Haustorial development of Peronospora tabacina infecting Nicotiana tabacum

1983 ◽  
Vol 61 (12) ◽  
pp. 3444-3453 ◽  
Author(s):  
R. N. Trigiano ◽  
C. G. Van Dyke ◽  
H. W. Spurr Jr.
Keyword(s):  
Cell Wall ◽  
Toluidine Blue ◽  
Mesophyll Cell ◽  
Wall Layer ◽  
Peronospora Tabacina ◽  
Host Cytoplasm ◽  
Transmission Electron ◽  
Mold Fungus ◽  
Host Cell Wall ◽  
Hyphal Wall

The development of haustoria in tobacco by the blue-mold fungus Peronospora tabacina was examined using light, scanning, and transmission electron microscopy. Electron-lucent, callose-like appositions were observed between the host plasmalemma and the host mesophyll cell wall prior to haustorial penetration. An electron-opaque penetration matrix was present between the apposition and the host cell wall. The intercellular hyphal wall consisted of two layers which differed in staining quality. The haustorial wall was also two layered, but was primarily composed of and continuous with the inner wall layer of the intercellular hypha. Haustoria were either finger-like or branched and were encased with callose-like material. Most encasements were thickened at the proximal regions of haustoria but were thinner along the distal portions. Vesicles were present in host cytoplasm and were occasionally attached to the invaginated host plasmalemma. These vesicles might contribute to the deposition of the encasement material. The encasement stained positively for callose using aniline blue; calcofluor and toluidine blue O tests for cellulose were inconclusive, and lignin was not detected using toluidine blue O or phloroglucinol–HCl.

Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. III. Host cell and tissue reactions

2006 ◽  
Vol 87 (1) ◽  
pp. 17-27 ◽  
Author(s):  
Guillemond B. Ouellette ◽  
Mohamed Cherif ◽  
Marie Simard
Keyword(s):  
Cell Wall ◽  
Fusarium Oxysporum ◽  
Host Cell ◽  
Cross Wall ◽  
Tissue Proliferation ◽  
Host Cytoplasm ◽  
Transmission Electron ◽  
Host Cell Wall ◽  
Tissue Reactions ◽  
Rhus Typhina

Abstract Various cell reactions occurred in staghorn sumac plants inoculated with Fusarium oxysporum f. sp. callistephi. Light and transmission electron microscopy observations and results of cytochemical tests showed: 1) increased laticifers and latex production in the phloem; 2) tylosis formation; 3) host cell wall modifications, including appositions or other cell wall thickenings; and 4) unusual cross wall formation in some cells, and cell hypertrophy and hyperplasia. Tylosis walls labelled for pectin and cellulose and many displayed inner suberin-like layers. These layers were also noted in cells of the medullary sheath and in many cells with dense content and thickened walls in the barrier zones that had formed. These zones also contained fibres with newly-formed gelatinous-like layers. In the vicinity of these cells, host cell walls were frequently altered, associated with opaque matter. Many small particles present in chains also occurred in some of these cells, which contained only remnants of host cytoplasm. Light microscopy observations showed that pronounced tissue proliferation and aberrant cells occurred in the outer xylem in the infected plants. Unusual neoplasmic tissue also formed from cells surrounding the pith and medullary sheath, and it spanned directly across the pre-existing xylem tissue and burst as large mounds on the stems.

The fine structure and development of chlamydospores of Fusarium oxysporum

1972 ◽  
Vol 18 (7) ◽  
pp. 997-1002 ◽  
Author(s):  
I. L. Stevenson ◽  
S. A. W. E. Becker
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Fine Structure ◽  
Electron Microscope ◽  
Cell Surface ◽  
Outer Layer ◽  
Outer Wall ◽  
Wall Layer ◽  
Thin Sections ◽  
Hyphal Wall

Methods have been developed for the rapid, reproducible induction of high-density populations of F. oxysporum chlamydospores. On transferring washed pregerminated conidia to a simple two-salts medium, chlamydospore morphogenesis was evident by 12 h and masses of mature spores could be harvested at the end of 4 days. Electron-microscope studies of thin sections of mature chlamydospores reveal a thick triple-layered cell wall. The cytoplasm contains, in addition to large lipid deposits, a nucleus, mitochondria, and endoplasmic reticulum all typical of fungal cells. Chlamydospores of F. oxysporum exhibit two distinct types of cell surface in thin section. The outer wall layer of two of the isolates studied was smooth-surfaced while the outer layer of the two other isolates was distinctly fibrillose. Some evidence is presented suggesting that the fibrillose material arises through the partial breakdown of the original hyphal wall.

