Mitochondrial Genome Variation Research Articles

Genomic analysis and phylogenetic characterization of Himalayan snow trout, Schizothorax esocinus based on mitochondrial protein-coding genes.

Mitochondrial DNA (mtDNA) has become a significant tool for exploring genetic diversity and delineating evolutionary links across diverse taxa. Within the group of cold-water fish species that are native to the Indian Himalayan region, Schizothorax esocinus holds particular importance due to its ecological significance and is potentially vulnerable to environmental changes. This research aims to clarify the phylogenetic relationships within the Schizothorax genus by utilizing mitochondrial protein-coding genes. Standard protocols were followed for the isolation of DNA from S. esocinus. For the amplification of mtDNA, overlapping primers were used, and then subsequent sequencing was performed. The genetic features were investigated by the application of bioinformatic approaches. These approaches covered the evaluation of nucleotide composition, codon usage, selective pressure using nonsynonymous substitution /synonymous substitution (Ka/Ks) ratios, and phylogenetic analysis. The study specifically examined the 13 protein-coding genes of Schizothorax species which belongs to the Schizothoracinae subfamily. Nucleotide composition analysis showed a bias towards A + T content, consistent with other cyprinid fish species, suggesting evolutionary conservation. Relative Synonymous Codon Usage highlighted leucine as the most frequent (5.18%) and cysteine as the least frequent (0.78%) codon. The positive AT-skew and the predominantly negative GC-skew indicated the abundance of A and C. Comparative analysis revealed significant conservation of amino acids in multiple genes. The majority of amino acids were hydrophobic rather than polar. The purifying selection was revealed by the genetic distance and Ka/Ks ratios. Phylogenetic study revealed a significant genetic divergence between S. esocinus and other Schizothorax species with interspecific K2P distances ranging from 0.00 to 8.87%, with an average of 5.76%. The present study provides significant contributions to the understanding of mitochondrial genome diversity and genetic evolution mechanisms in Schizothoracinae, hence offering vital insights for the development of conservation initiatives aimed at protecting freshwater fish species.

Mitochondrial genome variation and intergenomic sequence transfers in Hevea species.

Among the Hevea species, rubber tree (Hevea brasiliensis) is the most important source of natural rubber. In previous studies, we sequenced the complete nuclear and chloroplast genomes of Hevea species, providing an invaluable resource for studying their phylogeny, disease resistance, and breeding. However, given that plant mitochondrial genomes are more complex and more difficult to assemble than that of the other organelles, little is known about their mitochondrial genome, which limits the comprehensive understanding of Hevea genomic evolution. In this study, we sequenced and assembled the mitochondrial genomes of four Hevea species. The four mitochondrial genomes had consistent GC contents, codon usages and AT skews. However, there were significant differences in the genome lengths and sequence repeats. Specifically, the circular mitochondrial genomes of the four Hevea species ranged from 935,732 to 1,402,206 bp, with 34-35 unique protein-coding genes, 35-38 tRNA genes, and 6-13 rRNA genes. In addition, there were 17,294-46,552 bp intergenomic transfer fragments between the chloroplast and mitochondrial genomes, consisting of eight intact genes (psaA, rrn16S, tRNA-Val, rrn5S, rrn4.5S, tRNA-Arg, tRNA-Asp, and tRNA-Asn), intergenic spacer regions and partial gene sequences. The evolutionary position of Hevea species, crucial for understanding its adaptive strategies and relation to other species, was verified by phylogenetic analysis based on the protein-coding genes in the mitochondrial genomes of 21 Malpighiales species. The findings from this study not only provide valuable insights into the structure and evolution of the Hevea mitochondrial genome but also lay the foundation for further molecular, evolutionary studies, and genomic breeding studies on rubber tree and other Hevea species, thereby potentially informing conservation and utilization strategies.

