Angiosperm mitochondrial genomes are more complex than those of other organisms. Analyses of the mitochondrial genome sequences of at least 11 angiosperm species have showed several common properties; these cannot easily explain, however, how the diverse mitotypes evolved within each genus or species. We analyzed the evolutionary relationships of Brassica mitotypes by sequencing.

The Oxytricha trifallax mitochondrial genome contains the largest sequenced ciliate mitochondrial chromosome (~70 kb) plus a ~5-kb linear plasmid bearing mitochondrial telomeres. We identify two new ciliate split genes (rps3 and nad2) as well as four new mitochondrial genes (ribosomal small subunit protein genes: rps- 2, 7, 8, 10), previously undetected in ciliates due to their extreme divergence. The increased size of the Oxytricha mitochondrial genome relative to other ciliates is primarily a consequence of terminal expansions, rather than the retention of ancestral mitochondrial genes. Successive segmental duplications, visible in one of the two Oxytricha mitochondrial subterminal regions, appear to have contributed to the genome expansion. Consistent with pseudogene formation and decay, the subtermini possess shorter, more loosely packed open reading frames than the remainder of the genome. The mitochondrial plasmid shares a 251-bp region with 82% identity to the mitochondrial chromosome, suggesting that it most likely integrated into the chromosome at least once. This region on the chromosome is also close to the end of the most terminal member of a series of duplications, hinting at a possible association between the plasmid and the duplications. The presence of mitochondrial telomeres on the mitochondrial plasmid suggests that such plasmids may be a vehicle for lateral transfer of telomeric sequences between mitochondrial genomes. We conjecture that the extreme divergence observed in ciliate mitochondrial genomes may be due, in part, to repeated invasions by relatively error-prone DNA polymerase-bearing mobile elements.

Maintenance and replication of the mitochondrial genome (mtDNA) is essential to mitochondrial function and eukaryotic energy production through the electron transport chain. mtDNA is replicated by a core set of proteins: Pol γ, Twinkle, and the single-stranded DNA binding protein. Fewer pathways exist for repair of mtDNA than nuclear DNA, and unrepaired damage to mtDNA may accumulate and lead to dysfunctional mitochondria. The mitochondrial genome is susceptible to damage by both endogenous and exogenous sources. Missense mutations to the nuclear genes encoding the core mtDNA replisome (POLG, POLG2, TWNK, and SSBP1) cause changes to the biochemical functions of their protein products. These protein variants can damage mtDNA and perturb oxidative phosphorylation. Ultimately, these mutations cause a diverse set of diseases that can affect virtually every system in the body. Here, we briefly review the mechanisms of mtDNA damage and the clinical consequences of disease variants of the core mtDNA replisome.

A fraction of the Neanderthal mitochondrial genome sequence has a similarity with a 5,839-bp nuclear DNA sequence of mitochondrial origin (numt) on the human chromosome 1. This fact has never been interpreted. Although this phenomenon may be attributed to contamination and mosaic assembly of Neanderthal mtDNA from short sequencing reads, we explain the mysterious similarity by integration of this numt (mtAncestor-1) into the nuclear genome of the common ancestor of Neanderthals and modern humans not long before their reproductive split.

We described the complete mitochondrial genome of the Ctenophore Beroe cucumis, which is a circular molecule of 10,487 bp in length. The new mitochondrial genome comprised only 12 genes, making it one of the smallest animals' mtDNA. Both nucleotide substitution and gene order rearrangements exhibited extreme high evolutionary rate in mitogenomes of Ctenophore. The phylogenetic analysis based on mitogenomics failed to reveal the basal position of Ctenophore within metazoan, owing to the extreme evolutionary rate. Based on the available Ctenophora mitogenomes, we found the optimized primers designed by Geller et al. for DNA barcoding suited for the taxon.

Mitochondrial diseases are a clinically heterogeneous group of rare hereditary disorders that are defined by a genetic defect predominantly affecting mitochondrial oxidative phosphorylation. Mitochondrial diseases are caused by mutations of genes encoded by either nuclear DNA or mitochondrial DNA. Hundreds of different mitochondrial DNA point mutations and large-scale mitochondrial DNA rearrangements have been shown to cause mitochondrial diseases including Kearns–Sayre syndrome, Leber’s hereditary optic neuropathy, Leigh syndrome, myoclonic epilepsy with ragged-red fibers, mitochondrial encephalopathy lactic acidosis stroke.

