MBE Advance Access originally published online on October 5, 2007
Molecular Biology and Evolution 2007 24(12):2775-2786; doi:10.1093/molbev/msm212
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Research Articles |
Multiple Origins and Rapid Evolution of Duplicated Mitochondrial Genes in Parthenogenetic Geckos (Heteronotia binoei; Squamata, Gekkonidae)
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* Department of Integrative Biology, University of California, Berkeley
Museum of Vertebrate Zoology, University of California, Berkeley
Joint Genome Institute and Lawrence Berkeley National Laboratory, Walnut Creek, CA
Genome Project Solutions, Hercules, CA
E-mail: mkfujita{at}berkeley.edu.
Accepted for publication September 26, 2007.
Accumulating evidence for alternative gene orders demonstrates that vertebrate mitochondrial genomes are more evolutionarily dynamic than previously thought. Several lineages of parthenogenetic lizards contain large, tandem duplications that include rRNA, tRNA, and protein-coding genes, as well as the control region. Such duplications are hypothesized as intermediate stages in gene rearrangement, but the early stages of their evolution have not been previously studied. To better understand the evolutionary dynamics of duplicated segments of mitochondrial DNA, we sequenced 10 mitochondrial genomes from recently formed (
300,000 years ago) hybrid parthenogenetic geckos of the Heteronotia binoei complex and 1 from a sexual form. These genomes included some with an arrangement typical of vertebrates and others with tandem duplications varying in size from 5.7 to 9.4 kb, each with different gene contents and duplication endpoints. These results, together with phylogenetic analyses, indicate independent and frequent origins of the duplications. Small, direct repeats at the duplication endpoints imply slipped-strand error as a mechanism generating the duplications as opposed to a false initiation/termination of DNA replication mechanism that has been invoked to explain duplications in other lizard mitochondrial systems. Despite their recent origin, there is evidence for nonfunctionalization of genes due primarily to deletions, and the observed pattern of gene disruption supports the duplication–deletion model for rearrangement of mtDNA gene order. Conversely, the accumulation of mutations between these recent duplicates provides no evidence for gene conversion, as has been reported in some other systems. These results demonstrate that, despite their long-term stasis in gene content and arrangement in some lineages, vertebrate mitochondrial genomes can be evolutionary dynamic even at short timescales.
Key Words: mitochondrial genome • mtDNA • molecular evolution • Heteronotia • tandem duplication • parthenogenesis
Naoko Takezaki, Associate Editor
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