C-to-U RNA editing in plant mitochondria requires the participation of many nucleus-encoded factors, most of which are pentatricopeptide repeat (PPR) proteins. There is a large number of PPR proteins and the functions many of them are unknown. Here, we report a mitochondrion-localized DYW-subgroup PPR protein, PPR27, which functions in the editing of multiple mitochondrial transcripts in maize. The ppr27 mutant is completely deficient in C-to-U editing at the ccmF_N-1357 and rps3-707 sites, and editing at six other sites is substantially reduced. The lack of editing at ccmF_N-1357 causes a deficiency of CcmF_N protein. As CcmF_N functions in the maturation pathway of cytochrome proteins that are subunits of mitochondrial complex III, its deficiency results in an absence of cytochrome c₁ and cytochrome c proteins. Consequently, the assembly of mitochondrial complex III and super-complex I+III₂ is decreased, which impairs the electron transport chain and respiration, leading to arrests in embryogenesis and endosperm development in ppr27. In addition, PPR27 was found to physically interact with ZmMORF1, which interacts with ZmMORF8, suggesting that these three proteins may facilitate C-to-U RNA editing via the formation of a complex in maize mitochondria. This RNA editing is essential for complex III assembly and seed development in maize.

中文翻译：

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DYW亚群五肽重复蛋白PPR27与ZmMORF1相互作用，以促进玉米中线粒体RNA编辑和种子发育。

植物线粒体中的C到U RNA编辑需要许多核编码因子的参与，其中大多数是五肽重复序列（PPR）蛋白。PPR蛋白数量众多，其功能尚不清楚。在这里，我们报告线粒体定位的DYW-亚组PPR蛋白PPR27，它在玉米中多个线粒体转录本的编辑中起作用。所述ppr27突变体是在C-到-U编辑在完全缺陷CCMF _Ñ -1357和rps3-707位点，以及在其他六个站点编辑显着降低。ccmF _N -1357缺少编辑会导致CcmF _N蛋白缺乏。作为CcmF _N线粒体复合体III的亚基细胞色素蛋白在成熟途径中发挥着重要作用，其缺乏导致细胞色素c ₁和细胞色素c蛋白的缺失。因此，线粒体复合物III和超复合物I + III ₂的组装减少，从而损害了电子传输链和呼吸，导致ppr27的胚发生和胚乳发育停滞。此外，发现PPR27与ZmMORF1物理相互作用，而ZmMORF1与ZmMORF8相互作用，表明这三种蛋白可能通过玉米线粒体中复合物的形成促进C-to-U RNA编辑。RNA编辑对于玉米中复杂的III组装和种子发育至关重要。