Maize Empty Pericarp602 Encodes a P-Type PPR Protein That Is Essential for Seed Development

Area of Science:

• Plant Molecular Biology
• Mitochondrial Gene Expression
• RNA Splicing Mechanisms

Background:

• Pentatricopeptide repeat (PPR) proteins are vital for RNA processing, including intron splicing, crucial for gene expression.
• Understanding novel PPR proteins involved in RNA splicing can elucidate complex biological pathways.

Purpose of the Study:

• To identify and characterize a novel maize PPR protein involved in mitochondrial intron splicing.
• To investigate the function of the identified PPR protein in maize seed development and mitochondrial biogenesis.

Main Methods:

• Identification and cloning of the Emp602 gene from maize (Zea mays) emp602 mutants.
• Subcellular localization studies to determine the mitochondrial targeting of the EMP602 protein.
• Analysis of RNA splicing, transcript levels, mitochondrial complex assembly, and seed development in wild-type and emp602 mutant plants.
• Transcriptome analysis to identify gene expression changes in response to Emp602 mutation.

Main Results:

• The maize Emp602 gene encodes a mitochondrial P-type PPR protein.
• EMP602 is specifically required for the cis-splicing of mitochondrial Nad4 intron 1 and intron 3.
• Loss of EMP602 function results in the absence of mature Nad4 transcripts, impaired Complex I assembly, and arrested seed development.
• Upregulation of alternative oxidase (Aox) expression and other mitochondrial-related genes was observed in emp602 mutants.

Conclusions:

• EMP602 plays a critical role in maize mitochondrial RNA splicing, specifically for Nad4 introns.
• Disruption of EMP602 function leads to mitochondrial dysfunction and arrested seed development due to impaired Complex I assembly.
• This study reveals a key mechanism linking mitochondrial gene expression to plant development.