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Proc Natl Acad Sci U S A. 2018 May 29;115(22):E5203-E5212. doi: 10.1073/pnas.1802254115. Epub 2018 May 14.

Salicylic acid-independent role of NPR1 is required for protection from proteotoxic stress in the plant endoplasmic reticulum.

Author information

1
Michigan State University-US Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824.
2
Cell and Molecular Biology Program, Michigan State University, East Lansing, MI 48824.
3
Plant Biology Department, Michigan State University, East Lansing, MI 48824.
4
Howard Hughes Medical Institute, Michigan State University, East Lansing, MI 48824.
5
Michigan State University-US Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824; fb@msu.edu.

Abstract

The unfolded protein response (UPR) is an ancient signaling pathway designed to protect cells from the accumulation of unfolded and misfolded proteins in the endoplasmic reticulum (ER). Because misregulation of the UPR is potentially lethal, a stringent surveillance signaling system must be in place to modulate the UPR. The major signaling arms of the plant UPR have been discovered and rely on the transcriptional activity of the transcription factors bZIP60 and bZIP28 and on the kinase and ribonuclease activity of IRE1, which splices mRNA to activate bZIP60. Both bZIP28 and bZIP60 modulate UPR gene expression to overcome ER stress. In this study, we demonstrate at a genetic level that the transcriptional role of bZIP28 and bZIP60 in ER-stress responses is antagonized by nonexpressor of PR1 genes 1 (NPR1), a critical redox-regulated master regulator of salicylic acid (SA)-dependent responses to pathogens, independently of its role in SA defense. We also establish that the function of NPR1 in the UPR is concomitant with ER stress-induced reduction of the cytosol and translocation of NPR1 to the nucleus where it interacts with bZIP28 and bZIP60. Our results support a cellular role for NPR1 as well as a model for plant UPR regulation whereby SA-independent ER stress-induced redox activation of NPR1 suppresses the transcriptional role of bZIP28 and bZIP60 in the UPR.

KEYWORDS:

NPR1; endoplasmic reticulum; salicylic acid; unfolded protein response

PMID:
29760094
PMCID:
PMC5984531
DOI:
10.1073/pnas.1802254115
[Indexed for MEDLINE]
Free PMC Article

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