title: A PORR domain protein required for rpl2 and ccmF(C)  intron splicing and for the biogenesis of c-type cytochromes in Arabidopsis mitochondria.
abstract: Angiosperm mitochondria encode approximately 20 group II introns, which interrupt genes involved in the biogenesis and function of the respiratory chain. Nucleus-encoded splicing factors have been identified for approximately half of these introns. The splicing factors derive from several protein families defined by atypical RNA binding domains that function primarily in organelles. We show here that the Arabidopsis protein WTF9 is essential for the splicing of group II introns in two mitochondrial genes for which splicing factors had not previously been identified: rpl2 and ccmF(C). WTF9 harbors a recently recognized RNA binding domain, the PORR domain, which was originally characterized in the chloroplast splicing factor WTF1. These findings show that the PORR domain family also functions in plant mitochondria, and highlight the parallels between the machineries for group II intron splicing in plant mitochondria and chloroplasts. In addition, we used the splicing defects in wtf9 mutants as a means to functionally characterize the mitochondrial rpl2 and ccmF(C) genes. Loss of ccmF(C) expression correlates with the loss of cytochromes c and c₁, confirming a role for ccmF(C) in cytochrome biogenesis. By contrast, our results strongly suggest that splicing is not essential for the function of the mitochondrial rpl2 gene, and imply that the Rpl2 fragment encoded by rpl2 exon 1 functions in concert with a nuclear gene product that provides the remainder of this essential ribosomal protein in trans.
authors: Australian Research Council Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley 6009 WA, Australia. catherine.colasdesfrancs-small@uwa.edu.au
authors: Catherine Colas des
authors: CC
authors: Francs-Small
authors: Tiffany
authors: T
authors: Kroeger
authors: Michal
authors: M
authors: Zmudjak
authors: Oren
authors: O
authors: Ostersetzer-Biran
authors: Nima
authors: N
authors: Rahimi
authors: Ian
authors: I
authors: Small
authors: Alice
authors: A
authors: Barkan
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D018506:Gene Expression Regulation, Plant; D050259:Genes, Mitochondrial; D017343:Genes, Plant; D007438:Introns; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D016415:Sequence Alignment
chemical_list: D029681:Arabidopsis Proteins; D003574:Cytochrome c Group; D024101:Mitochondrial Proteins; D003576:Electron Transport Complex IV