Characteristics of a disease of Sphagnum fuscum caused by Scleroconidioma sphagnicola

2001 ◽  
Vol 79 (10) ◽  
pp. 1217-1224 ◽  
Author(s):  
A Tsuneda ◽  
M H Chen ◽  
R S Currah
Keyword(s):  
Cell Wall ◽  
Fungal Pathogen ◽  
Infected Leaf ◽  
Disease Development ◽  
Cortical Cells ◽  
Necrotrophic Pathogen ◽  
Sphagnum Fuscum ◽  
Entire Plant ◽  
Host Cell Wall ◽  
Advanced Stages

Scleroconidioma sphagnicola Tsuneda, Currah & Thormann, a dematiaceous hyphomycetous fungus, was found to cause a disease of Sphagnum fuscum (Schimp.) Klinggr. Hyphae of S. sphagnicola penetrated into chlorophyllose cells of host leaves and caused degeneration of chloroplasts, resulting in chlorosis of the infected leaves. Parasite hyphae often grew inside the host cell wall, and cavities were created around the hyphae. The invaded cell wall of Sp. fuscum appeared swollen and showed wavy deformation. In advanced stages of disease development, infected leaf chlorophyllose cells and stem cortical cells were necrotic and the entire plant became brown, shriveled, and brittle. Hyphae of S. sphagnicola began to form microsclerotia during early stages of disease development. Microsclerotia either formed conidiogenous cells on their surface or remained metabolically inactive and did not form conidiogenous cells. It was concluded that S. sphagnicola is a necrotrophic pathogen of Sp. fuscum, and its morphological and phenological features show remarkable adaptations for dispersal and colonization as a pathogen in bog habitats.Key words: moss, fungal pathogen, pathogenesis, chlorosis, necrosis, microsclerotia.

scholarly journals Curative and Suppressive Activities of Essential Tea Tree Oil against Fungal Plant Pathogens

Agronomy ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 609 ◽  
Author(s):  
Moshe Reuveni ◽  
Ethel Sanches ◽  
Marcel Barbier
Keyword(s):  
Cell Wall ◽  
Electron Microscope ◽  
Plant Pathogens ◽  
Fungal Cell Wall ◽  
Infected Leaf ◽  
Disease Development ◽  
Tea Tree Oil ◽  
Fungal Cell ◽  
Tea Tree ◽  
Fungal Plant Pathogens

Timorex Gold based on the essential tea tree oil (TTO) derived from the Australian tea tree oil (Melaleuca alternifolia) plant has demonstrated high efficacy and a strong curative activity against black Sigatoka in banana and controlled it in stages 1, 2, 3, and 4 of disease development. Transmission electron microscope (TEM) examination of infected leaf sections treated with Timorex Gold revealed disruption of the fungal cell membrane and destruction of the fungal cell wall in disease development stages 4 and 5. Mineral oil and the fungicide difenoconazole, when applied alone, had no curative effect and did not disrupt the fungal cell wall or membrane, similar to the untreated control tissue. A single spray of Timorex Gold effectively controlled and suppressed powdery mildew in cucumber by causing the disappearance of 99% of established colonies recorded 1 or 2 days after the application and was effective for up to 8 days after application. Scanning electron microscope (SEM) examination of infected and Timorex Gold-treated leaves indicated strong shrinkage and disruption of fungal hyphae and conidial cells. The curative and suppressive modes of action of the Timorex Gold may explain its success in controlling both diseases.

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 Trichoderma asperelloides Suppresses Nitric Oxide Generation Elicited by Fusarium oxysporum in Arabidopsis Roots

2014 ◽  
Vol 27 (4) ◽  
pp. 307-314 ◽  
Author(s):  
Kapuganti J. Gupta ◽  
Luis A. J. Mur ◽  
Yariv Brotman
Keyword(s):  
Nitric Oxide ◽  
Fusarium Oxysporum ◽  
No Production ◽  
Disease Development ◽  
Necrotrophic Pathogen ◽  
Trichoderma Spp ◽  
Promote Plant Growth ◽  
Induced Genes ◽  
Underlying Mechanisms ◽  
Lectin Protein

