Abstract
Signal peptide peptidases (SPPs) play a critical role in intramembrane proteolysis of signal peptides in mammals. However, their function in plants remains poorly understood. Here, we uncover the critical role of two rice SPP-like proteins, OsSPPL1/ 2, in ER-associated degradation (ERAD). Their expression is directly upregulated by OsbZIP50 under ER stress conditions. Mutations in OsSPPL1/2 result in increased ER stress sensitivity, whereas their overexpression enhance ER stress tolerance. We further demonstrate that OsSPPL1/2 localize in ER, and physically interact with the ERAD components OsDER1/2, indicating their involvement in ERAD. Using a GFP protein fused with a segment of maize floury-2 protein defective in signal peptide cleavage (ZmFL2m-GFP), we show that OsSPPL1/2 interact with ZmFL2m-GFP in ER and facilitate its degradation in tobacco leaves and rice plants. Additionally, OsSPPL1/2 double mutants exhibit exaggerated thermal sensitivity, while OsSPPL1/2-overexpressing plants display improved thermotolerance. Together, our findings identify OsSPPL1/2 as components of ERAD and highlight the importance of ERAD in plant thermotolerance.
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Acknowledgements
The authors would like to thank Dr. Lianguang Shang at AGIS for sharing the genomic data. Funding: This project was financially supported by grants from the National Key R&D Program of China (2022YFF1001603, J.-X.L), National Natural Science Foundation of China (32570331, H.-P.L), and Open Research Project of State Key Laboratory of Crop Germplasm Innovation and Molecular Breeding (J.-X.L).
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Lu, HP., Xu, JH., Chang, JX. et al. Signal peptide peptidase-like proteases OsSPPL1 and OsSPPL2 facilitate ER-associated protein degradation in rice. Nat Commun (2026). https://doi.org/10.1038/s41467-026-72830-w
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DOI: https://doi.org/10.1038/s41467-026-72830-w
