Institut Molekulare Botanik, Universität Ulm, D-89069 Ulm, Germany.
Plant Physiol. 2011 Nov;157(3):1430-9. doi: 10.1104/pp.111.181552. Epub 2011 Aug 29.
RNA PROCESSING FACTOR1 (RPF1) and RPF2 are pentatricopeptide repeat (PPR) proteins involved in 5' processing of different mitochondrial mRNAs in Arabidopsis (Arabidopsis thaliana). Both factors are highly similar to RESTORERS OF FERTILITY (RF), which are part of cytoplasmic male sterility/restoration systems in various plant species. These findings suggest a predominant role of RF-like PPR proteins in posttranscriptional 5' processing. To further explore the functions of this group of proteins, we examined a number of T-DNA lines carrying insertions in the corresponding PPR genes. This screening identified a nearly complete absence of mature ccmC transcripts in an At1g62930 T-DNA insertion line, a phenotype that could be restored by the introduction of the intact At1g62930 gene into the mutant. The insertion in this nuclear gene, which we now call RPF3, also leads to a severe reduction of the CcmC protein in mitochondria. The analysis of C24/rpf3-1 F2 hybrids lacking functional RPF3 genes revealed that this gene has less influence on the generation of the mature ccmC 5' transcript end derived from a distinct ccmC 5' upstream configuration found in mitochondrial DNAs from C24 and other accessions. These data show that a particular function of an RF-like protein is required only in connection with a distinct mtDNA configuration. Our new results further substantiate the fundamental role of RF-like PPR proteins in the posttranscriptional generation of plant mitochondrial 5' transcript termini.
RNA 加工因子 1（RPF1）和 RPF2 是五肽重复（PPR）蛋白，参与拟南芥（Arabidopsis thaliana）不同线粒体 mRNA 的 5' 加工。这两种因子与恢复育性的因子（RF）高度相似，RF 是各种植物种细胞质雄性不育/恢复系统的一部分。这些发现表明 RF 样 PPR 蛋白在转录后 5' 加工中起主要作用。为了进一步探索这组蛋白的功能，我们检查了许多携带相应 PPR 基因插入的 T-DNA 系。该筛选在一个 At1g62930 T-DNA 插入系中发现成熟的 ccmC 转录本几乎完全缺失，该表型可以通过将完整的 At1g62930 基因导入突变体来恢复。该核基因（我们现在称为 RPF3）中的插入也导致线粒体中 CcmC 蛋白的严重减少。对缺乏功能性 RPF3 基因的 C24/rpf3-1 F2 杂种的分析表明，该基因对源自 C24 和其他品系线粒体 DNA 中发现的独特 ccmC 5' 上游结构的成熟 ccmC 5' 转录本末端的产生影响较小。这些数据表明，RF 样蛋白的特定功能仅在与独特的 mtDNA 结构相关时才需要。我们的新结果进一步证实了 RF 样 PPR 蛋白在植物线粒体 5' 转录本末端转录后产生中的基本作用。
