Mitochondrial DNA Research Articles

Insights into phylogenetic relationships and gene rearrangements: complete mitogenomes of two sympatric species in the genus Rana (Anura, Ranidae).

Mitochondrial genomes (also known as mitogenomes) serve as valuable molecular markers and have found widespread applications in molecular biology and ecology. There is abundant sequence variation in vertebrate mitogenomes, and occasionally, they exhibit gene rearrangements. In this study, two Chinese endemic Rana species, Ranajiemuxiensis and Ranahanluica, were sequenced and analyzed to obtain their complete mitogenomes. The two species were sympatrically distributed in the Zhangjiajie National Forest Park, in Wulingyuan District, Zhangjiajie City, Hunan Province, China. The mitogenome of R.jiemuxiensis was 17,506 bp, while that of R.hanluica was 17,505 bp, each comprising 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes (rRNAs), and a non-coding control region (D-loop). The gene content, nucleotide composition, and evolutionary rates of each mitogenome were analyzed and compared with those of congeners. A phylogenetic analysis based on 22 mitogenomes in Rana revealed that the two sympatric species were in two different lineages, indicating that they were genetically separated to a certain extent. Three types of gene rearrangement patterns were identified when examining the gene orders of the 22 Rana mitogenomes. Most of the species shared a second and dominant gene rearrangement pattern that originated from the first ancient pattern. A "tandem duplication - multiple deletion" hypothesis was proposed to explain the evolution of these different gene rearrangement patterns. This study provided valuable data references and enhanced our understanding of the phylogenetic implications and gene rearrangements of Rana species.

The genome sequence of the red-crested pochard, Netta rufina (Pallas, 1773)

We present a genome assembly from a female specimen of Netta rufina (the red-crested pochard; Chordata; Aves; Anseriformes; Anatidae). The genome sequence has a total length of 1,167.00 megabases. Most of the assembly (98.76%) is scaffolded into 42 chromosomal pseudomolecules, including the Z and W sex chromosomes. The mitochondrial genome has also been assembled and is 16.62 kilobases in length.

New mitochondrial gene order arrangements and evolutionary implications in the class Octocorallia.

The complete mitochondrial genomes of octocorals typically range from 18.5 kb to 20.5 kb in length and include 14 protein-coding genes (PCGs), two ribosomal RNA genes and one tRNA. To date, seven different gene orders (A-G) have been described, yet comprehensive investigations of the actual number of arrangements, as well as comparative analyses and evolutionary reconstructions of mitochondrial genome evolution within the whole class Octocorallia, have been often overlooked. Here, we considered the complete mitochondrial genomes available for octocorals and explored their structure and gene order variability. Our results updated the actual number of mitochondrial gene order arrangements so far known for octocorals from 7 to 14 and allowed us to explore and preliminarily discuss the role of some of the structural and functional factors in the mitogenomes. We performed comparative mitogenomic analyses on the existing and novel octocoral gene orders, considering different mitogenomic structural features such as genome size, GC percentage, AT and GC skewness. The mitochondrial gene order history mapped on a recently published nuclear loci phylogeny showed that the most common rearrangement events in octocorals are inversions, inverted transpositions and transpositions. Furthermore, gene order rearrangement events were restricted only to some regions of the tree. Overall, different rearrangement events arose independently and from the ancestral and most common gene order, instead of being derived from other rearranged orders. Finally, our data demonstrate how the study of mitochondrial gene orders can be used to explore the evolution of octocorals and in some cases can be used to assess the phylogenetic placement of certain taxa.

