Complete nucleotide sequences and gene organization of mitochondrial genome of Bufo gargarizans

The complete mitochondrial genome of Bufo gargarizans was sequenced using overlapping polymerase chain reaction (PCR) amplicons (GenBank Accession No. DQ275350). The genome is 17,277 base pairs in length, containing 13 protein-coding genes (ATP6, ATP8, COI-III, ND1-6, ND4L, Cyt b), 2 ribosomal RNAs (12S rRNA and 16S rRNA), 22 transfer RNAs and a putative control region. We analyzed the sequence using bioinformatics methods comparing the obtained mtDNA sequence with other toads and frogs. Based on the concatenated nucleotide sequences of protein-coding genes, we constructed a phylogenetic tree with maximum likelihood (ML) and maximum parsimony (MP) methods and discussed the phylogenetic relationships among 11 species of Anura.     

Complete mitochondrial DNA genome sequences show that modern birds are not descended from transitional shorebirds

To test the hypothesis put forward by Feduccia of the origin of modern birds from transitional birds, we sequenced the first two complete mitochondrial genomes of shorebirds (ruddy turnstone and blackish oystercatcher) and compared their sequences with those of already published avian genomes. When corrected for rate heterogeneity across sites and non-homogeneous nucleotide compositions among lineages in maximum likelihood (ML), the optimal tree places palaeognath birds as sister to the neognaths including shorebirds. This optimal topology is a re-rooting of recently published ordinal-level avian trees derived from mitochondrial sequences. Using a penalized likelihood (PL) rate-smoothing process in conjunction with dates estimated from fossils, we show that the basal splits in the bird tree are much older than the Cretaceous-Tertiary (K-T) boundary, reinforcing previous molecular studies that rejected the derivation of modern birds from transitional shorebirds. Our mean estimate for the origin of modern birds at about 123 million years ago (Myr ago) is quite close to recent estimates using both nuclear and mitochondrial genes, and supports theories of continental break-up as a driving force in avian diversification. Not only did many modern orders of birds originate well before the K-T boundary, but the radiation of major clades occurred over an extended period of at least 40 Myr ago, thus also falsifying Feduccia's rapid radiation scenario following a K-T bottleneck.     

Complete mitochondrial DNA genome sequences of extinct birds: ratite phylogenetics and the vicariance biogeography hypothesis

The ratites have stimulated much debate as to how such large flightless birds came to be distributed across the southern continents, and whether they are a monophyletic group or are composed of unrelated lineages that independently lost the power of flight. Hypotheses regarding the relationships among taxa differ for morphological and molecular data sets, thus hindering attempts to test whether plate tectonic events can explain ratite biogeography. Here, we present the complete mitochondrial DNA genomes of two extinct moas from New Zealand, along with those of five extant ratites (the lesser rhea, the ostrich, the great spotted kiwi, the emu and the southern cassowary and two tinamous from different genera. The non-stationary base composition in these sequences violates the assumptions of most tree-building methods. When this bias is corrected using neighbour-joining with log-determinant distances and non-homogeneous maximum likelihood, the ratites are found to be monophlyletic, with moas basal, as in morphological trees. The avian sequences also violate a molecular clock, so we applied a non-parametric rate smoothing algorithm, which minimizes ancestor-descendant local rate changes, to date nodes in the tree. Using this method, most of the major ratite lineages fit the vicariance biogeography hypothesis, the exceptions being the ostrich and the kiwi, which require dispersal to explain their present distribution.     

Complete mitochondrial genome of the Korean stumpy bullhead Pseudobagrus brevicorpus (Siluriformes, Bagridae)

We describe the complete mitochondrial genome sequence of the Korean stumpy bullhead Pseudobagrus brevicorpus, which is an endangered species in Korea. The circle genome (16,526?bp) consists of 13 protein coding, 22 tRNA, 2 rRNA genes and 1 control region. It has the typical vertebrate mitochondrial gene arrangement.     

