Temasek Life Sciences Laboratory and Department of Biological Sciences; National University of Singapore; Singapore.
Autophagy. 2013 Nov 1;9(11):1818-27. doi: 10.4161/auto.26057. Epub 2013 Aug 15.
Macroautophagy-mediated glycogen catabolism is required for asexual differentiation in the blast fungus, Magnaporthe oryzae. However, the function(s) of selective subtypes of autophagy has not been studied therein. Here, we report that mitophagy, selective autophagic delivery of mitochondria to the vacuoles for degradation, occurs during early stages of Magnaporthe conidiation. Specifically, mitophagy was evident in the foot cells while being undetectable in aerial hyphae and/or conidiophores. We show that loss of MoAtg24, a sorting nexin related to yeast Snx4, disrupts mitophagy and consequently leads to highly reduced conidiation, suggesting that mitophagy in the foot cells plays an important role during asexual development in Magnaporthe. Ectopic expression of yeast ScATG32 partially suppressed the conidiation initiation defects associated with MoATG24 deletion. MoAtg24 was neither required for pexophagy nor for macroautophagy, or for MoAtg8 localization per se, but directly associated with and likely recruited mitochondria to the autophagic structures during mitophagy. Lastly, MoAtg24 was also required for oxidative stress response in Magnaporthe.
巨自噬介导的糖原分解对于稻瘟病菌无性分化是必需的。然而，在该菌中尚未研究选择性自噬亚型的功能。在这里，我们报告说，在稻瘟病菌分生孢子形成的早期阶段会发生线粒体的选择性自噬，即线粒体被输送到液泡中进行降解的现象。具体来说，在足细胞中可以观察到线粒体自噬，而在气生菌丝和/或分生孢子梗中则无法检测到。我们表明，缺失与酵母 Snx4 相关的分选连接蛋白 MoAtg24 会破坏线粒体自噬，从而导致分生孢子形成能力显著降低，这表明足细胞中的线粒体自噬在稻瘟病菌的无性发育过程中发挥着重要作用。酵母 ScATG32 的异位表达部分抑制了与 MoATG24 缺失相关的分生孢子起始缺陷。MoAtg24 既不需要 pexophagy 也不需要巨自噬，或者 MoAtg8 本身的定位，但它直接与线粒体相关，并在巨自噬过程中可能将线粒体募集到自噬结构中。最后，MoAtg24 对于稻瘟病菌的氧化应激反应也是必需的。
