title: The plastid-specific ribosomal proteins of Arabidopsis thaliana can be divided into non-essential proteins and genuine ribosomal proteins.
abstract: Plastid translation occurs on bacterial-type 70S ribosomes consisting of a large (50S) subunit and a small (30S) subunit. The vast majority of plastid ribosomal proteins have orthologs in bacteria. In addition, plastids also possess a small set of unique ribosomal proteins, so-called plastid-specific ribosomal proteins (PSRPs). The functions of these PSRPs are unknown, but, based on structural studies, it has been proposed that they may represent accessory proteins involved in translational regulation. Here we have investigated the functions of five PSRPs using reverse genetics in the model plant Arabidopsis thaliana. By analyzing T-DNA insertion mutants and RNAi lines, we show that three PSRPs display characteristics of genuine ribosomal proteins, in that down-regulation of their expression led to decreased accumulation of the 30S or 50S subunit of the plastid ribosomes, resulting in plastid translational deficiency. In contrast, two other PSRPs can be knocked out without visible or measurable phenotypic consequences. Our data suggest that PSRPs fall into two types: (i) PSRPs that have a structural role in the ribosome and are bona fide ribosomal proteins, and (ii) non-essential PSRPs that are not required for stable ribosome accumulation and translation under standard greenhouse conditions.
authors.affiliation: Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Tiller
authors.forename: Magdalena
authors.initials: M
authors.lastname: Weingartner
authors.forename: Wolfram
authors.initials: W
authors.lastname: Thiele
authors.forename: Eugenia
authors.initials: E
authors.lastname: Maximova
authors.forename: Mark A
authors.initials: MA
authors.lastname: Schöttler
authors.forename: Ralph
authors.initials: R
authors.lastname: Bock
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060365:Chloroplast Proteins / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D055786:Gene Knockout Techniques; D018745:Genome, Plant / Q000235:genetics; D016254:Mutagenesis, Insertional; D010641:Phenotype; D010788:Photosynthesis / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure; D018087:Plastids / Q000235:genetics / Q000378:metabolism*; D011132:Polyribosomes / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D059386:Reverse Genetics; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D060365:Chloroplast Proteins; D045332:Photosystem II Protein Complex; D012269:Ribosomal Proteins