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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

Light micrographs of the infected leaves of cucumber plants 5 days after inoculation with Colletotrichum orbiculare (2.5 × 105 conidia/ml). The plants were untreated (A) or colonized with mycorrhiza Glomus intraradices BEG 110 (B) 5 days before the fungal inoculation. Next, the samples were semi-thin (1 µm) sectioned. Inter- or intracellular hyphae were spread throughout the leaf tissue of the untreated cucumber (A) (circles and arrows). Inter- or intracellular hyphae were rarely found in the plants colonized with mycorrhiza G. intraradices BEG 110 (B) (square). A collar was observed at the penetration site, indicating an active response by the host cell (arrow in the square). The length of bars indicates 100 µm.
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Figure 1: Light micrographs of the infected leaves of cucumber plants 5 days after inoculation with Colletotrichum orbiculare (2.5 × 105 conidia/ml). The plants were untreated (A) or colonized with mycorrhiza Glomus intraradices BEG 110 (B) 5 days before the fungal inoculation. Next, the samples were semi-thin (1 µm) sectioned. Inter- or intracellular hyphae were spread throughout the leaf tissue of the untreated cucumber (A) (circles and arrows). Inter- or intracellular hyphae were rarely found in the plants colonized with mycorrhiza G. intraradices BEG 110 (B) (square). A collar was observed at the penetration site, indicating an active response by the host cell (arrow in the square). The length of bars indicates 100 µm.

Mentions: Five days after inoculation, abundant inter- and intra-cellular hyphe were found in the palisade and the spongy parenchyma layer of leaves in the control plants (Fig. 1A). Also, in the vascular bundle some intercellular hyphae were observed (Fig. 2D). The infection occurred via two different phases, the biotrophic phase and the necrotrophic phase. During the biotrophic phase, the morphology of host cells was unchanged around the penetration hyphae (Fig. 2A), suggesting the absence of direct response against the pathogen. Although thickened cytoplasm in penetrated cells was sometimes observed, such a defense reaction was not enough to prevent the attack by the pathogen (Fig. 2B and 2C).


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)

Light micrographs of the infected leaves of cucumber plants 5 days after inoculation with Colletotrichum orbiculare (2.5 × 105 conidia/ml). The plants were untreated (A) or colonized with mycorrhiza Glomus intraradices BEG 110 (B) 5 days before the fungal inoculation. Next, the samples were semi-thin (1 µm) sectioned. Inter- or intracellular hyphae were spread throughout the leaf tissue of the untreated cucumber (A) (circles and arrows). Inter- or intracellular hyphae were rarely found in the plants colonized with mycorrhiza G. intraradices BEG 110 (B) (square). A collar was observed at the penetration site, indicating an active response by the host cell (arrow in the square). The length of bars indicates 100 µm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Light micrographs of the infected leaves of cucumber plants 5 days after inoculation with Colletotrichum orbiculare (2.5 × 105 conidia/ml). The plants were untreated (A) or colonized with mycorrhiza Glomus intraradices BEG 110 (B) 5 days before the fungal inoculation. Next, the samples were semi-thin (1 µm) sectioned. Inter- or intracellular hyphae were spread throughout the leaf tissue of the untreated cucumber (A) (circles and arrows). Inter- or intracellular hyphae were rarely found in the plants colonized with mycorrhiza G. intraradices BEG 110 (B) (square). A collar was observed at the penetration site, indicating an active response by the host cell (arrow in the square). The length of bars indicates 100 µm.
Mentions: Five days after inoculation, abundant inter- and intra-cellular hyphe were found in the palisade and the spongy parenchyma layer of leaves in the control plants (Fig. 1A). Also, in the vascular bundle some intercellular hyphae were observed (Fig. 2D). The infection occurred via two different phases, the biotrophic phase and the necrotrophic phase. During the biotrophic phase, the morphology of host cells was unchanged around the penetration hyphae (Fig. 2A), suggesting the absence of direct response against the pathogen. Although thickened cytoplasm in penetrated cells was sometimes observed, such a defense reaction was not enough to prevent the attack by the pathogen (Fig. 2B and 2C).

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