Chloroplast ribonucleoprotein CP31A is required for editing and stability of specific chloroplast mRNAs
Chloroplast ribonucleoprotein CP31A is required for editing and stability of specific chloroplast mRNAs
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DOI：
10.1073/pnas.0808529106
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发表时间：
2009-04-07
影响因子：
11.1
通讯作者：
Schmitz-Linneweber, Christian
中科院分区：
文献类型：
--
作者：
Tillich, Michael;Hardel, Simone L.;Schmitz-Linneweber, Christian
叶绿体核糖核蛋白 (cpRNP) 是核编码、高丰度、光调节的 RNA 结合蛋白。它们已被证明参与叶绿体 RNA 的体外加工和稳定，并且在系统发育上与已充分描述的异质核核糖核蛋白 (hnRNP) 相关。 cpRNP 被发现与叶绿体中存在的 mRNA 相关，并被认为是叶绿体转录物的非特异性稳定剂。在这里，我们证明 cpRNP 家族成员 CP31A 的无效突变体在叶绿体 RNA 代谢中表现出高度特异性和多样化的缺陷。首先，对 cp31a 和 cp31a/cp31b 双突变体的分析发现，这两个旁系同源基因以组合方式非冗余地参与体内叶绿体编辑位点子集的处理。其次，对 cp31a 突变体中叶绿体转录物积累的全基因组分析发现，叶绿体 ndhF mRNA 几乎完全丧失，而特定其他 mRNA 的减少程度较小。荧光分析表明，NADH 脱氢酶复合物（还包括 NdhF 亚基）的活性在 cp31a 突变体中存在缺陷。这表明 cpRNP 在体内对于校准特定叶绿体 mRNA 的表达水平并影响叶绿体生理学非常重要。总而言之，所揭示的 cpRNP 功能的特异性和组合方面表明这些叶绿体蛋白是核胞质 hnRNP 的功能等价物。
Chloroplast ribonucleoproteins (cpRNPs) are nuclear-encoded, highly abundant, and light-regulated RNA binding proteins. They have been shown to be involved in chloroplast RNA processing and stabilization in vitro and are phylogenetically related to the well-described heterogeneous nuclear ribonucleoproteins (hnRNPs). cpRNPs have been found associated with mRNAs present in chloroplasts and have been regarded as nonspecific stabilizers of chloroplast transcripts. Here, we demonstrate that null mutants of the cpRNP family member CP31A exhibit highly specific and diverse defects in chloroplast RNA metabolism. First, analysis of cp31a and cp31a/cp31b double mutants uncovers that these 2 paralogous genes participate nonredundantly in a combinatorial fashion in processing a subset of chloroplast editing sites in vivo. Second, a genome-wide analysis of chloroplast transcript accumulation in cp31a mutants detected a virtually complete loss of the chloroplast ndhF mRNA and lesser reductions for specific other mRNAs. Fluorescence analyses show that the activity of the NADH dehydrogenase complex, which also includes the NdhF subunit, is defective in cp31a mutants. This indicates that cpRNPs are important in vivo for calibrating the expression levels of specific chloroplast mRNAs and impact chloroplast physiology. Taken together, the specificity and combinatorial aspects of cpRNP functions uncovered suggest that these chloroplast proteins are functional equivalents of nucleocytosolic hnRNPs.