Ginkgo and Welwitschia Mitogenomes Reveal Extreme Contrasts in Gymnosperm Mitochondrial Evolution

Mitochondrial genomes (mitogenomes) of flowering plants are well known for their extreme diversity in size, structure, gene content, and rates of sequence evolution and recombination. In contrast, little is known about mitogenomic diversity and evolution within gymnosperms. Only a single complete ge...

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Bibliographic Details
Published in:Molecular biology and evolution 2016-06, Vol.33 (6), p.1448-1460
Main Authors: Guo, Wenhu, Grewe, Felix, Fan, Weishu, Young, Gregory J, Knoop, Volker, Palmer, Jeffrey D, Mower, Jeffrey P
Format: Article
Language:English
Subjects:
Base Sequence
Biological Evolution
Chromosome Mapping
Deoxyribonucleic acid
DNA
Evolution, Molecular
Flowering plants
Genes, Plant
Genome, Mitochondrial
Genome, Plant
Genomes
Genomics
Ginkgo biloba - genetics
Gnetophyta - genetics
Mitochondria - genetics
Phylogeny
Pine trees
Plant mitochondria
RNA Editing
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Summary:Mitochondrial genomes (mitogenomes) of flowering plants are well known for their extreme diversity in size, structure, gene content, and rates of sequence evolution and recombination. In contrast, little is known about mitogenomic diversity and evolution within gymnosperms. Only a single complete genome sequence is available, from the cycad Cycas taitungensis, while limited information is available for the one draft sequence, from Norway spruce (Picea abies). To examine mitogenomic evolution in gymnosperms, we generated complete genome sequences for the ginkgo tree (Ginkgo biloba) and a gnetophyte (Welwitschia mirabilis). There is great disparity in size, sequence conservation, levels of shared DNA, and functional content among gymnosperm mitogenomes. The Cycas and Ginkgo mitogenomes are relatively small, have low substitution rates, and possess numerous genes, introns, and edit sites; we infer that these properties were present in the ancestral seed plant. By contrast, the Welwitschia mitogenome has an expanded size coupled with accelerated substitution rates and extensive loss of these functional features. The Picea genome has expanded further, to more than 4 Mb. With regard to structural evolution, the Cycas and Ginkgo mitogenomes share a remarkable amount of intergenic DNA, which may be related to the limited recombinational activity detected at repeats in Ginkgo Conversely, the Welwitschia mitogenome shares almost no intergenic DNA with any other seed plant. By conducting the first measurements of rates of DNA turnover in seed plant mitogenomes, we discovered that turnover rates vary by orders of magnitude among species.
ISSN:0737-4038
1537-1719
DOI:10.1093/molbev/msw024