Group II introns are large catalytic RNAs that are particularly prevalent in the organelles of terrestrial plants. In angiosperm mitochondria, group II introns reside in the coding-regions of many critical genes, and their excision is essential for respiratory-mediated functions. Canonical group II introns are self-splicing and mobile genetic elements, consisting of the catalytic intron-RNA and its cognate intron-encoded endonuclease factor (i.e. maturase, Pfam-PF01348). Plant organellar introns are extremely degenerate, and lack many regions that are critical for splicing, including their related maturase-ORFs. The high degeneracy of plant mitochondrial introns was accompanied during evolution by the acquisition of host-acting protein cofactors. These include several nuclear encoded maturases (nMATs) and various other splicing-cofactors that belong to a diverse set of RNA-binding families, e.g. RNA helicases (Pfam-PF00910), Mitochondrial Transcription Termination Factors (mTERF, Pfam-PF02536), Plant Organelle RNA Recognition (PORR, Pfam-PF11955), and Pentatricopeptide repeat (PPR, Pfam-PF13812) proteins. Previously, we established the roles of MatR and three nuclear-maturases, nMAT1, nMAT2, and nMAT4, in the splicing of different subsets of mitochondrial introns in Arabidopsis. The function of nMAT3 (AT5G04050) was found to be essential during early embryogenesis. Using a modified embryo-rescue method, we show that nMAT3-knockout plants are strongly affected in the splicing of nad1 introns i1, i3 and i4 in Arabidopsis mitochondria. The embryo-defect phenotype is tightly associated with complex I biogenesis defects. Functional complementation of nMAT3 restored the splicing defects and altered embryogenesis phenotypes associated with the nmat3 mutant-line.

中文翻译：

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nMAT3是拟南芥植物中完整复合体I生物发生和胚胎发育所需的重要成熟酶剪接因子。

II组内含子是大型催化RNA，在陆生植物的细胞器中特别普遍。在被子植物线粒体中，II组内含子位于许多关键基因的编码区，它们的切除对于呼吸调节功能至关重要。规范的II类内含子是自剪接和可移动的遗传元件，由催化内含子RNA及其同源内含子编码的核酸内切酶因子（即成熟酶，Pfam-PF01348）组成。植物细胞内含子非常简并，并且缺少许多对剪接至关重要的区域，包括其相关的成熟酶-ORF。植物线粒体内含子的高度简并性在进化过程中伴随着宿主作用蛋白辅因子的获得。这些包括几个核编码的成熟酶（nMATs）和各种不同的剪接辅因子，它们属于一组不同的RNA结合家族，例如RNA解旋酶（Pfam-PF00910），线粒体转录终止因子（mTERF，Pfam-PF02536），植物细胞器RNA识别（PORR，Pfam-PF11955）和五肽重复（PPR，Pfam-PF13812）蛋白。以前，我们在拟南芥中不同子集的线粒体内含子的剪接中建立了MatR和三个核maturases nMAT1，nMAT2和nMAT4的作用。发现nMAT3（AT5G04050）的功能在早期胚胎发生过程中至关重要。使用改良的胚胎营救方法，我们显示nMAT3-基因敲除植物在拟南芥线粒体中nad1内含子i1，i3和i4的剪接中受到强烈影响。胚胎缺陷表型与复杂的I生物发生缺陷紧密相关。nMAT3的功能互补恢复了与nmat3突变体相关的剪接缺陷和改变的胚胎发生表型。