The characterization of complete mitochondrial genome and phylogenetic relationship within Rattus genus (Rodentia: Muridae)

The genus Rattus is one of the main pest genus of rodent. Most species of the genus carry all kinds of pathogenic bacteria to human being. They are traditionally considered to be a least understood group. The complete mitochondrial genome of the White-Footed Indochinese Rat, Rattus nitidus was determined in this study. The characterization of mitochondrial genomes of Rattus genus was also analyzed based on comprehensive comparison. The result of evolutionary patterns of protein-coding genes (PCGs) suggested purifying selection was the predominant evolutionary forces in the mitochondrial genomes of Rattus genus. The NADH dehydrogenase 4 gene (ND4) showed a highly elevated Ka/Ks ratio compared to the other protein-coding genes, which indicated ND4 was most likely under relaxed selection pressure. Phylogenetic analysis provided a well-supported outline of Rattus genus, and revealed two groups in the genus. R. nitidus had a sister relationship with R. norvegicus.     

Positive and purifying selection in mitochondrial genomes of a bird with mitonuclear discordance

Diversifying selection on metabolic pathways can reduce intraspecific gene flow and promote population divergence. An opportunity to explore this arises from mitonuclear discordance observed in an Australian bird Eopsaltria australis. Across >1500 km, nuclear differentiation is low and latitudinally structured by isolation by distance, whereas two highly divergent, parapatric mitochondrial lineages (>6.6% in ND2) show a discordant longitudinal geographic pattern and experience different climates. Vicariance, incomplete lineage sorting and sex‐biased dispersal were shown earlier to be unlikely drivers of the mitonuclear discordance; instead, natural selection on a female‐linked trait was the preferred hypothesis. Accordingly, here we tested for signals of positive, divergent selection on mitochondrial genes in E. australis. We used codon models and physicochemical profiles of amino acid replacements to analyse complete mitochondrial genomes of the two mitochondrial lineages in E. australis, its sister species Eopsaltria griseogularis, and outgroups. We found evidence of positive selection on at least five amino acids, encoded by genes of two oxidative phosphorylation pathway complexes NADH dehydrogenase (ND4 and ND4L) and cytochrome bc₁ (cyt‐b) against a background of widespread purifying selection on all mitochondrial genes. Three of these amino acid replacements were fixed in ND4 of the geographically most widespread E. australis lineage. The other two replacements were fixed in ND4L and cyt‐b of the geographically more restricted E. australis lineage. We discuss whether this selection may reflect local environmental adaptation, a by‐product of other selective processes, or genetic incompatibilities, and propose how these hypotheses can be tested in future.     

Signatures of natural selection in the mitochondrial genomes of Tachycineta swallows and their implications for latitudinal patterns of the ‘pace of life’

Latitudinal variation in avian life histories can be summarized as a slow–fast continuum, termed the ‘pace of life’, that encompasses patterns in life span, reproduction, and rates of development among tropical and temperate species. Much of the variation in avian pace of life is tied to differences in rates of long-term metabolic energy expenditure. Given the vital role of the mitochondrion in metabolic processes, studies of variation in the mitochondrial genome may offer opportunities to establish mechanistic links between genetic variation and latitudinal ‘pace of life’ patterns. Using comparative genomic analyses, we examined complete mitochondrial genome sequences obtained from nine, broadly distributed Tachycineta swallow species to test for signatures of natural selection across the mitogenome within a phylogenetic framework. Our results show that although purifying selection is the dominant selective force acting on the mitochondrial genome in Tachycineta, three mitochondrial genes (ND2, ND5, and CYTB) contain regions that exhibit signatures of diversifying selection. Two of these genes (ND2 and ND5) encode interacting subunits of NADH dehydrogenase, and amino residues that were inferred to be targets of positive selection were disproportionately concentrated in these genes. Moreover, the positively selected sites exhibited a phylogenetic pattern that could be indicative of adaptive divergence between “fast” and “slow” lineages. These results suggest that functional variation in cytochrome b and NADH dehydrogenase could mechanistically contribute to latitudinal ‘pace of life’ patterns in Tachycineta.     

