Plant nucleotide-binding leucine-rich repeat (NLR) immune receptors with an N-terminal Toll/interleukin-1 receptor (TIR) domain mediate recognition of strain-specific pathogen effectors, typically via their C-terminal ligand-sensing domains¹. Effector binding enables TIR-encoded enzymatic activities that are required for TIR–NLR (TNL)-mediated immunity^2,3. Many truncated TNL proteins lack effector-sensing domains but retain similar enzymatic and immune activities^4,5. The mechanism underlying the activation of these TIR domain proteins remain unclear. Here we show that binding of the TIR substrates NAD⁺ and ATP induces phase separation of TIR domain proteins in vitro. A similar condensation occurs with a TIR domain protein expressed via its native promoter in response to pathogen inoculation in planta. The formation of TIR condensates is mediated by conserved self-association interfaces and a predicted intrinsically disordered loop region of TIRs. Mutations that disrupt TIR condensates impair the cell death activity of TIR domain proteins. Our data reveal phase separation as a mechanism for the activation of TIR domain proteins and provide insight into substrate-induced autonomous activation of TIR signalling to confer plant immunity.

具有 N 端 Toll/白细胞介素 1 受体 (TIR) 结构域的植物核苷酸结合富含亮氨酸重复序列 (NLR) 免疫受体通常通过其 C 端配体感应结构域介导对菌株特异性病原体效应子的识别¹。效应器结合可实现 TIR 编码的酶活性，这是 TIR–NLR (TNL) 介导的免疫所需的^2,3。许多截短的 TNL 蛋白缺乏效应子感应结构域，但保留相似的酶活性和免疫活性^4,5。这些 TIR 结构域蛋白激活的机制仍不清楚。在这里，我们证明 TIR 底物 NAD ⁺和 ATP 的结合在体外诱导 TIR 结构域蛋白的相分离。通过其天然启动子表达的 TIR 结构域蛋白也会发生类似的缩合，以响应植物中的病原体接种。TIR 冷凝物的形成是由保守的自缔合界面和预测的 TIR 固有无序环区域介导的。破坏 TIR 缩合物的突变会损害 TIR 结构域蛋白的细胞死亡活性。我们的数据揭示了相分离作为 TIR 结构域蛋白激活的机制，并提供了对底物诱导的 TIR 信号自主激活以赋予植物免疫力的见解。