Binding of a pathogen effector to rice Exo70 proteins tethered to the NOI/RIN4 integrated domain of the NLR receptor Pii2 confers immunity against fungi

  • Published:
  • Authors: Fujisaki K, Abe Y, Sugihara Y, Nemoto K, Ito K, Kanzaki E, Ishikawa K, Iwai M, Utsushi H, Saitoh H, Takagi H, Takeda T, Abe A, Zheng S, Bialas A, Banfield MJ, Kamoun S, Terauchi R (2024)
  • Reference: bioRxiv 239400; doi: https://doi.org/10.1101/239400

As much as 10% of plant immune receptors from the nucleotide-binding domain leucine-rich repeat (NLR) family carry integrated domains (IDs) that can directly bind pathogen effectors. However, it remains unclear whether direct binding to effectors is a universal feature of ID-containing NLRs given that only a few NLR-IDs have been functionally characterized. Here we show that the rice (Oryza sativa) sensor NLR-ID Pii2 confers resistance to strains of the rice blast fungus Magnaporthe oryzae that carry the effector AVR-Pii without directly binding this protein. First, we show that AVR-Pii binds the exocyst subunit OsExo70F2 in rice (Oryza sativa) to dissociate preformed complexes of OsExo70F2 with host RPM1 INTERACTING PROTEIN4 (RIN4) at the conserved NOI motif, facilitating a possible virulence function. Second, we show that in its resting state, Pii2 binds OsExo70F2 and OsExo70F3, essential components of Pii-mediated resistance, through its integrated NOI domain. Remarkably, AVR-Pii binding to OsExo70F2/F3 leads to dissociation of the Pii2–OsExo70F2 and Pii2–OsExo70F3 complexes, destabilization of Pii2, and activation of immunity. These findings support a novel conceptual model in which an NLR-ID monitors alterations of tethered host proteins targeted by pathogen effectors, providing insight into pathogen recognition mechanisms.

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