State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.
Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
Mol Plant Pathol. 2022 Sep;23(9):1290-1302. doi: 10.1111/mpp.13226. Epub 2022 May 8.
In the devastating rice blast fungus Magnaporthe oryzae, six Magnaporthe appressoria-specific (MAS) proteins are encoded by MoGAS1, MoGAS2 and MoMAS3-MoMAS6. MoGAS1 and MoGAS2 were previously characterized as M. oryzae virulence factors; however, the roles of the other four genes are unknown. Here, we found that, although the loss of any MAS gene did not affect appressorial formation or vegetative growth, ∆Momas3 and ∆Momas5 mutant strains (but not the others) were reduced in virulence on susceptible CO-39 rice seedlings. Focusing on ∆Momas3 and ∆Momas5 mutant strains, we found that they could penetrate host leaf surfaces and fill the first infected rice cell but did not spread readily to neighbouring cells, suggesting they were impaired for biotrophic growth. Live-cell imaging of fluorescently labelled MoMas3 and MoMas5 proteins showed that during biotrophy, MoMas3 localized to the apoplastic compartment formed between fungal invasive hyphae and the plant-derived extra-invasive hyphal membrane while MoMas5 localized to the appressoria and the penetration peg. The loss of either MoMAS3 or MoMAS5 resulted in the accumulation of reactive oxygen species (ROS) in infected rice cells, resulting in the triggering of plant defences that inhibited mutant growth in planta. ∆Momas3 and ∆Momas5 biotrophic growth could be remediated by inhibiting host NADPH oxidases and suppressing ROS accumulation. Thus, MoMas3 and MoMas5 are novel virulence factors involved in suppressing host plant innate immunity to promote biotrophic growth.
在毁灭性的稻瘟病菌（Magnaporthe oryzae）中，六个稻瘟病菌附着胞特异性（MAS）蛋白由 MoGAS1、MoGAS2 和 MoMAS3-MoMAS6 编码。MoGAS1 和 MoGAS2 先前被表征为 M.oryzae 的毒力因子；然而，其他四个基因的作用尚不清楚。在这里，我们发现尽管缺失任何 MAS 基因都不会影响附着胞的形成或营养生长，但 ∆Momas3 和 ∆Momas5 突变株（而不是其他突变株）在对易感 CO-39 水稻幼苗的毒力上降低了。我们集中研究了 ∆Momas3 和 ∆Momas5 突变株，发现它们可以穿透宿主叶表面并填充第一个被感染的水稻细胞，但不易扩散到邻近细胞，这表明它们在生物营养生长方面受到了损害。对荧光标记的 MoMas3 和 MoMas5 蛋白进行活细胞成像显示，在生物营养生长过程中，MoMas3 定位于真菌侵袭性菌丝和植物衍生的额外侵袭性菌丝膜之间形成的质外体隔室，而 MoMas5 定位于附着胞和穿透钉。任何一个 MoMAS3 或 MoMAS5 的缺失都会导致感染水稻细胞中活性氧物质（ROS）的积累，从而触发植物防御机制，抑制突变体在植物体内的生长。通过抑制宿主 NADPH 氧化酶和抑制 ROS 积累，可以修复 ∆Momas3 和 ∆Momas5 的生物营养生长。因此，MoMas3 和 MoMas5 是参与抑制宿主植物先天免疫以促进生物营养生长的新的毒力因子。
