Related Experiment Video
Updated: Jun 12, 2025
The Plant Infection Test: Spray and Wound-Mediated Inoculation with the Plant Pathogen Magnaporthe Grisea
Published on: August 4, 2018
The multifunctional ascorbate peroxidase MoApx1 secreted by Magnaporthe oryzae mediates the suppression of rice
Muxing Liu1, Ziqian Guo1, Jiexiong Hu1
1Sanya Institute of Nanjing Agricultural University, Department of Plant Pathology, College of Plant Protection, Nanjing Agricultural University, and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing 210095, China.
Abstract:
Fungi secrete effector proteins, including extracellular redox enzymes, to inhibit host immunity. Redox enzymes have been hypothesized to inhibit host reactive oxygen species (ROS); however, how they suppress host immunity remains unknown. We characterized an extracellular ascorbate peroxidase (MoApx1) that is secreted into rice chloroplasts by the rice blast fungus Magnaporthe oryzae. MoApx1 displays multifunctional capabilities that significantly contribute to fungal virulence. Firstly, MoApx1 neutralizes host-derived H2O2 within the chloroplast through its peroxidase activity, thereby inhibiting chloroplast ROS (cROS)-mediated defense responses. Secondly, MoApx1 targets the photosystem I subunit OsPsaD, disrupting photosynthetic electron transport to further suppress cROS production. Most importantly, MoApx1 has evolved a fungal-specific starch-binding domain that binds host starch, inhibiting its degradation and disrupting the energy supply required for host resistance. Our findings underscore the importance of a novel multifaceted strategy, potentially widely employed by other fungal pathogens, in suppressing host immunity during host-microbe interactions.
Insights
The rice blast fungus uses a secreted enzyme, MoApx1, to suppress plant immunity by neutralizing reactive oxygen species (ROS) and blocking energy supply. This enzyme targets chloroplasts and host starch, revealing a novel fungal virulence strategy.
Area of Science:
- Plant Pathology
- Mycology
- Biochemistry
Background:
- Fungi secrete effector proteins, including extracellular redox enzymes, to inhibit host immunity.
- The precise mechanisms by which these enzymes suppress host immunity are not fully understood.
Purpose of the Study:
- To characterize the extracellular ascorbate peroxidase (MoApx1) secreted by Magnaporthe oryzae into rice chloroplasts.
- To elucidate the multifunctional capabilities of MoApx1 in contributing to fungal virulence and suppressing host immunity.
Main Methods:
- Characterization of MoApx1's peroxidase activity in neutralizing hydrogen peroxide (H2O2).
- Investigation of MoApx1's interaction with photosystem I (PSI) subunit OsPsaD.
- Analysis of MoApx1's starch-binding domain and its effect on host starch degradation.
Main Results:
- MoApx1 neutralizes chloroplast reactive oxygen species (cROS) via peroxidase activity, inhibiting defense responses.
- MoApx1 disrupts photosynthetic electron transport by targeting OsPsaD, further reducing cROS production.
- MoApx1 binds host starch using a fungal-specific domain, blocking degradation and host energy supply for resistance.
Conclusions:
- MoApx1 employs a multifaceted strategy to suppress rice immunity, involving ROS neutralization, photosynthesis disruption, and energy deprivation.
- This study reveals a novel mechanism of fungal virulence potentially applicable to other host-pathogen interactions.
