THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: XV. FINE STRUCTURE IN RUST-INFECTED WHEAT LEAVES

1965 ◽  
Vol 43 (10) ◽  
pp. 1285-1292 ◽  
Author(s):  
Michael Shaw ◽  
M. S. Manocha
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Susceptible Variety ◽  
Host Cells ◽  
Resistant Variety ◽  
Subcellular Organelles ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Wheat Leaves ◽  
Host Parasite

Electron microscopy showed that the haustoria of P. graminis tritici on wheat were characterized by numerous mitochondria, an extensive endoplasmic reticulum, densely packed ribosomes, and a well-defined plasma membrane (plasmalemma), which was often invaginated by lomasomes. No evidence was obtained for cytoplasmic connections between the parasite and its host. Many of the haustoria formed on a resistant variety, Khapli, were necrotic but others were closely similar to those formed on a susceptible variety, Little Club. The haustorial necks were surrounded by a collar-like sheath formed by an extension of the host cell wall. The haustoria merely invaginated host protoplasts from which they were separated by granular encapsulations. The latter were apparently secreted mainly by the host and developed faster in Khapli than in Little Club. The presence of haustoria also induced the formation of an extensive, smooth-surfaced endoplasmic reticulum in the host, a contraction and fragmentation of the vacuole, an increase in the volume of the cytoplasm, and, ultimately, the complete degeneration of the host cells. The processes of breakdown of the subcellular organelles in the host were very similar to those which have been observed in uninfected cells in detached leaves senescing on water.

FINE STRUCTURE IN DETACHED, SENESCING WHEAT LEAVES

1965 ◽  
Vol 43 (6) ◽  
pp. 747-755 ◽  
Author(s):  
Michael Shaw ◽  
M. S. Manocha
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Osmium Tetroxide ◽  
Mesophyll Cells ◽  
Laboratory Bench ◽  
Detached Leaves ◽  
Petri Dishes ◽  
Wheat Leaves ◽  
Cytoplasmic Ribosomes

Detached leaves of Little Club wheat were allowed to senesce on water or on kinetin (10 mg/l.) in petri dishes on the laboratory bench. Samples taken at intervals of 24 to 48 hours for 8 to 10 days were fixed in permanganate or osmium tetroxide, embedded, usually in araldite or epon, and examined by electron microscopy. Abnormalities were noted in the endoplasmic reticulum (ER) of the mesophyll cells 2 days after the leaves were detached; ER and cytoplasmic ribosomes were not present after 4 or 5 days. Swelling of the mitochondria and degeneration of the cristae, collapse of the chloroplast grana, and abnormalities in nuclear structure were noted after 3 days. Vacuolar contraction occurred in some cells after 4 days but the plasma membrane usually remained unbroken until the seventh or eighth day, by which time the mitochondria were no longer recognizable and most of the chloroplasts and nuclei had also disintegrated.Kinetin induced an increase in the amount of ER and ribosomes and markedly delayed the degeneration of cellular fine structure.

Host – parasite relationships between the fungus Leptosphaerulina crassiasca and peanut

1992 ◽  
Vol 70 (9) ◽  
pp. 1724-1733 ◽  
Author(s):  
Mei-Lee Wu ◽  
Richard T. Hanlin
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Germ Tube ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Detached Leaves ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Germ Tubes ◽  
Infection Hypha

The mode of penetration and infection of the peanut leaf by Leptosphaerulina crassiasca were studied by means of light and electron microscopy. The attachment of the multicellular ascospores to the leaf surface was by a mucilagenous sheath that covered the ascospores at maturity. This sheath expanded rapidly in moisture and it extended along the germ tube as it elongated. Two types of germ tubes appeared to be formed, a short one and a relatively long one. Short germ tubes were not delimited by septa, and they penetrated the cuticle and host epidermal cell wall directly without appressorium formation. Penetration occurred 2–6 h after inoculation. The wall was breached by a relatively broad infection hypha that expanded in width inside the host cell wall. The lack of mechanical rupture at the infection site indicated that penetration may involve enzymatic activity. Intracellular hyphae were present in the epidermal cells, but only intercellular hyphae occurred in the palisade and spongy mesophyll tissues. The intercellular hyphae were frequently appressed to the outer surface of the host cell wall. Infected areas rarely exceeded 1 mm in diameter, and they were only sparsely colonized by hyphae of the pathogen. Host cells in the vicinity of hyphae underwent senescence and death. One to 2 months after inoculation, pseudothecia formed in the dead tissues of detached leaves. In some instances the presence of penetration hyphae by short germ tubes induced the formation of a papilla inside the host cell wall, which either restricted growth of the infection hypha or resulted in the death of the germ tube and the cell from which it arose. Long germ tubes were delimited by simple septa and they terminated in an appressorium; however, details of their behavior were not studied. Key words: Arachis hypogaea, Ascomycotina, Dothideales, leaf scorch, pepper spot.