The complete mitochondrial genome sequence and gene organization of the mud crab (Scylla paramamosain) with phylogenetic consideration

The complete mitochondrial genome is of great importance for better understanding the genome-level characteristics and phylogenetic relationships among related species. In the present study, we determined the complete mitochondrial genome DNA sequence of the mud crab (Scylla paramamosain) by 454 deep sequencing and Sanger sequencing approaches. The complete genome DNA was 15,824 bp in length and contained a typical set of 13 protein-coding genes, 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes and a putative control region (CR). Of 37 genes, twenty-three were encoded by the heavy strand (H-strand), while the other ones were encoded by light strand (L-strand). The gene order in the mitochondrial genome was largely identical to those obtained in most arthropods, although the relative position of gene tRNA^His differed from other arthropods. Among 13 protein-coding genes, three (ATPase subunit 6 (ATP6), NADH dehydrogenase subunits 1 (ND1) and ND3) started with a rare start codon ATT, whereas, one gene cytochrome c oxidase subunit I (COI) ended with the incomplete stop codon TA. All 22 tRNAs could fold into a typical clover-leaf secondary structure, with the gene sizes ranging from 63 to 73 bp. The phylogenetic analysis based on 12 concatenated protein-coding genes showed that the molecular genetic relationship of 19 species of 11 genera was identical to the traditional taxonomy.     

The complete mitochondrial genome of Biston panterinaria (Lepidoptera: Geometridae), with phylogenetic utility of mitochondrial genome in the Lepidoptera

The complete mitochondrial genome (mitogenome) of the Chinese pistacia looper Biston panterinaria was sequenced and annotated (15,517 bp). It contains the typical 37 genes of animal mitogenomes and a high A + T content (79.5%). All protein coding genes (PCGs) use standard ATN initiation codons except for cytochrome c oxidase 1 (COX1) with CGA. Eleven PCGs use a common stop codon of TAA or TAG, whereas COX2 and NADH dehydrogenase 4 (ND4) use a single T. All transfer RNA (tRNA) genes have the typical clover-leaf structure with the exception of tRNA^Ser(AGN). We reconstructed a preliminary mitochondrial phylogeny of six ditrysian superfamilies and performed comparative analyses of inference methods (Bayesian Inference (BI), Maximum Likelihood (ML), and Maximum Parsimony (MP)), dataset compositions (including and excluding 3rd codon positions), and alignment methods (Muscle, Clustal W, and MAFFT). Our analyses indicated that inference methods and dataset compositions more significantly affected the phylogenetic results than alignment methods. BI analysis consistently revealed uncontroversial relationships with all dataset compositions. By contrast, ML analysis failed to reconstruct stable phylogeny at two nodes, whereas MP analysis had more difficulties in the tree resolution and nodal support. Distinct from most previous studies, our analyses revealed that Geometroidea had a closer lineage relationship with Bombycoidea than Noctuoidea. Similar to previous molecular studies, our analyses revealed that Hesperiidae were nested in the Papilionoidea clade, providing further evidence to the previous concept that Papilionoidea was paraphyletic, and none of the butterflies were associated with the Macroheterocera.     

Genetic diversity and phylogenetic relationship among the western and the Asian honey bees based on two mitochondrial gene segments (COI and ND5)

