The Fungal Effector Avr-Pita Suppresses Innate Immunity by Increasing COX Activity in Rice Mitochondria

• Main Authors: Jingluan Han, Xiaoyu Wang, Fengpin Wang, Zhe Zhao, Gousi Li, Xiaoyuan Zhu, Jing Su, Letian Chen
• Format: Article
• Language: English
• Published: SpringerOpen 2021-01-01
• Series: Rice
• Subjects: Innate immunity; Effector; Avr-Pita; Mitochondrion; Cytochrome c oxidase (COX); Reactive oxygen species (ROS)
• Online Access: https://doi.org/10.1186/s12284-021-00453-4
• ISSN: 1939-8425; 1939-8433

Abstract Background Avr-Pita was the first effector identified in the blast fungus (Magnaporthe oryzae)–rice (Oryza sativa) pathosystem. However, the molecular mechanism underlying its effects on the host plant has remained a long-standing mystery. Results Here, we report that ectopically expressing Avr-Pita in rice enhances susceptibility to M. oryzae and suppresses pathogen-associated molecular pattern (PAMP)-triggered defense responses. Avr-Pita targets the host mitochondria and interacts with the cytochrome c oxidase (COX) assembly protein OsCOX11, a key regulator of mitochondrial reactive oxygen species (ROS) metabolism in rice. Overexpressing Avr-Pita or OsCOX11 increased COX activity and decreased ROS accumulation triggered by the fungal PAMP chitin. OsCOX11-overexpressing plants showed increased susceptibility to M. oryzae, whereas OsCOX11-knockdown plants showed resistance to M. oryzae. Conclusions Taken together, these findings suggest that the fungal pathogen M. oryzae delivers the effector Avr-Pita to the host plant, where it enhances COX activity thus decreasing ROS accumulation. Therefore, this effector suppresses host innate immunity by perturbing ROS metabolism in the mitochondria.