Dek504 Encodes a Mitochondrion-Targeted E+-Type Pentatricopeptide Repeat Protein Essential for RNA Editing and Seed Development in Maize.

Zheyuan Wang,Jiawen Lu,Song Zhang,Riliang Gu,Yu Cui,Weiwei Chen,Guoying Wang,Junjie Fu,Jianhua Wang,Rongrong Chen

doi:10.3390/ijms23052513

Abstract

In flowering plants, RNA editing is a post-transcriptional process that selectively deaminates cytidines (C) to uridines (U) in organellar transcripts. Pentatricopeptide repeat (PPR) proteins have been identified as site-specific recognition factors for RNA editing. Here, we report the map-based cloning and molecular characterization of the defective kernel mutant dek504 in maize. Loss of Dek504 function leads to delayed embryogenesis and endosperm development, which produce small and collapsed kernels. Dek504 encodes an E+-type PPR protein targeted to the mitochondria, which is required for RNA editing of mitochondrial NADH dehydrogenase 3 at the nad3-317 and nad3-44 sites. Biochemical analysis of mitochondrial protein complexes revealed a significant reduction in the mitochondrial NADH dehydrogenase complex I activity, indicating that the alteration of the amino acid sequence at nad3-44 and nad3-317 through RNA editing is essential for NAD3 function. Moreover, the amino acids are highly conserved in monocots and eudicots, whereas the events of C-to-U editing are not conserved in flowering plants. Thus, our results indicate that Dek504 is essential for RNA editing of nad3, which is critical for NAD3 function, mitochondrial complex I stability, and seed development in maize.

Highlights

RNA editing is a post-transcriptional modification occurring in vascular plant organelles through a deamination reaction at a specific nucleotide cytidine (C), which is converted to uridine (U) [1,2]
DEK504 Encodes an E+-Type Pentatricopeptide repeat (PPR) Protein Involved in Editing at nad3-44 and nad3-317
Previous studies have shown that PPR proteins serve vital roles in post-transcriptional processes, including RNA editing, splicing, cleavage, and translation in the mitochondria and chloroplasts [14]

Summary

Introduction

RNA editing is a post-transcriptional modification occurring in vascular plant organelles through a deamination reaction at a specific nucleotide cytidine (C), which is converted to uridine (U) [1,2]. The major consequence of RNA editing is that the amino acid (aa) sequence differs from that encoded from the genome sequence. The amino acids encoded by edited mRNAs are more conserved than the genome-encoded ones [3]. RNA editing is viewed as a remedial DNA mutation at the RNA level to restore the evolutionarily conserved amino acids [3,4,5]. Most organelle transcripts harbor hundreds of editing sites. When plant mitochondrial RNA editing was discovered over 30 years ago, little was known regarding the molecular apparatus involved in identifying the correct C editing targets [6,7]

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Conclusion