The Asian honey bee species i.e., Apis cerana (the eastern honey bee), A. dorsata (the giant honey bee), and the western or European honey bee (A. mellifera) collected from Pakistan were studied using partial sequences from two mitochondrial genes (i) the Cytochrome c oxidase I (COI) and (ii) the mitochondrially encoded NADH dehydrogenase 5 (ND5) and then compared with other honey bees sequences (already submitted from different countries around the globe) obtained after the national center for biotechnology information (NCBI). DNA sequences were analyzed employing molecular evolutionary genetics analysis and Kimura 2-parameter model, neighbor-joining method was applied to investigate phylogenetic relationships, and DNA sequence polymorphism was applied to measure the genetic diversity within the genus Apis. The phylogenetic analyses yielded consistent results. Based on COI gene fragment in two Asian and European honey bee species from Pakistan and from other countries showed considerable genetic diversity levels and deviation among the species. While in contrast the phylogenetic analyses based on ND5 gene fragment in Asian and European honey bee species from Pakistan and other countries showed comparatively higher genetic diversity indices and variations than the COI gene. So, in the genus Apis, the mitochondrial ND5 region has shown the possibility to answer the interactions among species. A further detailed work (by linking the analysis of other genomic and mitochondrial genes) is required for good quality solution to establish the concise genetic diversity and interaction among the Apis species. The objective of this study was to explore the extent of genetic differences and phylogenetic links among the three kinds of honey bee species from Pakistan and comparing them with other bee species around the globe.     

Mitochondrial DNA as effective molecular markers for the genetic variation and phylogeny of the family Osteoglossidae

The present study examined the genetic variation of the family Osteoglossidae from different geographical locations based on the mitochondrial NADH dehydrogenase subunit 2 (ND2) and ATPase subunit 6 (ATPase6) genes; we then re-constructed the phylogenetic relationships using the two sequences in combination. The results showed that the partial sequences of mitochondrial ND2 and ATPase6 of the family Osteoglossidae were 813 bp and 669 bp, respectively. A total of 42 species-specific nucleotide positions of the family Osteoglossidae were found to be useful for molecular identification. The sequence variation showed greater differences (8.3% ~ 28.1% for the combined sequences, 8.3% ~ 26.7% for the ND2 gene, and 9.3% ~ 28.7% for the ATPase6 gene) among the different species of Osteoglossidae, and there was a significant association between the genetic difference and geographical location. Phylogenetic analyses using neighbor-joining, Bayesian inference, and maximum parsimony (MP) methods based on the combined sequences of the two genes were able to distinguish the different species and were in agreement with the existing taxonomy based on morphological characters and in association with the geographical distribution among seven species of the family Osteoglossidae.     

Characteristics of the mitochondrial genome of Rana omeimontis and related species in Ranidae: Gene rearrangements and phylogenetic relationships

The Omei wood frog (Rana omeimontis), endemic to central China, belongs to the family Ranidae. In this study, we achieved detail knowledge about the mitogenome of the species. The length of the genome is 20,120 bp, including 13 protein‐coding genes (PCGs), 22 tRNA genes, two rRNA genes, and a noncoding control region. Similar to other amphibians, we found that only nine genes (ND6 and eight tRNA genes) are encoded on the light strand (L) and other genes on the heavy strand (H). Totally, The base composition of the mitochondrial genome included 27.29% A, 28.85% T, 28.87% C, and 15.00% G, respectively. The control regions among the Rana species were found to exhibit rich genetic variability and A + T content. R. omeimontis was clustered together with R. chaochiaoensis in phylogenetic tree. Compared to R. amurensis and R. kunyuensi, it was more closely related to R. chaochiaoensis, and a new way of gene rearrangement (ND6‐trnE‐Cytb‐D‐loop‐trnL2 (CUN)‐ND5‐D‐loop) was also found in the mitogenome of R. amurensis and R. kunyuensi. Our results about the mitochondrial genome of R. omeimontis will contribute to the future studies on phylogenetic relationship and the taxonomic status of Rana and related Ranidae species.     

Characterization of the complete mitochondrial genome of Bombyx mori strain H9 (Lepidoptera: Bombycidae)

