Phage-type RNA polymerase RPOTmp transcribes the rrn operon from the PC promoter at early developmental stages in Arabidopsis.
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.
Courtois
Florence
F
Laboratoire Plastes et Differenciation Cellulaire, Université Joseph Fourier and Centre National de la Recherche Scientifique, B.P. 53, F-38041 Grenoble, France.
Merendino
Livia
L
Demarsy
Emilie
E
Mache
Régis
R
Lerbs-Mache
Silva
S
D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D001435:Bacteriophages / Q000201:enzymology; D004269:DNA, Bacterial / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D016254:Mutagenesis, Insertional; D009876:Operon / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic
D004269:DNA, Bacterial; C036483:T-DNA; D012321:DNA-Directed RNA Polymerases