The segregation of mitochondrial DNA (mtDNA) is important for the maintenance and transmission of the genome between generations. Recently, we clarified that human mitochondrial transcription factor A (TFAM) is required for equal distribution and symmetric segregation of mtDNA in cultured cells; however, the molecular mechanism involved is largely unknown. ClpX is an ATPase associated with various cellular activities (AAA+) proteins that localize to the mitochondrial matrix and is suggested to associate with mtDNA. In this study, we found that RNAi-mediated knockdown of ClpX in HeLa cells resulted in enlarged mtDNA nucleoids, which is very similar to that observed in TFAM-knockdown cells in several properties. The expression of TFAM protein was not significantly reduced in ClpX-knockdown cells. However, the enlarged mtDNA nucleoids caused by ClpX-knockdown were suppressed by overexpression of recombinant TFAM and the phenotype was not observed in knockdown with ClpP, a protease subunit of ClpXP. Endogenous ClpX and TFAM exist in close vicinity, and ClpX enhanced DNA-binding activity of TFAM in vitro. These results suggest that human ClpX, a novel mtDNA regulator, maintains mtDNA nucleoid distribution through TFAM function as a chaperone rather than as a protease and its involvement in mtDNA segregation.

Mitochondria are organelles that perform major roles in cellular operation. Thus, alterations in mitochondrial genome (mtGenome) may lead to mitochondrial dysfunction and cellular deregulation, influencing carcinogenesis. Gastric cancer (GC) is one of the most incident and mortal types of cancer in Brazil, particularly in the Amazon region. Here, we sequenced and compared the whole mtGenome extracted from FFPE tissue samples of GC patients (tumor and internal control - IC) and cancer-free individuals (external control - EC) from this region. We found 3-fold more variants and up to 9-fold more heteroplasmic regions in tumor when compared to paired IC samples. Moreover, tumor presented more heteroplasmic variants when compared to EC, while IC and EC showed no significant difference when compared to each other. Tumor also presented substantially more variants in the following regions: MT-RNR1, MT-ND5, MT-ND4, MT-ND2, MT-DLOOP1 and MT-CO1. In addition, our haplogroup results indicate an association of Native American ancestry (particularly haplogroup C) to gastric cancer development. To the best of our knowledge, this is the first study to sequence the whole mtGenome from FFPE samples and to apply mtGenome analysis in association to GC in Brazil.

Trichoptera are a group of the benthic organism, almost all of which live in water during their life cycle. Trichoptera usually develop through egg, larva, pupa, and moth stages. In its larval stage, Trichoptera usually live in water and are often called the caddisfly. In this study, the mitochondrial genome of Macrostemum floridum was analyzed. The total length of the mitochondrial genome is 15,424 bp and consists of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and one control region. The genome has a typical mitochondrial gene sequence of Trichoptera. Phylogenetic analysis of the mitochondrial genomes of 23 species of Trichoptera and Lepidoptera showed that M. floridum forms a monophyletic group with other species of Lepidoptera.

Copepoda is the most diverse and abundant group of crustaceans, but its phylogenetic relationships are ambiguous. Mitochondrial (mt) genomes are useful for studying evolutionary history, but only six complete Copepoda mt genomes have been made available and these have extremely rearranged genome structures. This study determined the mt genome of Calanus hyperboreus, making it the first reported Arctic copepod mt genome and the first complete mt genome of a calanoid copepod. The mt genome of C. hyperboreus is 17,910 bp in length and it contains the entire set of 37 mt genes, including 13 protein-coding genes, 2 rRNAs, and 22 tRNAs. It has a very unusual gene structure, including the longest control region reported for a crustacean, a large tRNA gene cluster, and reversed GC skews in 11 out of 13 protein-coding genes (84.6%). Despite the unusual features, comparing this genome to published copepod genomes revealed retained pan-crustacean features, as well as a conserved calanoid-specific pattern. Our data provide a foundation for exploring the calanoid pattern and the mechanisms of mt gene rearrangement in the evolutionary history of the copepod mt genome.

