title: CRP1 Protein: (dis)similarities betweenArabidopsis thalianaandZea mays.
abstract: Biogenesis of chloroplasts in higher plants is initiated from proplastids, and involves a series of processes by which a plastid able to perform photosynthesis, to synthesize amino acids, lipids, and phytohormones is formed. All plastid protein complexes are composed of subunits encoded by the nucleus and chloroplast genomes, which require a coordinated gene expression to produce the correct concentrations of organellar proteins and to maintain organelle function. To achieve this, hundreds of nucleus-encoded factors are imported into the chloroplast to control plastid gene expression. Among these factors, members of the Pentatricopeptide Repeat (PPR) containing protein family have emerged as key regulators of the organellar post-transcriptional processing. PPR proteins represent a large family in plants, and the extent to which PPR functions are conserved between dicots and monocots deserves evaluation, in light of differences in photosynthetic metabolism (C3 vs. C4) and localization of chloroplast biogenesis (mesophyll vs. bundle sheath cells). In this work we investigated the role played in the process of chloroplast biogenesis by At5g42310, a member of the Arabidopsis PPR family which we here refer to asAtCRP1 (Chloroplast RNA Processing 1), providing a comparison with the orthologousZmCRP1 protein fromZea mays. Loss-of-functionatcrp1mutants are characterized by yellow-albinotic cotyledons and leaves owing to defects in the accumulation of subunits of the thylakoid protein complexes. As in the case ofZmCRP1,AtCRP1 associates with the 5' UTRs of bothpsaCand, albeit very weakly,petAtranscripts, indicating that the role of CRP1 as regulator of chloroplast protein synthesis has been conserved between maize and Arabidopsis.AtCRP1 also interacts with thepetB-petDintergenic region and is required for the generation ofpetBandpetDmonocistronic RNAs. A similar role has been also attributed toZmCRP1, although the direct interaction ofZmCRP1 with thepetB-petDintergenic region has never been reported, which could indicate thatAtCRP1 andZmCRP1 differ, in part, in their plastid RNA targets.
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano Milano, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Ferrari
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Tadini
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie Potsdam-Golm, Germany.
authors.forename: Fabio
authors.initials: F
authors.lastname: Moratti
authors.affiliation: Molecular Genetics, Institute of Biology, Humboldt University of Berlin Berlin, Germany.
authors.forename: Marie-Kristin
authors.initials: MK
authors.lastname: Lehniger
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano Milano, Italy.
authors.forename: Alex
authors.initials: A
authors.lastname: Costa
authors.affiliation: Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli studi di Milano Milano, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Rossi
authors.affiliation: Centro Ricerca e Innovazione, Fondazione Edmund Mach San Michele all'Adige, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Colombo
authors.affiliation: Dipartimento di Bioscienze, Università degli studi di Milano Milano, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Masiero
authors.affiliation: Molecular Genetics, Institute of Biology, Humboldt University of Berlin Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schmitz-Linneweber
authors.affiliation: Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia, Università degli studi di Milano Milano, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Pesaresi
keywords: PPR; RNA metabolism; anterograde signaling; biogenesis; chloroplast