Studies of the Penetration of Bdellovibrio into Host Cells

1971 ◽  
Vol 29 ◽  
pp. 336-337
Author(s):  
Dinah Abram ◽  
David Chou
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Cell Wall ◽  
Pseudomonas Fluorescens ◽  
Host Cell ◽  
Host Cells ◽  
Sequence Of Events ◽  
Host Cell Wall ◽  
Host Parasite ◽  
Infectious Cycle

The sequence of events in the infectious cycle of the endoparasite Bdello-vibrio bacteriovorus, from its attachment to the host surface to the release of progeny from lysed host are well established. However, the mechanisms involved in the parasite entry through a pore in the host cell wall into its periplasm have been topics for speculations but are not fully understood.Escherichia coli, Pseudomonas fluorescens and Spirillum serpens were infected by several Bdellovibrio strains (109, D and 6-5-S) in mixtures containing 109 to 1010 host cells/ml and host-parasite in ratios of 1:2 to 1:3, and were incubated at 30 C with shaking for 4 hr. At intervals specimens were prepared for electron microscopy and wet mounts were examined by phase optics.

THE PHYSIOLOGY OF HOST–PARASITE RELATIONS: XVIII. DISTRIBUTION OF TRITIUM-LABELLED CYTIDINE, URIDINE, AND LEUCINE IN WHEAT LEAVES INFECTED WITH THE STEM RUST FUNGUS

1967 ◽  
Vol 45 (5) ◽  
pp. 555-563 ◽  
Author(s):  
P. K. Bhattacharya ◽  
Michael Shaw
Keyword(s):  
Stem Rust ◽  
Rust Fungus ◽  
Host Cells ◽  
Fungal Mycelium ◽  
Puccinia Graminis ◽  
Mesophyll Cells ◽  
Wheat Leaves ◽  
Host Parasite

Wheat leaves were detached 6 days after inoculation with the stem rust fungus (Puccinia graminis var. tritici Erikss. and Henn.) and fed with tritiated leucine, cytidine, uridine, or thymidine. Mesophyll cells in infected zones incorporated more leucine into protein and more cytidine and uridine into RNA than did cells in adjacent uninfected tissue. Leucine, cytidine, and uridine were also heavily incorporated by fungal mycelium and developing uredospores. Grain counts over host nuclei in the infected zone were two to three-fold of those over nuclei in adjacent uninfected zones. There was no detectable incorporation of thymidinemethyl-3H into either the fungus or the host cells. The results are discussed.

scholarly journals Reovirus Forms Neo-Organelles for Progeny Particle Assembly within Reorganized Cell Membranes

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Isabel Fernández de Castro ◽  
Paula F. Zamora ◽  
Laura Ooms ◽  
José Jesús Fernández ◽  
Caroline M.-H. Lai ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Viral Replication ◽  
Cell Membranes ◽  
Light And Electron Microscopy ◽  
Host Cells ◽  
Pharmacological Intervention ◽  
Genome Replication ◽  
Particle Assembly ◽  
Intermediate Compartment

