scholarly journals Seed-transmitted beneficial endophytic Stagonospora sp. can penetrate the walls of the root epidermis, but does not proliferate in the cortex, of Phragmites australis

2006 ◽  
Vol 84 (6) ◽  
pp. 981-988 ◽  
Author(s):  
Kexiang Gao ◽  
Kurt Mendgen
Keyword(s):  
Phragmites Australis ◽  
Endophytic Fungus ◽  
Hyphal Growth ◽  
Root Surface ◽  
Cortical Layer ◽  
Epidermal Cells ◽  
Cortical Cells ◽  
Root Epidermis ◽  
Wall Appositions

Stagonospora sp. (4/99-1) is a beneficial endophytic fungus frequently transmitted by seeds of Phragmites australis [Cav.] Trin. ex Steudel. Here we show that this fungus also penetrates the root epidermis. At first, hyphae were attracted by the root and proliferated on the root surface, preferably over the anticlinal walls. Penetration occurred directly by undifferentiated hyphae or was facilitated by hyphopodia. Hyphal growth within the root was restricted to the walls of epidermal cells and the walls of the cells of the outermost cortical layer. Deeper growth by the fungus elicited wall appositions and ingress into the cytoplasm of cortical cells was blocked by papillae. In the rare cases, the fungus managed to penetrate into cortical cells, these reacted with necrosis. Immunological studies suggested that fungal material reached the host plasmalemma and may have been taken up by endocytotic events. Our observations explain the endophytic lifestyle of hyphae close to the epidermis and the restricted development within the cortex.

Structure and ontogeny of Alnus crispa – Alpova diplophloeus ectomycorrhizae

1986 ◽  
Vol 64 (1) ◽  
pp. 177-192 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
Y. Piché
Keyword(s):  
Structural Changes ◽  
Hyphal Growth ◽  
Root Surface ◽  
Epidermal Cells ◽  
Transfer Cells ◽  
Wall Ingrowths ◽  
Alnus Crispa ◽  
Hartig Net ◽  
Fungal Hyphae ◽  
Branching System

Alnus crispa (Ait.) Pursh seedlings were grown in plastic pouches and inoculated with Frankia to induce nodules and subsequently with Alpova diplophloeus (Zeller & Dodge) Trappe & Smith to form ectomycorrhizae. The earliest events in ectomycorrhiza formation involved contact of the root surface by hyphae, hyphal proliferation to form a thin mantle, and further hyphal growth to form a thick mantle. Structural changes in the host, the mycosymbiont, and the fungus–epidermis interface were described at various stages in the ontogeny of ectomycorrhizae. Fungal hyphae in contact with epidermal cells in the regions of intercellular penetration and paraepidermal Hartig net developed numerous rough endoplastic reticulum cisternae. In more proximal regions of the mycorrhiza, these gradually became fewer in number and smooth. A complicated labyrinthine wall branching system also developed in the fungus in these regions. Concurrently, epidermal cells formed wall ingrowths in regions adjacent to Hartig net hyphae. There was a gradient in the formation of these epidermal transfer cells as the mycorrhiza developed, and an additional deposition of secondary cell wall over the wall ingrowths occurred as transfer cells senesced. Nonmycorrhizal control roots did not develop epidermal wall ingrowths. Electron-dense material, which was also autofluorescent, was deposited in the outer tangential walls of the exodermis contiguous to the paraepidermal Hartig net.

scholarly journals Cytological Analysis of Defense-Related Mechanisms Induced in Pea Root Tissues in Response to Colonization by Nonpathogenic Fusarium oxysporum Fo47

2001 ◽  
Vol 91 (8) ◽  
pp. 730-740 ◽  
Author(s):  
Nicole Benhamou ◽  
Chantal Garand
Keyword(s):  
Fusarium Oxysporum ◽  
Fungal Growth ◽  
Defense Responses ◽  
Root Surface ◽  
Outer Cortex ◽  
Cortical Cells ◽  
Symbiotic Associations ◽  
Wall Appositions ◽  
Rapid Stimulation ◽  
Root Tissues

