Host cell penetration in kinetoplastida and coccidia: a fine structural study

Zinc plays a crucial role in the process of virion maturation inside the host cell. The accessory Cys-rich proteins expressed in SARS-CoV-2 by genes ORF7a and ORF8 are likely involved in zinc binding and in interactions with cellular antigens activated by extensive disulfide bonds. In this report we provide a proof of concept for the feasibility of a structural study of orf7a and orf8 proteins. A conceivable hypothesis is that lack of cellular zinc, or substitution thereof, might lead to a significant slowing down of viral maturation.

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Infection, Colonization, and Disease of Amaranthus hybridus Leaves by the Alternaria tenuissima Group

Plant Disease ◽

10.1094/pdis.2002.86.11.1199 ◽

2002 ◽

Vol 86 (11) ◽

pp. 1199-1205 ◽

Cited By ~ 15

Author(s):

J. T. Blodgett ◽

W. J. Swart

Keyword(s):

Host Cell ◽

Cell Penetration ◽

Amaranthus Hybridus ◽

Wound Site ◽

Alternaria Tenuissima ◽

Host Cell Response ◽

Leaf Surfaces ◽

Chamber Studies ◽

Growth Chamber Studies

With the increased use of Amaranthus hybridus as a leafy-vegetable crop in Africa and the recent identification of Alternaria leaf spot on this host in southern Africa, the role of this potentially damaging pathogen was investigated. The goals of this study were to test the pathogenicity of the Alternaria tenuissima group, determine how these fungi infect Amaranthus hybridus leaves, and examine the colonization pattern within host tissues. Asymptomatic leaves of Amaranthus hybridus were collected from two field sites in South Africa. Eight A. tenuissima group isolates collected from these leaves were used in inoculation experiments conducted in both greenhouse and growth chamber studies. Scanning electron microscopy revealed A. tenuissima-like conidia germinating on leaf surfaces and mycelia entering leaves only through stomata of both field-collected and artificially inoculated leaves. Unwounded, inoculated leaves had no symptoms, and light-microscopy observations of both asymptomatic field-collected and unwounded and inoculated leaves revealed hyphae in mesophyll tissue growing intercellularly with no host cell penetration or host-cell response. Seven of the eight isolates produced brown to black, circular to oval, necrotic lesions only at the wound site of injured and inoculated leaves. These results confirm that isolates of the A. tenuissima group can infect and colonize Amaranthus hybridus leaves in a manner consistent with other endophytic fungi, and suggest that these fungi can act as latent leaf pathogens when the host is altered by wounding.

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A Soluble Phospholipase ofToxoplasma gondiiAssociated with Host Cell Penetration

The Journal of Protozoology ◽

10.1111/j.1550-7408.1991.tb04816.x ◽

1991 ◽

Vol 38 (5) ◽

pp. 454-460 ◽

Cited By ~ 62

Author(s):

LINDA D. SAFFER ◽

JOSEPH D. SCHWARTZMAN

Keyword(s):

Host Cell ◽

Cell Penetration

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Cytochemical studies on Puccinia graminis f. sp. tritici in a compatible wheat host. II. Haustorium mother cell walls at the host cell penetration site, haustorial walls, and the extrahaustorial matrix

Canadian Journal of Botany ◽

10.1139/b86-339 ◽

1986 ◽

Vol 64 (11) ◽

pp. 2561-2575 ◽

Cited By ~ 36

Author(s):

J. Chong ◽

D. E. Harder ◽

R. Rohringer

Keyword(s):

Host Cell ◽

Mother Cell ◽

Cell Walls ◽

Distal Part ◽

Rust Fungus ◽

Neck Region ◽

Cell Penetration ◽

Wheat Stem Rust ◽

Reactive Material ◽

Extrahaustorial Matrix

Various cytochemical tests on the wheat stem rust fungus were used to determine differences in components of the walls of the haustorium mother cell at the host cell penetration site and the haustorial neck and body and to describe some of the chemical properties of the extrahaustorial matrix. There were two transition zones with respect to wall composition. The first was at the host cell penetration site; chitin, present in haustorium mother cell walls, was not detected in haustorial neck walls. The second transition zone was at the neck ring; compared with walls of the proximal neck region, those distal to the neck ring contained more protein and lost much of their periodate – thiocarbohydrazide – silver proteinate reactive material and all concanavalin A binding material after treatment with protease. The two wall layers of the distal part of the haustorial neck were continuous with those of the haustorium; the wall layers of young haustorial bodies shared their staining properties and lectin affinities with those of the distal part of the haustorial necks, reflecting their common origin. As the haustoria matured, their body walls bound wheat germ lectin, but the neck walls did not. Tests indicated that polysaccharide and glycoprotein were present in the extrahaustorial matrix.

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