核苷酸结合域富含亮氨酸的重复序列(NLR)免疫受体是植物和后生动物先天免疫的重要组成部分,可以作为单个单元或配对或网络发挥作用。激活后,NLR形成称为抗性体或炎性体的多蛋白复合物。虽然后生动物配对NLR,如NAIP/NLRC4,在激活时形成异质复合物,支持植物配对NLR活化的分子机制,尤其是它们是否结合在抗性异质复合物中,是未知的。在星号植物物种中,细胞死亡(NRC)免疫受体网络所需的NLR由多个抗性蛋白传感器和下游辅助蛋白组成,赋予对多种植物病原体的免疫力。这里,我们表明NLR蛋白Rx(赋予病毒抗性)的病原体效应子激活,和Bs2(赋予细菌抗性)导致其辅助NLR的寡聚化,NRC2。活化的Rx不与NRC2寡聚体寡聚化或进入稳定的复合物,并且保持细胞质。相比之下,激活的NRC2低聚物在膜相关的斑点中积累。我们提出了NRC免疫受体网络中NLR的激活和释放模型。这指向与哺乳动物配对NLR相比不同的激活模型。
Nucleotide-binding domain leucine-rich repeat (NLR) immune receptors are important components of plant and metazoan innate immunity that can function as individual units or as pairs or networks. Upon activation, NLRs form multiprotein complexes termed resistosomes or inflammasomes. Although metazoan paired NLRs, such as NAIP/NLRC4, form hetero-complexes upon activation, the molecular mechanisms underpinning activation of plant paired NLRs, especially whether they associate in
resistosome hetero-complexes, is unknown. In asterid plant species, the NLR required for cell death (NRC) immune receptor network is composed of multiple resistance protein sensors and downstream helpers that confer immunity against diverse plant pathogens. Here, we show that pathogen effector-activation of the NLR proteins Rx (confers virus resistance), and Bs2 (confers bacterial resistance) leads to oligomerization of their helper NLR, NRC2. Activated Rx does not oligomerize or enter into a stable complex with the NRC2 oligomer and remains cytoplasmic. In contrast, activated NRC2 oligomers accumulate in membrane-associated puncta. We propose an activation-and-release model for NLRs in the NRC immune receptor network. This points to a distinct activation model compared with mammalian paired NLRs.