Signal peptide peptidase-like proteases OsSPPL1 and OsSPPL2 facilitate ER-associated protein degradation in rice.
Signal peptide peptidase-like proteases just got a big moment in the spotlight, thanks to new research on rice. The study zeroes in on OsSPPL1 and OsSPPL2, two plant proteases with a clear job: helping cells clear out misfolded proteins in the endoplasmic reticulum (ER). If you’re tracking how plants manage stress and maintain protein quality, these results add some fresh clarity.
Nat Commun
by Lu HP, Xu JH, Chang JX et al.
“Signal peptide peptidase-like proteases OsSPPL1 and OsSPPL2 facilitate ER-associated protein degradation in rice. Lu HP(1)(2), Xu JH(3), Chang JX(3), Luo HD(3), Liu JX(4)(5). Author information: (1)State Key Laboratory of Plant Environmental Resilience, College of Life Sciences, Zhejiang University, Hangzhou, China. luhaiping@zju.edu.cn. (2)BLSA-ZJU Research Center, Zhejiang University, Hangzhou, China. luhaiping@zju.edu.cn. (3)State Key Laboratory of Plant Environmental Resilience, College of Life Sciences, Zhejiang University, Hangzhou, China. (4)State Key Laboratory of Plant Environmental Resilience, College of Life Sciences, Zhejiang University, Hangzhou, China. jianxiangliu@zju.edu.cn. (5)BLSA-ZJU Research Center, Zhejiang University, Hangzhou, China. jianxiangliu@zju.edu.cn. 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. © 2026. The Author(s). Conflict of interest statement: Competing interests: The authors declare that they have no competing interests.”
Here’s what matters. OsSPPL1 and OsSPPL2 get switched on by the stress-response regulator OsbZIP50. When these proteases are out of commission—mutated or knocked out—rice plants get hammered by ER stress. Flip side: overexpressing them means the plants handle ER stress better, and the effect is real enough to boost thermotolerance. That means these proteases aren’t just cleaning up the ER—they’re directly tied to how plants survive heat.
Key findings:
OsSPPL1/2 live in the ER and partner with known ER-associated degradation (ERAD) players OsDER1/2.
They interact directly with a model misfolded protein (ZmFL2m-GFP), speeding up its breakdown.
Double mutants are more sensitive to heat, while overexpressers shrug it off.
Why should peptide researchers care? This is another strong example of how signal peptide processing and ERAD machinery aren’t just passive background functions. They’re actively shaping how cells respond to environmental stress. If you work with plant peptides or are interested in protein quality control, this is a solid clue to dig deeper.
For more on advances like this, check out the peptide research index—the field is moving fast, especially in plant systems. The takeaway: smarter use of peptide-related pathways could mean tougher, more resilient crops. That’s worth watching.
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