Present-day chloroplast and mitochondrial genomes contain only a few dozen genes involved in ATP synthesis, photosynthesis, and gene expression. The proteins encoded by these genes are only a small fraction of the many hundreds of proteins that act in chloroplasts and mitochondria. Hence, the vast majority, including components of organellar gene expression (OGE) machineries, are encoded by nuclear genes, translated into the cytosol and imported to these organelles. Consequently, the expression of nuclear and organellar genomes has to be very precisely coordinated. Furthermore, OGE regulation is crucial to chloroplast and mitochondria biogenesis, and hence, to plant growth and development. Notwithstanding, the molecular mechanisms governing OGE are still poorly understood. Recent results have revealed the increasing importance of nuclear-encoded modular proteins capable of binding nucleic acids and regulating OGE. Mitochondrial transcription termination factor (mTERF) proteins are a good example of this category of OGE regulators. Plant mTERFs are located in chloroplasts and/or mitochondria, and have been characterized mainly from the isolation and analyses of Arabidopsis and maize mutants. These studies have revealed their fundamental roles in different plant development aspects and responses to abiotic stress. Fourteen mTERFs have been hitherto characterized in land plants, albeit to a different extent. These numbers are limited if we consider that 31 and 35 mTERFs have been, respectively, identified in maize and Arabidopsis. Notwithstanding, remarkable progress has been made in recent years to elucidate the molecular mechanisms by which mTERFs regulate OGE. Consequently, it has been experimentally demonstrated that plant mTERFs are required for the transcription termination of chloroplast genes (mTERF6 and mTERF8), transcriptional pausing and the stabilization of chloroplast transcripts (MDA1/mTERF5), intron splicing in chloroplasts (BSM/RUG2/mTERF4 and Zm-mTERF4) and mitochondria (mTERF15 and ZmSMK3) and very recently, also in the assembly of chloroplast ribosomes and translation (mTERF9). This review aims to provide a detailed update of current knowledge about the molecular functions of plant mTERF proteins. It principally focuses on new research that has made an outstanding contribution to unravel the molecular mechanisms by which plant mTERFs regulate the expression of chloroplast and mitochondrial genomes.

中文翻译：

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植物mTERF蛋白分子功能研究进展

当今的叶绿体和线粒体基因组仅包含几十个参与 ATP 合成、光合作用和基因表达的基因。这些基因编码的蛋白质只是作用于叶绿体和线粒体的数百种蛋白质中的一小部分。因此，绝大多数，包括细胞器基因表达 (OGE) 机器的组件，由核基因编码，翻译到细胞质中并输入到这些细胞器中。因此，核和细胞器基因组的表达必须非常精确地协调。此外，OGE 调节对叶绿体和线粒体的生物发生至关重要，因此对植物的生长和发育也至关重要。尽管如此，控制 OGE 的分子机制仍然知之甚少。最近的结果表明，能够结合核酸和调节 OGE 的核编码模块蛋白的重要性日益增加。线粒体转录终止因子 (mTERF) 蛋白是此类 OGE 调节剂的一个很好的例子。植物 mTERF 位于叶绿体和/或线粒体中，主要通过分离和分析拟南芥和玉米突变体。这些研究揭示了它们在不同植物发育方面和对非生物胁迫的反应中的基本作用。迄今为止，已经在陆地植物中表征了 14 种 mTERF，尽管程度不同。如果我们认为分别在玉米和拟南芥中鉴定了 31 和 35 个 mTERF，那么这些数字是有限的. 尽管如此，近年来在阐明 mTERF 调节 OGE 的分子机制方面取得了显着进展。因此，实验证明植物 mTERF 是叶绿体基因（mTERF6 和 mTERF8）的转录终止、叶绿体转录物的转录暂停和稳定（MDA1/mTERF5）、叶绿体中的内含子剪接（BSM/RUG2/mTERF4 和Zm-mTERF4）和线粒体（mTERF15 和 ZmSMK3），最近也在叶绿体核糖体的组装和翻译（mTERF9）中。本综述旨在提供有关植物 mTERF 蛋白分子功能的最新知识的详细更新。