Baylisascaris procyonis (Nematoda: Ascaridida), an intestinal nematode of raccoons, is emerging as an important helminthic zoonosis due to serious or fatal larval migrans in animals and humans. Despite its significant veterinary and public health impact, the epidemiology, molecular ecology and population genetics of this parasite remain largely unexplored. Mitochondrial (mt) genomes can provide a foundation for investigations in these areas and assist in the diagnosis and control of B. procyonis. In this study, the first complete mt genome sequence of B. procyonis was determined using a polymerase chain reaction (PCR)-based primer-walking strategy.

In this study, we determined the complete mitochondrial genome of Neolissochilus heterostomus. The genome is 16,585 bp in length, including 2 ribosomal RNA genes, 13 proteins-coding genes, 22 transfer RNA genes, and two non-coding control regions. Sequence analysis showed that the overall base composition of N. heterostomus is T 24.8%, C 27.7%, A 31.7%, and G 15.8%. The sequence is a slight A + T bias of 56.5%, which is similar to other fishes. We describe a phylogenetic analysis of 16 species of Cypriniformes based on the complete mitochondrial genome, and the result showed that N. stracheyi is most closely related to N. heterostomus. This mitogenome sequence data would play an important role in the investigation of phylogenetic relationship of the Cyprinidae.

Gastropod mitochondrial genomes exhibit an unusually great variety of gene orders compared to other metazoan mitochondrial genome such as e.g those of vertebrates. Hence, gastropod mitochondrial genomes constitute a good model system to study patterns, rates, and mechanisms of mitochondrial genome rearrangement. However, this kind of evolutionary comparative analysis requires a robust phylogenetic framework of the group under study, which has been elusive so far for gastropods in spite of the efforts carried out during the last two decades. Here, we report the complete nucleotide sequence of five mitochondrial genomes of gastropods (Pyramidella dolabrata, Ascobulla fragilis, Siphonaria pectinata, Onchidella celtica, and Myosotella myosotis), and we analyze them together with another ten complete mitochondrial genomes of gastropods currently available in molecular databases in order to reconstruct the phylogenetic relationships among the main lineages of gastropods.

The objective of this study was to analyse intraspecific sequence variation of Atlantic cod mitochondrial DNA, based on a comprehensive collection of completely sequenced mitochondrial genomes.

Parasitic plants rely on their host to cover their nutritional requirements either for their entire life or a smaller part of it. Depending on the level of parasitism, a proportional reduction on the plastid genome has been found. However, knowledge on gene loss and evolution of the mitogenome of parasitic plants is only available for four hemiparasitic Viscum species (Viscaceae), which lack many of the mitochondrial genes, while the remaining genes exhibit very fast molecular evolution rates. In this study, we include another genus, Phoradendron, from the Viscaceae, as well as 10 other hemiparasitic or holoparasitic taxa from across the phylogeny of the angiosperms to investigate how fast molecular evolution works on their mitogenomes, and the extent of gene loss.

In this study, we determined the complete mitochondrial genome of Geoemyda spengleri. The genome was 17,448bp in length and contained 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 main non-coding regions. The overall base composition of G. spengleri is A 33.67%, T 27.64%, C 25.56%, and G 13.14%, with a highly A + T bias of 61.31%. Here, we describe a phylogenetic analysis of 16 species of Tesudines based on the complete mitochondrial genome, the result showed that G. japonica is most closely related to G. spengleri. This mitogenome sequence data would play an important role in the investigation of phylogenetic relationship, taxonomic resolution and phylogeography of the Tesudines.

