title: pTAC2, -6, and -12 are components of the transcriptionally active plastid chromosome that are required for plastid gene expression.
abstract: Transcription in plastids is mediated by a plastid-encoded multimeric (PEP) and a nuclear-encoded single-subunit RNA polymerase (NEP) and a still unknown number of nuclear-encoded factors. By combining gel filtration and affinity chromatography purification steps, we isolated transcriptionally active chromosomes from Arabidopsis thaliana and mustard (Sinapis alba) chloroplasts and identified 35 components by electrospray ionization ion trap tandem mass spectrometry. Eighteen components, called plastid transcriptionally active chromosome proteins (pTACs), have not yet been described. T-DNA insertions in three corresponding genes, ptac2, -6, and -12, are lethal without exogenous carbon sources. Expression patterns of the plastid-encoded genes in the corresponding knockout lines resemble those of Deltarpo mutants. For instance, expression of plastid genes with PEP promoters is downregulated, while expression of genes with NEP promoters is either not affected or upregulated in the mutants. All three components might also be involved in posttranscriptional processes, such as RNA processing and/or mRNA stability. Thus, pTAC2, -6, and -12 are clearly involved in plastid gene expression.
authors.affiliation: Institute of General Botany and Plant Physiology, Friedrich-Schiller-University, Jena, Germany.
authors.forename: Jeannette
authors.initials: J
authors.lastname: Pfalz
authors.forename: Karsten
authors.initials: K
authors.lastname: Liere
authors.forename: Andrea
authors.initials: A
authors.lastname: Kandlbinder
authors.forename: Karl-Josef
authors.initials: KJ
authors.lastname: Dietz
authors.forename: Ralf
authors.initials: R
authors.lastname: Oelmüller
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D032461:Chromosomes, Plant / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009149:Mustard Plant / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D018087:Plastids / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic
chemical_list: D009687:Nuclear Proteins; D010940:Plant Proteins; D012321:DNA-Directed RNA Polymerases