Phytophthora infection signals‐induced translocation of NAC089 is required for endoplasmic reticulum stress response‐mediated plant immunity

SUMMARY Plants deploy various immune receptors to recognize pathogen‐derived extracellular signals and subsequently activate the downstream defense response. Recently, increasing evidence indicates that the endoplasmic reticulum (ER) plays a part in the plant defense response, known as ER stress‐mediated immunity (ERSI), that halts pathogen infection. However, the mechanism for the ER stress response to signals of pathogen infection remains unclear. Here, we characterized the ER stress response regulator NAC089, which was previously reported to positively regulate programed cell death (PCD), functioning as an ERSI regulator. NAC089 translocated from the ER to the nucleus via the Golgi in response to Phytophthora capsici culture filtrate (CF), which is a mixture of pathogen‐associated molecular patterns (PAMPs). Plasma membrane localized co‐receptor BRASSINOSTEROID INSENSITIVE 1‐associated receptor kinase 1 (BAK1) was required for the CF‐mediated translocation of NAC089. The nuclear localization of NAC089, determined by the NAC domain, was essential for immune activation and PCD. Furthermore, NAC089 positively contributed to host resistance against the oomycete pathogen P. capsici and the bacteria pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. We also proved that NAC089‐mediated immunity is conserved in Nicotiana benthamiana. Together, we found that PAMP signaling induces the activation of ER stress in plants, and that NAC089 is required for ERSI and plant resistance against pathogens. Significance Statement Plants recognize extracellular pathogen PAMPs and activate the ER stress response and ERSI as a defense barrier. We identified NAC089 as an ERSI regulator, which its ER‐to‐nucleus signal pathway contributes to plant resistance against pathogens.