背景回顾：Rapid production of H2O2 is a hallmark of plant responses to diverse pathogens and plays a crucial role in signalling downstream of various receptors that perceive immunogenic patterns. 

提出问题：However, mechanisms by which plants sense H2O2 to regulate immunity remain poorly understood. 

结果1-PRXIIB感知过氧化氢：We show that endogenous H2O2 generated upon immune activation is sensed by the thiol peroxidase PRXIIB via oxidation at Cys51, and this is essential for stomatal immunity against Pseudomonas syringae. 

结果2-PRXIIB传递氧化信号给ABI2：We further show that in immune-stimulated cells, PRXIIB conjugates via Cys51 with the type 2C protein phosphatase ABA insensitive 2 (ABI2), subsequently transducing H2O2 signal to ABI2. 

结果3-ABI2进一步作用于下游的气孔免疫：This oxidation dramatically sensitizes H2O2-mediated inhibition of the ABI2 phosphatase activity in vitro and is required for stomatal immunity in plants. 

结论：Together, our results illustrate a redox relay, with PRXIIB as a sensor for H2O2 and ABI2 as a target protein, that mediates reactive oxygen species signalling during plant immunity.

H2O2调控植物气孔免疫的工作模型

过氧化氢的快速产生是植物响应不同病原菌的一个典型特征，同时也在感知免疫原性模式受体的下游信号转导中发挥重要作用。但是，植物用来感知过氧化氢，以便调控植物免疫的机制仍不清楚。本文中，作者发现植物在免疫激活时产生的内源性过氧化氢是被巯基过氧化物酶PRXIIB通过Cys51的氧化来感知的，并且该过程对于植物的丁香假单胞菌气孔免疫是必要的。作者进一步发现在免疫刺激的细胞中，PRXIIB通过Cys51与ABI2偶联，随后将过氧化氢信号转导给ABI2。这种氧化作用在体外试验中显著增强了过氧化氢介导的ABI2磷酸酶活性抑制作用，这也是植物气孔免疫所必需的。综上，本文的研究结果揭示了PRXIIB感知体内过氧化氢，并与靶蛋白ABI2一起形成氧化传递，共同作用于植物免疫过程中的ROS信号转导。

** 周俭民 **