Organ-specific transcription of the rrn operon in spinach plastids

The spinach rrn operon is used as a model system to study transcriptional regulation in higher plant photosynthetic and non-photosynthetic plastids. We performed capping experiments to determine whether P1, PC, or P2 promoters are employed for rrn transcription start sites in cotyledon and root tiss...

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Veröffentlicht in:The Journal of biological chemistry 1997-05, Vol.272 (21), p.13676-13682
Hauptverfasser: Iratni, R, Diederich, L, Harrak, H, Bligny, M, Lerbs-Mache, S
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Sprache:eng
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Zusammenfassung:The spinach rrn operon is used as a model system to study transcriptional regulation in higher plant photosynthetic and non-photosynthetic plastids. We performed capping experiments to determine whether P1, PC, or P2 promoters are employed for rrn transcription start sites in cotyledon and root tissues. By using a new method of analysis of capped RNA we demonstrate for the first time that 1) in both organs the rrn operon is expressed in a constitutive manner by cotranscription with the preceding tRNA(GAC) Val gene, and 2) the PC transcription start site is used only in cotyledons and leaves, i.e. we demonstrate the organ-specific usage of a plastid promoter. Both start sites, PC and that of the tRNA(GAC) Val cotranscript, lack Escherichia coli -like consensus sequences. The cotranscript is initiated 457 base pairs upstream of the tRNA(GAC) Val gene. The PC-specific DNA-binding factor, CDF2, is not detectable in root tissues confirming its regulatory role in PC-initiated rrn expression and the organ specificity of PC expression. Furthermore, our results show that rrn operon expression patterns differ in spinach and tobacco indicating species-specific transcriptional regulation of plant plastid gene expression.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.272.21.13676