Investigating the roles of Arabidopsis STIC1 and STIC2 in chloroplast protein transport

研究拟南芥 STIC1 和 STIC2 在叶绿体蛋白转运中的作用

• 批准号: BB/J009369/1
• 负责人: Paul Jarvis
• 金额: $ 51.28万
• 依托单位: University of Leicester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FJ009369%2F1
• 关键词: Investigating; roles; Arabidopsis; STIC1; STIC2

Chloroplasts and mitochondria are normal components of many cells - they are sub-cellular structures called organelles. Interestingly, these two organelles evolved from bacteria that were engulfed by other cells over a billion years ago, and in many ways they still resemble free-living bacteria. Chloroplasts are found in plant cells, contain the green pigment chlorophyll, and are responsible for the reactions of photosynthesis (the process that captures sunlight energy and uses it to make sugars). As photosynthesis is the only significant mechanism of energy-input into the living world, chloroplasts are of inestimable importance, not just to plants but to all life on Earth. Chloroplasts are also important in many other ways, as they play essential roles in the synthesis of oils, proteins and starch. Although chloroplasts do contain DNA (a relic from their evolutionary past as free-living photosynthetic bacteria), and so can make some of their own proteins, >90% of the 3000 proteins needed to build a fully-functional chloroplast are encoded on DNA in the cell nucleus. Thus, most chloroplast proteins are made outside of the organelle in the cellular matrix known as the cytosol. As chloroplasts are each surrounded by a double membrane, or envelope, that is impervious to the passive movement of proteins, this presents a significant problem. To overcome the problem, chloroplasts evolved a sophisticated protein import apparatus, which uses energy (in the form of ATP) to drive the import of proteins from the cytosol. This import apparatus comprises two molecular machines: one in the outer envelope membrane called TOC (an abbreviation of "Translocon at the outer envelope of chloroplasts"), and another in the inner envelope membrane called TIC. Each machine is made up of several proteins which cooperate to ensure the efficiency of import. One of the features of the TIC machine is that it recruits a special class of proteins from the chloroplast interior, or stroma, called "chaperones". These stromal chaperones act like a motor as they use the energy from ATP to drive protein import. We work on a model plant called Arabidopsis that has many advantages for research, such as an availability of numerous mutants (each one with a mutation in a specific gene). One such mutant plant, tic40, has a defect in a TIC gene such that chloroplast protein import does not work efficiently. Several years ago we identified other mutations called stic1 and stic2 (stic stands for "suppressor of tic40") which significantly improve protein import efficiency in tic40. Recently, we discovered which genes (and therefore which proteins) the stic mutations affect: STIC1 belongs to a family of well-known protein transport factors that were not previously thought to act in the chloroplast envelope, while STIC2 is related to a group of bacterial proteins of unknown function. Interestingly, we have shown that STIC2 can bind to STIC1, as well to stromal chaperones and the TIC machine. Thus, we believe that STIC2 may be a new component of the aforementioned import motor. It may also help to guide newly-imported proteins from the TIC apparatus to their final destination, which is perhaps where STIC1 plays its role. We will do experiments to test these theories. As chloroplasts carry out essential functions, and because protein import is essential for chloroplast development, it is not surprising that plants without a functional chloroplast protein import machinery are unable to survive (in fact, they die as embryos). Similarly, as we are all ultimately dependent upon plant products for survival, it follows that chloroplast protein import is essential on a global scale. As chloroplasts play major roles in the synthesis of many economically important products (e.g., oils, starch), a better understanding of how these organelles develop will enable us to enhance the productivity of crop plants or otherwise manipulate their products.

