Ultrastructural analysis of responses of host and fungal cells during plant infection |
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| Authors: | Pyoyun Park Ken-ichi Ikeda |
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| Institution: | (1) Graduate School of Agricultural Science, Kobe University, Rokkodai-cho 1-1, Nada Ward, Kobe 657-8501, Japan |
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| Abstract: | Cellular responses in fungi and in susceptible or resistant hosts during fungus–plant interactions have been studied ultrastructurally
to examine their role in pathogenicity. Pathogenicity is determined in some saprophytic fungi by various factors: the production
of disease determinants such as the production of host-specific toxins (HSTs) or the extracellular matrix (ECM) by fungal
infection structures and H2O2 generation from penetration pegs. Three different target sites for HSTs have been identified in host cells in many ultrastructural
studies: plasma membranes, chloroplasts, and mitochondria. The mode of action of HSTs is characterized by the partial destruction
of the target structures only in susceptible genotypes of host plants, with the result that the fungus can colonize the host.
The infection structures of most fungal pathogen secrete ECM on plant surfaces during fungal differentiation, while the penetration
pegs of some pathogens produce reactive oxygen species (ROS) in the cell walls and plasma membranes. The pathological roles
of ECM and H2O2 generation are discussed here in light of ultrastructural evidence. Host and fungal characteristics in the incompatible interactions
include the rapid formation of lignin in host epidermal cell walls, failure of penetration pegs to invade lignin-fortified
pectin layers, the inhibition of subcuticular hyphal proliferation and the collapse of hyphae that have degraded cell walls
within pectin layers of the host. Apoptosis-like host resistant mechanism is also discussed. |
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| Keywords: | Pathogenicity Resistant responses Ultrastructure Host-specific toxins (HSTs) Reactive oxygen species (ROS) Extracellular matrix (ECM) |
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