ISSN:
1617-4623
Keywords:
Key wordsatpI/H/F/A Operon
;
Differential promoter usage
;
NCII promoter
;
Nicotiana tabacum
;
Transcriptional analysis
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004380050651
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