Cytonuclear evolution in fully heterotrophic plants: lifestyles and gene function determine scenarios

BackgroundEvidence shows that full mycoheterotrophs and holoparasites often have reduced plastid genomes with rampant gene loss, elevated substitution rates, and deeply altered to conventional evolution in mitochondrial genomes, but mechanisms of cytonuclear evolution is unknown. Endoparasitic Sapria himalayana and mycoheterotrophic Gastrodia and Platanthera guangdongensis represent different heterotrophic types, providing a basis to illustrate cytonuclear evolution. Here, we focused on nuclear-encoded plastid / mitochondrial (N-pt / mt) -targeting protein complexes, including caseinolytic protease (ClpP), ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCo), oxidative phosphorylation system (OXPHOS), DNA recombination, replication, and repair (DNA-RRR) system, and pentatricopeptide repeat (PPR) proteins, to identify evolutionary drivers for cytonuclear interaction.ResultsThe severity of gene loss of N-pt PPR and pt-RRR genes was positively associated with increased degree of heterotrophy in full mycoheterotrophs and S. himalayana, while N-mt PPR and mt-RRR genes were retained. Substitution rates of organellar and nuclear genes encoding N-pt/mt subunits in protein complexes were evaluated, cytonuclear coevolution was identified in S. himalayana, whereas disproportionate rates of evolution were observed in the OXPHOS complex in full mycoheterotrophs, only slight accelerations in substitution rates were identified in N-mt genes of full mycoheterotrophs.ConclusionsNuclear compensatory evolution was identified in protein complexes encoded by plastid and N-pt genes. Selection shaping codon preferences, functional constraint, mt-RRR gene regulation, and post-transcriptional regulation of PPR genes all facilitate mito-nuclear evolution. Our study enriches our understanding of genomic coevolution scenarios in fully heterotrophic plants.

The genome sequence of the Deathwatch beetle, Xestobium rufovillosum (De Geer, 1774)

We present a genome assembly from an individual female Xestobium rufovillosum (the Deathwatch beetle; Arthropoda; Insecta; Coleoptera; Ptinidae). The genome sequence has a total length of 475.50 megabases. Most of the assembly is scaffolded into 13 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 19.19 kilobases in length.

The genome sequence of a hoverfly, Cheilosia grossa (Fallén, 1817)

We present a genome assembly from an individual male Cheilosia grossa (a hoverfly; Arthropoda; Insecta; Diptera; Syrphidae). The genome sequence has a total length of 362.40 megabases. Most of the assembly is scaffolded into 6 chromosomal pseudomolecules, including the X sex chromosome. The mitochondrial genome has also been assembled and is 17.81 kilobases in length. Gene annotation of this assembly on Ensembl identified 20,196 protein-coding genes.

The genome sequence of the Bird-cherry Ermine moth, Yponomeuta evonymella (Linnaeus, 1758)

We present a genome assembly from an individual female Yponomeuta evonymella (the Bird-cherry Ermine; Arthropoda; Insecta; Lepidoptera; Yponomeutidae). The genome sequence has a total length of 572.70 megabases. Most of the assembly is scaffolded into 32 chromosomal pseudomolecules, including the trivalent sex chromosomes Z1, Z2 and W. The mitochondrial genome has also been assembled and is 16.16 kilobases in length.

Genetic Expression of Some Mitochondrial and Growth-Related Genes and its Impact on Productive Traits in Broilers during Pre- and Post-hatch

Genetic Expression of Some Mitochondrial and Growth-Related Genes and its Impact on Productive Traits in Broilers during Pre- and Post-hatch

A chromosome-level genome assembly for the desert scorpion Mesobuthus przewalskii from Asian drylands.

Scorpions are an ancient and charismatic group of arthropods with medical importance, but a high-quality reference genome for this group is still lacking. Here we perform whole-genome sequencing of Mesobuthus przewalskii, a desert scorpion endemic to the Taklimakan Desert. We combine PacBio HiFi sequencing and Hi-C chromosome conformation capturing to generate chromosomal-level, haplotype-resolved, and fully annotated genome assembly for this medically important scorpion. The assembly consists of two haplotypes (1052.01 Mbp and 1055.19 Mbp, respectively) reaching chromosome-level contiguity and >98% BUSCO completeness. Sequences were anchored in 13 chromosomes with a contig N50 of 34.44 Mbp and scaffold N50 of 81.43 Mbp. Several key genome features and the mitochondrial genome assembly were also provided. This genome represents the fifth but the most complete assembly for the order Scorpiones.

