Abstract
Organellar replication enzyme in plants and algae has remained elusive, because DNA polymerase γ, a mitochondrial replicase of yeasts and animals, is not present in photosynthetic eukaryotes. The genome of Cyanidioschyzon merolae contains two genes encoding PolA and PolB, which are distant homologs of Escherichia coli DNA polymerase I. Immunoblot analysis and targeting study with GFP-fusion proteins demonstrated that PolA was localized in plastids while PolB was in both plastids and mitochondria. The transcript and protein levels of PolB increased sharply 1-2 h before the peak of cell division rate in synchronously cultured cells. These results suggested that the PolB-type enzymes in plants and algae are involved in the replication of both plastids and mitochondria in photosynthetic eukaryotes. PolB is sensitive to phosphonoacetic acid (PAA) inhibitor. Effects of PAA in the growth of cells were examined.
