Plastid DNA is conserved, highly polyploid and uniform within a plant reflecting efficient plastid DNA replication/recombination/repair (DNA-RRR) pathways. We will review the current understanding of the DNA sequences, proteins, and mechanisms involved in plastid genome maintenance. This includes analysis of the topological forms of plastid DNA, models of plastid DNA replication, homologous recombination, replication slippage, DNA repair, and plastid DNA-RRR-proteins. We will focus on flowering plants but include information from algae when relevant. Plastid DNA is comprised of a multimeric series of circular, linear, and branched forms. Variant plastid DNA molecules include small linear palindromes with hairpin ends. Plastid transformation has demonstrated an efficient homologous recombination pathway, acting on short ~200 bp sequences, that is active throughout shoot development. These functional studies involving plastid transformation to manipulate DNA sequences, combined with genomics and reverse genetics to isolate mutants in plastid DNA-RRR proteins, will be particularly important for making progress in this field.
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