The Complete Mitochondrial Genome Sequence of the Hornwort <Emphasis Type="Italic">Megaceros</Emphasis><Emphasis Type="Italic">aenigmaticus</Emphasis> Shows a Mixed Mode of Conservative Yet Dynamic Evolution in Early Land Plant Mitochondrial Genomes |
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Authors: | Libo Li Bin Wang Yang Liu Yin-Long Qiu |
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Institution: | (1) Department of Ecology and Evolutionary Biology, The University Herbarium, University of Michigan, Ann Arbor, MI 48109-1048, USA |
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Abstract: | Land plants possess some of the most unusual mitochondrial genomes among eukaryotes. However, in early land plants these genomes
resemble those of green and red algae or early eukaryotes. The question of when during land plant evolution the dramatic change
in mtDNAs occurred remains unanswered. Here we report the first completely sequenced mitochondrial genome of the hornwort,
Megaceros aenigmaticus, a member of the sister group of vascular plants. It is a circular molecule of 184,908 base pairs, with 32 protein genes,
3 rRNA genes, 17 tRNA genes, and 30 group II introns. The genome contains many genes arranged in the same order as in those
of a liverwort, a moss, several green and red algae, and Reclinomonas americana, an early-branching eukaryote with the most ancestral form of mtDNA. In particular, the gene order between mtDNAs of the
hornwort and Physcomitrella patens (moss) differs by only 8 inversions and translocations. However, the hornwort mtDNA possesses 4 derived features relative
to green alga mtDNAs—increased genome size, RNA editing, intron gains, and gene losses—which were all likely acquired during
the origin and early evolution of land plants. Overall, this genome and those of other 2 bryophytes show that mitochondrial
genomes in early land plants, unlike their seed plant counterparts, exhibit a mixed mode of conservative yet dynamic evolution.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Libo Li and Bin Wang contributed equally to this work. |
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Keywords: | Evolution Gene order Genomic rearrangement Hornwort Land plants Mitochondrial genome |
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