scholarly journals Histology of Infection of Hydrilla verticillata by Macrophomina phaseolina

Weed Science ◽  
1992 ◽  
Vol 40 (2) ◽  
pp. 288-295 ◽  
Author(s):  
Gary F. Joye ◽  
Rex N. Paul
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Epidermal Cell ◽  
Cell Walls ◽  
Hydrilla Verticillata ◽  
Macrophomina Phaseolina ◽  
Host Cells ◽  
Outer Cell ◽  
Cell Wall Disruption ◽  
Outer Cell Wall

Infection of Hydrilla verticillata by Macrophomina phaseolina was investigated using scanning and transmission electron microscopy. Sprigs of plants in petri plates were inoculated with suspensions of fungal hyphae. Samples of inoculated and noninoculated plants were taken over time. Fungal cells attached to lower epidermal cell walls but not the upper epidermal cell walls of leaves. In less than 40 h, penetration through the cell wall was completed and colonization of host cells was observed. Penetration of upper epidermis was limited to the cell wall adjacent to a lower epidermal cell. No penetration was observed through the outer cell wall of upper epidermis. Inhibition of penetration through the outer cell wall of the upper epidermis may be attributable to an osmiophilic layer below the cell wall. Disruption of the host cell walls and subsequent host cell death was preceded by massive colonization of the host by this pathogen.

A freeze-etch study of plant cell walls for ectodesmata

1974 ◽  
Vol 52 (9) ◽  
pp. 2033-2036 ◽  
Author(s):  
N. C. Lyon ◽  
W. C. Mueller
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Leaf Tissue ◽  
Physicochemical Characteristics ◽  
Outer Cell ◽  
Plantago Major ◽  
Plant Cell Walls ◽  
Phaseolus Vulgaris L ◽  
Epidermal Cell Wall ◽  
Outer Cell Wall

Leaf tissue of Phaseolus vulgaris L. and Plantago major L. was prepared by the freeze-etch technique and examined in the electron microscope for the presence of ectodesmata. No structures analagous to ectodesmata observed with light microscopy could be found in freeze-etched preparations of chemically unfixed material or in material fixed only in glutaraldehyde. Objects appearing as broad, shallow, granular areas in the epidermal cell wall beneath the cuticle were observed in leaf replicas after fixation in complete sublimate fixative, the acid components of the sublimate fixative, or mercuric chloride alone. Because of their distribution and location, these objects can be considered analagous to ectodesmata observed by light microscopists. Because these areas occur only in chemically fixed walls and are localized within the walls in discrete areas, their presence supports the contention that ectodesmata are sites in the outer cell wall with defined physicochemical characteristics.

Ultrastructure of compatible and incompatible reactions of sunflower to Plasmopara halstedii

1979 ◽  
Vol 57 (4) ◽  
pp. 315-323 ◽  
Author(s):  
Glenn Wehtje ◽  
Larry J. Littlefield ◽  
David E. Zimmer
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Host Cell ◽  
Epidermal Cell ◽  
Cortical Cell ◽  
Hypersensitive Reaction ◽  
Host Cells ◽  
Plasmopara Halstedii ◽  
Host Cell Wall ◽  
Host Plasma Membrane

Penetration of sunflower, Heliantluis animus, root epidermal cells by zoospores of Plasmopara halstedii is preceded by formation of a papilla on the inner surface of the host cell wall that invaginates the host plasma membrane. Localized degradation and penetration of the host cell wall by the pathogen follow. The invading fungus forms an allantoid primary infection vesicle in the penetrated epidermal cell. The host plasma membrane invaginates around the infection vesicle but its continuity is difficult to follow. Upon exit from the epidermal cell the fungus may grow intercellularly, producing terminal haustorial branches which extend into adjacent host cells. The fungus may grow through one or two cortical cell is after growing from the epidermal cell before it becomes intercellular. Host plasma membrane is not penetrated by haustoria. Intercellular hyphae grow toward the apex of the plant and ramify the seedling tissue. Resistance in an immune cultivar is hypersensitive and is triggered upon contact of the host cell with the encysting zoospore before the host cell wall is penetrated. Degeneration of zoospore cytoplasm accompanies the hypersensitive reaction of the host. Zoospores were often parasitized by bacteria and did not germinate unless penicillin and streptomycin were added to the inoculum suspension.

