title: Chloroplast ribonucleoprotein CP31A is required for editing and stability of specific chloroplast mRNAs.
abstract: Chloroplast ribonucleoproteins (cpRNPs) are nuclear-encoded, highly abundant, and light-regulated RNA binding proteins. They have been shown to be involved in chloroplast RNA processing and stabilization in vitro and are phylogenetically related to the well-described heterogeneous nuclear ribonucleoproteins (hnRNPs). cpRNPs have been found associated with mRNAs present in chloroplasts and have been regarded as nonspecific stabilizers of chloroplast transcripts. Here, we demonstrate that null mutants of the cpRNP family member CP31A exhibit highly specific and diverse defects in chloroplast RNA metabolism. First, analysis of cp31a and cp31a/cp31b double mutants uncovers that these 2 paralogous genes participate nonredundantly in a combinatorial fashion in processing a subset of chloroplast editing sites in vivo. Second, a genome-wide analysis of chloroplast transcript accumulation in cp31a mutants detected a virtually complete loss of the chloroplast ndhF mRNA and lesser reductions for specific other mRNAs. Fluorescence analyses show that the activity of the NADH dehydrogenase complex, which also includes the NdhF subunit, is defective in cp31a mutants. This indicates that cpRNPs are important in vivo for calibrating the expression levels of specific chloroplast mRNAs and impact chloroplast physiology. Taken together, the specificity and combinatorial aspects of cpRNP functions uncovered suggest that these chloroplast proteins are functional equivalents of nucleocytosolic hnRNPs.
authors.affiliation: Institute of Biology, Humboldt-University of Berlin, 10115 Berlin, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Tillich
authors.forename: Simone L
authors.initials: SL
authors.lastname: Hardel
authors.forename: Christiane
authors.initials: C
authors.lastname: Kupsch
authors.forename: Ute
authors.initials: U
authors.lastname: Armbruster
authors.forename: Etienne
authors.initials: E
authors.lastname: Delannoy
authors.forename: José M
authors.initials: JM
authors.lastname: Gualberto
authors.forename: Pascal
authors.initials: P
authors.lastname: Lehwark
authors.forename: Dario
authors.initials: D
authors.lastname: Leister
authors.forename: Ian D
authors.initials: ID
authors.lastname: Small
authors.forename: Christian
authors.initials: C
authors.lastname: Schmitz-Linneweber
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018745:Genome, Plant; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D017393:RNA Editing; D020871:RNA Stability; D018749:RNA, Plant / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D012261:Ribonucleoproteins