Complete Mitochondrial Genome of Three Species of the Genus Microtus (Arvicolinae, Rodentia)

The mitochondrial genome of the mountain wooly tapir, Tapirus pinchaque and a formal test of the effect of altitude on the adaptive evolution of mitochondrial protein coding genes in odd-toed ungulates

BACKGROUND

The harsh conditions of high-altitude environments are known to drive the evolution of physiological and morphological traits in endothermic animals. These conditions are expected to result in the adaptive evolution of protein coding genes encoded in mitochondrial genomes that are vital for the oxidative phosphorylation pathway. In this study, we formally tested for signatures of adaptive evolution on mitochondrial protein coding genes in Tapirus pinchaque and other odd-toed ungulates inhabiting high-elevation environments.

RESULTS

The AT-rich mitochondrial genome of T. pinchaque is 16,750 bp long. A phylomitogenomic analysis supports the monophyly of the genus Tapirus and families in the Perissodactyla. The ratio of non-synonymous to synonymous substitutions demonstrated that all mitochondrial genes undergo purifying selection in T. pinchaque and other odd ungulates living at high elevations. Over this negative background selection, Branch Models suggested that cox3 and nad6 might be undergoing stronger purifying selection than other mitochondrial protein coding genes. Furthermore, Site Models suggested that one and four sites in nad2 and nad5, respectively, could be experiencing positive selection. However, these results were supported by Likelihood Ratio Tests but not Bayesian Empirical Bayes posterior probabilities. Additional analyses (in DataMonkey) indicated a relaxation of selection strength in nad6, evidence of episodic diversifying selection in cob, and revealed episodic positive/diversifying selection signatures for two sites in nad1, and one site each in nad2 and nad4.

CONCLUSION

The mitochondrial genome of T. pinchaque is an important genomic resource for conservation of this species and this study contributes to the understanding of adaptive evolution of mitochondrial protein coding genes in odd-toed ungulates inhabiting high-altitude environments.

The complete mitochondrial genome of Talpa martinorum (Mammalia: Talpidae), a mole species endemic to Thrace: genome content and phylogenetic considerations

The complete mitogenome sequence of Talpa martinorum, a recently described Balkan endemic mole, was assembled from next generation sequence data. The mitogenome is similar to that of the three other Talpa species sequenced to date, being 16,835 bp in length, and containing 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, an origin of L-strand replication, and a control region or D-loop. Compared to other Talpa mitogenomes sequenced to date, that of T. martinorum differs in the length of D-loop and stop codon usage. TAG and T-- are the stop codons for the ND1 and ATP8 genes, respectively, in T. martinorum, whilst TAA acts as a stop codon for both ND1 and ATP8 in the other three Talpa species sequenced. Phylogeny reconstructions based on Maximum Likelihood and Bayesian inference analyses yielded phylogenies with similar topologies, demonstrating that T. martinorum nests within the western lineage of the genus, being closely related to T. aquitania and T. occidentalis.

The Complete Mitochondrial Genome of a Neglected Breed, the Peruvian Creole Cattle (Bos taurus), and Its Phylogenetic Analysis

Cattle spread throughout the American continent during the colonization years, originating creole breeds that adapted to a wide range of climate conditions. The population of creole cattle in Peru is decreasing mainly due to the introduction of more productive breeds in recent years. During the last 15 years, there has been significant progress in cattle genomics. However, little is known about the genetics of the Peruvian creole cattle (PCC) despite its importance to (i) improving productivity in the Andean region, (ii) agricultural labor, and (iii) cultural traditions. In addition, the origin and phylogenetic relationship of the PCC are still unclear. In order to promote the conservation of the PCC, we sequenced the mitochondrial genome of a creole bull, which also possessed exceptional fighting skills and was employed for agricultural tasks, from the highlands of Arequipa for the first time. The total mitochondrial genome sequence is 16,339 bp in length with the base composition of 31.43% A, 28.64% T, 26.81% C, and 13.12% G. It contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a control region. Among the 37 genes, 28 were positioned on the H-strand and 9 were positioned on the L-strand. The most frequently used codons were CUA (leucine), AUA (isoleucine), AUU (isoleucine), AUC (isoleucine), and ACA (threonine). Maximum likelihood reconstruction using complete mitochondrial genome sequences showed that the PCC is related to native African breeds. The annotated mitochondrial genome of PCC will serve as an important genetic data set for further breeding work and conservation strategies.

