Regulation of Chloroplast Protein Import by the Ubiquitin E3 Ligase SP1 Is Important for Stress Tolerance in Plants.
Regulation of Chloroplast Protein Import by the Ubiquitin E3 Ligase SP1 Is Important for Stress Tolerance in Plants.
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DOI：
10.1016/j.cub.2015.08.015
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发表时间：
2015-10-05
期刊：
影响因子：
--
通讯作者：
Jarvis P
中科院分区：
文献类型：
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作者：
Ling Q;Jarvis P
叶绿体是植物中负责光合作用的细胞器。叶绿体蛋白质组由大约3000种不同的蛋白质组成，包括光合装置的成分，数量非常丰富。大多数叶绿体蛋白是核编码的，在细胞质中合成后输入。这种输入是由围绕每个细胞器的包膜中的多蛋白复合物介导的。叶绿体外包膜上的易位介导了客户蛋白的识别和早期输入。TOC装置受泛素-蛋白酶体系统（UPS）的调控，该过程受ppi1locus1的包膜定位泛素E3连接酶抑制子（SP1）的控制。先前的研究表明，sp1介导的叶绿体蛋白进口调控有助于植物发育过程中（如去黄化过程中）发生的细胞器蛋白质组变化。在这里，我们揭示了SP1在植物响应非生物胁迫中的关键作用，非生物胁迫是全球农业产量损失的主要和日益增加的原因。缺乏SP1的拟南芥植物对盐、渗透和氧化胁迫敏感，而过表达SP1的植物比野生型更具耐受性。我们提供的证据表明，SP1在胁迫条件下耗尽TOC装置，限制光合装置成分的进口，这可能会减弱光合活性，减少活性氧产生和光氧化损伤的可能性。我们的研究结果表明，叶绿体蛋白的输入是对环境信号的响应，实现了细胞器蛋白质组的动态调节，并为提高作物的抗逆性提供了新的途径。叶绿体E3连接酶SP1的水平影响植物的非生物胁迫耐受性SP1对胁迫耐受性的影响与活性氧水平有关SP1在胁迫下消耗叶绿体蛋白质进口（TOC）机制SP1消耗TOC与叶绿体光合作用蛋白进口减少有关非生物胁迫对植物的有害影响是光氧化，与光合作用机制产生的活性氧（ROS）过剩有关。Ling和Jarvis表明E3连接酶SP1通过消耗叶绿体蛋白质输入装置来促进胁迫耐受性，这限制了光系统组装和ROS形成的潜力。
Chloroplasts are the organelles responsible for photosynthesis in plants. The chloroplast proteome comprises ∼3,000 different proteins, including components of the photosynthetic apparatus, which are highly abundant. Most chloroplast proteins are nucleus-encoded and imported following synthesis in the cytosol. Such import is mediated by multiprotein complexes in the envelope membranes that surround each organelle. The translocon at the outer envelope membrane of chloroplasts (TOC) mediates client protein recognition and early stages of import. The TOC apparatus is regulated by the ubiquitin-proteasome system (UPS) in a process controlled by the envelope-localized ubiquitin E3 ligase SUPPRESSOR OF PPI1 LOCUS1 (SP1). Previous work showed that SP1-mediated regulation of chloroplast protein import contributes to the organellar proteome changes that occur during plant development (e.g., during de-etiolation). Here, we reveal a critical role for SP1 in plant responses to abiotic stress, which is a major and increasing cause of agricultural yield losses globally. Arabidopsis plants lacking SP1 are hypersensitive to salt, osmotic, and oxidative stresses, whereas plants overexpressing SP1 are considerably more stress tolerant than wild-type. We present evidence that SP1 acts to deplete the TOC apparatus under stress conditions to limit the import of photosynthetic apparatus components, which may attenuate photosynthetic activity and reduce the potential for reactive oxygen species production and photo-oxidative damage. Our results indicate that chloroplast protein import is responsive to environmental cues, enabling dynamic regulation of the organellar proteome, and suggest new approaches for improving stress tolerance in crops. Levels of the chloroplast E3 ligase SP1 influence plant abiotic stress tolerance Effects of SP1 on stress tolerance are linked to reactive oxygen species levels SP1 acts to deplete the chloroplast protein import (TOC) machinery under stress TOC depletion by SP1 is linked to reduced plastid import of photosynthesis proteins A harmful effect of abiotic stress in plants is photo-oxidation linked to overproduction of reactive oxygen species (ROS) by the photosynthetic machinery. Ling and Jarvis show that the E3 ligase SP1 promotes stress tolerance by depleting the chloroplast protein import apparatus, which limits photosystem assembly and the potential for ROS formation.