Flax rust resistance involving the K gene: an ultrastructural survey

1976 ◽  
Vol 54 (13) ◽  
pp. 1443-1457 ◽  
Author(s):  
Michael D. Coffey
Keyword(s):  
Major Gene ◽  
Rust Fungus ◽  
Progressive Increase ◽  
Host Cells ◽  
Electron Microscopic ◽  
Susceptible Host ◽  
Melampsora Lini ◽  
Major Gene Resistance ◽  
Complete Layer ◽  
Extrahaustorial Matrix

An electron microscopic study of major gene resistance involving the flax K gene and the rust fungus Melampsora lini revealed several interesting ultrastructural features. Up to 9 days after infection, most haustoria-containing resistant host cells appeared viable. During this period there was a progressive increase in a fibrillar deposit in the extrahaustorial matrix which was not detected in the susceptible host. This material was in direct continuity with the distal wall of the haustorial neck. It frequently constituted an apparently complete layer or 'encapsulation' around the haustorium and was present in 75% of the extrahaustorial matrices as early as 4 days after infection. Initially, callose-like encasements formed around only a small percentage of haustoria in the resistant host; however, by day 9, about 20% of the haustoria were encased. No encasements were found around susceptible haustoria at this stage. Hypersensitive host cell collapse occurred in a small percentage of resistant infections.

Etude ultrastructurale des relations hôte–parasite au cours de l'infection des pommes par le Phytophthora cactorum

1981 ◽  
Vol 59 (2) ◽  
pp. 251-263 ◽  
Author(s):  
X. Mourichon ◽  
G. Sallé
Keyword(s):  
Cell Walls ◽  
Susceptible Variety ◽  
Host Cells ◽  
Phytophthora Cactorum ◽  
Electron Microscopic ◽  
Susceptible Host ◽  
Golden Delicious ◽  
Extrahaustorial Matrix ◽  
Apple Fruits

An electron microscopic study was performed on haustoria of Phytophthora cactorum (L. et C.) Schroeter developed in tissues of two cultivars of apple fruits: a susceptible variety ('Golden delicious') and a resistant one ('Belle de Boskoop'). Ultrastructure of intercellular hyphae and some aspects of their penetration between contiguous host cells were described. A light dissolution of the host cell walls was observed. Ontogenic investigations indicated that in the susceptible host, the wall of the fungal haustoria was covered with a dense-stained extrahaustorial matrix. Its origin and its polysaccharide nature were demonstrated. On the other hand, the resistant host developed, immediately after the inoculation, a papilla which gave rise, later on, to a sheath enclosing adult haustoria. The role of these callosic structures in the phenomenon of resistance was discussed.

A quantitative histological and ultrastructural analysis of interactions between the flax rust and near-isogenic host lines varying in their degree of incompatibility

1983 ◽  
Vol 61 (7) ◽  
pp. 1831-1850 ◽  
Author(s):  
Michael D. Coffey ◽  
Frances H. E. Allen
Keyword(s):  
Phosphotungstic Acid ◽  
Rust Fungus ◽  
Periodic Acid ◽  
Fungal Growth ◽  
Host Cells ◽  
Similar Proportion ◽  
Thin Sections ◽  
Melampsora Lini ◽  
Uninfected Host ◽  
Electron Lucent

Histological differences were evident in the leaves of eight near-isogenic lines of flax infected with the rust fungus Melampsora lini. Compared with the compatible L9 and M1 interactions, fungal growth was progressively more restricted in the moderately incompatible K and M4, incompatible M and P, and highly incompatible L and M3 interactions. This restriction took place in advance of appreciable necrosis of host cells in K, M4, M, and P. At 72 h the proportion of haustoria-containing cells which were necrotic was only 10–15% in K and M4. In M at 72 h necrosis was 80% or more at infection sites with small colonies but was negligible at sites with large colonies. In P, by contrast, a similar proportion of necrosis, 40% at 72 h, was present at all infection sites. However, in L and M3 host necrosis was much more rapid and the fungus was restricted to a few host cells. An early ultrastructural event was the appearance of extensive fibrillar deposits in the initially electron-lucent extrahaustorial matrices of both the incompatible M and P and moderately incompatible M4 and K interactions. A positive reaction with silver proteinate indicated that these matrical deposits contained carbohydrate, possibly a mucopolysaccharide or glycoprotein, but they were not extracted by either cellulase, pectinase, or chitinase. The extrahaustorial membrane, surrounding the haustoria in the compatible L9 and M1 interactions and the moderately incompatible K interaction was not stained by the periodic acid – phosphotungstic acid – chromic acid (PACP) procedure believed specific for the plasmalemma. In incompatible reactions clusters of electron-dense particles sometimes replaced starch in plastids of infected host cells. This event usually coincided with the appearance of extensive matrical deposits around fungal haustoria. At the same time particles were also found in plastids in uninfected host cells immediately adjacent to infection sites, particularly in the M and P interactions. These particles were extracted from thin sections by using pullulanase followed by α-amylase, indicating that they consisted of highly branched amylopectin.