The ability of nonpathogenic Fusarium oxysporum, strain Fo47, to trigger plant defense reactions was investigated using Ri T-DNA-transformed pea roots. Cytological investigations of strain Fo47-inoculated roots showed that the fungus grew actively at the root surface and colonized a number of epidermal and cortical cells, inducing marked host cell metabolic changes. In roots inoculated with pathogenic F. oxysporum f. sp. pisi, the pathogen multiplied abundantly through much of the tissues, whereas in Fo47-inoculated roots, fungal growth was restricted to the epidermis and the outer cortex. Invading cells of strain Fo47 suffered from serious alterations, a phenomenon that was not observed in control roots in which F. oxysporum f. sp. pisi grew so actively that the vascular stele was invaded within a few days. Strain Fo47 establishment in the root tissues resulted in a massive elaboration of hemispherical wall appositions and in the deposition of an electron-opaque material frequently encircling pathogen hyphae and accumulating in the noninfected xylem vessels. This suggests that the host roots were signaled to defend themselves through the rapid stimulation of a general cascade of nonspecific defense responses. The specific relationship established between strain Fo47 and the root tissues is discussed in relation to other types of plant-fungus interactions, including pathogenic and symbiotic associations.

Characterization of the interaction between the dark septate fungus Phialocephala fortinii and Asparagus officinalis roots

2001 ◽  
Vol 47 (8) ◽  
pp. 741-753 ◽  
Author(s):  
T Yu ◽  
A Nassuth ◽  
R L Peterson
Keyword(s):  
Root Hairs ◽  
Root Surface ◽  
Epidermal Cells ◽  
Asparagus Officinalis ◽  
Structural Basis ◽  
Root Penetration ◽  
Root Tips ◽  
Cortical Cells ◽  
Phialocephala Fortinii

Phialocephala fortinii Wang & Wilcox is a member of root-inhabiting fungi known collectively as dark septate endophytes (DSE). Although very common and distributed worldwide, few studies have documented their interaction with roots on a structural basis. The objective of this study was to determine the early colonization events and formation of microsclerotia of P. fortinii in roots of Asparagus officinalis L., a species known to have DSE. A loose network of hyphae accumulated at the root surface, and coils formed around root hairs and external to epidermal cells overlying short cells of the dimorphic, suberized exodermis. Root penetration occurred via swollen, appressorium-like structures into epidermal cells where coiling of hyphae occurred along the periphery of the cells. Hyphae penetrated from the epidermis into short exodermal cells and from these into cortical cells. Hyphae colonized the cortex up to the endodermis and sometimes entered the vascular cylinder. Some root tips were colonized as well. Microsclerotia in epidermal and exodermal short cells accumulated glycogen, protein, and polyphosphate. Energy-dispersive X-ray spectroscopy on distinct bodies visible in microsclerotial hyphae revealed high levels of phosphorus.Key words: Mycelium radicis atrovirens, Phialocephala fortinii, microsclerotia, DSE.

Ectomycorrhizal and ectendomycorrhizal associations of Phialophorafinlandia with Pinusresinosa, Picearubens, and Betulaalleghaniensis

1987 ◽  
Vol 17 (8) ◽  
pp. 976-990 ◽  
Author(s):  
H. E. Wilcox ◽  
C. J. K. Wang
Keyword(s):  
Large Diameter ◽  
Root Surface ◽  
Epidermal Cells ◽  
Cortical Cells ◽  
Hartig Net ◽  
Mycorrhizal Associations ◽  
Intracellular Invasion ◽  
Inner Cortex ◽  
Root Axis ◽  
Distributed Clusters

Mycorrhizal associations formed by Phialophorafinlandia in Pinusresinosa were both ectomycorrhizal and ectendomycorrhizal with randomly distributed clusters of spherical hyphae within cells of the cortex. The ectomycorrhizal condition was common for short distances in the apices of short roots and in smaller diameter long roots, but intracellular invasion from the Hartig net occurred proximal to this zone, resulting in an ectendomycorrhizal structure. In large diameter long-root branches both conditions were found at different positions along the root axis. In addition, sclerotia-like inclusions occurred in the inner cortical cells, often radially opposite to the protoxylem. Mycorrhizal associations in Picearubens and Betulaalleghaniensis were predominantly ectomycorrhizal in all roots; sclerotial bodies could be present in the inner cortex of both hosts. The Hartig net extended to the endodermis in the spruce, but it surrounded only the epidermis in birch. The epidermal cells of birch ectendomycorrhizae elongated radially and obliquely to the root surface, but in spruce the mycorrhizal condition had no effect on radial dimensions of cortical cells.