Expanding the Role of Molecular Genetic Expertise in Crime Detection and Investigation

Molecular genetic testing using DNA plays a crucial role in the field of justice. Beyond the analysis of genomic DNA sequences, advanced methods such as mitochondrial DNA analysis, epigenetic marker identification, and RNA profiling are being developed. A particularly promising approach is forensic phenotyping, which involves predicting human characteristics from DNA samples, including appearance, biogeographic origin, and age.

A Report on the Tabanus Species Tabanus rufofrater in Mithun (Bos frontalis)

Background: Mithun (Bos frontalis) experience infestations from various ectoparasites, including several types of flies that cause painful bites, stress, blood loss and transmit a range of microorganisms. In the Mithun-inhabited forested regions of Phek, Nagaland, the Tabanus fly is particularly prevalent. Methods: Researchers studied Tabanus flies infesting free-range mithun in Phek District, Nagaland. The flies were collected and processed at the ICAR-NRC on Mithun in Nagaland. Both morphological (using stereoscopic microscopes) and molecular methods (employing ribosomal and mitochondrial gene markers) were utilized for identification. Additionally, DNA barcoding was done at Eurofins Genomics India Pvt. Ltd. to further ascertain the flies’ identities. Climate attributes (Temperature, Rainfall and Humidity) was recorded during the study. Result: Through morphological and molecular investigations, it was conclusively determined to be Tabanus rufofrater. The highest occurrence of Tabanus rufofrater encounters takes place between May and August, aligning with the pre-monsoon and monsoon seasons, before gradually declining thereafter. The prevalence of Tabanus rufofrater attacks peaks from May to August, coinciding with the pre-monsoon and monsoon periods and subsequently decreases.

Comprehensive multi-omics integration uncovers mitochondrial gene signatures for prognosis and personalized therapy in lung adenocarcinoma

The therapeutic efficacy of lung adenocarcinoma (LUAD), the most prevalent histological subtype of primary lung cancer, remains inadequate, with accurate prognostic assessment posing significant challenges. This study sought to elucidate the prognostic significance of mitochondrial-related genes in LUAD through an integrative multi-omics approach, aimed at developing personalized therapeutic strategies. Utilizing transcriptomic and single-cell RNA sequencing (scRNA-seq) data, alongside clinical information from publicly available databases, we first applied dimensionality reduction and clustering techniques to the LUAD single-cell dataset, focusing on the subclassification of fibroblasts, epithelial cells, and T cells. Mitochondrial-related prognostic genes were subsequently identified using TCGA-LUAD data, and LUAD cases were stratified into distinct molecular subtypes through consensus clustering, allowing for the exploration of gene expression profiles and clinical feature distributions across subtypes. By leveraging an ensemble of machine learning algorithms, we developed an Artificial Intelligence-Derived Prognostic Signature (AIDPS) model based on mitochondrial-related genes and validated its prognostic accuracy across multiple independent datasets. The AIDPS model demonstrated robust predictive power for LUAD patient outcomes, revealing significant differences in responses to immunotherapy and chemotherapy, as well as survival outcomes between risk groups. Furthermore, we conducted comprehensive analyses of tumor mutation burden (TMB), immune microenvironment characteristics, and genome-wide association study (GWAS) data, providing additional insights into the mechanistic roles of mitochondrial-related genes in LUAD pathogenesis. This study not only offers a novel approach to improving prognostic assessments in LUAD but also establishes a strong foundation for the development of personalized therapeutic interventions.

Mitochondrial genome of the Indian spot-billed duck and its phylogenetic and conservation implications.