Complete genome sequences of 138 mycobacteriophages

Bacteriophages are the most numerous biological entities in the biosphere, and although their genetic diversity is high, it remains ill defined. Mycobacteriophages-the viruses of mycobacterial hosts-provide insights into this diversity as well as tools for manipulating Mycobacterium tuberculosis. We report here the complete genome sequences of 138 new mycobacteriophages, which-together with the 83 mycobacteriophages previously reported-represent the largest collection of phages known to infect a single common host, Mycobacterium smegmatis mc(2) 155.     

Genome-wide detection and characterization of positive selection in Korean Native Black Pig from Jeju Island

Background

In the 1980s, Korean native black pigs from Jeju Island (Jeju black pigs) served as representative sample of Korean native black pigs, and efforts were made to help the species rebound from the brink of extinction, which occurred as a result of the introduction of Western pig breeds. Geographical separation of Jeju Island from the Korean peninsula has allowed Jeju black pigs not only to acquire unique characteristics but also to retain merits of rare Korean native black pigs.

Results

To further analyze the Jeju black pig genome, we performed whole-genome re-sequencing (average read depth of 14×) of 8 Jeju black pig and 6 Korean pigs (which live on the Korean peninsula) to compare and identify putative signatures of positive selection in Jeju black pig, the true and pure Korean native black pigs. The candidate genes potentially under positive selection in Jeju black pig support previous reports of high marbling score, rare occurrence of pale, soft, exudative (PSE) meat, but low growth rate and carcass weight compared to Western breeds.

Conclusions

Several candidate genes potentially under positive selection were involved in fatty acid transport and may have contributed to the unique characteristics of meat quality in JBP. Jeju black pigs can offer a unique opportunity to investigate the true genetic resource of once endangered Korean native black pigs. Further genome-wide analyses of Jeju black pigs on a larger population scale are required in order to define a conservation strategy and improvement of native pig resources.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-014-0160-1) contains supplementary material, which is available to authorized users.     

Complete mitochondrial genome sequences of three Crocodylus species and their comparison within the Order Crocodylia

Host-pathogen interactions are complex processes, and revealing these interactions is challenging. Beauveria bassiana is a destructive pathogen to the economically beneficial silkworm, Bombyx mori, but is also a good pathogenic material for investigating insect responses to fungal infection. For better understanding of the molecular regulation of immune response and the interactive mechanism between the silkworm and B. bassiana, suppression subtractive hybridization was employed to identify differentially expressed genes in the pathogen-stimulated silkworm larvae. Complementary DNA libraries were constructed, in which 240 clones were sequenced. A total of 77 genes were found to be involved in the infection process, among which 55 were known genes and 22 were novel. Expression profiling of 6 genes by quantitative PCR showed that they were induced by fungal challenge. This study establishes the first step to understanding the molecular mechanisms by which silkworm responds to fungal infection.     

Complete genome sequences of a Korean virulent porcine epidemic diarrhea virus and its attenuated counterpart

A virulent porcine epidemic diarrhea virus (PEDV) strain, DR13, was obtained from suckling pigs suspected of having porcine epidemic diarrhea in 1999 in Korea, and its attenuated counterpart was derived from virulent strain DR13 by serial propagation in Vero cells. This report describes the first complete genome sequences of virulent PEDV and its attenuated counterpart, which will provide important insights into the molecular basis of the attenuation of PEDV.     

Complete sequences of mitochondrial genomes from the Baltic mussel Mytilus trossulus

Marine mussels Mytilus possess two mitochondrial (mt) genomes, which undergo doubly uniparental inheritance (DUI). Female (F) and male (M) genomes are usually highly diverged at the sequence level. Both genomes contain the same set of metazoan genes (for 12 proteins, 2 rRNAs and 23 tRNAs), both lack the atp8 gene and have two tRNAs for methionine. However, recently recombination between those variants has been reported. Both original F and M mt genomes of M. trossulus were replaced by M. edulis mtDNA in the Baltic populations. Highly diverged M genome occurs rarely in the Baltic mussels. Full sequences of the M genome identified in males (sperm) and F genome in females (eggs) were obtained. Both genomes were diverged by 24% in nucleotide sequence, but had similar nucleotide composition and codon usage bias. Constant domain (CD) of the control region (CR), the tRNA and rRNA genes were the most conserved. The most diverged was the variable domain 1 (VD1) of the control region. The F genome was longer than M by 147 bp. and the main difference was localised in the VD1 region. No recombination was observed in whole mtDNA of both studied variants. Nuclear mitochondrial pseudogenes (numts) have not been found by hybridisation with probes complementary to several fragments of the Baltic M. trossulus mtDNA.     