Structure and ontogeny of Betula alleghaniensis – Pisolithus tinctorius ectomycorrhizae

1990 ◽  
Vol 68 (3) ◽  
pp. 579-593 ◽  
Author(s):  
H. B. Massicotte ◽  
R. L. Peterson ◽  
C. A. Ackerley ◽  
L. H. Melville
Keyword(s):  
Root Hairs ◽  
Root Surface ◽  
Pisolithus Tinctorius ◽  
Initial Contact ◽  
Broad Host Range ◽  
Betula Alleghaniensis ◽  
Cortical Cells ◽  
Structural Modifications ◽  
Hartig Net ◽  
Primary Roots

The ontogeny and ultrastructure of ectomycorrhizae synthesized between Betula alleghaniensis (yellow birch) and Pisolithus tinctorius, a broad host range fungus, were studied to determine the structural modifications in both symbionts during ectomycorrhiza establishment. A number of stages, including initial contact of hyphae with the root surface, early mantle formation, and mature mantle formation, were distinguished. Interactions between hyphae and root hairs were frequent. As a paraepidermal Hartig net developed, root epidermal cells elongated in a radial direction, but wall ingrowths were not formed. Repeated branching of Hartig net hyphae resulted in extensive fine branches and the compartmentalization of hyphal cytoplasm. Nuclei and elongated mitochondria were frequently located in the narrow cytoplasmic compartments, and [Formula: see text] thickenings developed along walls of cortical cells in primary roots.

Refining the Life Cycle of Plasmodiophora brassicae

2020 ◽  
Vol 110 (10) ◽  
pp. 1704-1712 ◽  
Author(s):  
Lijiang Liu ◽  
Li Qin ◽  
Zhuqing Zhou ◽  
Wilhelmina G. H. M. Hendriks ◽  
Shengyi Liu ◽  
...  
Keyword(s):  
Life Cycle ◽  
Plasmodiophora Brassicae ◽  
Secondary Infection ◽  
Life Stage ◽  
Infection Process ◽  
Epidermal Cells ◽  
Sexual Life ◽  
Cortical Cells ◽  
Susceptible Host ◽  
Clubroot Disease

As a soilborne protist pathogen, Plasmodiophora brassicae causes the devastating clubroot disease on Brassicaceae crops worldwide. Due to its intracellular obligate biotrophic nature, the life cycle of P. brassicae is still not fully understood. Here, we used fluorescent probe-based confocal microscopy and transmission electron microscopy (TEM) to investigate the infection process of P. brassicae on the susceptible host Arabidopsis under controlled conditions. We found that P. brassicae can initiate the primary infection in both root hairs and epidermal cells, producing the uninucleate primary plasmodium at 1 day postinoculation (dpi). After that, the developed multinucleate primary plasmodium underwent condensing and cytoplasm cleavage into uninucleate zoosporangia from 1 to 4 dpi. This was subsequently followed by the formation of multinucleate zoosporangia and the production of secondary zoospores within zoosporangium. Importantly, the secondary zoospores performed a conjugation in the root epidermal cells after their release. TEM revealed extensive uninucleate secondary plasmodium in cortical cells at 8 dpi, indicating the establishment of the secondary infection. The P. brassicae subsequently developed into binucleate, quadrinucleate, and multinucleate secondary plasmodia from 10 to 15 dpi, during which the clubroot symptoms appeared. The uninucleate resting spores were first observed in the cortical cells at 24 dpi, marking the completion of a life cycle. We also provided evidence that the secondary infection of P. brassicae may represent the diploid sexual life stage. From these findings, we propose a refined life cycle of P. brassicae which will contribute to understanding of the complicated infection biology of P. brassicae.

scholarly journals Effect of Temperature on and Histopathology of the Interaction Between Meloidogyne incognita and Thielaviopsis basicola on Cotton

1999 ◽  
Vol 89 (8) ◽  
pp. 613-617 ◽  
Author(s):  
N. R. Walker ◽  
T. L. Kirkpatrick ◽  
C. S. Rothrock
Keyword(s):  
Meloidogyne Incognita ◽  
Vascular Tissue ◽  
Root Surface ◽  
Effect Of Temperature ◽  
Infested Soil ◽  
Thielaviopsis Basicola ◽  
Root Knot Nematode ◽  
Cortical Cells ◽  
Node Ratio ◽  
Cotton Seeds

