Mitochondrial and plastid genome architecture: Reoccurring themes, but significant differences at the extremes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 33; pp. 10177 - 10184
• Main Authors: Smith, David Roy, Patrick J. Keeling
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 18.08.2015; National Acad Sciences
• Subjects: Animals; Biological Evolution; Biological Sciences; Cell Lineage; Cell Nucleus - genetics; chloroplast; chromosomes; Chromosomes - ultrastructure; Deoxyribonucleic acid; DNA; DNA Repair; DNA, Mitochondrial - genetics; endosymbiosis; Genetics, Population; Genome; Genome, Mitochondrial; Genomes; Genomics; Humans; Mitochondria; mitochondrial genome; mitochondrion; Mutation; nuclear-encoded proteins; Nucleotides - genetics; Plants; plastid genome; Plastids; Plastids - genetics; Proteins; RNA Processing, Post-Transcriptional; Sequence Analysis, DNA; Symbioses Becoming Permanent: The Origins and Evolutionary Trajectories of Organelles Sackler; Symbiosis - genetics; plastid genome; mitochondrial genome; chloroplast; endosymbiosis; mitochondrion
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1422049112

Mitochondrial and plastid genomes show a wide array of architectures, varying immensely in size, structure, and content. Some organelle DNAs have even developed elaborate eccentricities, such as scrambled coding regions, nonstandard genetic codes, and convoluted modes of posttranscriptional modification and editing. Here, we compare and contrast the breadth of genomic complexity between mitochondrial and plastid chromosomes. Both organelle genomes have independently evolved many of the same features and taken on similar genomic embellishments, often within the same species or lineage. This trend is most likely because the nuclear-encoded proteins mediating these processes eventually leak from one organelle into the other, leading to a high likelihood of processes appearing in both compartments in parallel. However, the complexity and intensity of genomic embellishments are consistently more pronounced for mitochondria than for plastids, even when they are found in both compartments. We explore the evolutionary forces responsible for these patterns and argue that organelle DNA repair processes, mutation rates, and population genetic landscapes are all important factors leading to the observed convergence and divergence in organelle genome architecture.