Identification of reference genes for normalization of gene expression in thoroughbred and Jeju native horse(Jeju pony) tissues

Quantitative analysis of horse gene expression profiles under diverse experimental conditions is limited by the lack of reliable reference genes for normalization of mRNA levels. Therefore, in this study, the expression of potential reference genes was compared between thoroughbred and Jeju native horse (Jeju pony). We compared the expression of nine genes by quantitative real-time RT-PCR in fourteen tissues between the two horse breeds and analyzed their stability using the geNorm and NormFinder programs. The data obtained in this study suggest that the UBB gene could serve as a reference gene in gene expression analysis of thoroughbred and Jeju native horses.     

Complete mitochondrial genome of Locusta migratoria migratoria (Orthoptera: Oedipodidae): three tRNA-like sequences on the N-strand

The complete 16053 bp mitochondrial genome (mitogenome) sequence of Locusta migratoria migratoria has been determined. This mitogenome contains the base compositional biases and codon usage typical of metazoans, and the RSCU values indicate a negative correlation with the C and G contents in codon. The orientation and gene order of the L. migratoria migratoria is identical to Locusta migratoria migratoiodes. An unusual feature of the L. migratoria migratoria mitogenome is the presence of three tRNA-like structures on the N-strand: one tRNA(Ile)-like and two tRNA(Leu(CUN))-like sequences. The tRNA-like sequences have proper folding structures and anticodons sequences. Two repeated DNA sequences, Rpt I and Rpt II, were found in the A+T-rich region of the L. migratoria migratoria mitogenome. Both repeated sequences have various features. In the 5' region of Rpt I, a 51 bp fragment is localized in the srRNA gene; and there are two tandemly sub-repeated DNA sequences (sub-Rpts), Rpt 1-4, within Rpt I and Rpt II. One stem-loop structure on the N-strand that may be involved in the N-strand replication initiation was found in the A+T-rich region.     

Complete mitochondrial genome sequence of the Tyrolean Iceman

The Tyrolean Iceman was a witness to the Neolithic-Copper Age transition in Central Europe 5350-5100 years ago, and his mummified corpse was recovered from an Alpine glacier on the Austro-Italian border in 1991 [1]. Using a mixed sequencing procedure based on PCR amplification and 454 sequencing of pooled amplification products, we have retrieved the first complete mitochondrial-genome sequence of a prehistoric European. We have then compared it with 115 related extant lineages from mitochondrial haplogroup K. We found that the Iceman belonged to a branch of mitochondrial haplogroup K1 that has not yet been identified in modern European populations. This is the oldest complete Homo sapiens mtDNA genome generated to date. The results point to the potential significance of complete-ancient-mtDNA studies in addressing questions concerning the genetic history of human populations that the phylogeography of modern lineages is unable to tackle.     

Complete mitochondrial genome sequence of the Korean water deer Hydropotes inermis argyropus (Cervidae, Capreolinae)

The complete mitochondrial genome sequence of Hydropotes inermis argyropus consists of 13 protein-coding, 22 tRNA, and two rRNA genes, and 1 control region (CR). Three overlaps among the 13 protein-coding genes were found: ATP8/ATP6, ND4L/ND4, and ND5/ND6. The CR was located between the tRNA-Pro and tRNA-Phe genes and is 928 bp in length. The typical conserved domains, such as TAS and CSB, were identified in the CR.     