ABSTRACTMost viruses that replicate in the cytoplasm of host cells form neo-organelles that serve as sites of viral genome replication and particle assembly. These highly specialized structures concentrate viral replication proteins and nucleic acids, prevent the activation of cell-intrinsic defenses, and coordinate the release of progeny particles. Despite the importance of inclusion complexes in viral replication, there are key gaps in the knowledge of how these organelles form and mediate their functions. Reoviruses are nonenveloped, double-stranded RNA (dsRNA) viruses that serve as tractable experimental models for studies of dsRNA virus replication and pathogenesis. Following reovirus entry into cells, replication occurs in large cytoplasmic structures termed inclusions that fill with progeny virions. Reovirus inclusions are nucleated by viral nonstructural proteins, which in turn recruit viral structural proteins for genome replication and particle assembly. Components of reovirus inclusions are poorly understood, but these structures are generally thought to be devoid of membranes. We used transmission electron microscopy and three-dimensional image reconstructions to visualize reovirus inclusions in infected cells. These studies revealed that reovirus inclusions form within a membranous network. Viral inclusions contain filled and empty viral particles and microtubules and appose mitochondria and rough endoplasmic reticulum (RER). Immunofluorescence confocal microscopy analysis demonstrated that markers of the ER and ER-Golgi intermediate compartment (ERGIC) codistribute with inclusions during infection, as does dsRNA. dsRNA colocalizes with the viral protein σNS and an ERGIC marker inside inclusions. These findings suggest that cell membranes within reovirus inclusions form a scaffold to coordinate viral replication and assembly.IMPORTANCEViruses alter the architecture of host cells to form an intracellular environment conducive to viral replication. This step in viral infection requires the concerted action of viral and host components and is potentially vulnerable to pharmacological intervention. Reoviruses form large cytoplasmic replication sites called inclusions, which have been described as membrane-free structures. Despite the importance of inclusions in the reovirus replication cycle, little is known about their formation and composition. We used light and electron microscopy to demonstrate that reovirus inclusions are membrane-containing structures and that the endoplasmic reticulum (ER) and the ER-Golgi intermediate compartment interact closely with these viral organelles. These findings enhance our understanding of the cellular machinery usurped by viruses to form inclusion organelles and complete an infectious cycle. This information, in turn, may foster the development of antiviral drugs that impede this essential viral replication step.

An ultrastructural study of the marine diatom Licmophora hyalina and its parasite Ectrogella perforons. I. Infection of host cells

1980 ◽  
Vol 58 (11) ◽  
pp. 1280-1290 ◽  
Author(s):  
Chandralata Raghu Kumar
Keyword(s):  
Plasma Membrane ◽  
Germ Tube ◽  
Host Cells ◽  
Marine Diatom ◽  
Electron Microscopic ◽  
Fungal Parasite ◽  
Successful Infection ◽  
Host Cell Wall ◽  
Host Plasma Membrane ◽  
Host Parasite

An electron microscopic study has been made on the infection and penetration of the marine diatom Licmophora hyalina Agardh by Ectrogella perforons Petersen, an obligate fungal parasite of diatoms. The zoospores encyst on the host cell wall. The nucleus of the cyst may be situated proximal or distal to the host wall. A germ tube is produced from the side where the nucleus is situated. The germ tube may be branched or unbranched. The penetrating germ tube swells distally, develops an appressorium at the site of penetration of the host wall, and pierces the host wall in the form of an infection peg. The infection peg is smaller in diameter than the germ tube and the appressorium. Successful infection takes place always at the areolae of the diatom wall. The infection peg may directly inject its contents by piercing the subfrustular layer of the diatom wall or may grow for some distance beneath the subfrustular layer. At the site of entry the host plasma membrane invaginates and surrounds the fungal protoplast. Initially, the host–parasite interface consists of a two-layered envelope of which the outer one is the host plasma membrane and the inner one the fungal plasma membrane.

INCORPORATION OF CYTIDINE-H3 INTO THE PRIMARY LEAF OF WHEAT FOLLOWING INFECTION WITH PUCCINIA RECONDITA ROB. EX DESM.

