背景回顾：The plant immune system is fundamental for plant survival in natural ecosystems and for productivity in crop fields. Substantial evidence supports the prevailing notion that plants possess a two-tiered innate immune system, called pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI is triggered by microbial patterns via cell surface-localized pattern-recognition receptors (PRRs), whereas ETI is activated by pathogen effector proteins via predominantly intracellularly localized receptors called nucleotide-binding, leucine-rich repeat receptors (NLRs). PTI and ETI are initiated by distinct activation mechanisms and involve different early signalling cascades. 

结果1-PRR关键组分突变影响ETI：：Here we show that Arabidopsis PRR and PRR co-receptor mutants—fls2 efr cerk1 and bak1 bkk1 cerk1 triple mutants—are markedly impaired in ETI responses when challenged with incompatible Pseudomonas syrinage bacteria. 

结果2-RBOHD关联PTI和ETI：We further show that the production of reactive oxygen species by the NADPH oxidase RBOHD is a critical early signalling event connecting PRR- and NLR-mediated immunity, and that the receptor-like cytoplasmic kinase BIK1 is necessary for full activation of RBOHD, gene expression and bacterial resistance during ETI. 

结果3-胞内受体增强PTI关键组分：Moreover, NLR signalling rapidly augments the transcript and/or protein levels of key PTI components. 

总结：Our study supports a revised model in which potentiation of PTI is an indispensable component of ETI during bacterial infection.

结论：This revised model conceptually unites two major immune signalling cascades in plants and mechanistically explains some of the long-observed similarities in downstream defence outputs between PTI and ETI.

 摘 要 

植物免疫系统对于植物在自然生态系统下的生存以及大田种植下的作物产量都至关重要。越来越多的证据表明，植物具有两层天然的免疫系统，即模式触发免疫（PTI）和效应子触发免疫（ETI）。PTI由微生物模式通过细胞表面局部模式识别受体（PRRs）触发，而ETI则由病原体效应蛋白通过称为核苷酸结合、富含亮氨酸重复受体（NLRs）的主要胞内受体激活。PTI和ETI由不同的激活机制启动，并涉及不同的早期信号级联。本文中，作者发现拟南芥的PRR和PRR共受体突变体fls2 efr cerk1和bak1 bkk1 cerk1三突植株在受到丁香假单胞菌攻击时，ETI响应明显受损。作者进一步的试验发现由NADPH氧化酶RBOHD产生的活性氧物质是关联PRR和NLR所介导免疫的一个重要的早期信号事件，并且类受体胞质激酶BIK1是ETI过程中RBOHD充分激活、基因表达和细菌抗性所必需的。此外，NLR信号转导快速增强PTI关键组分的转录本和/或蛋白质水平。本文的研究支持一个修正的模型，即在细菌病害侵染期间，植物PTI的增强是ETI不可或缺的组成部分。这一修正模型概念上统一了植物中两个主要的免疫信号级联，并从机制上解释了长期观察到的PTI和ETI之间下游防御输出的一些相似之处。

背景回顾：The plant immune system involves cell-surface receptors that detect intercellular pathogen-derived molecules, and intracellular receptors that activate immunity upon detection of pathogen-secreted effector proteins that act inside the plant cell. 

提出问题：Immunity mediated by surface receptors has been extensively studied, but that mediated by intracellular receptors has rarely been investigated in the absence of surface-receptor-mediated immunity. Furthermore, interactions between these two immune pathways are poorly understood. 

主要研究：Here, by activating intracellular receptors without inducing surface-receptor-mediated immunity, we analyse interactions between these two distinct immune systems in Arabidopsis. 

结果1-PTI需要ETI：Pathogen recognition by surface receptors activates multiple protein kinases and NADPH oxidases, and we find that intracellular receptors primarily potentiate the activation of these proteins by increasing their abundance through several mechanisms. 

结果2-ETI也需要PTI：Likewise, the hypersensitive response that depends on intracellular receptors is strongly enhanced by the activation of surface receptors. 

结果3-激活其中一个抗病效果不明显：Activation of either immune system alone is insufficient to provide effective resistance against the bacterial pathogen Pseudomonas syringae. 

总结：Thus, immune pathways activated by cell-surface and intracellular receptors in plants mutually potentiate to activate strong defences against pathogens. 

结论：These findings reshape our understanding of plant immunity and have broad implications for crop improvement.

 摘 要 

植物免疫系统涉及细胞表面受体（检测细胞间的源自于病原菌的分子）和胞内受体（在感知到病原菌分泌的效应蛋白后激活免疫）。由细胞表面受体介导的植物免疫相关研究已经很深入了，但是对于在没有表面受体介导的免疫情况下，细胞内受体介导的免疫相关研究还有待深入。此外，这两个免疫途径之间的相互作用还不清楚。本文中，通过激活胞内受体，而不诱导表面受体介导的免疫，作者分析了这两套植物免疫途径在拟南芥中的相互作用。由表面受体介导的病原菌识别激活了多个蛋白激酶和NADPH氧化酶，并且作者发现胞内受体通过多种机制增加这些蛋白质的丰度，从而增强这些蛋白质的活性。同样，表面受体的激活能够显著增强依赖于胞内受体的超敏反应。单独激活其中任何一个免疫途径都不足以使植株产生对细菌病原菌丁香假单胞菌的有效抗性。因此，由细胞表面和胞内受体激活的免疫途径互相增强，从而激活对病原菌的强力防御。本文的研究结果刷新了我们对于植物免疫的理解，并且对于作物的遗传改良具有广泛而有深远的意义。