title: Proteome analysis of the rice etioplast: metabolic and regulatory networks and novel protein functions.
abstract: We report an extensive proteome analysis of rice etioplasts, which were highly purified from dark-grown leaves by a novel protocol using Nycodenz density gradient centrifugation. Comparative protein profiling of different cell compartments from leaf tissue demonstrated the purity of the etioplast preparation by the absence of diagnostic marker proteins of other cell compartments. Systematic analysis of the etioplast proteome identified 240 unique proteins that provide new insights into heterotrophic plant metabolism and control of gene expression. They include several new proteins that were not previously known to localize to plastids. The etioplast proteins were compared with proteomes from Arabidopsis chloroplasts and plastid from tobacco Bright Yellow 2 cells. Together with computational structure analyses of proteins without functional annotations, this comparative proteome analysis revealed novel etioplast-specific proteins. These include components of the plastid gene expression machinery such as two RNA helicases, an RNase II-like hydrolytic exonuclease, and a site 2 protease-like metalloprotease all of which were not known previously to localize to the plastid and are indicative for so far unknown regulatory mechanisms of plastid gene expression. All etioplast protein identifications and related data were integrated into a data base that is freely available upon request.
authors.affiliation: Institute of Plant Science and Functional Genomics Center Zurich, Swiss Federal Institute of Technology, Eidgenössische Technische Hochschule (ETH) Zurich, 8092 Zurich, Switzerland.
authors.forename: Anne
authors.initials: A
authors.lastname: von Zychlinski
authors.forename: Torsten
authors.initials: T
authors.lastname: Kleffmann
authors.forename: Nandini
authors.initials: N
authors.lastname: Krishnamurthy
authors.forename: Kimmen
authors.initials: K
authors.lastname: Sjölander
authors.forename: Sacha
authors.initials: S
authors.lastname: Baginsky
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Gruissem
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics; D002736:Chloroplasts; D019295:Computational Biology; D015180:Electrophoresis, Gel, Two-Dimensional; D005092:Exonucleases / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D013058:Mass Spectrometry; D045726:Metalloproteases / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000737:chemistry*; D010940:Plant Proteins / Q000032:analysis / Q000737:chemistry / Q000145:classification / Q000378:metabolism*; D018087:Plastids / Q000737:chemistry*; D020543:Proteome / Q000032:analysis; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D010940:Plant Proteins; D020543:Proteome; D005092:Exonucleases; D045726:Metalloproteases