A PRA-Rab trafficking machinery modulates NLR immune receptor plasma membrane microdomain anchoring and blast resistance in rice

Nucleotide-binding leucine-rich repeat (NLR) receptors mediate pathogen effector-triggered immunity (ETI) in plants, and a subclass of NLRs are hypothesized to function at the plasma membrane (PM). However, how NLR traffic and PM delivery are regulated during immune responses remains largely unknown. The rice NLR PigmR confers broad-spectrum resistance to the blast fungus Magnaporthe oryzae. Here, we report that a PRA (Prenylated Rab acceptor) protein, PIBP4 (PigmR-INTERACTING and BLAST RESISTANCE PROTEIN 4), interacts with both PigmR and the active form of the Rab GTPase, OsRab5a, thereby loads a portion of PigmR on trafficking vesicles that target to PM microdomains. Microdomain-localized PigmR interacts with and activates the small GTPase OsRac1, which triggers reactive oxygen species signaling and hypersensitive response, leading to immune responses against blast infection. Thus, our study discovers a previously unknown mechanism that deploys a PRA-Rab protein delivering hub to ensure ETI, linking the membrane trafficking machinery with NLR function and immune activation in plants.