A Major Role for the Plastid-Encoded RNA Polymerase Complex in the Expression of Plastid Transfer RNAs1[W][OPEN]
A Major Role for the Plastid-Encoded RNA Polymerase Complex in the Expression of Plastid Transfer RNAs1[W][OPEN]
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DOI：
10.1104/pp.113.228726
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发表时间：
2013-11
期刊：
影响因子：
7.4
通讯作者：
R. Williams-Carrier;Reimo Zoschke;Susan Belcher;J. Pfalz;A. Barkan
中科院分区：
文献类型：
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作者：
R. Williams-Carrier;Reimo Zoschke;Susan Belcher;J. Pfalz;A. Barkan
与叶绿体编码的RNA聚合酶相关的蛋白质是大量叶绿体tRNAs强健表达所必需的。陆地植物的叶绿体转录依赖于蓝藻祖先的叶绿体编码的RNA聚合酶(PEP)和噬菌体祖先的核编码的RNA聚合酶之间的协作。PEP与其他与细菌转录因子无关的蛋白质结合，其中许多蛋白质已被证明对拟南芥的PEP活性具有重要作用。然而，这些PEP相关蛋白的生化作用尚不清楚。我们描述了在编码玉米(Zea Mays)五种蛋白质ZmPTAC2、ZmMurE、ZmPTAC10、ZmPTAC12和ZmPRIN2的同源基因中插入转座子的表型。这些突变体具有类似的象牙/绿色色素，以及类似的叶绿体核糖体和光合作用复合体的减少。RNA凝胶印迹和微阵列杂交显示，在叶绿体转录体群体中发生了大量的变化，其中许多与已报道的拟南芥中的同源突变体相似。然而，大量转移RNA(TRNAs)丰度的意外减少主导了微阵列数据，并在RNA凝胶印迹中得到了验证。一些tRNA的缺失程度与受影响最严重的信使RNA相似，其中trnL-UAA的缺失尤为严重。这些发现表明，PEP及其相关蛋白对于许多叶绿体tRNA的强劲转录至关重要，并且这一功能对于光合作用装置安装过程中所需的叶绿体编码蛋白的大量翻译是必不可少的。
Proteins that associate with the plastid-encoded RNA polymerase are required for robust expression of numerous plastid tRNAs. Chloroplast transcription in land plants relies on collaboration between a plastid-encoded RNA polymerase (PEP) of cyanobacterial ancestry and a nucleus-encoded RNA polymerase of phage ancestry. PEP associates with additional proteins that are unrelated to bacterial transcription factors, many of which have been shown to be important for PEP activity in Arabidopsis (Arabidopsis thaliana). However, the biochemical roles of these PEP-associated proteins are not known. We describe phenotypes conditioned by transposon insertions in genes encoding the maize (Zea mays) orthologs of five such proteins: ZmPTAC2, ZmMurE, ZmPTAC10, ZmPTAC12, and ZmPRIN2. These mutants have similar ivory/virescent pigmentation and similar reductions in plastid ribosomes and photosynthetic complexes. RNA gel-blot and microarray hybridizations revealed numerous changes in plastid transcript populations, many of which resemble those reported for the orthologous mutants in Arabidopsis. However, unanticipated reductions in the abundance of numerous transfer RNAs (tRNAs) dominated the microarray data and were validated on RNA gel blots. The magnitude of the deficiencies for several tRNAs was similar to that of the most severely affected messenger RNAs, with the loss of trnL-UAA being particularly severe. These findings suggest that PEP and its associated proteins are critical for the robust transcription of numerous plastid tRNAs and that this function is essential for the prodigious translation of plastid-encoded proteins that is required during the installation of the photosynthetic apparatus.