Ultrastructure of the host–pathogen interface in Arabidopsis thaliana leaves infected by the downy mildew Hyaloperonospora parasitica

2004 ◽  
Vol 82 (7) ◽  
pp. 1001-1008 ◽  
Author(s):  
C W Mims ◽  
E A Richardson ◽  
B F Holt III ◽  
J L Dangl
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Arabidopsis Thaliana ◽  
High Pressure ◽  
Cell Wall ◽  
Host Cell ◽  
Hyaloperonospora Parasitica ◽  
Transmission Electron ◽  
Host Pathogen ◽  
Host Cell Wall

Transmission electron microscopy was used to examine the host–pathogen interface in Arabidopsis thaliana (L.) Heynh. leaves infected by the biotrophic downy mildew pathogen Hyaloperonospora parasitica (Pers.:Fr.) Constant. Both conventionally fixed as well as high-pressure frozen samples were examined. Excellent preservation of the host–pathogen interface was obtained in many of our high-pressure frozen samples and provided information not available in conventionally fixed samples. Mature haustoria of H. parasitica were distinctly pyriform in shape. A small collar of host cell wall material surrounded the neck of each haustorium near the host cell wall penetration site. The presence of callose in collars was demonstrated using immunogold labeling with a monoclonal antibody specific for (1→3)-β-glucans. The body of each haustorium was ensheathed by an invaginated portion of the invaded host-cell plasma membrane known as the extrahaustorial membrane. Lying between this membrane and the haustorial wall was a layer of electron-dense material known as the extrahaustorial matrix (EHM). The EHM typically was thicker at the distal end of a haustorium than at the proximal end. The surface of the EHM covered by the extrahaustorial membrane was highly irregular in outline. Considerable vesicular activity was observed in association with the extrahaustorial membrane.Key words: transmission electron microscopy, high-pressure freezing, haustoria, Peronospora parasitica.

The ultrastructure of Olpidium brassicae. III. Infection of host roots

1969 ◽  
Vol 47 (3) ◽  
pp. 421-424 ◽  
Author(s):  
J. H. M. Temmink ◽  
R. N. Campbell
Keyword(s):  
Cell Wall ◽  
Host Cell ◽  
Cyst Wall ◽  
Virus Transmission ◽  
Central Channel ◽  
Root Cells ◽  
Host Cytoplasm ◽  
Host Root ◽  
Host Cell Wall ◽  
Olpidium Brassicae

As zoospores of Olpidium brassicae (Wor.) Dang. encyst on host root cells, they retract their axoneme, secrete a cyst wall, and form an adhesive substance that keeps them in place. The axonemal fibrils have been observed within young cysts but disappear later. The host cell forms a papillum that seems to be an inward extension of the host cell wall. In the cyst, a vacuole develops and enlarges while the cyst protoplast moves through the host wall via a central channel in the papillum, penetrates the host ectoplast, and establishes itself within the host cytoplasm. The ectoplast present around the cyst protoplast remains in the cyst, along with parts of the tonoplast, after infection is complete. This information permits evaluation of hypotheses concerning virus transmission by zoospores.

scholarly journals THE STRUCTURAL ORGANISATION OF THE S1 CELL WALL LAYER OF NORWAY SPRUCE TRACHEIDS

IAWA Journal ◽  
2003 ◽  
Vol 24 (1) ◽  
pp. 27-40 ◽  
Author(s):  
Jonas Brändström ◽  
Stig L. Bardage ◽  
Geoffrey Daniel ◽  
Thomas Nilsson
Keyword(s):  
Cell Wall ◽  
Norway Spruce ◽  
Outer Part ◽  
Soft Rot ◽  
Wall Layer ◽  
Fibrillar Structure ◽  
Gradual Change ◽  
Cell Wall Layer ◽  
Microfibril Orientation ◽  
Transmission Electron