Controlled environments were used to study the relationship between the root-knot nematode (Meloidogyne incognita) and Thielaviopsis basicola on cotton. Temperature treatments were continuous 20, 24, and 28°C or two cyclic linear regimes with ranges of 14 to 32 or 18 to 28°C over 24 h. Cotton seeds were planted in fumigated soil infested with T. basicola, M. incognita, or both. After 42 days, pathogen effects on plant growth and pathogen development were evaluated. Histology was conducted on roots collected 14, 28, and 42 days after planting in the continuous 24°C treatment. Reductions in plant height-to-node ratio and total fresh weight were observed for soils infested with both pathogens compared with the control or with soils infested with either pathogen, except for M. incognita-infested soil at 28°C. T. basicola reduced root galling and reproduction of the nematode at all temperatures. Vascular discoloration caused by T. basicola was greater in the presence of M. incognita compared with that by T. basicola alone. At 2 and 4 weeks, histological studies showed that plants grown in all T. basicola-infested soils contained chlamydospore chains on the root surface and in cortical cells. The fungus was not observed inside the vascular cylinder. Roots from 4-week-old plants from soils infested with T. basicola and M. incognita showed fungal sporulation in vascular tissue and localized necrosis of vascular tissue adjacent to the nematodes. At 6 weeks, plants grown in soil infested with T. basicola alone exhibited no remaining cortical tissue and no evidence of vascular colonization by the fungus. Six-week-old plants grown in T. basicola + M. incognita-infested soils exhibited extensive vascular necrosis and sporulation within vascular tissue. These studies suggest that coinfection expands the temperature ranges at which the pathogens are able to cause plant damage. Further, M. incognita greatly increases the access of T. basicola to vascular tissue.

Anatomy and ultrastructure of a Rhododendron root–fungus association

1980 ◽  
Vol 58 (23) ◽  
pp. 2421-2433 ◽  
Author(s):  
T. A. Peterson ◽  
W. C. Mueller ◽  
L. Englander
Keyword(s):  
Fungal Infection ◽  
Secondary Growth ◽  
Cortical Layer ◽  
Electron Microscopic ◽  
Cortical Cells ◽  
Host Cytoplasm ◽  
Hair Roots ◽  
Short Period ◽  
Infected Cells ◽  
Hyphal Coils

Light and electron microscopic investigations of the roots of Rhododendron and other ericaceous plants growing in the vicinity of Clavaria fruiting structures showed a fungal infection consistently associated with the epidermal and cortical cells of the "hair roots." Uninfected hair roots consisted of an epidermis and a one cell thick cortical layer surrounding the stele. Secondary growth in the stele and formation of a cork layer by division of the pericycle caused the cortex and epidermis to slough as the root matured. The structure of the infected hair roots was similar except for the presence of fungus in epidermal and cortical cells. As judged by the appearance of septa, at least two fungi were involved, one with dolipore septa that formed hyphal coils in the infected cells, and one with septa associated with Woronin bodies that occurred as single hyphal strands. Hyphae were found penetrating the cells from the exterior of the root and also passing from cell to cell. No correlation between fungal infection and the phenolic content of the cells could be made. Dissolution of both the fungal and host cytoplasm appeared to occur as the cells were sloughed. It appears that the fungus–root relationship is complex and is limited in duration to a short period of time during the development of the hair roots.

Interactions of the nonhost French bean plant (Phaseolus vulgaris) with parasitic and saprophytic fungi. IV. Effect of preinoculation with the bean rust fungus on growth of parasitic fungi nonpathogenic on beans

1991 ◽  
Vol 69 (8) ◽  
pp. 1642-1646 ◽  
Author(s):  
Myriam R. Fernandez ◽  
Michèle C. Heath
Keyword(s):  
Rust Fungus ◽  
Fungal Growth ◽  
Hyphal Growth ◽  
French Bean ◽  
Bean Rust ◽  
Protein Synthesis Inhibitors ◽  
Rust Infection ◽  
Parasitic Fungi ◽  
Wall Appositions ◽  
Bean Leaves

Bean leaves inoculated 24 h previously with the bean rust fungus were inoculated with spores of Cochliobolus heterostrophus, Stemphylium sarcinaeforme, Stemphylium botryosum, or Cladosporium fulvum. For all species except C. fulvum, hyphal growth resulting from stomatal penetrations was greater than that in leaves that were not rust-infected but did not continue for more than about 24 h. The incidence of direct penetrations for these three fungi also was increased by prior rust infection, and the incidence of epidermal wall appositions was reduced. Growth of C. fulvum in rust-infected leaves only exceeded that in control leaves when spores were injected into the intercellular spaces of the mesophyll tissue. Rust infection either had little effect on the incidence of cell death, normally induced by all of the tested fungi except C. fulvum, or it enhanced this response in association with greater fungal growth. From this and previous studies, it seems that successful rust infection increases the growth of a wider array of fungi nonparasitic to beans than treatments with growth regulators or intercellular washing fluids from rusted tissue. Its effect is most closely mimicked by preinoculation treatments with heat or protein synthesis inhibitors, but it does not induce indiscriminate susceptibility. Its effect may, in part, be due to the suppression of defenses involving wall modifications. Key words: Uromyces appendiculatus, induced susceptibility, nonhost resistance.

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