两类免疫受体强强联手筑牢植物免疫防线

doi:10.11983/CBB21042

摘要/Abstract

摘要： 植物先天免疫系统在抵御病原菌入侵过程中发挥至关重要的作用, 主要包括两个层次, 即病原菌相关分子模式和效应因子分别触发的PTI和ETI免疫反应。PTI和ETI分别由植物细胞膜表面模式识别受体(PRRs)和胞内免疫受体(NLRs)激活, 具有特异的激活机制, 但是两者激活的下游免疫事件相互重叠。PTI和ETI是否为泾渭分明的两道防线, 以及ETI与PTI下游事件为何如此相似, 一直是植物免疫领域最受关注的问题之一。最近, 中国科学院分子植物科学卓越创新中心辛秀芳团队与合作者利用拟南芥(Arabidopsis thaliana)与丁香假单胞杆菌(Pseudomonas syringae)互作系统对PTI和ETI在机制上的联系进行了研究。他们发现PRRs和共受体参与ETI, 而活性氧的产生是联系PRRs和NLRs所介导的免疫早期信号事件。他们还发现NLRs信号能够迅速增强PTI关键因子的转录和蛋白水平, PTI的增强在ETI免疫反应中不可或缺。该研究从机制上解析了植物免疫领域中长期悬而未决的PTI与ETI相似性之谜, 是该领域的一项突破性进展, 为未来作物分子设计育种提供了新的启示。

Abstract: Innate immune system plays a crucial role to defend against pathogens attack and is classified into two layers, which include pathogen-associated molecular pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). The PTI and ETI are activated by cell-surface localized pattern-recognition receptors (PRRs) and mostly intracellularly-localized nucleotide-binding, leucine-rich repeat receptors (NLRs), respectively, with specific activation mechanisms, but largely overlapped downstream immune events and components. One of the top unanswered questions in the field of plant immunity is whether ETI and PTI are really distinct, considering the high similarity of the downstream of the recognition processes and components. Recently, a team led by Prof. Xiufang Xin, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, used the Arabidopsis thaliana and Pseudomonas syringae pathosystem to study the functional link between PTI and ETI, and demonstrated that PRRs and the co-receptor of PRRs contribute to ETI, and the production of reactive oxygen species (ROS) is the early signal event that connects PTI and ETI. They also showed that ETI enhances the transcript and protein levels of key components of PTI, and the increased PTI is crucial for full activation of ETI. This study provides mechanistic explanation to a long-lasting enigma in the field of plant immunity regarding the mechanistic connections of PTI and ETI, and the high similarity of these two layers of immunity. This work represents an important breakthrough in the field of plant immunity, and will have implications for the future molecular breeding in crops.

Key words: plant immunity, pattern-triggered immunity (PTI), effector-triggered immunity (ETI), reactive oxygen species, nucleotide-binding site and leucine-rich repeat domain receptors (NLRs), pattern-recognition receptors (PRRs)

王伟, 唐定中. 两类免疫受体强强联手筑牢植物免疫防线. 植物学报, 2021, 56(2): 142-146.

Wei Wang, Dingzhong Tang. Synergistic Cooperation Between Cell Surface and Intracellular Immune Receptors Potentiates to Activate Robust Plant Defense. Chinese Bulletin of Botany, 2021, 56(2): 142-146.

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链接本文: https://www.chinbullbotany.com/CN/10.11983/CBB21042

https://www.chinbullbotany.com/CN/Y2021/V56/I2/142

图/表 1

图1 植物先天免疫系统示意图植物通过细胞膜表面PRRs受体和共受体识别病原菌PAMPs, 并磷酸化胞质型类受体激酶BIK1。激活的BIK1通过磷酸化RbohD正调控活性氧(ROS)爆发, 抑制病原菌生长。成功入侵的病原菌通过向植物细胞内分泌效应因子抑制免疫反应。宿主细胞内的NLRs受体识别特定的效应因子后, 不仅能够激活下游免疫反应, 而且能提升BIK1和RbohD等免疫关键蛋白的丰度, 增强活性氧爆发和免疫通路重要基因的表达, 导致更加强烈的免疫反应。

Figure 1 Schematic representation of the plant immune system Plants recognize the PAMPs of pathogens via the cell surface-localized PRRs, leads to phosphorylation of the receptor-like cytoplasmic kinase BIK1. The activated BIK1 positively regulates reactive oxygen species (ROS) burst by phosphorylation of RbohD, resulting in the inhibition of pathogen growth. Successful invaded pathogens deliver effectors into plant cell to inhibit immune responses. Upon perception of specific effectors, the host intracellular NLRs activate downstream immune responses, and boost the abundance of key immune-related proteins such as BIK1 and RbohD to enhance ROS burst and the transcripts of important genes in immune signaling, leading to robust immune responses.

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