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.

中文翻译：

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真菌效应子Avr-Pita通过增加水稻线粒体的COX活性来抑制先天免疫。

背景

Avr-Pita是在稻瘟病菌（Magnaporthe oryzae）-大米（Oryza sativa）病理系统中发现的第一个效应子。然而，影响宿主植物的分子机制仍然是一个长期的谜。

结果

在这里，我们报道在水稻中异位表达Avr-Pita增强了对米曲霉的敏感性，并抑制了病原体相关的分子模式（PAMP）触发的防御反应。Avr-Pita靶向宿主线粒体，并与细胞色素c氧化酶（COX）装配蛋白OsCOX11相互作用，OsCOX11是水稻中线粒体活性氧（ROS）代谢的关键调节剂。过表达Avr -Pita或OsCOX11增加了真菌PAMP几丁质引发的COX活性并减少了ROS积累。过表达OsCOX11的植物对米曲霉的敏感性增加，而OsCOX11击倒的植物显示出对米曲霉的抗性。

结论

综上所述，这些发现表明，真菌病原体米曲霉将效应子Avr-Pita递送至宿主植物，在宿主植物中其增强了COX活性，从而减少了ROS的积累。因此，该效应子通过干扰线粒体中的ROS代谢来抑制宿主的先天免疫。