Witnessing the evolution of transcription in mitochondria: the mitochondrial genome of the primitive brown alga Pylaiella littoralis (L.) Kjellm. encodes a T7-like RNA polymerase

• Published in: Journal of molecular biology Vol. 277; no. 5; pp. 1047 - 1057
• Main Authors: Rousvoal, S, Oudot, M.-P, Fontaine, J.-M, Kloareg, B, Goër, S.Loiseaux-de
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 17.04.1998
• Subjects: brown algae; Chromosome Mapping; Cloning, Molecular; DNA, Mitochondrial - genetics; DNA-Directed RNA Polymerases - chemistry; Eukaryota - enzymology; evolution; Evolution, Molecular; linear plasmid; mitochondria; Mitochondria - genetics; Models, Genetic; Phage T7; Phylogeny; Plasmids - genetics; Promoter Regions, Genetic - genetics; Pylaiella littoralis; RNA polymerase; RNA, Messenger - analysis; Sequence Alignment; Sequence Analysis, DNA; Space life sciences; Transcription, Genetic - genetics; ORF; RT; mitochondria; IR; evolution; RNA polymerase; brown algae; linear plasmid
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1998.1679

A region of the mitochondrial genome of the primitive brown alga Pylaiella littoralis containing a plasmid-like insert which contains a transcribed T7-phage-type RNA polymerase gene is described. This is a first report of a phage-type RNA polymerase gene integrated in a mitochondrial genome. As the mitochondrial genome of this alga also contains σ-70 proteobacterial promoter regions, i.e. traces of the ancestral α 2ββ′σ-70 proteobacterial RNA polymerase, this genome witnesses two types of RNA polymerases. As such the mitochondrial genome of P. littoralis represents a unique stage in the evolution of transcription in mitochondria, which contrasts with that of the primitive protist Reclinomonas americana, which still retains the ancestral α 2ββ′σ-70 proteobacterial RNA polymerase genes, and with animals, land plants and fungi, which use phage-type polymerases.