Teubner Marlene, Fuß Janina, Kühn Kristina, Krause Kirsten, Schmitz-Linneweber Christian
Humboldt-Universität Berlin, Institut für Biologie, Chausseestrasse 117, 10115, Berlin, Germany.
Department of Arctic and Marine Biology, UiT The Arctic University of Norway, Dramsvegen 201, 9037, Tromsø, Norway.
Plant J. 2017 Feb;89(3):472-485. doi: 10.1111/tpj.13396. Epub 2017 Jan 25.
Chloroplast RNA metabolism depends on a multitude of nuclear-encoded RNA-binding proteins (RBPs). Most known chloroplast RBPs address specific RNA targets and RNA-processing functions. However, members of the small chloroplast ribonucleoprotein family (cpRNPs) play a global role in processing and stabilizing chloroplast RNAs. Here, we show that the cpRNP CP33A localizes to a distinct sub-chloroplastic domain and is essential for chloroplast development. The loss of CP33A yields albino seedlings that exhibit aberrant leaf development and can only survive in the presence of an external carbon source. Genome-wide RNA association studies demonstrate that CP33A associates with all chloroplast mRNAs. For a given transcript, quantification of CP33A-bound versus free RNAs demonstrates that CP33A associates with the majority of most mRNAs analyzed. Our results further show that CP33A is required for the accumulation of a number of tested mRNAs, and is particularly relevant for unspliced and unprocessed precursor mRNAs. Finally, CP33A fails to associate with polysomes or to strongly co-precipitate with ribosomal RNA, suggesting that it defines a ribodomain that is separate from the chloroplast translation machinery. Collectively, these findings suggest that CP33A contributes to globally essential RNA processes in the chloroplasts of higher plants.
叶绿体RNA代谢依赖于众多核编码的RNA结合蛋白（RBPs）。大多数已知的叶绿体RBPs作用于特定的RNA靶标和RNA加工功能。然而，小叶绿体核糖核蛋白家族（cpRNPs）的成员在叶绿体RNA的加工和稳定中发挥着全局性作用。在此，我们表明cpRNP CP33A定位于叶绿体的一个独特亚结构域，并且对叶绿体发育至关重要。CP33A缺失会产生白化苗，这些白化苗表现出异常的叶片发育，并且只能在有外部碳源的情况下存活。全基因组RNA关联研究表明CP33A与所有叶绿体mRNA结合。对于给定的转录本，对CP33A结合的RNA与游离RNA进行定量分析表明，CP33A与大多数分析的mRNA的大部分结合。我们的结果进一步表明，CP33A是许多测试mRNA积累所必需的，并且对未剪接和未加工的前体mRNA尤为重要。最后，CP33A无法与多核糖体结合，也不能与核糖体RNA强烈共沉淀，这表明它定义了一个与叶绿体翻译机制分开的核糖结构域。总体而言，这些发现表明CP33A对高等植物叶绿体中全局必需的RNA过程有贡献。
