Pentatricopeptide repeat (PPR) proteins are RNA binding proteins that function in posttranscriptional regulation as gene-specific regulators of RNA metabolism in plant organelles. Plant PPR proteins are divided into four classes: P, PLS, E and DYW. The E- and DYW-class proteins are mainly implicated in RNA editing, whereas most of the P-class proteins predominantly participate in RNA cleavage, splicing and stabilization. In contrast, the functions of PLS-class proteins still remain obscure. Here, we report the function of PLS-class PpPPR_31 and PpPPR_9 in Physcomitrella patens. The knockout (KO) mutants of PpPPR_31 and PpPPR_9 exhibited slower protonema growth compared to the wild type. The PpPPR_31 KO mutants showed a considerable reduction in the splicing of nad5 intron 3 and atp9 intron 1. The PpPPR_9 KO mutants displayed severely reduced splicing of cox1 intron 3. An RNA electrophoresis mobility shift assay showed that the recombinant PpPPR_31 protein bound to the 5' region of nad5 exon 4 and the bulged A region in domain VI of atp9 group II intron 1 while the recombinant PpPPR_9 bound to the translated region of ORF622 in cox1 intron 3. These results suggest that a certain set of PLS-class PPR proteins may influence the splicing efficiency of mitochondrial group II introns.

中文翻译：

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两个新的PLS类五肽重复蛋白与苔藓小立碗藓线粒体转录物的II组内含子剪接有关。

五肽重复序列（PPR）蛋白是RNA结合蛋白，在转录后调控中起着植物细胞器RNA代谢的基因特异性调控剂的作用。植物PPR蛋白分为四类：P，PLS，E和DYW。E和DYW类蛋白主要与RNA编辑有关，而大多数P类蛋白主要参与RNA的切割，剪接和稳定作用。相反，PLS类蛋白的功能仍然不清楚。在这里，我们报告了Physcomitrella patens中的PLS类PpPPR_31和PpPPR_9的功能。与野生型相比，PpPPR_31和PpPPR_9的基因敲除（KO）突变体显示出较慢的前体生长。该PpPPR_31KO突变体显示nad5内含子3和atp9内含子1的剪接显着减少。PpPPR_9 KO突变体显示cox1内含子3的剪接显着减少。RNA电泳迁移率漂移分析表明重组PpPPR_31蛋白与Ax9内含子5的结合。nad5外显子4和凸出中的域VI的区域ATP9 II组内含子1，而重组PpPPR_9绑定到的翻译区ORF622在COX1内含子3。这些结果表明，一组特定的PLS-PPR类蛋白的可能影响剪接线粒体第二组内含子的效率。