scholarly journals Conidial Hydrophobins of Aspergillus fumigatus

2003 ◽  
Vol 69 (3) ◽  
pp. 1581-1588 ◽  
Author(s):  
Sophie Paris ◽  
Jean-Paul Debeaupuis ◽  
Reto Crameri ◽  
Marilyn Carey ◽  
Franck Charlès ◽  
...  
Keyword(s):  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Amorphous Layer ◽  
Wall Layer ◽  
Host Cells ◽  
Outer Cell ◽  
Host Immune System ◽  
Wild Type ◽  
Cell Wall Layer ◽  
Outer Cell Wall

ABSTRACT The surface of Aspergillus fumigatus conidia, the first structure recognized by the host immune system, is covered by rodlets. We report that this outer cell wall layer contains two hydrophobins, RodAp and RodBp, which are found as highly insoluble complexes. The RODA gene was previously characterized, and ΔrodA conidia do not display a rodlet layer (N. Thau, M. Monod, B. Crestani, C. Rolland, G. Tronchin, J. P. Latgé, and S. Paris, Infect. Immun. 62:4380-4388, 1994). The RODB gene was cloned and disrupted. RodBp was highly homologous to RodAp and different from DewAp of A. nidulans. ΔrodB conidia had a rodlet layer similar to that of the wild-type conidia. Therefore, unlike RodAp, RodBp is not required for rodlet formation. The surface of ΔrodA conidia is granular; in contrast, an amorphous layer is present at the surface of the conidia of the ΔrodA ΔrodB double mutant. These data show that RodBp plays a role in the structure of the conidial cell wall. Moreover, rodletless mutants are more sensitive to killing by alveolar macrophages, suggesting that RodAp or the rodlet structure is involved in the resistance to host cells.

Axenic culture of flax rust isolated from cotyledons by cell-wall digestion

1972 ◽  
Vol 50 (12) ◽  
pp. 2601-2603 ◽  
Author(s):  
W. David Lane ◽  
Michael Shaw
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Cell Walls ◽  
Hydrolytic Enzymes ◽  
Axenic Culture ◽  
Rust Fungi ◽  
Host Cells ◽  
Melampsora Lini ◽  
Large Numbers ◽  
Axenic Cultures

A technique is described for the isolation of colonies of flax rust (Melampsora lini (Ehrenb.) Lév., Race No. 3) from infected cotyledons. The technique depends on the digestion of the host cell walls with hydrolytic enzymes and washing of the liberated colonies. It is thus possible to collect large numbers of flax-rust colonies with only a few host cells adhering to them. Axenic cultures were established from colonies isolated in this way. This technique may be useful in establishing axenic cultures of other rust fungi.

High Pressure Freezing/Freeze Substituion: Comparison of Chemical Fixation Versus Cryoimmobilization of Candida Albicans Cultured in Cellulose Tubing

1999 ◽  
Vol 5 (S2) ◽  
pp. 434-435
Author(s):  
S. Erlandsen ◽  
A Holzer ◽  
M. Gavin ◽  
C. Frethem ◽  
C. Wells
Keyword(s):  
High Pressure ◽  
Cell Wall ◽  
Candida Albicans ◽  
Freeze Substitution ◽  
Host Cells ◽  
Yeast Cells ◽  
Outer Cell ◽  
High Pressure Freezing ◽  
Outer Cell Wall

In the interactions of Candida albicans with host cells, the cell wall of the yeast may play important roles in the adhesion of yeast cells to tissues. The outer cell wall of yeast (e.g. Saccharomyces cerevisiae, C. albicans) has been shown to consist of a dense network of radially projecting fibrils composed of mannoproteins that are known as fimbriae and which previously have required cryopreservation either by jet propane freezing or by plunge freezeing for their visualization. High pressure freezing provides an advantage over jet or plunge freezing in terms of the higher consistancey in the quality of freezing, and the minimization of formation of ice I with this method. Hohenberg et al reported a method utilizing cellulose capillary tubes to cryoimmobilize suspensions of microoganisms by high pressure freezing (HPF) and freeze substitution (FS), and herein, we describe an adaptation of this method by culturing microorganisms within the tubing to increase cell density prior to high pressure freezing and freeze substution.

