title: An essential pentatricopeptide repeat protein facilitates 5' maturation and translation initiation of rps3 mRNA in maize mitochondria.
abstract: Pentatricopeptide repeat (PPR) proteins are members of one of the largest nucleus-encoded protein families in plants. Here, we describe the previously uncharacterized maize (Zea mays) PPR gene, MPPR6, which was isolated from a Mutator-induced collection of maize kernel mutants by a cDNA-based forward genetic approach. Identification of a second mutant allele and cosegregation analysis confirmed correlation with the mutant phenotype. Histological investigations revealed that the mutation coincides with abnormities in the transfer cell layer, retardation of embryo development, and a considerable reduction of starch level. The function of MPPR6 is conserved across a wide phylogenetic distance as revealed by heterologous complementation of the Arabidopsis thaliana mutant in the orthologous APPR6 gene. MPPR6 appeared to be exclusively present in mitochondria. RNA coimmunoprecipitation and in vitro binding studies revealed a specific physical interaction of MPPR6 with the 5' untranslated region of ribosomal protein S3 (rps3) mRNA. Mapping of transcript termini showed specifically extended rps3 5' ends in the mppr6 mutant. Considerable reduction of mitochondrial translation was observed, indicating loss of RPS3 function. This is consistent with the appearance of truncated RPS3 protein lacking the N terminus in mppr6. Our results suggest that MPPR6 is directly involved in 5' maturation and translation initiation of rps3 mRNA.
authors: Biozentrum Klein Flottbek und Botanischer Garten, Universität Hamburg, 22609 Hamburg, Germany.
authors: Nikolay
authors: N
authors: Manavski
authors: Virginie
authors: V
authors: Guyon
authors: Jörg
authors: J
authors: Meurer
authors: Udo
authors: U
authors: Wienand
authors: Reinhold
authors: R
authors: Brettschneider
mesh_terms: D020121:5' Untranslated Regions / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D056625:Endosperm / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009928:Organ Specificity; D010641:Phenotype; D010802:Phylogeny; D018515:Plant Leaves / Q000166:cytology / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D003313:Zea mays / Q000166:cytology / Q000196:embryology / Q000235:genetics / Q000378:metabolism*
chemical_list: D020121:5' Untranslated Regions; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D012333:RNA, Messenger; D018749:RNA, Plant; D011993:Recombinant Fusion Proteins; D012269:Ribosomal Proteins; C044152:ribosomal protein S3