title: The light-dependent accumulation of the P700 chlorophyll a protein of the photosystem I reaction center in barley. Evidence for translational control.
abstract: The light-dependent accumulation of the P700 chlorophyll a protein of the photosystem I reaction center has been studied in greening barley (Hordeum vulgare L.) seedlings. Immunoblot analysis of total cellular protein fractions and immunogold labelling of the P700 chlorophyll a protein in ultrathin sections of Lowicryl-embedded leaf tissue revealed that the concentration of this chlorophyll-binding protein in plastids of dark-grown barley seedlings is below the limit of detection. Upon illumination with white light, a rapid accumulation of this protein is induced. This light effect seems not to be regulated at the level of transcription. The gene for the P700 chlorophyll a protein has been mapped within the large single-copy region of the plastid DNA of barley. High levels of transcripts of this gene are present already in dark-grown seedlings and remain fairly constant throughout an extended illumination period. Polysomes were isolated from etioplasts and chloroplasts. The same high relative concentration of mRNA encoding the P700 chlorophyll a protein was present in both polysome fractions. This result suggests that the light-dependent accumulation of the P700 chlorophyll a protein during chloroplast formation in barley seedlings is regulated at the translational, or posttranslational, level.
mesh_terms: D002734:Chlorophyll / Q000235:genetics*; D002736:Chloroplasts / Q000378:metabolism; D002874:Chromosome Mapping; D005786:Gene Expression Regulation / Q000528:radiation effects*; D001467:Hordeum / Q000235:genetics; D007120:Immunochemistry; D008027:Light; D045342:Light-Harvesting Protein Complexes; D009693:Nucleic Acid Hybridization; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000235:genetics*; D011132:Polyribosomes; D014176:Protein Biosynthesis / Q000528:radiation effects; D014158:Transcription, Genetic / Q000528:radiation effects
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll