Richter Uwe, Richter Björn, Weihe Andreas, Börner Thomas
Institut für Biologie-Genetik, Humboldt-Universität zu Berlin, Chausseestr. 117, 10115, Berlin, Germany.
Curr Genet. 2014 Feb;60(1):25-34. doi: 10.1007/s00294-013-0405-y. Epub 2013 Sep 12.
In most organisms, the mitochondrial genes are transcribed by RNA polymerases related to the single-subunit RNA polymerases of bacteriophages like T3 and T7. In flowering plants, duplication(s) of the RpoTm gene coding for the mitochondrial RNA polymerase (RPOTm) led to the evolution of additional RNA polymerases transcribing genes in plastids (RPOTp) or in both mitochondria and plastids (RPOTmp). Two putative RPOTmp enzymes were previously described to be encoded by the nuclear genes RpoTmp1 and RpoTmp2 in the moss Physcomitrella patens. Here, we report on a third Physcomitrella RpoT gene. We determined the sequence of the cDNA. Comparison of the deduced amino acid sequence with sequences of plant organellar RNA polymerases suggests that this gene encodes a functional phage-type RNA polymerase. The 78 N-terminal amino acids of the putative RNA polymerase were fused to GFP and found to target the fusion protein exclusively to mitochondria in Arabidopsis protoplasts. P. patens is the only known organism to possess three mitochondrial RNA polymerases.
在大多数生物体中，线粒体基因由与T3和T7等噬菌体的单亚基RNA聚合酶相关的RNA聚合酶转录。在开花植物中，编码线粒体RNA聚合酶（RPOTm）的RpoTm基因的重复导致了在质体（RPOTp）或线粒体和质体两者（RPOTmp）中转录基因的其他RNA聚合酶的进化。先前已描述在小立碗藓中，两种假定的RPOTmp酶由核基因RpoTmp1和RpoTmp2编码。在此，我们报道了小立碗藓的第三个RpoT基因。我们确定了cDNA的序列。将推导的氨基酸序列与植物细胞器RNA聚合酶的序列进行比较表明，该基因编码一种功能性噬菌体类型的RNA聚合酶。假定的RNA聚合酶的78个N端氨基酸与绿色荧光蛋白（GFP）融合，并发现该融合蛋白仅靶向拟南芥原生质体中的线粒体。小立碗藓是唯一已知拥有三种线粒体RNA聚合酶的生物体。