叶绿体和线粒体是许多细胞的正常组成部分 - 它们是称为细胞器的亚细胞结构。有趣的是，这两种细胞器是从十亿多年前被其他细胞吞噬的细菌进化而来的，并且在许多方面它们仍然类似于自由生活的细菌。叶绿体存在于植物细胞中，含有绿色色素叶绿素，负责光合作用（捕获阳光能量并利用其制造糖的过程）的反应。由于光合作用是向生命世界输入能量的唯一重要机制，叶绿体不仅对植物而且对地球上的所有生命都具有不可估量的重要性。叶绿体在许多其他方面也很重要，因为它们在油、蛋白质和淀粉的合成中发挥着重要作用。尽管叶绿体确实含有 DNA（作为自由生活的光合细菌的进化过程中的遗物），因此可以制造一些自己的蛋白质，但构建全功能叶绿体所需的 3000 种蛋白质中，90% 以上都是由 DNA 编码的细胞核。因此，大多数叶绿体蛋白是在细胞器外部的细胞基质（称为胞质溶胶）中产生的。由于每个叶绿体都被双层膜或包膜包围，而蛋白质的被动运动不受其影响，因此这提出了一个重大问题。为了克服这个问题，叶绿体进化出了一种复杂的蛋白质输入装置，它使用能量（以 ATP 的形式）来驱动从细胞质中输入蛋白质。该输入装置包括两个分子机器：一个位于外被膜中，称为 TOC（“叶绿体外膜 Translocon”的缩写），另一个位于内被膜中，称为 TIC。每台机器都是由多种蛋白质组成，它们相互配合，保证导入的效率。 TIC 机器的特点之一是它从叶绿体内部或基质中招募一类特殊的蛋白质，称为“伴侣”。这些基质伴侣就像发动机一样，利用 ATP 的能量来驱动蛋白质输入。我们研究一种名为拟南芥的模型植物，它对研究具有许多优势，例如可以获得大量突变体（每个突变体都具有特定基因的突变）。其中一种突变植物 tic40 的 TIC 基因存在缺陷，导致叶绿体蛋白导入无法有效进行。几年前，我们发现了其他称为 stic1 和 stic2 的突变（stic 代表“tic40 的抑制子”），它们显着提高了 tic40 中的蛋白质导入效率。最近，我们发现了 stic 突变影响哪些基因（以及哪些蛋白质）：STIC1 属于一个众所周知的蛋白质转运因子家族，以前认为这些因子不会在叶绿体包膜中发挥作用，而 STIC2 与一组细菌相关功能未知的蛋白质。有趣的是，我们已经证明 STIC2 可以与 STIC1 结合，也可以与基质伴侣和 TIC 机器结合。因此，我们认为STIC2可能是上述进口电机的新部件。它还可能有助于引导新导入的蛋白质从 TIC 装置到达最终目的地，这可能就是 STIC1 发挥作用的地方。我们将做实验来检验这些理论。由于叶绿体执行基本功能，并且蛋白质输入对于叶绿体发育至关重要，因此没有功能性叶绿体蛋白质输入机制的植物无法生存（事实上，它们作为胚胎而死亡）也就不足为奇了。同样，由于我们最终都依赖植物产品生存，因此叶绿体蛋白的进口在全球范围内至关重要。由于叶绿体在许多重要经济产品（例如油、淀粉）的合成中发挥着重要作用，因此更好地了解这些细胞器的发育方式将使我们能够提高农作物的生产力或以其他方式操纵其产品。

项目成果

Supplementary tables and figures from Retrograde signalling in a virescent mutant triggers an anterograde delay of chloroplast biogenesis that requires GUN1 and is essential for survival

绿色突变体中逆行信号传导的补充表格和数据触发叶绿体生物发生的顺行延迟，这需要 GUN1，并且对于生存至关重要

• DOI: 10.6084/m9.figshare.12095826
• 发表时间: 2020
• 作者: Loudya N

Functional Analysis of the Hsp93/ClpC Chaperone at the Chloroplast Envelope

• DOI: 10.1104/pp.15.01538
• 发表时间: 2016-01-01
• 期刊: PLANT PHYSIOLOGY
• 影响因子: 7.4
• 作者: Flores-Perez, Ursula;Bedard, Jocelyn;Jarvis, Paul
• 通讯作者: Jarvis, Paul

Mutations in TIC100 impair and repair chloroplast protein import and impact retrograde signalling

TIC100 突变损害和修复叶绿体蛋白输入并影响逆行信号传导

• DOI: 10.1101/2022.01.18.476798
• 发表时间: 2022
• 作者: Loudya N

Evolutionary, molecular and genetic analyses of Tic22 homologues in Arabidopsis thaliana chloroplasts.

• DOI: 10.1371/journal.pone.0063863
• 发表时间: 2013
• 期刊: PloS one
• 影响因子: 3.7
• 作者: Kasmati AR;Töpel M;Khan NZ;Patel R;Ling Q;Karim S;Aronsson H;Jarvis P
• 通讯作者: Jarvis P

Mutations in the chloroplast inner envelope protein TIC100 impair and repair chloroplast protein import and impact retrograde signaling.

• DOI: 10.1093/plcell/koac153
• 发表时间: 2022-07-30
• 期刊: The Plant cell