The complete mitochondrial genome (mitogenome) of Bombyx mori strain H9 (Lepidoptera: Bombycidae) is 15,670 base pairs (bp) in length, encoding 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes and a control region. The nucleotide composition of the genome is highly A + T biased, accounting for 81.31%, with a slightly positive AT skewness (0.059). The arrangement of 13 PCGs is similar to that of other sequenced lepidopterans. All the PCGs are initiated by ATN codons, except for the cytochrome c oxidase subunit 1 (cox1) gene, which is proposed by the TTAG sequence as observed in other lepidopterans. Unlike the other PCGs, the cox1 and cytochrome c oxidase subunit 2 (cox2) genes have incomplete stop codons consisting of just a T. All tRNAs have typical structures of insect mitochondrial tRNAs, which is different from other sequenced lepidopterans. The structure of A + T-rich region is similar to that of other sequenced lepidopterans, including non-repetitive sequences, the ATAGA binding domain, a 18 bp poly-T stretch and a poly-A element upstream of transfer RNA M (trnM) gene. Phylogenetic analysis shows that the domesticated silkmoth B. mori originated from the Chinese Bombyx mandarina.     

Interglacial refugia preserved high genetic diversity of the Chinese mole shrew in the mountains of southwest China

The mountains of southwest China (MSC) harbor extremely high species diversity; however, the mechanism behind this diversity is unknown. We investigated to what degree the topography and climate change shaped the genetic diversity and diversification in these mountains, and we also sought to identify the locations of microrefugia areas in these mountains. For these purposes, we sampled extensively to estimate the intraspecific phylogenetic pattern of the Chinese mole shrew (Anourosorex squamipes) in southwest China throughout its range of distribution. Two mitochondrial genes, namely, cytochrome b (CYT B) and NADH dehydrogenase subunit 2 (ND2), from 383 archived specimens from 43 localities were determined for phylogeographic and demographic analyses. We used the continuous-diffusion phylogeographic model, extensive Bayesian skyline plot species distribution modeling (SDM) and approximate Bayesian computation (ABC) to explore the changes in population size and distribution through time of the species. Two phylogenetic clades were identified, and significantly higher genetic diversity was preserved in the southern subregion of the mountains. The results of the SDM, continuous-diffusion phylogeographic model, extensive Bayesian skyline plot and ABC analyses were congruent and supported that the Last Interglacial Maximum (LIG) was an unfavorable period for the mole shrews because of a high degree of seasonality; A. squamipes survived in isolated interglacial refugia mainly located in the southern subregion during the LIG and rapidly expanded during the last glacial period. These results furnished the first evidence for major Pleistocene interglacial refugia and a latitudinal effect in southwest China, and the results shedding light on the higher level of species richness in the southern subregion.     

High‐altitude adaptation in vertebrates as revealed by mitochondrial genome analyses

The high‐altitude environment may drive vertebrate evolution in a certain way, and vertebrates living in different altitude environments might have different energy requirements. We hypothesized that the high‐altitude environment might impose different influences on vertebrate mitochondrial genomes (mtDNA). We used selection pressure analyses and PIC (phylogenetic independent contrasts) analysis to detect the evolutionary rate of vertebrate mtDNA protein‐coding genes (PCGs) from different altitudes. The results showed that the ratio of nonsynonymous/synonymous substitutions (dN/dS) in the mtDNA PCGs was significantly higher in high‐altitude vertebrates than in low‐altitude vertebrates. The seven rapidly evolving genes were shared by the high‐altitude vertebrates, and only one positive selection gene (ND5 gene) was detected in the high‐altitude vertebrates. Our results suggest the mtDNA evolutionary rate in high‐altitude vertebrates was higher than in low‐altitude vertebrates as their evolution requires more energy in a high‐altitude environment. Our study demonstrates the high‐altitude environment (low atmospheric O₂ levels) drives vertebrate evolution in mtDNA PCGs.     

The first complete mitochondrial genome of the Indian Tent Turtle,Pangshura tentoria (Testudines: Geoemydidae): Characterization and comparative analysis

