Department of Plant Pathology, Washington State University, Pullman, WA, 99164-6430, USA.
College of Biological Science and Engineering, Beijing University of Agriculture, Beijing, 102206, China.
New Phytol. 2019 May;222(3):1561-1572. doi: 10.1111/nph.15676. Epub 2019 Feb 13.
Fungal plant pathogens, like rust-causing biotrophic fungi, secrete hundreds of effectors into plant cells to subvert host immunity and promote pathogenicity on their host plants by manipulating specific physiological processes or signal pathways, but the actual function has been demonstrated for very few of these proteins. Here, we show that the PgtSR1 effector proteins, encoded by two allelic genes (PgtSR1-a and PgtSR1-b), from the wheat stem rust pathogen Puccinia graminis f. sp. tritici (Pgt), suppress RNA silencing in plants and impede plant defenses by altering the abundance of small RNAs that serve as defense regulators. Expression of the PgtSR1s in plants revealed that the PgtSR1s promote susceptibility to multiple pathogens and partially suppress cell death triggered by multiple R proteins. Overall, our study provides the first evidence that the filamentous fungus P. graminis has evolved to produce fungal suppressors of RNA silencing and indicates that PgtSR1s suppress both basal defenses and effector triggered immunity.
真菌植物病原体，如引起锈病的生物营养型真菌，会向植物细胞中分泌数百种效应子，通过操纵特定的生理过程或信号通路来颠覆宿主的免疫防御并促进在其宿主植物上的致病性，但这些蛋白质中的实际功能仅在极少数情况下得到证实。在这里，我们表明，小麦茎锈病病原菌 Puccinia graminis f. sp. tritici (Pgt) 中的两个等位基因（PgtSR1-a 和 PgtSR1-b）编码的 PgtSR1 效应蛋白通过改变作为防御调节剂的小 RNA 的丰度来抑制植物中的 RNA 沉默并阻碍植物防御。在植物中表达 PgtSR1s 表明，PgtSR1s 促进了对多种病原体的易感性，并部分抑制了由多种 R 蛋白触发的细胞死亡。总的来说，我们的研究首次提供了证据表明丝状真菌 P. graminis 已经进化出产生真菌 RNA 沉默抑制剂，并表明 PgtSR1s 抑制了基础防御和效应触发免疫。
