MBE Advance Access published online on March 22, 2007
Molecular Biology and Evolution, doi:10.1093/molbev/msm054
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Research Article |
The Mitochondrial Genome of the Lizard Calotes versicolor and a Novel Gene Inversion in South Asian Draconine Agamids
a Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
b Zoology Department, Cairo University, Giza, Egypt
Corresponding author: Sayed A.M. Amer, Zoology Department, Faculty of Science, Cairo University, Giza, Egypt. yasser92us{at}yahoo.com
Received for publication December 8, 2006. Revision received February 17, 2007. Accepted for publication March 15, 2007.
A complete mitochondrial DNA (mtDNA) sequence was determined for the lizard Calotes versicolor (Reptilia; Agamidae). The 16,670-bp genome with notable shorter genes for some protein-coding and tRNA genes had the same gene content as that found in other vertebrates. However, a novel gene arrangement was found in which the proline tRNA gene (trnP) is located in the light strand instead of its typical heavy strand position, providing the first known example of gene inversion in vertebrate mtDNAs. A segment of mtDNA encompassing the trnP gene and its flanking genes and the control region was amplified and sequenced for various agamid taxa to investigate timing and mechanism of the gene inversion. The inverted trnP gene organization was shared by all South Asian draconine agamids examined but by none of the other Asian and African agamids. Phylogenetic analyses including clock-free Bayesian analyses for divergence time estimation suggested a single occurrence of the gene inversion on a lineage leading to the draconine agamids during the Paleogene period. This gene inversion could not be explained by the tandem duplication/random loss model for mitochondrial gene rearrangements. Our available sequence data did not provide evidence for remolding of the trnP gene by an anticodon switch in a duplicated tRNA gene. Based on results of sequence comparisons and other circumstantial evidence, we hypothesize that inversion of the trnP gene was originally mediated by a homologous DNA recombination and that the de novo gene organization that does not disrupt expression of mitochondrial genes has been maintained in draconine mtDNAs for such a long period of time.
Key Words: Calotes versicolor • Agamidae • mitochondrial genome • gene inversion • homologous DNA recombination • gene rearrangement
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