The characterization of a complete mitogenome is widely used in genomics studies for systematics and evolutionary research. However, the sequences and structural motifs contained within the mitogenome of Testudines taxa have rarely been examined. The present study decodes the first complete mitochondrial genome of the Indian Tent Turtle, Pangshura tentoria (16,657 bp) by using next‐generation sequencing. This denovo assembly encodes 37 genes: 13 protein‐coding genes (PCGs), 22 transfer RNA (tRNAs), two ribosomal RNA, and one control region (CR). Most of the genes were encoded on majority strand, except for one PCG (NADH dehydrogenase subunit 6) and eight tRNAs. Most of the PCGs were started with an ATG initiation codon, except for Cytochrome oxidase subunit 1 with “GTG” and NADH dehydrogenase subunit 5 with “ATA.” The termination codons, “TAA” and “AGA” were observed in two subunits of NADH dehydrogenase gene. The relative synonymous codon usage analysis revealed the maximum abundance of alanine, isoleucine, leucine, and threonine. The nonsynonymous/synonymous ratios were <1 in all PCGs, which indicates strong negative selection among all Geoemydid species. The study also found the typical cloverleaf secondary structure in most of the tRNA genes, except for serine with the lack of the conventional DHU arm. The comparative study of Geoemydid mitogenomes revealed the occurrence of tandem repeats was frequent in the 3′ end of CR. Further, two copies of a unique tandem repeat “TTCTCTTT” were identified in P. tentoria. The Bayesian and maximum‐likelihood phylogenetic trees using concatenation of 13 PCGs revealed the close relationships of P. tentoria with Batagur trivittata in the studied dataset. All the Geoemydid species showed distinct clustering with high bootstrap support congruent with previous evolutionary hypotheses. We suggest that the generations of more mitogenomes of Geoemydid species are required, to improve our understanding of their in‐depth phylogenetic and evolutionary relationships.     

Molecular Identification of Diphyllobothrium nihonkaiense from 3 Human Cases in Heilongjiang Province with a Brief Literature Review in China

Human diphyllobothriasis is a widespread fish-borne zoonosis caused by the infection with broad tapeworms belonging to the genus Diphyllobothrium. In mainland China, so far 20 human cases of Diphyllobothrium infections have been reported, and the etiologic species were identified as D. latum and D. nihonkaiense based on morphological characteristics or molecular analysis. In the present study, proglottids of diphyllobothriid tapeworms from 3 human cases that occurred in Heilongjiang Province, China were identified as D. nihonkaiense by sequencing mitochondrial cytochrome c oxidase subunit I (cox1) and NADH dehydrogenase subunit 5 (nad5) genes. Two different cox1 gene sequences were obtained. One sequence showed 100% homology with those from humans in Japan. The remaining cox1 gene sequence and 2 different nad5 gene sequences obtained were not described previously, and might reflect endemic genetic characterizations. D. nihonkaiense might also be a major causative species of human diphyllobothriasis in China. Meanwhile, the finding of the first pediatric case of D. nihonkaiense infection in China suggests that infants infected with D. nihonkaiense should not be ignored.     

Cloning and sequence analysis of a mitochondrial gene cluster encoding two NADH dehydrogenase subunits and seven tRNA molecules from Trichoderma reesei

A mitochondrial gene cluster, encoding proteins homologous to NADH dehydrogenase subunits II and III (ND2 and ND3) and seven tRNAs, from Trichoderma reesei QM9414 was cloned and sequenced. These genes are clustered tandemly on the mitochondrial genome of QM9414. Phylogenetic analysis showed that ND2 and ND3 were most closely related to the mitochondrial ND subunits II (71% identity) and III (70% identity) from Podospora anserine. Northern dot blot analysis showed that the nd2 and nd3 genes are actively transcribed in the T. reesei mitochondria.     

The mitochondrial genome of red-necked phalarope <Emphasis Type="Italic">Phalaropus lobatus</Emphasis> (Charadriiformes: Scolopacidae) and phylogeny analysis among Scolopacidae

