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<p>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 <i>OsSPPL1/2</i> 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 <i>floury-2</i> 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, <i>OsSPPL1/2</i> double mutants exhibit exaggerated thermal sensitivity, while <i>OsSPPL1/2</i>-overexpressing plants display improved thermotolerance. Together, our findings identify OsSPPL1/2 as components of ERAD and highlight the importance of ERAD in plant thermotolerance.</p>

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Signal peptide peptidase-like proteases OsSPPL1 and OsSPPL2 facilitate ER-associated protein degradation in rice

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月7日

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  • Hai-Ping Lu,
  • Jian-Hang Xu,
  • Jia-Xin Chang,
  • Hui-Dan Luo,
  • Jian-Xiang Liu

摘要

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.