The Indian spot-billed duck, Anas poecilorhyncha is a large dabbling and non-migratory breeding bird. The identification and phylogenetic relationship of A. poecilorhyncha remain uncertain due to the presence of overlapping meristic characters and hybridization with closely related species. Molecular data aids when there are challenges in morphological identification. However, genetic characterization of A. poecilorhyncha has been paid less attention. Apart from their functional and physiological role, mitochondrial genome can also be used for various purposes, including species identification, phylogenetic analysis, understanding the domestication history of species etc. Therefore, the present study aimed to sequence the mitochondrial genome of A. poecilorhyncha and its closely related domestic species A. platyrhynchos (mallard duck) to understand their mitochondrial genome structure and phylogenetic relationships. The length of mitochondrial genome of A. poecilorhyncha and A. platyrhynchos was 16,608 and 16,604bp respectively. Mitochondrial genome contained 37 genes and a non-coding control region. Overall, the characteristics of mitochondrial genome of both species were found to be conserved. The phylogenetic tree exhibited seven major clades (A to G) with a high bootstrap support. Notably, the Indian A. poecilorhyncha population formed a distinct clade (C) whereas the A. poecilorhyncha that were probably sampled from China grouped along with A. zonorhyncha (clade B). Besides, one of the A. poecilorhyncha probably sampled from China was placed in the clade A, which predominantly consisted of A. platyrhynchos. It suggests that Indian A. poecilorhyncha population is genetically different from Chinese A. poecilorhyncha population. Further, it sheds light on the importance of conducting a comprehensive phylogenetic study on these species. The newly sequenced mitochondrial genome of A. poecilorhyncha and A. platyrhynchos would be useful not only to have a better understanding of the phylogeny and evolution of Anas species but also to help in the conservation of A. poecilorhyncha which is under constant threat from rapid urbanization, interspecific hybridization and other human activities.

Potential role of heteroplasmic mitochondrial DNA mutations in modulating the subtype-specific adaptation of oral squamous cell carcinoma to cisplatin therapy

Cancer cells are constantly evolving to adapt to environmental changes, particularly during exposure to drug treatment. In this work, we aimed to characterize genetic and epigenetic changes in mitochondrial DNA (mtDNA) that may increase the resistance of oral squamous cell carcinoma (OSCC) to cisplatin. We first derived drug-resistant cells from two human OSCC cell lines, namely SAS and H103, by continual cisplatin treatments for about 4 months. To determine mtDNA changes induced by cisplatin, we performed nanopore sequencing and quantitative polymerase chain reaction analysis of mtDNA extracted from the cells pre- and post-treatment. We also assessed the mitochondrial functions of the cells and their capacity to generate intracellular reactive oxygen species (ROS). We found that in the cisplatin-resistant cells derived from SAS, there was a reduction in mtDNA content and significant enrichment of a m.3910G > C mutation in the MT-ND1 gene. However, such changes were not detected in cisplatin-resistant H103 cells. The cisplatin treatment also altered methylation patterns in both SAS and H103 cells and decreased their sensitivity to ROS-induced cytotoxicity. We suggest that the sequence alterations and epigenetic changes in mtDNA and the reduction in mtDNA content could be key drivers of cisplatin resistance in OSCC. These mtDNA alterations may participate in cellular adaptation that serves as a response to adverse changes in the environment, particularly exposure to cytotoxic agents. Importantly, the observed mtDNA changes may be influenced by the distinct genetic landscapes of various cancer subtypes. Overall, this study reveals significant insights into cisplatin resistance driven by complex mtDNA dynamics, particularly in OSCC. This underscores the need for targeted therapies tailored to the genetic profiles of individual OSCC patients to improve disease prognosis.

Evidence of Intraspecific Adaptive Variation in the American Pika (Ochotona princeps) on a Continental Scale Using a Target Enrichment and Mitochondrial Genome Skimming Approach.