Inoculations with saprophytic fungus Trichoderma spp. are now extensively used both to promote plant growth and to suppress disease development. The underlying mechanisms for both roles have yet to be fully described so that the use of Trichoderma spp. could be optimized. Here, we show that Trichoderma asperelloides effects include the manipulation of host nitric oxide (NO) production. NO was rapidly formed in Arabidopsis roots in response to the soil-borne necrotrophic pathogen Fusarium oxysporum and persisted for about 1 h but is only transiently produced (approximately 10 min) when roots interact with T. asperelloides (T203). However, inoculation of F. oxysporum–infected roots with T. asperelloides suppressed F. oxysporum–initiated NO production. A transcriptional study of 78 NO-modulated genes indicated most genes were suppressed by single and combinational challenge with F. oxysporum or T. asperelloides. Only two F. oxysporum–induced genes were suppressed by T. asperelloides inoculation undertaken either 10 min prior to or after pathogen infection: a concanavlin A-like lectin protein kinase (At4g28350) and the receptor-like protein RLP30. Thus, T. asperelloides can actively suppress NO production elicited by F. oxysporum and impacts on the expression of some genes reported to be NO-responsive. Of particular interest was the reduced expression of receptor-like genes that may be required for F. oxysporum–dependent necrotrophic disease development.

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.

scholarly journals The Cek1 and Hog1 Mitogen-Activated Protein Kinases Play Complementary Roles in Cell Wall Biogenesis and Chlamydospore Formation in the Fungal Pathogen Candida albicans

2006 ◽  
Vol 5 (2) ◽  
pp. 347-358 ◽  
Author(s):  
B. Eisman ◽  
R. Alonso-Monge ◽  
E. Román ◽  
D. Arana ◽  
C. Nombela ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Map Kinase ◽  
Fungal Pathogen ◽  
Hog Pathway ◽  
Cell Wall Biogenesis ◽  
Chlamydospore Formation ◽  
Mitogen Activated Protein ◽  
Morphological Transitions ◽  
Relationship Of

ABSTRACT The Hog1 mitogen-activated protein (MAP) kinase mediates an adaptive response to both osmotic and oxidative stress in the fungal pathogen Candida albicans. This protein also participates in two distinct morphogenetic processes, namely the yeast-to-hypha transition (as a repressor) and chlamydospore formation (as an inducer). We show here that repression of filamentous growth occurs both under serum limitation and under other partially inducing conditions, such as low temperature, low pH, or nitrogen starvation. To understand the relationship of the HOG pathway to other MAP kinase cascades that also play a role in morphological transitions, we have constructed and characterized a set of double mutants in which we deleted both the HOG1 gene and other signaling elements (the CST20, CLA4, and HST7 kinases, the CPH1 and EFG1 transcription factors, and the CPP1 protein phosphatase). We also show that Hog1 prevents the yeast-to-hypha switch independent of all the elements analyzed and that the inability of the hog1 mutants to form chlamydospores is suppressed when additional elements of the CEK1 pathway (CST20 or HST7) are altered. Finally, we report that Hog1 represses the activation of the Cek1 MAP kinase under basal conditions and that Cek1 activation correlates with resistance to certain cell wall inhibitors (such as Congo red), demonstrating a role for this pathway in cell wall biogenesis.

scholarly journals Changes in cell ultrastructure and morphology of Arabidopsis thaliana roots after coumarins treatment

2014 ◽  
Vol 70 (3) ◽  
pp. 187-198
Author(s):  
Ewa Kupidłowska
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Root Elongation ◽  
Inhibitory Effect ◽  
Cell Ultrastructure ◽  
Radial Expansion ◽  
Elongation Zone ◽  
Cortical Cells ◽  
Mother Cell Wall

The ultrastructure and morphology of roots treated with coumarin and umbelliferone as well as the reversibility of the coumarins effects caused by exogenous GA, were studied in <em>Arabidopsis thaliana</em>. Both coumarins suppressed root elongation and appreciably stimulated radial expansion of epidermal and cortical cells in the upper part of the meristem and in the elongation zone. The gibberellic acid applied simultaneously with coumarins decreased their inhibitory effect on root elongation and reduced cells swelling.Microscopic observation showed intensive vacuolization of cells and abnormalities in the structure of the Golgi stacks and the nuclear envelope. The detection of active acid phosphatase in the cytosol of swollen cells indicated increased membrane permeability. Significant abnormalities of newly formed cell walls, e.g. the discontinuity of cellulose layer, uncorrect position of walls and the lack of their bonds with the mother cell wall suggest that coumarins affected the cytoskeleton.

