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Ultrastructures of Colletotrichum orbiculare in the Leaves of Cucumber Plants Expressing Induced Systemic Resistance Mediated by Glomus intraradices BEG110.

Jeun YC, Lee YJ, Kim KW, Kim SJ, Lee SW - Mycobiology (2008)

Bottom Line: However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls.These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast.In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Bioscience and Industry, College of Applied Life Sciences, the Research Institute for Subtropical Agriculture and Biotechnology, Cheju National University, Jeju 690-756, Korea.

ABSTRACT
The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

No MeSH data available.


Related in: MedlinePlus

Transmission electron micrographs of the leaves of cucumber plants pre-inoculated with mycorrhiza Glomus intraradices BEG 110 5 days after challenge inoculation with Colletotrichum orbiculare. Some electron non-transmissible materials accumulated around the intracellular hyphae in the biotrophic phase (A and B) (arrow). A thickening of the cytoplasm was observed around an intracellular hypha (C) (arrow). Numerous vesicles accumulated around the intracellular hyphae in the cytoplasm (D) (arrow). A barrier-like cell well was found in the necrotrophic phase (E) (arrow). The host cell wall was thickened adjacent to the intercellular hypha (F) (double arrows). All bars = 1 µm. Abbreviations: h, intercellular hypha; ih, intracellular hypha; is, intercellular space; me, mesophyll cell; ml, meddle lamella.
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Figure 3: Transmission electron micrographs of the leaves of cucumber plants pre-inoculated with mycorrhiza Glomus intraradices BEG 110 5 days after challenge inoculation with Colletotrichum orbiculare. Some electron non-transmissible materials accumulated around the intracellular hyphae in the biotrophic phase (A and B) (arrow). A thickening of the cytoplasm was observed around an intracellular hypha (C) (arrow). Numerous vesicles accumulated around the intracellular hyphae in the cytoplasm (D) (arrow). A barrier-like cell well was found in the necrotrophic phase (E) (arrow). The host cell wall was thickened adjacent to the intercellular hypha (F) (double arrows). All bars = 1 µm. Abbreviations: h, intercellular hypha; ih, intracellular hypha; is, intercellular space; me, mesophyll cell; ml, meddle lamella.

Mentions: Fungal infection structures in the leaves of plants colonized by G. intraradices BEG110 were different when compared to those in untreated plants. Hyphae were rarely found in the parenchyma or the spongy palisade layer of plants colonized by G. intraradices BEG110 5 days after fungal inoculation (Fig. 1B). Furthermore, at the penetration sites the plant cells actively reacted to the pathogen as evidenced by a thickening of cytoplasm in many cells. These active responses were observed in both the biothrophic and necrothrophic phases. Sheath was often observed around intracellular hyphae (Fig. 1B and 3A~3D). In some cases, a thickening of the cell wall around intracellular hyphae (Fig. 3E) or matrix between the cell wall and the cytoplasm of the plant cells adjusted to fungal hyphae (Fig. 3F) was observed. All of the host cytoplasm around the fungal hyphae showed evidence of a defense reaction indicating that the resistance may be expressed in the symplast of the host cells.


Ultrastructures of Colletotrichum orbiculare in the Leaves of Cucumber Plants Expressing Induced Systemic Resistance Mediated by Glomus intraradices BEG110.

Jeun YC, Lee YJ, Kim KW, Kim SJ, Lee SW - Mycobiology (2008)

Transmission electron micrographs of the leaves of cucumber plants pre-inoculated with mycorrhiza Glomus intraradices BEG 110 5 days after challenge inoculation with Colletotrichum orbiculare. Some electron non-transmissible materials accumulated around the intracellular hyphae in the biotrophic phase (A and B) (arrow). A thickening of the cytoplasm was observed around an intracellular hypha (C) (arrow). Numerous vesicles accumulated around the intracellular hyphae in the cytoplasm (D) (arrow). A barrier-like cell well was found in the necrotrophic phase (E) (arrow). The host cell wall was thickened adjacent to the intercellular hypha (F) (double arrows). All bars = 1 µm. Abbreviations: h, intercellular hypha; ih, intracellular hypha; is, intercellular space; me, mesophyll cell; ml, meddle lamella.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3755202&req=5

Figure 3: Transmission electron micrographs of the leaves of cucumber plants pre-inoculated with mycorrhiza Glomus intraradices BEG 110 5 days after challenge inoculation with Colletotrichum orbiculare. Some electron non-transmissible materials accumulated around the intracellular hyphae in the biotrophic phase (A and B) (arrow). A thickening of the cytoplasm was observed around an intracellular hypha (C) (arrow). Numerous vesicles accumulated around the intracellular hyphae in the cytoplasm (D) (arrow). A barrier-like cell well was found in the necrotrophic phase (E) (arrow). The host cell wall was thickened adjacent to the intercellular hypha (F) (double arrows). All bars = 1 µm. Abbreviations: h, intercellular hypha; ih, intracellular hypha; is, intercellular space; me, mesophyll cell; ml, meddle lamella.
Mentions: Fungal infection structures in the leaves of plants colonized by G. intraradices BEG110 were different when compared to those in untreated plants. Hyphae were rarely found in the parenchyma or the spongy palisade layer of plants colonized by G. intraradices BEG110 5 days after fungal inoculation (Fig. 1B). Furthermore, at the penetration sites the plant cells actively reacted to the pathogen as evidenced by a thickening of cytoplasm in many cells. These active responses were observed in both the biothrophic and necrothrophic phases. Sheath was often observed around intracellular hyphae (Fig. 1B and 3A~3D). In some cases, a thickening of the cell wall around intracellular hyphae (Fig. 3E) or matrix between the cell wall and the cytoplasm of the plant cells adjusted to fungal hyphae (Fig. 3F) was observed. All of the host cytoplasm around the fungal hyphae showed evidence of a defense reaction indicating that the resistance may be expressed in the symplast of the host cells.

Bottom Line: However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls.These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast.In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

View Article: PubMed Central - PubMed

Affiliation: Faculty of Bioscience and Industry, College of Applied Life Sciences, the Research Institute for Subtropical Agriculture and Biotechnology, Cheju National University, Jeju 690-756, Korea.

ABSTRACT
The colonization of an arbuscular mycorrhizal fungus Glomus intraradices BEG110 in the soil caused a decrease in disease severity in cucumber plants after fungal inoculation with Colletotrichum orbiculare. In order to illustrate the resistance mechanism mediated by G. intraradices BEG110, infection patterns caused by C. orbiculare in the leaves of cucumber plants and the host cellular responses were characterized. These properties were characterized using transmission electron microscopy on the leaves of cucumber plants grown in soil colonized with G. intraradices BEG110. In the untreated plants, inter- and intra-cellular fungal hyphae were observed throughout the leaf tissues during both the biotrophic and necrotrophic phases of infection. The cytoplasm of fungal hyphae appeared intact during the biotrophic phase, suggesting no defense response against the fungus. However, several typical resistance responses were observed in the plants when treated with G. intraradices BEG110 including the formation of sheaths around the intracellular hyphae or a thickening of host cell walls. These observations suggest that the resistance mediated by G. intraradices BEG110 most often occurs in the symplast of the host cells rather than in the apoplast. In addition, this resistance is similar to those mediated by biotic inducers such as plant growth promoting rhizobacteria.

No MeSH data available.


Related in: MedlinePlus