Extended Data Fig. 5: Mechanism of substrate-induced condensation of TIR ___domain proteins.

a, Tetrameric structure of the RPP1-TIR ___domain. Shown in the left, middle and right panels are the crystal structure of the RPP-TIR ___domain in a substrate-free form (PDB 5TEB), the crystal structure of the RPP1-TIR ___domain in an NAD⁺-bound form (PDB 7XOZ) and Cryo-EM structure of the RPP1-TIR ___domain from the RPP1 resistosome (PDB 7CRC). b, Substrate binding induces BB-loop open to mediate TIR-TIR interaction. The closed BB-loop blocks substrate-binding site (left panel). Substrate binding triggers BB-loop open (middle panel). Opened BB-loop mediates TIR-TIR interactions (right panel). c, A proposed mechanism for substrate-induced condensation to activate TIR ___domain signaling. Biotic or abiotic stresses induce TIR ___domain protein upregulation. Binding of ATP/NAD⁺ induces conformational change of BB-loop and phase separation of TIR ___domain proteins. The TIR condensation stabilizes head-to-tail TIR dimers as catalytically active centers to catalyze ATP/NAD⁺ hydrolysis, producing small molecules for TIR immune signaling. d, A schematic of working model on phase separation-activated TIR-only signaling linking PTI, ETI and abiotic stress response. The cartoon images were created with BioRender.com.