Enzymes involved in organellar DNA replication in photosynthetic eukaryotes.

Naoki Sato,Takashi Moriyama

doi:10.3389/fpls.2014.00480

Abstract

Plastids and mitochondria possess their own genomes. Although the replication mechanisms of these organellar genomes remain unclear in photosynthetic eukaryotes, several organelle-localized enzymes related to genome replication, including DNA polymerase, DNA primase, DNA helicase, DNA topoisomerase, single-stranded DNA maintenance protein, DNA ligase, primer removal enzyme, and several DNA recombination-related enzymes, have been identified. In the reference Eudicot plant Arabidopsis thaliana, the replication-related enzymes of plastids and mitochondria are similar because many of them are dual targeted to both organelles, whereas in the red alga Cyanidioschyzon merolae, plastids and mitochondria contain different replication machinery components. The enzymes involved in organellar genome replication in green plants and red algae were derived from different origins, including proteobacterial, cyanobacterial, and eukaryotic lineages. In the present review, we summarize the available data for enzymes related to organellar genome replication in green plants and red algae. In addition, based on the type and distribution of replication enzymes in photosynthetic eukaryotes, we discuss the transitional history of replication enzymes in the organelles of plants.

Highlights

Plastids and mitochondria are semi-autonomous organelles that contain their own genomes, encoding the genes necessary to perform their respective metabolic functions
The Atpop2 mutant displayed high sensitivity to ciprofloxacin, an inducer of DNA double-strand breaks. These results indicate that two distinct POPs are involved in genome replication for plastids and mitochondria, and that AtPOP2 functions in DNA repair in both organelles
With regard to polymerase I (PolI), as green plants have enzymes with 5 –3 exonuclease domain, but lack 3 –5 exonuclease and DNA polymerase domains (Figure 3F), phylogenetic analysis of the 5 –3 exonuclease domain in bacteria and photosynthetic eukaryotes was performed (Figures 3D,E). These results suggest that the organelle replication apparatus of both green plants and red algae is composed of enzymes of various origins, including α-proteobacteria, cyanobacteria, and eukaryotes

Summary

INTRODUCTION

Plastids and mitochondria are semi-autonomous organelles that contain their own genomes, encoding the genes necessary to perform their respective metabolic functions. These organellar genomes are replicated by specific enzymes, such as DNA polymerase, DNA primase, and DNA helicase, as occurs in bacteria and the nuclei of eukaryotes. DNA polymerase γ (Polγ) functions in the replication and repair of animal mitochondrial DNA. The animal mitochondrial primase, POLRMT, which has homology to the RNA polymerase of T3/T7 phage, was recently indicated to function in both primer synthesis and transcription, it was previously thought to function only in transcription (Wanrooij et al, 2008). An in vitro reconstituted mitochondrial replisome composed of Polγ, TWINKLE, and SSB displayed rolling-circle replication with high processivity (Korhonen et al, 2004)

Organellar genome replication in plants

OTHER REPLICATION ENZYMES OF ORGANELLAR GENOMES

PHYLOGENETIC DISTRIBUTION OF ORGANELLAR REPLICATIVE ENZYMES

DNA polymerase POP

Recombinase Recombination mediator