• Plastid‐encoded genes are coordinately transcribed by the nucleus‐encoded RNA polymerase (NEP) and the plastid‐encoded RNA polymerase (PEP). Resulting primary transcripts are frequently subject to RNA editing by cytidine‐to‐uridine conversions at specific sites. The physiological role of many editing events is largely unknown.
• Here, we have used the CRISPR/Cas9 technique in rice to knock out a member of the PLS‐DYW subfamily of pentatricopeptide repeat (PPR) proteins.
• We found that OsPPR16 is responsible for a single editing event at position 545 in the chloroplast rpoB messenger RNA (mRNA), resulting in an amino acid change from serine to leucine in the β‐subunit of the PEP. In striking contrast to loss‐of‐function mutations of the putative orthologue in Arabidopsis, which were reported to have no visible phenotype, knockout of OsPPR16 leads to impaired accumulation of RpoB, reduced expression of PEP‐dependent genes, and a pale phenotype during early plant development. Thus, by editing the rpoB mRNA, OsPPR16 is required for faithful plastid transcription, which in turn is required for Chl synthesis and efficient chloroplast development.
• Our results provide new insights into the interconnection of the finely tuned regulatory mechanisms that operate at the transcriptional and post‐transcriptional levels of plastid gene expression.

中文翻译：

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RNA聚合酶亚基RpoB的积累取决于OsPPR16对RNA的编辑，并影响水稻早期叶片发育过程中叶绿体的发育。

• 质体编码的基因由核编码的RNA聚合酶（NEP）和质体编码的RNA聚合酶（PEP）协调转录。产生的初级转录本通常在特定位点通过胞苷-尿苷转化进行RNA编辑。许多编辑事件的生理学作用在很大程度上是未知的。
• 在这里，我们在水稻中使用了CRISPR / Cas9技术来敲除五肽重复序列（PPR）蛋白PLS-DYW亚家族的成员。
• 我们发现OsPPR16负责叶绿体rpoB信使RNA（mRNA）中位置545的单个编辑事件，从而导致PEP的β亚基中的氨基酸从丝氨酸变为亮氨酸。与据报道没有可见表型的拟南芥中直系同源物的功能丧失突变形成鲜明对比的是，OsPPR16的敲除导致RpoB的积累受损，PEP依赖基因的表达减少以及早期的苍白表型。植物发展。因此，通过编辑rpoB mRNA，忠实的质体转录需要OsPPR16，而Chl合成和有效的叶绿体发育则需要OsPPR16。
• 我们的结果为在质体基因表达的转录和转录后水平上运行的精细调节机制的相互联系提供了新见解。