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First published online September 20, 2007; 10.1104/pp.107.103846 Plant Physiology 145:712-721 (2007) © 2007 American Society of Plant Biologists Phage-Type RNA Polymerase RPOTmp Transcribes the rrn Operon from the PC Promoter at Early Developmental Stages in Arabidopsis1,[C],[W]Laboratoire Plastes et Differenciation Cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, F–38041 Grenoble, France
The plastid genome of higher plants is transcribed by two different types of RNA polymerases named nucleus encoded RNA polymerase (NEP) and plastid encoded RNA polymerase. Plastid encoded RNA polymerase is a multimeric enzyme comparable to eubacterial RNA polymerases. NEP enzymes represent a small family of monomeric phage-type RNA polymerases. Dicotyledonous plants harbor three different phage-type enzymes, named RPOTm, RPOTp, and RPOTmp. RPOTm is exclusively targeted to mitochondria, RPOTp is exclusively targeted to plastids, and RPOTmp is targeted to plastids as well as to mitochondria. In this article, we have made use of RPOTp and RPOTmp T-DNA insertion mutants to answer the question of whether both plastid-located phage-type RNA polymerases have overlapping or specific functions in plastid transcription. To this aim, we have analyzed accD and rpoB messenger RNAs (mRNA; transcribed from type I NEP promoters), clpP mRNA (transcribed from the –59 type II NEP promoter), and the 16S rRNA (transcribed from the exceptional PC NEP promoter) by primer extension. Results suggest that RPOTp represents the principal RNA polymerase for transcribing NEP-controlled mRNA genes during early plant development, while RPOTmp transcribes specifically the rrn operon from the PC promoter during seed imbibition.
1 This work was supported by the European Community (grant no. FP6–2002–LifeSciHealth, PLASTOMICS, proposal no. 503238, L.M. was employed under this contract). 2 These authors contributed equally to the article. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Silva Lerbs-Mache (silva.lerbs-mache{at}ujf-grenoble.fr). [C] Some figures in this article are displayed in color online but in black and white in the print edition. [W] The online version of this article contains Web-only data. www.plantphysiol.org/cgi/doi/10.1104/pp.107.103846 * Corresponding author; e-mail silva.lerbs-mache{at}ujf-grenoble.fr. Received June 12, 2007; accepted September 7, 2007; published September 20, 2007. This article has been cited by other articles:
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