Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
J Exp Bot. 2023 Jan 1;74(1):118-129. doi: 10.1093/jxb/erac403.
Encasements formed around haustoria and biotrophic hyphae as well as hypersensitive reaction (HR) cell death are essential plant immune responses to filamentous pathogens. In this study we examine the components that may contribute to the absence of these responses in susceptible barley attacked by the powdery mildew fungus. We find that the effector CSEP0162 from this pathogen targets plant MONENSIN SENSITIVITY1 (MON1), which is important for the fusion of multivesicular bodies to their target membranes. Overexpression of CSEP0162 and silencing of barley MON1 both inhibit encasement formation. We find that the Arabidopsis ecotype No-0 has resistance to powdery mildew, and that this is partially dependent on MON1. Surprisingly, we find the MON1-dependent resistance in No-0 not only includes an encasement response, but also an effective HR. Similarly, silencing of MON1 in barley also blocks Mla3-mediated HR-based powdery mildew resistance. Our results indicate that MON1 is a vital plant immunity component, and we speculate that the barley powdery mildew fungus introduces the effector CSEP0162 to target MON1 and hence reduce encasement formation and HR.
围绕吸器和生物营养菌丝形成的套膜以及过敏反应（HR）细胞死亡是植物对丝状病原体的重要免疫反应。在这项研究中，我们研究了可能导致易感性大麦被白粉菌攻击时缺乏这些反应的成分。我们发现，来自这种病原体的效应因子 CSEP0162 靶向植物 MONENSIN 敏感性 1（MON1），这对于多泡体与靶膜融合很重要。CSEP0162 的过表达和大麦 MON1 的沉默都抑制了套膜的形成。我们发现拟南芥 No-0 型对白粉病具有抗性，并且这种抗性部分依赖于 MON1。令人惊讶的是，我们发现 No-0 型中 MON1 依赖性抗性不仅包括套膜反应，还包括有效的 HR。同样，大麦中 MON1 的沉默也阻止了 Mla3 介导的基于 HR 的白粉病抗性。我们的结果表明 MON1 是一个重要的植物免疫成分，我们推测大麦白粉菌引入效应因子 CSEP0162 来靶向 MON1，从而减少套膜形成和 HR。
