Article

Phage-type RNA polymerase RPOTmp transcribes the rrn operon from the PC promoter at early developmental stages in Arabidopsis.

Laboratoire Plastes et Differenciation Cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, F-38041 Grenoble, France.
Plant physiology (impact factor: 6.53). 12/2007; 145(3):712-21. DOI:10.1104/pp.107.103846 pp.712-21
Source: PubMed

ABSTRACT 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.

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Keywords

clpP mRNA
 
different types
 
eubacterial RNA polymerases
 
exceptional PC NEP promoter
 
higher plants
 
monomeric phage-type RNA polymerases
 
multimeric enzyme comparable
 
nucleus encoded RNA polymerase
 
plastid encoded RNA polymerase
 
plastid genome
 
plastid transcription
 
plastid-located phage-type RNA polymerases
 
principal RNA polymerase
 
RNA polymerases
 
rpoB messenger RNAs
 
RPOTmp T-DNA insertion mutants
 
RPOTmp transcribes
 
rrn operon
 
seed imbibition
 
transcribing NEP-controlled mRNA genes