1963 ◽  
Vol 41 (10) ◽  
pp. 1501-1508 ◽  
Author(s):  
J. Nielsen ◽  
R. Rohringer
Keyword(s):  
Host Cell ◽  
Ribonucleic Acid ◽  
Host Tissue ◽  
Host Cells ◽  
Puccinia Recondita ◽  
Infected Leaf ◽  
Cell Nuclei ◽  
Short Term ◽  
Wheat Leaves ◽  
Host Parasite

In short-term experiments, cytidine-H3 was fed to rusted and healthy areas of wheat leaves. The incorporated activity, presumably residing in ribonucleic acid, was detected by microautoradiographic methods. Most of the label was found to be incorporated in host cell nuclei. Little incorporation occurred in extranuclear structures of host cells, including chloroplasts. Very long autoradiographic exposure times failed to reveal any incorporation into the fungus.Host cells in infected leaf areas contained considerably less label in their nuclei and cytoplasm than those in cells further from the site of infection. This effect of the fungus extended over some distance into uninvaded host tissue, but not beyond 100 μ from the periphery of the mycelium. The decreased cytidine incorporation in the affected host tissue is not caused by possible changes in pool size of endogenous cytidine. The significance of these results for the host–parasite interaction is briefly discussed.

Ultrastructure of the Host-Parasite Relationships of Pseudoperonospora humuli on Hops

1977 ◽  
Vol 25 (6) ◽  
pp. 585 ◽  
Author(s):  
RD Pares ◽  
AD Greenwood
Keyword(s):  
Leaf Tissue ◽  
Host Cells ◽  
Wall Structure ◽  
Infected Leaf ◽  
Cell Penetration ◽  
Pseudoperonospora Humuli ◽  
Host Cell Wall ◽  
Staining Techniques ◽  
Host Parasite ◽  
Infected Leaf Tissue

Infected leaf tissue was examined at 3, 4, 5 and 6 days after inoculation, after different fixing and staining techniques. One example of stomata1 penetration was seen. Examples of cell penetration and haustorium development were examined in detail. Haustoria penetrate host cells by altering host cell wall structure, and lomasomes are frequently present in the haustorium neck. Haustoria do not have nuclei and in early stages have abundant mitochondria that gradually decrease in number as infection advances.

The effect of rust infection on DNA, RNA, and protein in nuclei of Khapli wheat leaves

1968 ◽  
Vol 46 (1) ◽  
pp. 96-99 ◽  
Author(s):  
P. K. Bhattacharya ◽  
Michael Shaw
Keyword(s):  
Total Protein ◽  
Nuclear Dna ◽  
Rust Fungus ◽  
Susceptible Variety ◽  
Resistant Variety ◽  
Total Protein Content ◽  
Fast Green ◽  
Mesophyll Cells ◽  
Wheat Leaves

The effects were determined of infection with Race 15B of the stem rust fungus on the levels of nuclear DNA (Feulgen), RNA (azure B), histone (fast green pH 8.1), and total protein (fast green pH 2.0) and on the size of the nuclei in the mesophyll cells of the primary leaf of Khapli wheat (rust reaction type 1). Nuclear size, RNA, and total protein content increased and histone content decreased by 3 days after inoculation. DNA content decreased from 4 days after inoculation. These results for the resistant variety Khapli are similar to those reported earlier for the susceptible variety, Little Club, but the observed changes occur more rapidly after inoculation than they do in Little Club.

The Alternaria brassicae – Nectria inventa host–parasite interface

1977 ◽  
Vol 55 (4) ◽  
pp. 448-454 ◽  
Author(s):  
A. Tsuneda ◽  
W. P. Skoropad
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Host Cells ◽  
Alternaria Brassicae ◽  
Adhesive Material ◽  
Large Hole ◽  
Mature Conidium ◽  
Host Cell Wall ◽  
Host Parasite

The Verticillium state of Nectria inventa is a destructive parasite of Alternaria brassicae. Tropic growth of parasite hyphae towards hyphae and conidia of A. brassicae occurs in the vicinity of the host. Upon contact, the parasite hyphae often form appressorium-like bodies on the host cells and produce fibrous adhesive material at the host–parasite interface. Conidia are penetrated more commonly than hyphae. Penetration of the septa in hyphae results in a separation of cells. Penetration of a mature conidium also occurs commonly at a septum. The presence of a large hole in the wall of the host cell and the meshwork of material at the penetration site suggest that enzymatic breakdown of host cell wall occurs. Juvenile conidia are penetrated usually at the basal pore.

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