Pfannschmidt Thomas, Liere Karsten
Department for General Botany and Plant Physiology, Friedrich-Schiller-University Jena, Jena, Germany.
Antioxid Redox Signal. 2005 May-Jun;7(5-6):607-18. doi: 10.1089/ars.2005.7.607.
Chloroplasts are typical organelles of plant cells and represent the site of photosynthesis. As one very remarkable feature, they possess their own genome and a complete machinery to express the genetic information in it. The plastid gene expression machinery is a unique assembly of prokaryotic-, eukaryotic-, and phage-like components because chloroplasts acquired a great number of regulatory proteins during evolution. Such proteins can be found at all levels of gene expression. They significantly expand the functional and especially the regulatory properties of the "old" gene expression system that chloroplasts inherited from their prokaryotic ancestors. Recent results show that photosynthesis has a strong regulatory effect on plastid gene expression. The redox states of electron transport components, redox-active molecules coupled to photosynthesis, and pools of reactive oxygen species act as redox signals. They provide a functional feedback control, which couples the expression of chloroplast genes to the actual function of photosynthesis and, by this means, helps to acclimate the photosynthetic process to environmental cues. The redox signals are mediated by various specific signaling pathways that involve many of the "new" regulatory proteins. Chloroplasts therefore are an ideal model to study redox-regulated mechanisms in gene expression control. Because of the multiple origins of the expression machinery, these observations are of great relevance for many other biological systems.
叶绿体是植物细胞的典型细胞器，是光合作用的场所。其一个非常显著的特征是，它们拥有自己的基因组以及一套完整的机制来表达其中的遗传信息。质体基因表达机制是原核、真核和噬菌体样成分的独特组合，因为叶绿体在进化过程中获得了大量调控蛋白。这些蛋白可在基因表达的各个层面找到。它们显著扩展了叶绿体从原核祖先那里继承而来的 “古老” 基因表达系统的功能，尤其是调控特性。最近的研究结果表明，光合作用对质体基因表达具有强烈的调控作用。电子传递成分的氧化还原状态、与光合作用相关的氧化还原活性分子以及活性氧物质库作为氧化还原信号。它们提供了一种功能性反馈控制，将叶绿体基因的表达与光合作用的实际功能联系起来，从而有助于使光合过程适应环境线索。氧化还原信号由涉及许多 “新” 调控蛋白的各种特定信号通路介导。因此，叶绿体是研究基因表达控制中氧化还原调节机制的理想模型。由于表达机制的多种起源，这些观察结果对许多其他生物系统具有重要意义。