The red-necked phalarope is a wonderful species with specific morphological characters and lifestyles. Mitochondrial genomes, encoding necessary proteins involved in the system of energy metabolism, are important for the evolution and adaption of species. In this study, we determined the complete mitogenome sequence of Phalaropus lobatus (Charadriiformes: Scolopacidae). The circular genome is 16714 bp in size, containing 13 PCGs, two ribosomal RNAs and 22 tRNAs and a high AT-rich control region. The AT skew and GC skew of major strand is positive and negative respectively. Most of PCGs are biased towards A-rich except ND1. A codon usage analysis shows that 3 start codons (ATG, GTG and ATA), 4 stop codons (TAA, TAG, AGG, AGA) and two incomplete terminate codons (T–). Twenty two transfer RNAs have the typical cloverleaf structure, and a total of ten base pairs are mismatched throughout the nine tRNA genes. The phylogenetic tree based on 13 PCGs and 2 rRNA genes indicates that monophyly of the family and genus Phalaropus is close to genus Xenus plus Tringa. The analysis of selective pressure shows 13 protein-coding genes are evolving under the purifying selection and P. lobatus is different from other Scolopacidae species on the selective pressure of gene ND4. This study helps us know the inherent mechanism of mitochondrial structure and natural selection.     

Complete mitochondrial genome of <Emphasis Type="Italic">Ampittia dioscorides</Emphasis> (Lepidoptera: Hesperiidae) and its phylogenetic analysis

The complete mitochondrial genome of Ampittia dioscorides (Lepidoptera: Hesperiidae) was determined. The sequenced genome is a circular molecule of 15313 bp, containing 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and an A + T-rich region. The gene arrangements and transcribing directions are identical to those in most of the reported lepidopteran mitogenomes. The base composition of the whole genome and genes or regions are also similar to those in other lepidopteran species. All the PCGs are initiated by typical ATN codons; the exception being COI, which begins with a CGA codon. Eight genes (ND2, ATPase8, ATPase6, COIII, ND5, ND4L, ND6, and Cytb) end with a TAA stop codon, and two genes (ND1 and ND3) end with TAG. The remaining three genes (COI and COII, which end with TA-, and ND4, which ends with T-) have incomplete stop codons. All tRNAs have the typical clover-leaf structure of mitochondrial tRNAs, with the exception of tRNA^Ser(AGY). On the basis of the concatenated nucleotide and amino acid sequences of the 13 PCGs and wingless gene of 22 butterfly species, maximum parsimony (MP) and Bayesian inference (BI) trees were constructed, respectively. Both MP and BI trees had the same topological structure: ((((Nymphalidae + Danaidae) + Lycaenidae) + Pieridae) + Papilionidae) + Hesperiidae). The results provide support for Hesperiidae as a superfamily-level taxon.     

Mitochondrial DNA sequence-based phylogenetic relationship among flesh flies of the genus <Emphasis Type="Italic">Sarcophaga</Emphasis> (Sarcophagidae: Diptera)

The phylogenetic relationships among flesh flies of the family Sarcophagidae has been based mainly on the morphology of male genitalia. However, the male genitalic character-based relationships are far from satisfactory. Therefore, in the present study mitochondrial DNA has been used as marker to unravel genetic relatedness and to construct phylogeny among five sympatric species of the genus Sarcophaga. Two mitochondrial genes viz., cytochrome oxidase subunit 1 (COI) and NAD dehydrogenase subunit 5 (ND5) were sequenced and genetic distance values were calculated on the basis of sequence differences in both the mitochondrial genes. The data revealed very few genetic difference among the five species for the COI and ND5 gene sequences.     

Characterization of the complete mitochondrial genome of Diaphania pyloalis (Lepidoptera: Pyralididae)

The complete mitochondrial genome (mitogenome) of Diaphania pyloalis (Lepidoptera: Pyralididae) was determined to be 15,298 bp and has the typical gene organization of mitogenomes from lepidopteran insects. It consists of 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes and an A + T-rich region. The A + T content of this mitogenome is 80.83% and the AT skew is slightly positive. All PCGs are initiated by ATN codons, except for cytochrome c oxidase subunit 1 (cox1) gene which is initiated by CGA. Only the cox2 gene has an incomplete stop codon consisting of just a T. All the tRNA genes display a typical clover-leaf structure of mitochondrial tRNA. The A + T-rich region of the mitogenome is 332 bp in length, including several common features found in lepidopteran mitogenomes. Phylogenetic analysis showed that the D. pyloalis is close to Pyralididae.