Unfolded Protein Response signaling restricts PTI and limits salicylic acid-dependent cell death under ER stress
- 1Institute of Experimental Botany of the Czech Academy of Sciences, Rozvojova 263, 165 02, Prague 6, Czech Republic
Abstract
The Unfolded Protein Response (UPR) maintains endoplasmic reticulum (ER) homeostasis during proteotoxic stress while also contributing to plant immunity. However, the functional relationship between UPR signaling, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and salicylic acid (SA) remains poorly understood. Here, we investigated this interplay using Arabidopsis mutants impaired in the two major UPR branches. Mutants defective in the INOSITOL-REQUIRING ENZYME 1 (IRE1)-bZIP60 branch displayed enhanced resistance to Pseudomonas syringae pv. tomato DC3000 and to the type III secretion-deficient strain hrcC-, indicating potentiation of PTI. Consistently, the ire1a ire1b double mutant exhibited increased flg22-induced callose deposition, whereas reactive oxygen species production was unaffected. Despite enhanced basal resistance, all UPR mutants retained full responsiveness to benzothiadiazole, demonstrating that downstream SA signaling remains functional independently of UPR integrity. Conversely, acute ER stress induced by tunicamycin promoted SA accumulation and extensive leaf necrosis. Reverse genetics revealed that SA-deficient mutants were largely protected from ER stress-induced cell death, whereas mutants over-accumulating SA exhibited enhanced susceptibility, demonstrating that endogenous SA is required for the full execution of this response. Analysis of an independent transcriptomic dataset further showed that loss of IRE1 de-represses genes involved in SA biosynthesis, PTI and defense under ER stress. Together, our results identify IRE1 as a key regulator coordinating ER homeostasis with immune signaling by limiting SA-dependent defense activation during ER stress, while simultaneously preventing excessive cell death.
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BibTeX
@misc{cehulova2026unfolded,
title = {{Unfolded Protein Response signaling restricts PTI and limits salicylic acid-dependent cell death under ER stress}},
author = {V. Cehulova and A. Antonova and H. Leontovycova and L. Burketova and A. Ducloy and M. Azzopardi and J.-L. Cacas and T. Kalachova},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.02.755983},
url = {https://www.biorxiv.org/content/10.64898/2026.10.02.755983v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Unfolded Protein Response signaling restricts PTI and limits salicylic acid-dependent cell death under ER stress
AU - V. Cehulova
AU - A. Antonova
AU - H. Leontovycova
AU - L. Burketova
AU - A. Ducloy
AU - M. Azzopardi
AU - J.-L. Cacas
AU - T. Kalachova
PY - 2026
DA - 2026/10/02
PB - bioRxiv
DO - 10.64898/2026.10.02.755983
UR - https://www.biorxiv.org/content/10.64898/2026.10.02.755983v1
AB - The Unfolded Protein Response (UPR) maintains endoplasmic reticulum (ER) homeostasis during proteotoxic stress while also contributing to plant immunity. However, the functional relationship between UPR signaling, pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and salicylic acid (SA) remains poorly understood. Here, we investigated this interplay using Arabidopsis mutants impaired in the two major UPR branches. Mutants defective in the INOSITOL-REQUIRING ENZYME 1 (IRE1)-bZIP60 branch displayed enhanced resistance to Pseudomonas syringae pv. tomato DC3000 and to the type III secretion-deficient strain hrcC-, indicating potentiation of PTI. Consistently, the ire1a ire1b double mutant exhibited increased flg22-induced callose deposition, whereas reactive oxygen species production was unaffected. Despite enhanced basal resistance, all UPR mutants retained full responsiveness to benzothiadiazole, demonstrating that downstream SA signaling remains functional independently of UPR integrity. Conversely, acute ER stress induced by tunicamycin promoted SA accumulation and extensive leaf necrosis. Reverse genetics revealed that SA-deficient mutants were largely protected from ER stress-induced cell death, whereas mutants over-accumulating SA exhibited enhanced susceptibility, demonstrating that endogenous SA is required for the full execution of this response. Analysis of an independent transcriptomic dataset further showed that loss of IRE1 de-represses genes involved in SA biosynthesis, PTI and defense under ER stress. Together, our results identify IRE1 as a key regulator coordinating ER homeostasis with immune signaling by limiting SA-dependent defense activation during ER stress, while simultaneously preventing excessive cell death.
ER -