The self‐splicing of group II introns during RNA processing depends on their catalytic structure and is influenced by numerous factors that promote the formation of that structure through direct binding. Here we report that C‐to‐U editing at a specific position in two nad7 introns is essential to splicing, which also implies that the catalytic activity of non‐functional group II introns could be restored by editing. We characterized a maize (Zea mays) mutant, dek46, with a defective kernel phenotype; Dek46 encodes a pentatricopeptide repeat DYW protein exclusively localized in mitochondria. Analyses of the coding regions of mitochondrial transcripts did not uncover differences in RNA editing between dek46 mutant and wild‐type maize, but showed that splicing of nad7 introns 3 and 4 is severely reduced in the mutant. Furthermore, editing at nucleotide 22 of domain 5 (D5‐C22) of both introns is abolished in dek46. We constructed chimeric introns by swapping D5 of P.li.LSUI2 with D5 of nad7 intron 3. In vitro splicing assays indicated that the chimeric intron containing D5‐U22 can be self‐spliced, but the one containing D5‐C22 cannot. These results indicate that DEK46 functions in the C‐to‐U editing of D5‐C22 of both introns, and the U base at this position is critical to intron splicing.

中文翻译：

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DEK46对线粒体nad7内含子中的特定位点执行从C到U的编辑，这对于玉米中的内含子剪接和种子发育至关重要。

II组内含子在RNA加工过程中的自我剪接取决于其催化结构，并受许多因素的影响，这些因素可通过直接结合促进该结构的形成。在这里我们报告说，在两个nad7内含子的特定位置进行C到U编辑对于剪接至关重要，这也意味着非功能性II组内含子的催化活性可以通过编辑恢复。我们表征了具有缺陷的核表型的玉米（Zea mays）突变体dek46。Dek46编码仅位于线粒体中的五肽重复DYW蛋白。线粒体转录本编码区的分析未发现dek46之间RNA编辑的差异突变体和野生型玉米，但显示nad7内含子3和4的剪接在该突变体中大大减少。此外，在dek46中取消了两个内含子的结构域5（D5-C22）第22位核苷酸的编辑。我们通过将P.li.LSUI2的D5与nad7内含子3的D5交换来构建嵌合内含子。体外剪接分析表明，含有D5-U22的嵌合内含子可以自剪接，而含有D5-C22的嵌合内含子不能自剪接。这些结果表明，DEK46在两个内含子的D5-C22的C到U编辑中起作用，并且此位置的U碱基对于内含子剪接至关重要。