Excision sequences in the mitochondrial genome of yeast

We report an analysis of the sequences used in the excision of the mitochondrial genomes of 22 spontaneous and ten ethidium bromide (EtBr)-induced Saccharomyces cerevisiae petite mutants. In all cases, excision sequences were found to be perfect direct repeats, often flanked on one or both sides by regions of patchy homology. Sequences used in the excision of the genomes of spontaneous petites were always located in the AT spacers and GC clusters of intergenic regions of the genome; the GC clusters corresponded to ori and ori^s sequences, namely to canonical and surrogate origins of DNA replication, respectively. In the case of the ethidium bromide-induced petites, excision sequences were found not only in intergenic sequences, but also in the introns and exons of mitochondrial genes.     

Complete mitochondrial genome of the mudskipper Boleophthalmus pectinirostris (Perciformes, Gobiidae): repetitive sequences in the control region

The mudskipper, Boleophthalmus pectinirostris (Perciformes, Gobiidae), is an amphibious gobioid fish. In this paper, the complete mitochondrial genome of B. pectinirostris was firstly determined. The mitogenome (17,111 bp) comprises 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 1 putative control region. 130-bp tandem repeat was identified in the control region, which was almost identical among the 10 individuals examined, and three different frequencies of the repeat unit (five, six or seven) were found among these individuals.     

Complete mitochondrial genome sequences of the three pelagic chaetognaths Sagitta nagae,Sagitta decipiens and Sagitta enflata

The complete nucleotide sequences of the mitochondrial genomes were determined for the three pelagic chaetognaths, Sagitta nagae, Sagitta decipiens, and Sagitta enflata. The mitochondrial genomes of these species which were 11,459, 11,121, and 12,631 bp in length, respectively, contained 14 genes (11 protein-coding genes, one transfer RNA gene, and two ribosomal RNA genes), and were found to have lost 23 genes that are present in the typical metazoan mitochondrial genome. The same mitochondrial genome contents have been reported from the benthic chaetognaths belonging to the family Spadellidae, Paraspadella gotoi and Spadella cephaloptera. Within the phylum Chaetognatha, Sagitta and Spadellidae are distantly related, suggesting that the gene loss occurred in the ancestral species of the phylum. The gene orders of the three Sagitta species are markedly different from those of the other non-Chaetognatha metazoans. In contrast to the region with frequent gene rearrangements, no gene rearrangements were observed in the gene cluster encoding COII–III, ND1–3, srRNA, and tRNA^met. Within this conserved gene cluster, gene rearrangements were not observed in the three Sagitta species or between the Sagitta and Spadellidae species. The gene order of this cluster was also assumed to be the ancestral state of the phylum.     

Complete genome sequences of six strains of the genus methylobacterium

The complete and assembled genome sequences were determined for six strains of the alphaproteobacterial genus Methylobacterium, chosen for their key adaptations to different plant-associated niches and environmental constraints.     

Complete genome sequences of porcine reproductive and respiratory syndrome viruses: perspectives on their temporal and spatial dynamics

Porcine reproductive and respiratory syndrome virus (PRRSV) has been investigated extensively at the molecular level. Nevertheless, genome wide study on the temporal and spatial dynamics of the virus is non-existed. To explore this topic, we determined complete coding genome sequences for four PRRSV isolates and analyzed them together with 122 global published ones using the Bayesian coalescent approach as well as Bayesian inferences and maximum likelihood methods. All EU-type viruses belonged to one of two groups or were unclassified (5 isolates), and all NA-type isolates were divided into one of three major groups or were unclassified (1 isolate). Here, there was no apparent association between temporal or geographic origin and heterogeneity of global PRRSVs. Of the eight ORFs, ORF1a showed the most powerful evolutionary signal. Our findings also indicated that the PRRS virus evolved at a rate of 1.98 × 10^?3 substitutions/site/year, and the most recent common ancestor of the virus existed 786.4 years ago. Here, EU-type viruses segregated 115.7 years ago, while NA-type isolates diverged 179.8 years before the present. In addition, our reconstruction of the effective population size depicted five phases of epidemic growth: an initial constant, followed sequentially by slow decrease, slight increase, sharp decline, and then a rapid expansion approaching the present.