◽  
Negative Mutant

The NH2-terminus of the plasma membrane H+-ATPase is one of the least conserved segments of this protein among fungi. We constructed and expressed a mutant H+-ATPase from Saccharomyces cerevisiae deleted at an internal peptide within the cytoplasmic NH2-terminus (D44-F116). When the enzyme was subjected to limited trypsinolysis it was digested more rapidly than wild type H+-ATPase. Membrane fractionation experiments and immunofluorescence microscopy, using antibodies against H+-ATPase showed that the mutant ATPase is retained in the endoplasmic reticulum. The pattern observed in the immunofluorescence microscopy resembled structures similar to Russell bodies (modifications of the endoplasmic reticulum membranes) recently described in yeast. When the wild type H+-ATPase was co-expressed with the mutant, wild type H+-ATPase was also retained in the endoplasmic reticulum. Co-expression of both ATPases in a wild type yeast strain was lethal, demonstrating that this is a dominant negative mutant.

Ultrastructural changes during germination of Geotrichum candidum arthrospores

1973 ◽  
Vol 19 (8) ◽  
pp. 1031-1034 ◽  
Author(s):  
S. D. Steele ◽  
T. W. Fraser
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Germ Tube ◽  
Tube Wall ◽  
Geotrichum Candidum ◽  
Spore Wall ◽  
Ultrastructural Changes ◽  
Wall Material ◽  
Apparent Increase ◽  
Tube Emergence

The dormant arthrospore in Geotrichum candidum has three, possibly four, layers making up the spore wall. Nuclei, mitochondria, free ribosomes, fragments of endoplasmic reticulum, various small vacuoles, and particles of glycogen were observed within the protoplasm. During germination a new layer of wall material forms between the original spore wall and the cytoplasm. This new layer is confined to the region where germ-tube emergence occurs and is continuous with the germ-tube wall. After germ-tube emergence vesicles were seen at the apices of germlings. Another feature of germination was an apparent increase in the amount of endoplasmic reticulum, some of which appears to assume the function of the Golgi apparatus.

Ultrastructure of dormant basidiospores of Agaricus campestris

1988 ◽  
Vol 66 (3) ◽  
pp. 583-587 ◽  
Author(s):  
Donald G. Ruch ◽  
Mary C. North
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Short Distance ◽  
Mitochondrial Membrane ◽  
Lipid Droplets ◽  
Wall Material ◽  
Outer Mitochondrial Membrane ◽  
The Third ◽  
Membrane Bound ◽  
Agaricus Campestris

The basidiospore wall of Agaricus campestris Fr. consists of three distinct layers. The outer two layers are continuous around the spore, while the third layer originates only a short distance from the hilar appendage and quickly thickens to form the bulk of the wall material of the hilar appendage. The protoplast is surrounded by a typical plasma membrane which lacks distinct invaginations. Centrally located nonmembrane-bound lipid droplets comprise the bulk of the protoplasm. Spores are binucleate, but the two nuclei do not exhibit any distinct relationship to each other. Sausage-shaped mitochondria with only a few but well-delineated plate-like cristae are present. Scant endoplasmic reticulum occurs just beneath the plasma membrane. Ribosomes occur regularly attached to the endoplasmic reticulum and outer mitochondrial membrane, as well as being densely packed throughout the cytoplasm. The structure and possible functions of single membrane bound vacuoles and microbody-like organelles are discussed in relation to other basidiospores.

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