Abstract
Plants are sessile organisms, and their DNA is particularly exposed to damaging agents. The integrity of plant mitochondrial and plastid genomes is necessary for cell survival. During evolution, plants have evolved mechanisms to replicate their mitochondrial genomes while minimizing the effects of DNA damaging agents. The recombinogenic character of plant mitochondrial DNA, absence of defined origins of replication, and its linear structure suggest that mitochondrial DNA replication is achieved by a recombination-dependent replication mechanism. Here, I review the mitochondrial proteins possibly involved in mitochondrial DNA replication from a structural point of view. A revision of these proteins supports the idea that mitochondrial DNA replication could be replicated by several processes. The analysis indicates that DNA replication in plant mitochondria could be achieved by a recombination-dependent replication mechanism, but also by a replisome in which primers are synthesized by three different enzymes: Mitochondrial RNA polymerase, Primase-Helicase, and Primase-Polymerase. The recombination-dependent replication model and primers synthesized by the Primase-Polymerase may be responsible for the presence of genomic rearrangements in plant mitochondria.
Highlights
The analysis indicates that DNA replication in plant mitochondria could be achieved by a recombination-dependent replication mechanism, and by a replisome in which primers are synthesized by three different enzymes: Mitochondrial RNA polymerase, Primase-Helicase, and Primase-Polymerase
Human mitochondrial DNA replication starts by a strand-displacement model of replication in which human mitochondrial RNA polymerase (RNAP) transcribes the heavy-strand promoter generating a primer that is processed and passed on to the mitochondrial
We focus on the proteins from the model plant Arabidopsis thaliana as a representative of flowering plants
Summary
Mitochondria arose from a monophyletic endosymbiotic event between an archaea and an α-proteobacteria approximately two billion years ago [1]. Metazoan mitochondrial genomes are circular molecules that vary in sizes between 10 to 30 kb [3]. Plant mitochondrial genomes are predominantly large linear DNA molecules Besides the differences between the physical structure of the plant and metazoan genomes (linear versus circular), the most remarkable characteristics of plant mitochondrial genomes are their ability to rearrange, their low nucleotide substitution rate, and the evolution of new mitochondrial open reading frames. Plants 2019, 8, 533 ago, shows that both genomes exhibit different configurations because of a large inverted repeat [5,7,8,9]. Even though plant mitochondrial genomes rearrange, the substitution rate in their coding regions is almost negligible, in contrast with the highly mutable human mitochondrial genome [10,11]
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