In land plants, the pentatricopeptide repeat (PPR) proteins form a large family involved in post-transcriptional processing of RNA in mitochondria and chloroplasts, which is critical for plant development and evolutionary adaption. Although studies showed a number of PPR proteins generally influence the editing of organellar genes, few of them were characterized in detail in rice. Here, we report a PLS-E subclass PPR protein in rice, PPR756, loss of function of which led to the abolishment of RNA editing events among three mitochondrial genes including atp6, ccmC, and nad7. Their defective C-to-U transformation then resulted in improper amino acid retention which could cause abortive pollen development. Furthermore, PPR756 could bind to the three target genes directly and interact with three OsMORFs (multiple organellar RNA editing factors): OsMORF1, OsMORF8-1, and OsMORF8-2. The knock-out plants of PPR756 exhibited retarded growth and greener leaves during the early vegetative stages, along with sterile pollen and lower seed setting at the reproductive stage. These results established a role for PPR756 in rice development, participating in RNA editing of three various transcripts and cooperating with OsMORFs via an editosome manner in rice.

中文翻译：

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水稻五肽重复序列蛋白PPR756通过影响线粒体中的多个RNA编辑参与花粉发育

在陆地植物中，五肽重复序列（PPR）蛋白形成一个大家族，参与线粒体和叶绿体中RNA的转录后加工，这对于植物发育和进化适应至关重要。尽管研究表明许多PPR蛋白通常会影响细胞器基因的编辑，但在水稻中却很少对其进行详细表征。在这里，我们报道了水稻中的PLS-E亚类PPR蛋白PPR756，其功能丧失导致取消了atp6，ccmC和nad7这三个线粒体基因之间的RNA编辑事件。然后，它们从C到U的缺陷转化会导致氨基酸保留不当，从而导致花粉流产。此外，PPR756可以直接结合三个靶基因并与三个OsMORFs（多个细胞器RNA编辑因子）相互作用：OsMORF1，OsMORF8-1和OsMORF8-2。PPR756的敲除植物在早期营养阶段表现出生长迟缓和较绿的叶子，在繁殖阶段表现出不育的花粉和较低的结实率。这些结果为PPR756在水稻发育中发挥了作用，参与了三种转录物的RNA编辑，并通过水稻中的编辑体方式与OsMORFs进行了合作。