Cell wall differentiation during early somatic embryogenesis in plants. II. Ultrastructural study and pectin immunolocalization on chicory embryos

2000 ◽  
Vol 78 (6) ◽  
pp. 824-831 ◽  
Author(s):  
Audrey Chapman ◽  
Anne-Sophie Blervacq ◽  
Théo Hendriks ◽  
Christian Slomianny ◽  
Jacques Vasseur ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cell Wall ◽  
Somatic Embryogenesis ◽  
Cell Walls ◽  
Ultrastructural Changes ◽  
Outer Cell ◽  
Embryogenic Cell ◽  
Transmission Electron ◽  
Outer Cell Wall

In Cichorium hybrid clone 474 (C. intybus L. var. sativum × C. endivia L. var. latifolia), direct somatic embryogenesis was induced from roots. Using transmission electron microscopy, we followed the ultrastructural changes of the outer cell wall in relation to embryo developmental stage. During the transition from an embryogenic cell to a somatic embryo, the differentiation of the outer cell wall involved both deposition and rearrangement processes. During the first divisions, the cell wall of few-celled embryos still enclosed in the root tissue appeared as a large amorphous layer of cellulose, thicker than the cell walls of the root cortex cells. When the proembryo emerged from the root cells, the outer wall surface exhibited a fibrillar material designated as the supraembryonic network. As this network disappeared, the outer cell wall changed organization, and two domains were distinguished. At the torpedo stage, the outer cell wall was more compact without any gaps and the protoderm was differentiated. Immunolocalization of an epitope recognised by JIM5 antibody revealed the unesterified nature of the supraembryonic network. Such pectins were also located at the outer third of the outer cell wall of protodermal cells as well as in the intercellular spaces. Highly methylesterified pectins recognized by JIM7 antibodies were slightly present in the cell walls during the embryogenesis process. The different stages of the outer cell wall differentiation as well as the development of the transient supraembryonic network are described, and its possible roles in somatic embryogenesis are proposed.Key words: cell differentiation, cell wall, Cichorium (chicory), pectin, somatic embryogenesis, transmission electron microscopy.

Changes of plasmolysis form in epidermal cells of Hordeum vulgare infected by Erysiphe graminis: evidence for increased membrane–wall adhesion

1984 ◽  
Vol 62 (8) ◽  
pp. 1714-1723 ◽  
Author(s):  
O. Y. Lee-Stadelmann ◽  
W. R. Bushnell ◽  
E. J. Stadelmann
Keyword(s):  
Cell Wall ◽  
Hordeum Vulgare ◽  
Host Cell ◽  
Cell Walls ◽  
Membrane Structure ◽  
Epidermal Cells ◽  
Erysiphe Graminis ◽  
Infected Tissue ◽  
Host Cells

When coleoptile epidermal tissues of Hordeum vulgare were plasmolyzed with α-methylglucose or mannitol, 24–72 h after inoculation with Erysiphe graminis f. sp. hordei, host protoplasts tended to pull away from one or more sites on longitudinal host cell walls producing a concave pocket at each site. This contrasted with the usual convex form of plasmolysis in uninfected tissue in which protoplasts pulled from the short transversal end walls of host cells forming protoplasts with convex ends. The tendency for concave plasmolysis encompassed entire inoculated areas at 5 colonies/mm2 and above. The concave response occurred in coleoptiles inoculated 7–12 days after planting, but not in ones inoculated at 5 days. It occurred in four of five barley lines tested at 48 h postinoculation. Treatment before plasmolysis with 10 mM Ca2+ promoted the disease-induced concavities; treatment with 15 mM K+ partially inhibited them. The concave form in plasmolyzed infected tissue was changed to the convex form by addition of 250 μM octylguanidine to the plasmolyticum or by replacement of α-methylglucose with isosmolar urea or methyl urea solutions. The results suggest that Erysiphe graminis infection increased adhesion of the host plasmalemma to the cell wall, probably as a consequence of change in membrane structure and bridging by Ca2+ ions.

