Nucleic Acids Research Advance Access originally published online on October 24, 2007
Nucleic Acids Research 2007 35(21):7256-7266; doi:10.1093/nar/gkm679
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Nucleic Acids Research, 2007, Vol. 35, No. 21 7256-7266
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Faithful transcription initiation from a mitochondrial promoter in transgenic plastids
1Institute of Biology (Genetics), Humboldt University Berlin, Chausseestrasse 117, D-10115 Berlin and 2Max Planck Institute for Molecular Plant Physiology, Am Mühlenberg 1, D-14476 Potsdam-Golm, Germany
*To whom correspondence should be addressed. Tel: +49 30 2093 8814; Fax: +49 30 2093 8141; Email: thomas.boerner{at}rz.hu-berlin.de Correspondence may also be addressed to Ralph Bock. Tel: +49 331 567 8700; Fax: +49 331 567 8701; Email: rbock{at}mpimp-golm.mpg.de
Received June 19, 2007. Revised August 3, 2007. Accepted August 19, 2007.
The transcriptional machineries of plastids and mitochondria in higher plants exhibit striking similarities. All mitochondrial genes and part of the plastid genes are transcribed by related phage-type RNA polymerases. Furthermore, the majority of mitochondrial promoters and a subset of plastid promoters show a similar structural organization. We show here that the plant mitochondrial atpA promoter is recognized by plastid RNA polymerases in vitro and in vivo. The Arabidopsis phage-type RNA polymerase RpoTp, an enzyme localized exclusively to plastids, was found to recognize the mitochondrial atpA promoter in in vitro assays suggesting the possibility that mitochondrial promoters might function as well in plastids. We have, therefore, generated transplastomic tobacco plants harboring in their chloroplast genome the atpA promoter fused to the coding region of the bacterial nptII gene. The chimeric nptII gene was found to be efficiently transcribed in chloroplasts. Mapping of the 5' ends of the nptII transcripts revealed accurate recognition of the atpA promoter by the chloroplast transcription machinery. We show further that the 5' untranslated region (UTR) of the mitochondrial atpA transcript is capable of mediating translation in chloroplasts. The functional and evolutionary implications of these findings as well as possible applications in chloroplast genome engineering are discussed.