The NOI/RIN4 integrated domain of the rice NLR Pii-2 binds to OsExo70-F3, an accessory protein required for Pii-dependent resistance
K. FUJISAKI (1), Y. Abe (1), H. Saitoh (1), H. Kanzaki (1), H. Takagi (1), E. Kanzaki (1), A. Uemura (1), S. Kamoun (2), R. Terauchi (1) (1) Iwate Biotechnology Research Center, Japan; (2) The Sainsbury Laboratory, United Kingdom

A subset of plant NLR immune receptor proteins carry extraneous integrated domains (ID) that have been proposed to function as effector baits or decoys. To date, these NLR-integrated domains have been shown to bind a pathogen AVR effector. Here, we propose a hybrid model of AVR effector recognition by a NLR-ID receptor in which the integrated domain appears to sense a host protein targeted by the effector. Rice Exo70 protein OsExo70-F3 interacts with AVR-Pii, an avirulence effector of rice blast fungus, and is required for Pii-dependent resistance triggered by AVR-Pii. Exo70 is a member of exocyst complex regulating exocytosis pathway. However, in contrast of OsExo70-F3, knockdown of other members of exocyst complex did not affect Pii-dependent resistance, suggesting that the exocyst complex per se is not involved in activation of Pii. We discovered that OsExo70-F3 binds the C-terminal region of Pii-2. Remarkably, this region harbors the core motif (PxFGxW) of NOI domain that is also found in Arabidopsis RIN4 protein, which is targeted by several bacterial effectors. Mutations in the NOI core motif abrogated the interaction between OsExo70-F3 and Pii-2 indicating that the integrated NOI domain of Pii-2 is involved in recognition of AVR-Pii via OsExo70-F3. These findings indicate that NLR-integrated domains may function by detecting host proteins targeted by pathogen effectors. This also points to the NOI-Exo70 complex as a major target of plant pathogen effectors.

Abstract Number: C24-4, P17-651
Session Type: Concurrent