The Pelagophyceae are marine stramenopile algae that include Aureoumbra lagunensis and Aureococcus anophagefferens, two microbial species notorious for causing harmful algal blooms. Despite their ecological significance, relatively few genomic studies of pelagophytes have been carried out. To improve understanding of the biology and evolution of pelagophyte algae, we sequenced complete mitochondrial genomes for A. lagunensis (CCMP1510), Pelagomonas calceolata (CCMP1756), and five strains of Aureoc. anophagefferens (CCMP1707, CCMP1708, CCMP1850, CCMP1984, and CCMP3368) using Nanopore long-read sequencing. All pelagophyte mitochondrial genomes assembled into single, circular mapping contigs between 39,376 bp (P. calceolata) and 55,968 bp (A. lagunensis) in size. Mitochondrial genomes for the five Aureoc. anophagefferens strains varied slightly in length (42,401-42,621 bp) and were 99.4-100.0% identical. Gene content and order were highly conserved between the Aureoc. anophagefferens and P. calceolata genomes, with the only major difference being a unique region in Aureoc. anophagefferens containingDNA adenine and cytosine methyltransferase (dam/dcm) genes that appear to be the product of lateral gene transfer from a prokaryotic or viral donor. Although the A. lagunensis mitochondrial genome shares seven distinct syntenic blocks with the other pelagophyte genomes, it has a tandem repeat expansion comprising ∼40% of its length, and lacks identifiable rps19 and glycine tRNA genes. Laterally acquired self-splicing introns were also found in the 23S rRNA (rnl) gene of P. calceolata and the coxI gene of the five Aureoc. anophagefferens genomes. Overall, these data provide baseline knowledge about the genetic diversity of bloom-forming pelagophytes relative to nonbloom-forming species.

Echinolaelaps echidninus is a gamasid mite that is of medical and veterinary significance as parasites and vectors of disease agents, which can carry pathogens of zoonosis such as Rickettsia tsutsugamushi, Rickettsia Q fever, Rickettsia mooseri, Rickettsia pox pathogens, Corynebacterium pseudotuberculosis and Leptospira. At present, only single mitochondrial genes have been analysed for E. echidninus in the world, and no complete mitochondrial genome has been reported. However, information carried by a single gene is limited. Therefore, the complete mitochondrial genome of E. echidninus was determined for the first time by Illumina Hiseq X-Ten platform in this study. The mitochondrial genome is 15 736 bp in length and contains 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region of 1561 bp in length. Codon analysis of 13 protein-coding genes revealed that UUU, UUA, AUU, AUA and AAU were the most frequently used, while cox2 had the fastest evolutionary rate and cob the slowest. Comparative analysis of genome structure and breakpoint distances of the mitochondrial genomes of 23 species in 17 genera from 10 families of Gamasida deposited in GenBank revealed a novel gene arrangement type of the E. echidninus mitochondrial genome, and different degrees of rearrangement among different taxa of Gamasida. Phylogenetic analyses of Gamasida were performed using the maximum likelihood and Bayesian inference methods. Echinolaelaps echidninus was clustered with Dermanyssoidea and formed a more supportive sister group with Varroa destructor. This study provides novel insights into rearrangement patterns and evolution of mitochondrial genomes of Gamasida.

The mitochondrial genome (mitogenome) plays an important role in revealing molecular evolution. In this study, the complete mitogenome of Grammodes geometrica (G. geometrica) (Lepidoptera: Erebidae) was sequenced and characterized. The nucleotide composition of the genome is highly A + T biased, accounting for 80.49%. Most protein-coding genes (PCGs) are initiated by ATN codons except for the cytochrome oxidase subunit 1 (cox1) gene, which was initiated by CGA. The order and orientation of genes with the order trnM-trnI-trnQ-nad2 is a typical rearrangement compared with those ancestral insects in which trnM is located between trnQ and nad2. Most tRNA genes were folded into the typical cloverleaf structure except for trnS1 (AGN). The A + T-rich region contains the conserved motif "ATAGA" followed by a 19 bp poly-T stretch, which was also observed in other Noctuoidea species. In addition, we reconstructed phylogenetic trees among the nucleotide alignments of five families of Noctuoidea species except the Oenosandridae. Finally, we achieved a well-supported tree, which showed that G. geometrica belongs to the Erebidae family. Moreover, the relationships at the family-level can be displayed as follows: (Notodontidae + (Erebidae + (Nolidae + (Euteliidae + Noctuidae)))).

We have determined a mitochondrial genome of Ricania speculum (Walker, 1851) collected in Jeollabuk-do, Republic of Korea. The circular mitogenome of R. speculum is 15,530 bp long which is shorter than that of the previous mitogenome of R. speculum by 199 bp. It includes 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNAs. Intraspecific variation between two mitogenome of R. speculum was investigated: 171 SNPs and 18 INDELs were identified, presenting a high level of intraspecific variations on mitochondrial genome.