Comparative Mitogenomics of True Frogs (Ranidae, Anura), and Its Implications for the Phylogeny and Evolutionary History of Rana

Simple Summary

The true frogs of the genus Rana are a complex and diverse group. Many new species have been discovered with the help of molecular markers and morphological traits. However, the evolutionary history in Rana were not well understood. In this study, we sequenced and annotated the complete mitochondrial genome of R. longicrus and R. zhenhaiensis. In 13 protein codon genes, the COI was the most conserved, and ATP8 had a fast rate of evolution. The Ka/Ks ratio analysis among Rana indicated the protein-coding genes were suffering purify selection. There were three kinds of gene arrangement patterns found. This study provides mitochondrial genetic information, improving our understanding of mitogenomic structure and evolution, and recognizes the phylogenetic relationship and taxonomy among Rana.

Abstract

The true frogs of the genus Rana are a complex and diverse group, containing approximately 60 species with wide distribution across Eurasia and the Americas. Recently, many new species have been discovered with the help of molecular markers and morphological traits. However, the evolutionary history in Rana was not well understood and might be limited by the absence of mitogenome information. In this study, we sequenced and annotated the complete mitochondrial genome of R. longicrus and R. zhenhaiensis, containing 22 tRNAs, 13 protein-coding genes, two ribosomal RNAs, and a non-coding region, with 17,502 bp and 18,006 bp in length, respectively. In 13 protein codon genes, the COI was the most conserved, and ATP8 had a fast rate of evolution. The Ka/Ks ratio analysis among Rana indicated the protein-coding genes were suffering purify selection. There were three kinds of gene arrangement patterns found. The mitochondrial gene arrangement was not related to species diversification, and several independent shifts happened in evolutionary history. Climate fluctuation and environmental change may have played an essential role in species diversification in Rana. This study provides mitochondrial genetic information, improving our understanding of mitogenomic structure and evolution, and recognizes the phylogenetic relationship and taxonomy among Rana.

Characterisation of the Complete Mitochondrial Genome of Critically Endangered Mustela lutreola (Carnivora: Mustelidae) and Its Phylogenetic and Conservation Implications

In this paper, a complete mitochondrial genome of the critically endangered European mink Mustela lutreola L., 1761 is reported. The mitogenome was 16,504 bp in length and encoded the typical 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes, and harboured a putative control region. The A+T content of the entire genome was 60.06% (A > T > C > G), and the AT-skew and GC-skew were 0.093 and −0.308, respectively. The encoding-strand identity of genes and their order were consistent with a collinear gene order characteristic for vertebrate mitogenomes. The start codons of all protein-coding genes were the typical ATN. In eight cases, they were ended by complete stop codons, while five had incomplete termination codons (TA or T). All tRNAs had a typical cloverleaf secondary structure, except tRNA^Ser(AGC) and tRNA^Lys, which lacked the DHU stem and had reduced DHU loop, respectively. Both rRNAs were capable of folding into complex secondary structures, containing unmatched base pairs. Eighty-one single nucleotide variants (substitutions and indels) were identified. Comparative interspecies analyses confirmed the close phylogenetic relationship of the European mink to the so-called ferret group, clustering the European polecat, the steppe polecat and the black-footed ferret. The obtained results are expected to provide useful molecular data, informing and supporting effective conservation measures to save M. lutreola.