title: A small multifunctional pentatricopeptide repeat protein in the chloroplast of Chlamydomonas reinhardtii.
abstract: Organellar biogenesis is mainly regulated by nucleus-encoded factors, which act on various steps of gene expression including RNA editing, processing, splicing, stabilization, and translation initiation. Among these regulatory factors, pentatricopeptide repeat (PPR) proteins form the largest family of RNA binding proteins, with hundreds of members in flowering plants. In striking contrast, the genome of the unicellular green alga Chlamydomonas reinhardtii encodes only 14 such proteins. In this study, we analyzed PPR7, the smallest and most highly expressed PPR protein in C. reinhardtii. Green fluorescent protein-based localization and gel-filtration analysis revealed that PPR7 forms a part of a high-molecular-weight ribonucleoprotein complex in the chloroplast stroma. RIP-chip analysis of PPR7-bound RNAs demonstrated that the protein associates with a diverse set of chloroplast transcripts in vivo, i.e. rrnS, psbH, rpoC2, rbcL, atpA, cemA-atpH, tscA, and atpI-psaJ. Furthermore, the investigation of PPR7 RNAi strains revealed that depletion of PPR7 results in a light-sensitive phenotype, accompanied by altered levels of its target RNAs that are compatible with the defects in their maturation or stabilization. PPR7 is thus an unusual type of small multifunctional PPR protein, which interacts, probably in conjunction with other RNA binding proteins, with numerous target RNAs to promote a variety of post-transcriptional events.
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-University, Grosshaderner Straße 2-4, 82152 Planegg-Martinsried, Germany.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Jalal
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-University, Grosshaderner Straße 2-4, 82152 Planegg-Martinsried, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schwarz
authors.affiliation: Molecular Genetics, Institute of Biology, Humboldt University of Berlin, 10115 Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schmitz-Linneweber
authors.affiliation: UMR7141 CNRS/Université Pierre et Marie Curie, Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Vallon
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-University, Grosshaderner Straße 2-4, 82152 Planegg-Martinsried, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Nickelsen
authors.affiliation: Molecular Plant Sciences, Ludwig-Maximillians-University, Grosshaderner Straße 2-4, 82152 Planegg-Martinsried, Germany. Electronic address: alexandra.bohne@lmu.de.
authors.forename: Alexandra-Viola
authors.initials: AV
authors.lastname: Bohne
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D016601:RNA-Binding Proteins
keywords: RIP-chip; RNA binding protein; RNA maturation; RNA stabilization; chloroplast gene expression; pentatricopeptide repeat protein