A complete mitochondrial genome sequence of the wild two-humped camel (Camelus bactrianus ferus): an evolutionary history of camelidae

Peng Cui,He Meng,Dan Qi,Rimutu Ji,Heping Zhang,Songnian Hu,Jun Yu,Feng Ding,Hongwei Gao

doi:10.1186/1471-2164-8-241

Abstract

BackgroundThe family Camelidae that evolved in North America during the Eocene survived with two distinct tribes, Camelini and Lamini. To investigate the evolutionary relationship between them and to further understand the evolutionary history of this family, we determined the complete mitochondrial genome sequence of the wild two-humped camel (Camelus bactrianus ferus), the only wild survivor of the Old World camel.ResultsThe mitochondrial genome sequence (16,680 bp) from C. bactrianus ferus contains 13 protein-coding, two rRNA, and 22 tRNA genes as well as a typical control region; this basic structure is shared by all metazoan mitochondrial genomes. Its protein-coding region exhibits codon usage common to all mammals and possesses the three cryptic stop codons shared by all vertebrates. C. bactrianus ferus together with the rest of mammalian species do not share a triplet nucleotide insertion (GCC) that encodes a proline residue found only in the nd1 gene of the New World camelid Lama pacos. This lineage-specific insertion in the L. pacos mtDNA occurred after the split between the Old and New World camelids suggests that it may have functional implication since a proline insertion in a protein backbone usually alters protein conformation significantly, and nd1 gene has not been seen as polymorphic as the rest of ND family genes among camelids. Our phylogenetic study based on complete mitochondrial genomes excluding the control region suggested that the divergence of the two tribes may occur in the early Miocene; it is much earlier than what was deduced from the fossil record (11 million years). An evolutionary history reconstructed for the family Camelidae based on cytb sequences suggested that the split of bactrian camel and dromedary may have occurred in North America before the tribe Camelini migrated from North America to Asia.ConclusionMolecular clock analysis of complete mitochondrial genomes from C. bactrianus ferus and L. pacos suggested that the two tribes diverged from their common ancestor about 25 million years ago, much earlier than what was predicted based on fossil records.

Highlights

The family Camelidae that evolved in North America during the Eocene survived with two distinct tribes, Camelini and Lamini
Genome organization Since mammalian mitochondrial genome sequences are very similar, we designed a set of PCR primers based on highly conserved sequences of an alignment with fulllength mitochondrial genomes from the available public data, including those of cow, deer, sheep, pig, and lama (Table 1)
The minor length variation mainly occurred in the tandem repeat (ACGTAC)n of the control region

Summary

Introduction

The family Camelidae that evolved in North America during the Eocene survived with two distinct tribes, Camelini and Lamini. To investigate the evolutionary relationship between them and to further understand the evolutionary history of this family, we determined the complete mitochondrial genome sequence of the wild two-humped camel (Camelus bactrianus ferus), the only wild survivor of the Old World camel. The wild bactrian camel (C. bactrianus ferus) appears to be the only wild survivor of the Old World camel. Mainly focusing on the sequence of mitochondrial cytochrome b gene, have made significant contributions to understanding the evolutionary history of Camelidae [2], and yet there has not been any significant comparative studies on the evolutionary relationship between Camelini and Lamini

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