Cytoplasmic male sterility (MS) in plants is caused by MS-inducing mitochondria, which have emerged frequently during plant evolution. Nuclear restorer-of-fertility (Rf)genes can suppress their cognate MS-inducing mitochondria. Whereas many Rfs encode a class of RNA-binding protein, the sugar beet (Caryophyllales) Rf encodes a protein resembling Oma1, which is involved in the quality control of mitochondria. In this study, we investigated the molecular evolution of Oma1 homologs in plants. We analyzed 37 plant genomes and concluded that a single copy is the ancestral state in Caryophyllales. Among the sugar beet Oma1 homologs, the orthologous copy is located in a syntenic region that is preserved in Arabidopsis thaliana. The sugar beet Rf is a complex locus consisting of a small Oma1 homolog family (RF-Oma1 family) unique to sugar beet. The gene arrangement in the vicinity of the locus is seen in some but not all Caryophyllalean plants and is absent from Ar. thaliana. This suggests a segmental duplication rather than a whole-genome duplication as the mechanism of RF-Oma1 evolution. Of thirty-seven positively selected codons in RF-Oma1, twenty-six of these sites are located in predicted transmembrane helices. Phylogenetic network analysis indicated that homologous recombination among the RF-Oma1 members played an important role to generate protein activity related to suppression. Together, our data illustrate how an evolutionarily young Rf has emerged from a lineage-specific paralog. Interestingly, several evolutionary features are shared with the RNA-binding protein type Rfs. Hence, the evolution of the sugar beet Rf is representative of Rf evolution in general.

中文翻译：

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Oma1 的谱系特异性旁系同源物进化成一个基因家族，从该基因家族中，植物中出现了诱导雄性不育的线粒体抑制因子。

植物中的细胞质雄性不育 (MS) 是由 MS 诱导线粒体引起的，线粒体在植物进化过程中经常出现。生育力核恢复( Rf ) 基因可以抑制其同源的 MS 诱导线粒体。许多Rf编码一类 RNA 结合蛋白，而甜菜（石竹目）Rf编码一种类似于Oma1的蛋白质，其参与线粒体的质量控制。在这项研究中，我们研究了植物中Oma1同源物的分子进化。我们分析了 37 个植物基因组并得出结论，单个拷贝是石竹目的祖先状态。其中甜菜Oma1同系物，直系同源副本位于保存在拟南芥中的同线区域。甜菜Rf是一个复杂的基因座，由甜菜特有的小Oma1同源家族（RF-Oma1家族）组成。基因座附近的基因排列在一些但不是所有石竹植物中可见，而在Ar 中不存在。大利亚那。这表明RF-Oma1进化的机制是节段重复而不是全基因组重复。RF-Oma1 中的 37个正选密码子，这些位点中有 26 个位于预测的跨膜螺旋中。系统发育网络分析表明，RF-Oma1成员之间的同源重组在产生与抑制相关的蛋白质活性方面发挥了重要作用。总之，我们的数据说明了进化上年轻的Rf 是如何从特定谱系的旁系同源物中出现的。有趣的是，一些进化特征与 RNA 结合蛋白类型Rf s共享。因此，甜菜Rf的进化通常代表Rf 的进化。