植物核苷酸结合的富含亮氨酸的重复受体(NLR)感知病原体效应子并激活效应子触发的免疫(ETI)。许多植物NLR与其他NLR形成配对以识别效应子并启动ETI。BL1(Pib)中的稻瘟病抗性,水稻中的一种NLR蛋白,通过识别稻瘟病效应子AvrPib激活抗性。在不存在AvrPib的情况下,Pib的活化被含SH3结构域蛋白2(OsSH3P2)抑制。然而,Pib如何触发防御响应以及Pib是否与另一个NLR配对尚不清楚。在这项研究中,我们通过基于图的克隆鉴定了Pib,并显示了Pib的同源物,PIB同型8(PibH8),与Pib互动。Pib和PibH8介导对稻瘟病菌分离株Guy11的抗性,后者是携带AvrPib的稻瘟病菌株。有趣的是,与单突变体相比,pib/pibh8双突变体对Guy11的易感性增强.此外,PibH8可以通过其卷曲螺旋(CC)结构域寡聚化,这也有助于Pib-PibH8的相互作用,这表明Pib和PibH8可能形成一个识别AvrPib的复合体。OsSH3P2通过与PibH8的CC结构域结合抑制Pib和PibH8的相互作用。一起来看,这些结果表明,水稻对携带AvrPib的米曲霉的稻瘟病抗性需要Pib和PibH8,受OsSH3P2负调控。这项研究不仅确定了在稻瘟病抗性中起作用的NLR,而且还揭示了一种可能的复杂免疫策略,其中同源NLR蛋白可以调节植物免疫的完全激活。
Plant nucleotide-binding leucine-rich repeat receptors (NLRs) sense pathogen effectors and activate effector-triggered immunity (ETI). Many plant NLRs form pairs with other NLRs to recognize effectors and initiate ETI. PIRICULARIA ORYZAE RESISTANCE IN BL1 (Pib), an NLR protein in rice (Oryza sativa), activates resistance by recognizing the rice blast effector AvrPib. The activation of Pib is suppressed by SH3 DOMAIN-CONTAINING PROTEIN 2 (OsSH3P2) in the absence of AvrPib. However, how Pib triggers defense responses and whether Pib pairs with another NLR are not clear. In this study, we identified Pib by map-based cloning and showed that a homolog of Pib, PIB HOMOLOGUE 8 (PibH8), interacts with Pib. Pib and PibH8 mediate resistance to the Magnaporthe oryzae isolate Guy11, a rice blast strain carrying AvrPib. Interestingly, the pib/pibh8 double mutant exhibited enhanced susceptibility to Guy11 compared to the single mutant. Furthermore, PibH8 can oligomerize through its coiled-coil (CC) domain, which also contributes to the Pib-PibH8 interaction, suggesting that Pib and PibH8 may form a complex to recognize AvrPib. OsSH3P2 inhibited the interaction of Pib and PibH8 through association with the CC domain of PibH8. Taken together, these results indicate that both Pib and PibH8 are required for rice blast resistance to M. oryzae carrying AvrPib, which is negatively regulated by OsSH3P2. This study not only identifies an NLR that functions in rice blast resistance but also reveals a possible complex immune strategy in which homologous NLR proteins may regulate the complete activation of plant immunity.