Montane landscapes present an array of abiotic challenges that drive adaptive evolution amongst organisms. These adaptations can promote habitat specialisation, which may heighten the risk of extirpation from environmental change. For example, higher metabolic rates in an endothermic species may contribute to heightened cold tolerance, whilst simultaneously limiting heat tolerance. Here, using the climate-sensitive American pika (Ochotona princeps), we test for evidence of intraspecific adaptive variation amongst environmental gradients across the Intermountain West of North America. We leveraged results from previous studies on pika adaptation to generate a custom nuclear target enrichment design to sequence several hundred candidate genes related to cold, hypoxia and dietary detoxification. We also applied a 'genome skimming' approach to sequence mitochondrial DNA. Using genotype-environment association tests, we identified rare genomic variants associated with elevation and temperature variation amongst populations. Amongst mitochondrial genes, we identified intraspecific variation in selective signals and significant changes to the amino acid property equilibrium constant, which may relate to electron transport chain efficiency. These results illustrate a complex dynamic of adaptive variation amongst O. princeps where lineages and populations have adapted to unique regional conditions. Some of the clearest signals of selection were in a genetic lineage that includes pikas of the Great Basin region, which is also where recent localised extirpations have taken place and highlights the risk of losing adaptive alleles during environmental change.

Differential expression of nuclear-derived mitochondrial succinate dehydrogenase genes in metabolically active buffalo tissues.

Buffaloes are crucial to agriculture, yet mitochondrial biology in these animals is less studied compared to humans and laboratory animals. This research examines tissue-specific variations in mitochondrial succinate dehydrogenase (SDH) gene expression across buffalo kidneys, hearts, brains, and ovaries. Understanding these variations sheds light on mitochondrial energy metabolism and its impact on buffalo health and productivity, revealing insights into enzyme regulation and potential improvements in livestock management. RNA-seq data from buffalo kidney, heart, brain, and ovary tissues were reanalyzed to explore mitochondrial SDH gene expression. The expression of SDH subunits (SDHA, SDHB, SDHC, SDHD) and assembly factors (SDHAF1, SDHAF2, SDHAF3, SDHAF4) was assessed using a log2 fold-change threshold of + 1 for up-regulated and - 1 for down-regulated transcripts, with significance set at p < 0.05. Hierarchical clustering and differential expression analyses were performed to identify tissue-specific expression patterns and regulatory mechanisms, while Gene Ontology and KEGG pathway analyses were conducted to uncover functional attributes and pathway enrichments across different tissues. Reanalysis of RNA-seq data from different tissues of healthy female buffaloes revealed distinct expression patterns for SDH subunits and assembly factors. While SDHA, SDHB, and SDHC showed variable expression across tissues, SDHAF2, SDHAF3, and SDHAF4 exhibited tissue-specific profiles. Significant up-regulation of SDHA, SDHB, and several assembly factors was observed in specific tissue comparisons, with fewer down-regulated transcripts. Gene ontology and KEGG pathway analyses linked the up-regulated transcripts to mitochondrial ATP synthesis and the respiratory electron transport chain. Notably, tissue-specific variations in mitochondrial function were particularly evident in the ovary. This study identifies distinct SDH gene expression patterns in buffalo tissues, highlighting significant down-regulation of SDHA, SDHB, SDHC, and assembly factors in the ovary. These findings underscore the critical role of mitochondria in tissue-specific energy production and metabolic regulation, suggest potential metabolic adaptations, and emphasize the importance of mitochondrial complex II. The insights gained offer valuable implications for improving feed efficiency and guiding future research and therapies for energy metabolism disorders.

Monitoring the genetic diversity in holothurian populations from the Italian coasts with mitochondrial DNA sequences

Sea cucumbers are deposit feeding members of marine benthic communities. The over-exploitation of sea cucumber natural stocks, especially in the Mediterranean basin, is having negative impacts on the marine ecosystem. This concerns had led the Italian government to take legal actions to preserve these important marine resources. The aim of this study was to evaluate the level of genetic diversity and population structures within two sympatric Holothuria sea cucumber species, H. polii and H. tubulosa, across ten Mediterranean areas along Italy. A 323 bp portion of the COI mitochondrial gene was sequenced in a total of 441 holothurians (251 H. polii, 177 H. tubulosa and 13 from other species). Genetic diversity analyses and analysis of molecular variance (AMOVA) suggest that H. polii and H. tubulosa species are distinct, but within and among populations are homogeneous, indicating active gene flows across the Mediterranean areas investigated. H. polii showed a lower genetic diversity than H. tubulosa, probably related to differences in life history traits. Phylogenetic analyses showed a clear differentiation between the two species, even if six specimens morphologically assigned to a species clustered within the other species, indicating a possible occurrence of hybridization events. These data will be useful in implementing conservation actions for these holothurian genetic resources.