Ultrastructure of the haustorium of the peanut late leaf spot fungus Cercosporidium personatum

1989 ◽  
Vol 67 (4) ◽  
pp. 1198-1202 ◽  
Author(s):  
C. W. Mims ◽  
E. S. Luttrell ◽  
S. C. Alderman
Keyword(s):  
Host Cell ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cercosporidium Personatum ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Biotrophic Fungi ◽  
Leaf Spot Fungus ◽  
Extrahaustorial Matrix ◽  
Cell Protoplast

Data from scanning and transmission electron microscopic observations support light microscopic reports of the production of haustoria by the hemibiotrophic fungus Cercosporidium personatum. The trunklike base of the haustorium extended a short distance into the host cell where it formed three to five slightly thinner primary branches. These branches terminated in multiple, smaller, mostly opposite branch tips that gave the end of the haustorium a coralloid appearance. The morphology of this haustorium was distinctly different from the more extensively studied haustoria of various biotrophic fungi. Haustoria of C. personatum were observed in both living and dead host cells. In living cells an extrahaustorial matrix and extrahaustorial membrane separated the haustorium wall from the host cell protoplast. In dead cells the extrahaustorial membrane was absent. Haustoria in dead cells remained intact and appeared healthy.

scholarly journals Exposure of ichnovirus particles to digitonin leads to enhanced infectivity and induces fusion from without in an in vitro model system

2007 ◽  
Vol 88 (11) ◽  
pp. 2977-2984 ◽  
Author(s):  
Don Stoltz ◽  
Renée Lapointe ◽  
Andrea Makkay ◽  
Michel Cusson
Keyword(s):  
Outer Membrane ◽  
In Vitro Model ◽  
Model System ◽  
Host Cells ◽  
Fusion Event ◽  
Susceptible Host ◽  
In Vitro Model System ◽  
Vitro Model

Unlike most viruses, the mature ichnovirus particle possesses two unit membrane envelopes. Following loss of the outer membrane in vivo, nucleocapsids are believed to gain entry into the cytosol via a membrane fusion event involving the inner membrane and the plasma membrane of susceptible host cells; accordingly, experimentally induced damage to the outer membrane might be expected to increase infectivity. Here, in an attempt to develop an in vitro model system for studying ichnovirus infection, we show that digitonin-induced disruption of the virion outer membrane not only increases infectivity, but also uncovers an activity not previously associated with any polydnavirus: fusion from without.

scholarly journals Structural genomic applied on the rust fungus Melampsora larici-populina reveals two candidate effector proteins adopting cystine-knot and nuclear transport factor 2-like protein folds

2019 ◽  
Author(s):  
Karine de Guillen ◽  
Cécile Lorrain ◽  
Pascale Tsan ◽  
Philippe Barthe ◽  
Benjamin Petre ◽  
...  
Keyword(s):  
Plant Pathogens ◽  
Nuclear Transport ◽  
Sequence Similarity ◽  
Rust Fungus ◽  
Parasitic Infection ◽  
Effector Proteins ◽  
Host Cells ◽  
Dimensional Structure ◽  
Structural Genomic ◽  
Transport Factor

ABSTRACTRust fungi are plant pathogens that secrete an arsenal of effector proteins interfering with plant functions and promoting parasitic infection. Effectors are often species-specific, evolve rapidly, and display low sequence similarities with known proteins or domains. How rust fungal effectors function in host cells remains elusive, and biochemical and structural approaches have been scarcely used to tackle this question. In this study, we used a strategy based on recombinant protein production in Escherichia coli to study eleven candidate effectors of the leaf rust fungus Melampsora larici-populina. We successfully purified and solved the three-dimensional structure of two proteins, MLP124266 and MLP124017, using NMR spectroscopy. Although both proteins show no sequence similarity with known proteins, they exhibit structural similarities to knottin and nuclear transport factor 2-like proteins, respectively. Altogether, our findings show that sequence-unrelated effectors can adopt folds similar to known proteins, and encourage the use of biochemical and structural approaches to functionally characterize rust effector candidates.

Cell interactions of Listeria monocytogenes L forms and peritoneal exudative cells in rats

