title: Localization and phylogenetic analysis of enzymes related to organellar genome replication in the unicellular rhodophyte Cyanidioschyzon merolae.
abstract: Plants and algae possess plastids and mitochondria harboring their own genomes, which are replicated by the apparatus consisting of DNA polymerase, DNA primase, DNA helicase, DNA topoisomerase, single-stranded DNA maintenance protein, DNA ligase, and primer removal enzyme. In the higher plant Arabidopsis thaliana, organellar replication-related enzymes (OREs) are similar in plastids and mitochondria because many of them are dually targeted to plastids and mitochondria. In the red algae, there is a report about a DNA replicase, plant/protist organellar DNA polymerase, which is localized to both plastids and mitochondria. However, other OREs remain unclear in algae. Here, we identified OREs possibly localized to organelles in the unicellular rhodophyte Cyanidioschyzon merolae. We then examined intracellular localization of green fluorescent protein-fusion proteins of these enzymes in C. merolae, whose cell has a single plastid and a single mitochondrion and is suitable for localization analysis, demonstrating that the plastid and the mitochondrion contain markedly different components of replication machinery. Phylogenetic analyses revealed that the organelle replication apparatus was composed of enzymes of various different origins, such as proteobacterial, cyanobacterial, and eukaryotic, in both red algae and green plants. Especially in the red alga, many enzymes of cyanobacterial origin remained. Finally, on the basis of the results of localization and phylogenetic analyses, we propose a model on the succession of OREs in eukaryotes.
authors.affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Moriyama
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tajima
authors.forename: Kohsuke
authors.initials: K
authors.lastname: Sekine
authors.forename: Naoki
authors.initials: N
authors.lastname: Sato
mesh_terms: D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D019143:Evolution, Molecular; D054628:Genome, Chloroplast; D054629:Genome, Mitochondrial; D018745:Genome, Plant; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D000461:Rhodophyta / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; C023140:DNA replicase; D004259:DNA-Directed DNA Polymerase; D004265:DNA Helicases
keywords: GFP-fusion proteins; evolution of replication apparatus; mitochondria and plastids; red algae; subcellular localization