Complementing aculiferan mitogenomics: comparative characterization of mitochondrial genomes of Solenogastres (Mollusca, Aplacophora).

With the advances in high-throughput sequencing and bioinformatic pipelines, mitochondrial genomes have become increasingly popular for phylogenetic analyses across different clades of invertebrates. Despite the vast rise in available mitogenomic datasets of molluscs, one class of aplacophoran molluscs - Solenogastres (or Neomeniomorpha) - is still neglected. Here, we present six new mitochondrial genomes from five families of Solenogastres (Amphimeniidae, Gymnomeniidae, Proneomeniidae, Pruvotinidae, Simrothiellidae), including the first complete mitogenomes, thereby now representing three of the four traditional orders. Solenogaster mitogenomes are variable in size (ranging from approximately 15,000bp to over 17,000bp). The gene order of the 13 protein coding genes and two rRNA genes is conserved in three blocks, but considerable variation occurs in the order of the 22 tRNA genes. Based on phylogenetic analyses and reconstruction of ancestral mitochondrial genomes of Aculifera, the position of (1) trnD gene between atp8 and atp6, (2) trnT and P genes between atp6 and nad5, and (3) trnL1 gene between G and E, resulting in a 'MCYWQGL1E'-block of tRNA genes, are all three considered synapomorphies for Solenogastres. The tRNA gene block 'KARNI' present in Polyplacophora and several conchiferan taxa is dissolved in Solenogastres. Our study shows that mitogenomes are suitable to resolve the phylogenetic relationships among Aculifera and within Solenogastres, thus presenting a cost and time efficient compromise to approach evolutionary history in these clades.

Relation of mitochondrial DNA copy number and variants with the clinical characteristics of polycystic ovary syndrome

Mounting evidences suggests mitochondrial dysfunction as a novel contributor in the pathogenesis of PCOS. Herein, we analyzed mtDNA copy number, a biomarker of mitochondrial function in women with PCOS and non-PCOS participants and study its correlation with their clinical characteristics. In this study, we further analyzed association of 383 mtDNA variants, as reported previously by us, with characteristic traits of PCOS and perform structural analysis of mutated protein. Our results indicate relative mitochondrial DNA (mtDNA) copy number to be significantly reduced in women with PCOS compared to non-PCOS group and significantly inversely related to waist to hip ratio (WHR), triglycerides and positively related to high density lipoprotein-cholesterol (HDL-C). After adjustment of the age in the PCOS group, significantly negative correlation of mtDNA copy number with WHR was observed. Unsupervised hierarchical clustering analysis revealed rare, low heteroplasmic mtDNA variants such as 12556G, 1488T, 9200G, 9670G, 3308G, 14480G, 15914T and 5426G to be strongly associated with PCOS related traits. Among these variants, variant 12256G in ND5 gene affected both the flexibility and overall stability of the protein structure. This study is first to reveal significant correlation of mtDNA copy number with WHR in women with PCOS indicating link between mitochondrial dysfunction with central obesity in PCOS. we also first time showed association of rare mtDNA variants with characteristics traits of PCOS highlighting the clinical significance of rare mtDNA variants, which may cumulatively act as early predictors of risk of PCOS and its related comorbidities which may help in the management of PCOS.

The genome sequence of the oak pinhole borer, Platypus cylindrus (Fabricius, 1792)

We present a genome assembly from an individual male Platypus cylindrus (the oak pinhole borer; Arthropoda; Insecta; Coleoptera; Curculionidae). The genome sequence is 147.5 megabases in span. Most of the assembly is scaffolded into 8 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 19.29 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,468 protein coding genes.