1993 ◽  
Vol 39 (11) ◽  
pp. 1014-1021 ◽  
Author(s):  
L. Mihailova ◽  
N. Markova ◽  
T. Radoucheva ◽  
D. Veljanov ◽  
S. Radoevska
Keyword(s):  
Listeria Monocytogenes ◽  
Peritoneal Cavity ◽  
Electron Microscopic Examination ◽  
Lavage Fluid ◽  
Host Cells ◽  
Electron Microscopic ◽  
Cellular Defense ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Listeria monocytogenes 4b and its forms without cell walls (L forms of a protoplastic type) were used to study in vivo interactions with host cells. Samples of peritoneal lavage fluid were obtained from rats intraperitoneally inoculated at intervals between 1 and 15 days after challenge, for scanning electron microscopic, bacteriological, biochemical, and cytometrical investigations. Scanning electron microscopic examination revealed continuous adhesion of L forms on the macrophage surface up to 15 days after inoculation. The persistence of the L forms within the peritoneal cavity was also shown bacteriologically at all sample times, while the parental bacterial forms were isolated from the peritoneal cavity up to 7 days after challenge. The total count of peritoneal exudative cells determined by automated flow peroxidase cytometry peaked on the 15th day in animals infected with parental forms, while in animals infected with L forms the peak was lower and the macrophage population was predominant. The glycolytic and acid phosphatase activity of peritoneal exudative cells was two times higher in rats infected with L forms as compared with rats infected with the L. monocytogenes parental forms on the 3rd day after challenge. An understanding of the nature of the interactions between L forms of L. monocytogenes and peritoneal exudative cells found in vivo could be used to establish the influence of L forms on host cellular defense mechanisms.Key words: Listeria monocytogenes, L forms, peritoneal exudative cells, electron microscopy.

Immunogold localization of callose and other plant cell wall components in soybean roots infected with the oomycete Phytophthora sojae

1997 ◽  
Vol 75 (9) ◽  
pp. 1509-1517 ◽  
Author(s):  
K. Enkerli ◽  
C. W. Mims ◽  
M. G. Hahn
Keyword(s):  
Plasma Membrane ◽  
Plant Cell Wall ◽  
Arabinogalactan Proteins ◽  
Phytophthora Sojae ◽  
Arabinogalactan Protein ◽  
Electron Microscopic ◽  
Rhamnogalacturonan I ◽  
Host Plasma Membrane ◽  
Wall Appositions ◽  
Extrahaustorial Matrix

Immunolabeling and transmission electron microscopic techniques were used to investigate the chemical nature of wall appositions in roots of susceptible and resistant soybean plants inoculated with Phytophthora sojae race 2. The extrahaustorial matrix associated with the haustorium of Phytophthora sojae also was examined. Antibodies against (1 → 3)-β-glucan, a terminal α-fucosyl-containing epitope present in xyloglucan and rhamnogalacturonan I, and an arabinosylated (1 → 6)-β-galactan epitope present in arabinogalactan proteins were used. (1 → 3)-β-Glucan (callose), xyloglucan, and arabinogalactan proteins were found to be localized in all wall appositions regardless of how long after inoculation the appositions developed or whether plants were susceptible or resistant to Phytophthora sojae. (1 → 3)-β-Glucan also was found in fungal walls and at host cell plasmodesmata. None of the four antibodies labeled the extrahaustorial matrix. The antibody against arabinogalactan protein recognized the host plasma membrane, but not the invaginated host plasma membrane associated with the extrahaustorial matrix. This result indicates that the properties or the composition of the host plasma membrane may change locally once it becomes an extrahaustorial membrane. Key words: Phytophthora sojae, Glycine max, callose, immunolabeling, wall appositions, papillae.

Metabolism of glucose-14C, pyruvate-14C, and mannitol-14C by Melampsora lini. II. Conversion to soluble products

1968 ◽  
Vol 46 (4) ◽  
pp. 453-460 ◽  
Author(s):  
D. Mitchell ◽  
Michael Shaw
Keyword(s):  
Pentose Phosphate Pathway ◽  
Tricarboxylic Acid Cycle ◽  
Rust Fungus ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Pentose Phosphate ◽  
Soluble Carbohydrates ◽  
Melampsora Lini ◽  
Carbohydrate Fraction ◽  
The Tca Cycle

Mycelium of the flax rust fungus (Melampsora lini (Pers.) Lév.), grown on flax cotyledons in tissue culture, had a mean [Formula: see text]of 4.1 and a mean C6/C1 ratio of 0.14, measured after 4 hours in radioactive glucose. The C6/C1 ratio increased with time and also after treatment with 10−5 M 2,4-dinitrophenol. The relative labelling of the (80%) ethanol-soluble carbohydrates, and organic and amino acid fractions after incubation with glucose-1-, -2-, or -6-14C also indicated preferential release of C1 as 14CO2. Trehalose (unknown A) was tentatively identified in the carbohydrate fraction and was mildly radioactive after incubation of the mycelium with labelled glucose for 3 hours. The principal radioactive products of glucose in this fraction were two unknowns, B and C, which were tentatively identified as mannitol and arabitol. The labelling patterns were consistent with their formation from intermediates of the pentose phosphate pathway. The distribution of radioactivity derived from glucose in alanine, glutamate, and aspartate also indicated that hexose or triose units formed in the pentose phosphate pathway were converted to pyruvate, which either gave rise to alanine or was further oxidized in the tricarboxylic acid cycle. Incubation with pyruvate-1-, -2-, or -3-14C for 3 hours gave rise to 14CO2 and labelled alanine, glutamate, and aspartate in a manner consistent with the operation of the TCA cycle. Mannitol-1-6-14C was not metabolized to any appreciable extent in this period, but did give rise to 14CO2 and to several unidentified compounds in the carbohydrate fraction.

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