The Modern Facilities Horticultural Engineering Technology Center, Shenyang Agricultural University, Shenyang 110866, China; The Key Laboratory of Protected Horticulture, Ministry of Education, Shenyang 110866, China; Yazhouwan National Laboratory, Sanya 572024, China.
Key Laboratory of Agriculture Biotechnology, College of Biosciences and Biotechnology, Shenyang Agricultural University, Shenyang 110866, China.
Cell Rep. 2024 Oct 22;43(10):114757. doi: 10.1016/j.celrep.2024.114757. Epub 2024 Sep 19.
PsbS protein is essential for the rapid induction of non-photochemical quenching (NPQ) under low night temperatures (LNTs), but its stability is often affected by adverse environmental conditions. However, the regulatory mechanism for the stability of PsbS or chloroplast proteins remains to be fully characterized. We show that LNT decreases NPQ levels and SlPsbS protein abundance in tomato leaves. LNT-activated chloroplast vesicles (SlCVs) targeting the chloroplasts induce the formation of CV-containing vesicles (CCVs) containing SlPsbS, exported from the chloroplasts. Subsequently, SlCV and SlPsbS contact COP9 signalosome subunit 5A (SlCSN5A) in the cytosol and are ubiquitinated and degraded. Genetic evidence demonstrates that the overexpression of SlCV aggravates SlPsbS protein degradation, whereas silencing of SlCSN5 and SlCV delays LNT-induced NPQ reduction and SlPsbS protein turnover. This study reveals a ubiquitin-dependent degradation pathway of chloroplast proteins co-mediated by CV and CSN5A, thereby providing a basic reference for the regulation of chloroplast protein stability under stress conditions.
PsbS 蛋白对于低温下（LNTs）非光化学猝灭（NPQ）的快速诱导至关重要，但它的稳定性常常受到不利环境条件的影响。然而，PsbS 或叶绿体蛋白稳定性的调控机制仍有待充分阐明。我们发现，LNT 降低了番茄叶片中的 NPQ 水平和 SlPsbS 蛋白丰度。靶向叶绿体的 LNT 激活的叶绿体囊泡（SlCVs）诱导形成含有 SlPsbS 的囊泡（CCVs），这些囊泡从叶绿体中被输出。随后，SlCV 和 SlPsbS 在细胞质中与 COP9 信号体亚基 5A（SlCSN5A）接触，并被泛素化和降解。遗传证据表明，SlCV 的过表达加剧了 SlPsbS 蛋白的降解，而 SlCSN5 和 SlCV 的沉默则延迟了 LNT 诱导的 NPQ 降低和 SlPsbS 蛋白周转。本研究揭示了叶绿体蛋白的一种依赖泛素的降解途径，该途径由 CV 和 CSN5A 共同介导，从而为胁迫条件下叶绿体蛋白稳定性的调控提供了基本参考。
