title: Transcript analysis of the tobacco plastid operon rps2/atpI/H/F/A reveals the existence of a non-consensus type II (NCII) promoter upstream of the atpI coding sequence.
abstract: The plastid ATP synthase complex is composed of nine subunits, of which six are encoded in the plastome. The plastid-encoded genes are arranged in two transcriptional units: atpB/E and atpI/H/F/A. We have recently reported that besides containing four -10 and -35 consensus-type (CT) promoters, the atpB/E operon also contains a non-consensus type (NCII) promoter that alone is responsible for its expression in non-photosynthetic plastids. As the functionality of ATP synthase requires expression of all nine subunits, NCII promoter-driven transcription of the atpI/H/F/A operon is to be expected in non-photosynthetic plastids. Therefore, a detailed transcriptional analysis of this operon was carried out using RNA samples from tobacco leaf, cultured cells (BY-2) and seedlings grown on streptomycin and spectinomycin; which contain chloroplasts, translationally active non-photosynthetic plastids and translationally inactive plastids, respectively. We identified a total of three transcription initiation sites (TIS) and four transcript processing sites in the non-coding regions of this operon. Our results also demonstrate that rps2 is co-transcribed with the atpI/H/F/A genes. One of the TIS (-208 atpI) is characterized by an NCII type promoter, while other two primary transcripts (-131 atpI and -384 atpH) initiate from CT promoters. In non-photosynthetic plastids the atpI/H/F/A-specific transcript pool seems to be solely contributed by initiation at the -208 atpI (NCII type) promoter, because transcripts from CT promoters do not accumulate in these plastid types.
authors.affiliation: Center for Gene Research, Nagoya University, Chikusa, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Miyagi
authors.forename: S
authors.initials: S
authors.lastname: Kapoor
authors.forename: M
authors.initials: M
authors.lastname: Sugita
authors.forename: M
authors.initials: M
authors.lastname: Sugiura
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D010947:Plants, Toxic; D018087:Plastids / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D006180:Proton-Translocating ATPases / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis*; D016415:Sequence Alignment; D014026:Nicotiana; D014158:Transcription, Genetic
chemical_list: D012333:RNA, Messenger; D006180:Proton-Translocating ATPases