scholarly journals Latency- and Defense-Related Ultrastructural Characteristics of Apple Fruit Tissues Infected with Botryosphaeria dothidea

2001 ◽  
Vol 91 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Ki Woo Kim ◽  
Eun Woo Park ◽  
Young Ho Kim ◽  
Kyung-Ku Ahn ◽  
Pan Gi Kim ◽  
...  
Keyword(s):  
Cell Wall ◽  
Fungal Growth ◽  
Apple Fruit ◽  
White Rot ◽  
Ultrastructural Changes ◽  
Disease Development ◽  
Botryosphaeria Dothidea ◽  
Transmission Electron ◽  
Thin Electron ◽  
Apple Fruits

Apple fruit tissues infected with Botryosphaeria dothidea were examined by transmission electron microscopy using susceptible cv. Fuji and resistant cv. Jonathan. Immature (green) and mature (red) fruits of cv. Fuji with restricted or expanding lesions were also examined to reveal subcellular characteristics related with latent and restricted disease development. In infected susceptible mature fruits, cytoplasmic degeneration and organelle disruption commonly occurred, accompanying cell wall dissolution around invading hyphae. Cell wall dissolution around invading hyphae in subepidermis was rare in immature, red halo-symptomed cv. Fuji and resistant cv. Jonathan fruits. In infected immature fruits of cv. Fuji, presumably at the latent state of disease development, cellular degeneration was less severe, and invading hyphae contained prominent microbody-lipid globule complexes or the deposition of thin electron-dense outer layer around cell wall of intercellular hyphae. Both mature fruits with red halos and resistant apple fruits formed cell wall protuberances at the outside of cell walls. In addition, electron-dense extramural layers were formed in the resistant apple fruits. Aberrant hyphal structures such as intrahyphal hyphae were found only in resistant fruit tissues, indicating the physiologically altered fungal growth. These ultrastructural changes of host tissues and fungal hyphae may reflect the pathogenesis of apple white rot under varying conditions of apple fruits.

scholarly journals Melanin Externalization in Candida albicans Depends on Cell Wall Chitin Structures

2010 ◽  
Vol 9 (9) ◽  
pp. 1329-1342 ◽  
Author(s):  
Claire A. Walker ◽  
Beatriz L. Gómez ◽  
Héctor M. Mora-Montes ◽  
Kevin S. Mackenzie ◽  
Carol A. Munro ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Cell Walls ◽  
Chitin Synthesis ◽  
Melanin Production ◽  
Content Type ◽  
Encoding Gene ◽  
Chitinase Genes

ABSTRACT The fungal pathogen Candida albicans produces dark-pigmented melanin after 3 to 4 days of incubation in medium containing l-3,4-dihydroxyphenylalanine (l-DOPA) as a substrate. Expression profiling of C. albicans revealed very few genes significantly up- or downregulated by growth in l-DOPA. We were unable to determine a possible role for melanin in the virulence of C. albicans. However, we showed that melanin was externalized from the fungal cells in the form of electron-dense melanosomes that were free or often loosely bound to the cell wall exterior. Melanin production was boosted by the addition of N-acetylglucosamine to the medium, indicating a possible association between melanin production and chitin synthesis. Melanin externalization was blocked in a mutant specifically disrupted in the chitin synthase-encoding gene CHS2. Melanosomes remained within the outermost cell wall layers in chs3Δ and chs2Δ chs3Δ mutants but were fully externalized in chs8Δ and chs2Δ chs8Δ mutants. All the CHS mutants synthesized dark pigment at equivalent rates from mixed membrane fractions in vitro, suggesting it was the form of chitin structure produced by the enzymes, not the enzymes themselves, that was involved in the melanin externalization process. Mutants with single and double disruptions of the chitinase genes CHT2 and CHT3 and the chitin pathway regulator ECM33 also showed impaired melanin externalization. We hypothesize that the chitin product of Chs3 forms a scaffold essential for normal externalization of melanosomes, while the Chs8 chitin product, probably produced in cell walls in greater quantity in the absence of CHS2, impedes externalization.

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