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Updated: Jun 14, 2025

Discrimintion and Mapping of the Primary and Processed Transcripts in Maize Mitochondrion Using a Circular RT-PCR-based Strategy
Published on: July 29, 2019
PPR21 is involved in the splicing of nad2 introns via interacting with PPR-SMR1 and SPR2 and is essential to maize
Yan-Zhuo Yang1, Xin-Yuan Liu1, Song Gao1
1The Key Laboratory of Plant Development and Environment Adaptation Biology, Ministry of Education, School of Life Sciences, Shandong University, Qingdao, Shandong 266237, China.
Abstract:
Pentatricopeptide repeat (PPR) proteins are a large group of eukaryote-specific RNA-binding proteins that play pivotal roles in plant organelle gene expression. Here, we report the function of PPR21 in mitochondrial intron splicing and its role in maize kernel development. PPR21 is a typical P-type PPR protein targeted to mitochondria. The ppr21 mutants are arrested in embryogenesis and endosperm development, leading to embryo lethality. Null mutations of PPR21 reduce the splicing efficiency of nad2 intron 1, 2, and 4 and impair the assembly and activity of mitochondrial complex I. Previous studies show that the P-type PPR protein EMP12 is required for the splicing of identical introns. However, our protein interaction analyses reveal that PPR21 does not interact with EMP12. Instead, both PPR21 and EMP12 interact with the small MutS-related (SMR) domain-containing PPR protein 1 (PPR-SMR1) and the short P-type PPR protein 2 (SPR2). PPR-SMR1 interacts with SPR2, and both proteins are required for the splicing of many introns in mitochondria, including nad2 intron 1, 2, and 4. These results suggest that a PPR21-(PPR-SMR1/SPR2)-EMP12 complex is involved in the splicing of nad2 introns in maize mitochondria.
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