The purpose of the present study was to investigate the ultrastructure of the outer layer of the secondary cell wall (S1) of Norway spruce (Picea abies (L.) Karst.) tracheids with emphasis on microfibril orientation. Several methods were used to obtain complementary results. Macerated tracheids and wood blocks were exposed to degradation by soft rot fungi, different chemicals and mechanical forces. Observations were made using scanning and transmission electron microscopy and light microscopy. It was concluded that the S1 layer is rather homogeneous with respect to microfibril orientation. The major part of the S1 is composed of microfibrils oriented approximately perpendicular to the tracheid axis. Evidence for a crossed fibrillar structure with microfibrils in alternate S- and Z-helices was not obtained. The transition of microfibril orientation from the S1 to the S2 layer appeared abrupt. The transitional/intermediate lamella, where a gradual change in microfibril orientation occurs, should be considered to belong to the outer part of S2.

scholarly journals Ultrastructural Studies of the Mode of Penetration by Phoma macdonaldii in Sunflower Seedlings

2000 ◽  
Vol 90 (8) ◽  
pp. 915-920 ◽  
Author(s):  
A. Roustaee ◽  
G. Dechamp-Guillaume ◽  
B. Gelie ◽  
C. Savy ◽  
R. Dargent ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Integrity ◽  
Time Intervals ◽  
Ultrastructural Studies ◽  
Host Cytoplasm ◽  
Transmission Electron ◽  
Parasite Relationship ◽  
Host Parasite ◽  
Phoma Macdonaldii ◽  
Host Tissues

An ultrastructural investigation of the artificial inoculation of sunflower with Phoma macdonaldii conidia was undertaken using light, scanning, and transmission electron microscopy to elucidate the host-parasite relationship. The behavior of the conidia deposited on the cotyledon petiole was investigated at various time intervals after inoculation. Conidia adhesion and germination were observed first. The cotyledon petiole was invaded by the fungus directly through the cuticle and via stomata. Externally, the spore and germ tube were covered with a mucilaginous polysaccharide sheath of a cotton-like appearance and of variable thickness. At the time of penetration, the host cuticle was perforated mechanically. The cuticle was slightly depressed and no enzymatic alteration could be observed. The fungus did not form appressoria on the surface of the host tissues but developed an infection peg. As soon as the cuticle barrier was crossed, the fungus rapidly colonized the host parietal layer. In a first step, the plasmalemma of the host cell appeared to be stuck against the cell wall. As soon as the fungus passed through the epidermal cell wall to reach the host cytoplasm, the plasmalemma was disrupted, and the subsequent rapid breakdown of cell integrity favored the colonization of the tissues by the pathogen.

Host–parasite relations in mycoparasite. I. Fine structure of host, parasite, and their interface

1971 ◽  
Vol 49 (9) ◽  
pp. 1677-1681 ◽  
Author(s):  
M. S. Manocha ◽  
K. Y. Lee
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Host Cell ◽  
Higher Plants ◽  
Host Cytoplasm ◽  
Host Cell Wall ◽  
Choanephora Cucurbitarum ◽  
A Cell ◽  
Host Parasite

A mycoparasite, Piptocephalis virginiana, shows resemblance to other fungal parasites of higher plants in the fine structure of hyphae and haustoria. The mode of penetration of the host cell, Choanephora cucurbitarum, probably involves mechanical forces. Although the presence of a cell wall degrading enzyme was not detected by conventional techniques, its role in penetration can not be ruled out. A collar around the haustorial neck is formed as an extension of the host cell wall. No papilla was detected although appressorium was seen during penetration. The young haustorium is enclosed in highly invaginating plasmalemma of the host cell and numerous cisternae of endoplasmic reticulum (ER). Appearance of an electron-dense sheath around the mature haustorium seems to coincide with the disappearance of cisternae of ER from the host cytoplasm in the vicinity of the haustorium. The role of host cytoplasm, particularly of ER, in the development of the sheath is discussed. Extensive accumulation of spherosome-like bodies, containing lipids, is found in haustorium, parasite, and host hypha.