Studies on the haustorium of Castilleja (Scrophulariaceae). II. The endophyte

1973 ◽  
Vol 51 (5) ◽  
pp. 923-931 ◽  
Author(s):  
David R. Dobbins ◽  
Job Kuijt
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Light Microscope ◽  
Cell Walls ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cell Wall ◽  
Dark Staining ◽  
Host Tissues

The portion of the Castilleja haustorium within the host, the endophyte, was examined at the light-and electron-microscopic levels. The endophyte consists of a stalk of lipid-containing cells and digitate cells at its tip. Vessels run the length of the endophyte. There is a harmonious meshing between host cortical cells and those of the endophyte flank, suggesting that penetration is accomplished, in part, by cell dissolution. Crushing of cells also occurs during endophyte invasion as host phloem tissues are severely buckled and cell walls are greatly folded. Some features of digitate cells include dense cytoplasm, an abundance of endoplasmic reticulum, lateral walls that are thickened as well as those on the side adjacent to the host, and an ability to conform to the contours of host tissues. Often digitate cells are divided by very thin walls that are hardly visible under the light microscope. It is suggested that the thick cell walls may function as "free space" in the absorption of materials from the host. Within the endophyte, vessels differentiate and may contain either a finely granular, dark-staining material or a more coarsely granular, light-staining material. The particles of the latter have irregular shapes. Although granular materials are thus carried by some vessels, cells resembling the structurally intermediate "phloeotracheids" were not seen. Connections through the cell wall were not observed between parasite and host; however, within the endophyte plasmodesmata were highly branched and often contained median nodules. Transfer-like cells which have irregularly thickened walls occurred in the endophyte. Host tissues next to digitate cells appeared to be in a degraded state. Invaginations of the plasmalemma were common and small flattened vesicles were formed in some host cells from the disrupted tonoplast. In several instances, the cytoplasm had receded from the host cell wall and a "beaded" material was present in both vacuoles and large vesicles. The host cell wall at times had a very loose fibrillar appearance. Some host tracheids were occluded with a dense and dark-staining material. The xylem strands of the parasite are connected to the host xylem either by cell wall dissolution or by actual penetration of a digitate cell into a host xylary cell. The penetrating cell subsequently differentiates into a vessel member. A summary and general discussion are given to relate the two portions of the haustorium, the upper haustorium and the endophyte. The mass of new information gained in this study leads us to encourage the application of plastic embedding and sectioning techniques to further light-microscope studies on haustoria.

scholarly journals Spreading of a mycobacterial cell-surface lipid into host epithelial membranes promotes infectivity

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
CJ Cambier ◽  
Steven M Banik ◽  
Joseph A Buonomo ◽  
Carolyn R Bertozzi
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Immune Activation ◽  
Cholesterol Synthesis ◽  
Membrane Lipids ◽  
Preventive Therapy ◽  
Outer Cell ◽  
Surface Lipid ◽  
Epithelial Membranes ◽  
Outer Cell Wall

Several virulence lipids populate the outer cell wall of pathogenic mycobacteria. Phthiocerol dimycocerosate (PDIM), one of the most abundant outer membrane lipids, plays important roles in both defending against host antimicrobial programs and in evading these programs altogether. Immediately following infection, mycobacteria rely on PDIM to evade Myd88-dependent recruitment of microbicidal monocytes which can clear infection. To circumvent the limitations in using genetics to understand virulence lipids, we developed a chemical approach to track PDIM during Mycobacterium marinum infection of zebrafish. We found that PDIM's methyl-branched lipid tails enabled it to spread into host epithelial membranes to prevent immune activation. Additionally, PDIM’s affinity for cholesterol promoted this phenotype; treatment of zebrafish with statins, cholesterol synthesis inhibitors, decreased spreading and provided protection from infection. This work establishes that interactions between host and pathogen lipids influence mycobacterial infectivity and suggests the use of statins as tuberculosis preventive therapy by inhibiting PDIM spread.

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