Microscopic detection of reactive oxygen species generation in the compatible and incompatible interactions of Alternaria alternata Japanese pear pathotype and host plants |
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| Authors: | Takeshi Shinogi Tomoko Suzuki Takayuki Kurihara Yoshihiro Narusaka Pyoyun Park |
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| Institution: | (1) The Graduate School of Science and Technology, Kobe University, 1-1 Rokkoudai, Nada, Kobe 657-8501, Japan, JP;(2) The Medical Research Institute, Kanazawa Medical University, Ishikawa, Japan, JP |
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| Abstract: | Reactive oxygen species (ROS) generation was examined in the interaction of Alternaria alternata Japanese pear pathotype and host plants using three methods: nitro blue tetrazolium (NBT) method for microscopic detection
of O2
−, diaminobenzidine (DAB) methods for microscopic detection of H2O2, and cerium chloride methods for ultrastructural detection of H2O2. ROS generation was detected by NBT and DAB methods at appressoria on leaves of susceptible cultivars and heat-shocked leaves
of resistant cultivars but not in leaves of resistant cultivars. Ultrastructural detection by the cerium chloride method identified
ROS generation at cell walls of appressoria and penetration pegs in susceptible, resistant leaves and heat-shocked leaves.
These differences in the ultrastructural and microscopic data in resistant areas were due to the restriction of ROS generation
in limited areas, the side facing the plant surface, of appressoria and penetration pegs. Therefore, ROS generation was apparently
induced regardless of the resistance or susceptibility of the cultivar with the difference being in the volumes generated.
After evaluating the pathological role of ROS generation in fungal structures, such generation was found to be associated
with early penetration of cell walls in pear plants. Additionally, ROS generation in plants was also found in degrading pectin
layers near infected hyphae and in plasma membrane modification sites in susceptible leaves but not in resistant leaves. ROS
generation in susceptible leaves might be accompanied with plasma membrane damage, although the role of ROS generation in
the pectin layers is not clear. ROS generation in both fungal and plant cells during their interaction was likely associated
with the expression of susceptibility.
Received: June 3, 2002 / Accepted: July 31, 2002 |
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| Keywords: | Reactive oxygen species Alternaria alternata Japanese pear pathotype Penetration Susceptibility |
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