A fine-structural study of the pea downy mildew fungus Peronospora pisi in its host Pisum sativum

1977 ◽  
Vol 55 (23) ◽  
pp. 2845-2858 ◽  
Author(s):  
Edward L. Hickey ◽  
Michael D. Coffey
Keyword(s):  
Cell Wall ◽  
Pisum Sativum ◽  
Host Cell ◽  
Downy Mildew ◽  
Specific Interaction ◽  
Young Shoot ◽  
Host Cytoplasm ◽  
Shoot Tissue ◽  
Host Cell Wall ◽  
Membrane Bound

Downy mildew disease of the cultivated pea Pisum sativum L. caused by the fungus Peronospora pisi Sydow was studied in mature leaves and young shoots of the host plant. Particularly in systemic infections of young shoot tissue, a common occurrence was an extremely electron-opaque membrane-bound, hemispherical deposit extending through the host cell wall into the host cytoplasm. This material which abutted directly onto the intercellular hyphal wall was termed the penetration matrix. Its formation was apparently the result of a specific interaction between the host and obligate fungal parasite. Similar apparently solid or gellike material constituted the matrix surrounding the digitlike intracellular haustorium. This membrane-bound extrahaustorial matrix was present through the penetrated host cell wall and formed a relatively thick layer around haustoria in young shoot tissue, but was much thinner distally around haustoria in mature leaf mesophyll cells. An unusual, regularly arranged, tubular network of ribosome-free endoplasmic reticulum was occasionally found in the host cytoplasm in systemically infected shoot tissue adjacent to haustoria.

Host cell responses in susceptible hard pine tissue infected with Endocronartium harknessii

1988 ◽  
Vol 66 (12) ◽  
pp. 2511-2517 ◽  
Author(s):  
A. A. Hopkin ◽  
J. Reid
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Host Cell ◽  
Pinus Banksiana ◽  
Outer Cortex ◽  
Transmission Electron ◽  
Endocronartium Harknessii ◽  
Host Cell Wall ◽  
Infected Cells ◽  
Hypocotyl Tissue

Compatible interactions between susceptible hypocotyl tissue of Pinus banksiana Lamb, and Endocronartium harknessii (J. P. Moore) Y. Hirat. were studied using light and transmission electron microscopy. Host endoplasmic reticulum was observed to be closely associated with the haustorial body, although staining with silver proteinate failed to show any similarity between the contents of the endoplasmic reticulum and extrahaustorial matrix. The haustorium was also commonly observed to be closely associated with the host nucleus, often indenting the latter, though never in direct contact. Chloroplasts in recently infected cells appeared similar to those in uninfected cells, but in more advanced infections large starch grains were observed in the chloroplasts of the outer cortex; such chloroplasts normally contained little starch. Collars were another common feature of infected cells. Collars were continuous with the host cell wall and reacted to silver proteinate in a similar manner to the cell wall; callose was not evident. Collars were associated with portions of the cell wall that were inwardly displaced by the fungus; however, cytoplasmic vesicles were also observed in association with the collar and possibly contributed to their development.

Influence of Cell Wall Composition on the Fossilisation of Bacteria and the Implications for the Search for Early Life Forms

1997 ◽  
Vol 161 ◽  
pp. 491-504 ◽  
Author(s):  
Frances Westall
Keyword(s):  
Cell Wall ◽  
Life Forms ◽  
Cation Binding ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Transmission Electron ◽  
Hydrothermal Sediments ◽  
Identification Of Bacteria ◽  
The Difference

AbstractThe oldest cell-like structures on Earth are preserved in silicified lagoonal, shallow sea or hydrothermal sediments, such as some Archean formations in Western Australia and South Africa. Previous studies concentrated on the search for organic fossils in Archean rocks. Observations of silicified bacteria (as silica minerals) are scarce for both the Precambrian and the Phanerozoic, but reports of mineral bacteria finds, in general, are increasing. The problems associated with the identification of authentic fossil bacteria and, if possible, closer identification of bacteria type can, in part, be overcome by experimental fossilisation studies. These have shown that not all bacteria fossilise in the same way and, indeed, some seem to be very resistent to fossilisation. This paper deals with a transmission electron microscope investigation of the silicification of four species of bacteria commonly found in the environment. The Gram positiveBacillus laterosporusand its spore produced a robust, durable crust upon silicification, whereas the Gram negativePseudomonas fluorescens, Ps. vesicularis, andPs. acidovoranspresented delicately preserved walls. The greater amount of peptidoglycan, containing abundant metal cation binding sites, in the cell wall of the Gram positive bacterium, probably accounts for the difference in the mode of fossilisation. The Gram positive bacteria are, therefore, probably most likely to be preserved in the terrestrial and extraterrestrial rock record.

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