title: Unique architecture of the plastid ribosomal RNA operon promoter recognized by the multisubunit RNA polymerase in tobacco and other higher plants.
abstract: Expression of the plastid rRNA operon (rrn) during development is highly regulated at the level of transcription. The plastid rrn operon in most higher plants is transcribed by the plastid-encoded RNA polymerase (PEP), the multisubunit plastid RNA polymerase from PrrnP1, a sigma(70)-type promoter with conserved -10 and -35 core promoter elements. To identify functionally important sequences, the tobacco PrrnP1 was dissected in vivo and in vitro. Based on in vivo deletion analysis, sequences upstream of nucleotide -83 do not significantly contribute to promoter function. The in vitro analyses identified an essential hexameric sequence upstream of the -35 element (GTGGGA; the rRNA operon upstream activator [RUA]) that is conserved in monocot and dicot species and suggested that the -10 element plays only a limited role in PrrnP1 recognition. Mutations in the initial transcribed sequence (+9 to +14) enhanced transcription, the characteristic of strong promoters in prokaryotes. We propose that sigma interaction with the -10 element in PrrnP1 is replaced in part by direct PEP-RUA (protein-DNA) interaction or by protein-protein interaction between the PEP and an RUA binding transcription factor.
authors.affiliation: Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8020, USA.
authors.forename: Jon Y
authors.initials: JY
authors.lastname: Suzuki
authors.forename: Priya
authors.initials: P
authors.lastname: Sriraman
authors.forename: Zora
authors.initials: Z
authors.lastname: Svab
authors.forename: Pal
authors.initials: P
authors.lastname: Maliga
mesh_terms: D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D001467:Hordeum / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011401:Promoter Regions, Genetic / Q000235:genetics; D018747:RNA, Chloroplast / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000201:enzymology / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics; D012407:rRNA Operon / Q000235:genetics*
chemical_list: D018747:RNA, Chloroplast; D012335:RNA, Ribosomal; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases