Regulator of Chromosome Condensation 1-Domain Protein DEK47 Functions on the Intron Splicing of Mitochondrial Nad2 and Seed Development in Maize.

Shi-Kai Cao,Xiaomin Wang,Bao-Cai Tan,Xiaojie Li,Zhihui Xiu,Ruolin Song,Aqib Sayyed,Feng Sun,Rui Liu

doi:10.3389/fpls.2021.695249

Abstract

In flowering plants, mitochondrial genes contain approximately 20–26 introns. Splicing of these introns is essential for mitochondrial gene expression and function. Recent studies have revealed that both nucleus- and mitochondrion-encoded factors are required for intron splicing, but the mechanism of splicing remains largely unknown. Elucidation of the mechanism necessitates a complete understanding of the splicing factors. Here, we report the identification of a regulator of chromosome condensation 1 (RCC1)-domain protein DEK47 that is required for mitochondrial intron splicing and seed development in maize. Loss of function in Dek47 severely arrests embryo and endosperm development, resulting in a defective kernel (dek) phenotype. DEK47 harbors seven RCC1 domains and is targeted to mitochondria. Null mutation of DEK47 causes a deficiency in the splicing of all four nad2 introns, abolishing the production of mature nad2 transcript and resulting in the disassembly and severely reduced activity of mitochondrial complex I. In response, the expression of the alternative oxidase AOX2 is sharply increased in dek47. These results indicate that Dek47 is required for the splicing of all the nad2 introns in mitochondria, and essential for complex I assembly, and kernel development in maize.

Highlights

Mitochondria are the sites of oxidative phosphorylation (OXPHOS) and essential metabolic pathways, such as the beta oxidation, the citric acid cycle, amino acid breakdown, and apoptosis (Millar et al, 2011; Spinelli and Haigis, 2018)
These results indicate that the embryo development is arrested at the coleoptilar stage and the endosperm development is delayed in dek47-1
DEK47 is Essential for the Splicing of Nad2 Introns, Complex I Biogenesis, and Seed Development in Maize

Summary

Introduction

Mitochondria are the sites of oxidative phosphorylation (OXPHOS) and essential metabolic pathways, such as the beta oxidation, the citric acid cycle, amino acid breakdown, and apoptosis (Millar et al, 2011; Spinelli and Haigis, 2018). Studies in the last 10 years have shown that RNA-binding proteins from distinct protein families are required for the splicing of mitochondrial and chloroplast introns These protein families include the chloroplast RNA splicing and ribosome maturation (CRM) proteins (Ostersetzer et al, 2005; Asakura et al, 2008; Zmudjak et al, 2013; Chen et al, 2019), nuclear-encoded maturases (Nakagawa and Sakurai, 2006; Keren et al, 2009, 2012; Cohen et al, 2014; Zmudjak et al, 2017; Shevtsov-Tal et al, 2021), RNA DEAD-box helicases (Asakura et al, 2012), mitochondrial transcription termination factors (Hsu et al, 2014), plant organellar RNA recognition (PORR) proteins (Colas des FrancsSmall et al, 2012), pentatricopeptide repeat (PPR) proteins (de Longevialle et al, 2007; Koprivova et al, 2010; Xiu et al, 2016), and regulator of chromosome condensation (RCC1) family proteins (Kuhn et al, 2011)

Methods

Results

Conclusion