Mitochondrial Pentatricopeptide Repeat Protein, EMB2794, Plays a Pivotal Role in NADH Dehydrogenase Subunit nad2 mRNA Maturation in Arabidopsis thaliana

SOFÍA SHEVTSOV; AXEL BRENNICKE; OREN OSTERSETZER-BIRAN; MAXIMILIANO CAINZOS; ,LAURE DORA SULTAN; GABRIELA PAGNUSSAT; FERNANDA MARCHETTI; JUAN PABLO CÓRDOBA; MIZUKI TAKENAKA; EDUARDO ZABALETA

PLANT AND CELL PHYSIOLOGY

OXFORD UNIV PRESS

Año: 2020 vol. 61 p. 1080 - 1094

0032-0781

The Arabidopsis genome encodes more than 450 proteins containing the pentatricopeptide repeat (PPR) motif. The PPR proteins are classified into two groups, termed as P and PLS classes. Typically, the PLS subclass proteins are mainly involved in the RNA editing of mitochondrial and chloroplast transcripts, whereas most of the analyzed P sub-class proteins have been mainly implicated in RNA metabolism, such as 5′ or 3′ transcript stabilization and processing, splicing and translation. Mutations of PPR genes often result in embryogenesis and altered seedling developmental defect phenotypes, but only a limited number of ppr mutants have been characterized in detail. In this report, we show that null mutations in EMB2794 gene result in embryo arrest, due to altered splicing of nad2 transcripts in Arabidopsis mitochondria. In angiosperms, nad2 gene has five exons that are transcribed individually from two mitochondrial DNA regions. Biochemical and in vivo analyses further indicate that recombinant or transgenic EMB2794 protein bind to the nad2 pre-mRNAs in vitro as well as in vivo, suggesting a role for this protein in trans-splicing of nad2 intron 2 and possibly in the stability of the second pre-mRNA of nad2. Homozygous emb2794 lines, showing embryo-defective phenotypes, can be partially rescued by the addition of sucrose to the growth medium. Mitochondria of rescued homozygous mutant plants contain only traces of respiratory complex I, which lack NADH-dehydrogenase activity.