Mitogenome-based genetic management of captive Great Hornbill in Thailand: Implications for reintroduction

The Great Hornbill (Buceros bicornis) is globally vulnerable due to high rates of deforestation and hunting and are therefore a target for restoration. Captive breeding programs in Thailand maintain many Great Hornbills, however active genetic management of captive hornbills was not incorporated into the species recovery plan. With Great Hornbill reintroductions planned for northern Thailand in the immediate future, lack of genetic profiles and phylogenetic relationships among potential founders might hamper population recovery efforts. We assessed the mitochondrial genome (mitogenome) diversity, genetic structure, and evolutionary history of 97 captive Great Hornbills across five zoos in Thailand. Among the 97 samples, we found 21 haplotypes with a haplotype and nucleotide diversity of h = 0.81336 ± 0.021 and pi = 0.00108 ± 0.00040, respectively. The maintenance of mitogenome diversity and no genetic differentiation between five captive populations (FST = 0.00000–0.09723, p > 0.05) might be a result of frequent founder exchange among facilities. Phylogenetic analysis revealed the existence of a southern clade BBITH13, indicating a genetically distinct southern population. To protect these genetic lineages and maintain adaptability of hornbills that have been reintroduced, breeding facilities that contain unique haplotypes should be given high priority in breeding plans. Our data support the evolutionary value of the captive hornbill population in Thailand and highlight the significance of incorporating active genetic management strategies into the species recovery plan for Great Hornbills.

Evaluating the mitochondrial genomic diversity, global distribution and niche overlap of two invasive Phthorimaea species

This study sought to evaluate the genetic diversity of two invasive Phthorimaea species (Phthorimaea operculella Zeller and Phthorimaea absoluta Meyrick), and identify potential niche overlap of both species. The complete mitogenomes of P. operculella and P. absoluta were sequenced and compared. Furthermore, the diversity within the family Gelechiidae was assessed. Subsequently, two species distribution models (MaxEnt and BIOCLIM) were used to identify niche overlaps of both species globally. The complete mitogenomes of both species were similar in size and structure, with a pairwise identity of 92.3%. The models showed a niche overlap of both species and revealed areas of marginal to high suitability for both pests in countries where they have not been reported. Therefore, these results present a compelling case for a deeper genetic and ecological investigation of the Gelechiidae family for taxonomic harmonization, an early warning for surveillance, stricter phytosanitary considerations and preventive management against the spread of the pests.

Approaches and challenges in identifying, quantifying, and manipulating dynamic mitochondrial genome variations

Mitochondria, the cellular powerhouses, possess their own unique genetic system, including replication, transcription, and translation. Studying these processes is crucial for comprehending mitochondrial disorders, energy production, and their related diseases. Over the past decades, various approaches have been applied in detecting and quantifying mitochondrial genome variations with also the purpose of manipulation of mitochondria or mitochondrial genome for therapeutics. Understanding the scope and limitations of above strategies is not only fundamental to the understanding of basic biology but also critical for exploring disease-related novel target(s), as well to develop innovative therapies. Here, this review provides an overview of different tools and techniques for accurate mitochondrial genome variations identification, quantification, and discuss novel strategies for the manipulation of mitochondria to develop innovative therapeutic interventions, through combining the insights gained from the study of mitochondrial genetics with ongoing single cell omics combined with advanced single molecular tools.

Screening for Rare Mitochondrial Genome Variants Reveals a Potentially Novel Association between MT-CO1 and MT-TL2 Genes and Diabetes Phenotype.

Variations in several nuclear genes predisposing humans to the development of MODY diabetes have been very well characterized by modern genetic diagnostics. However, recent reports indicate that variants in the mtDNA genome may also be associated with the diabetic phenotype. As relatively little research has addressed the entire mitochondrial genome in this regard, the aim of the present study is to evaluate the genetic variations present in mtDNA among individuals susceptible to MODY diabetes. In total, 193 patients with a MODY phenotype were tested with a custom panel with mtDNA enrichment. Heteroplasmic variants were selected for further analysis via further sequencing based on long-range PCR to evaluate the potential contribution of frequent NUMTs (acronym for nuclear mitochondrial DNA) insertions. Twelve extremely rare variants with a potential damaging character were selected, three of which were likely to be the result of NUMTs from the nuclear genome. The variant m.3243A>G in MT-TL1 was responsible for 3.5% of MODY cases in our study group. In addition, a novel, rare, and possibly pathogenic leucine variant m.12278T>C was found in MT-TL2. Our findings also found the MT-CO1 gene to be over-represented in the study group, with a clear phenotype-genotype correlation observed in one family. Our data suggest that heteroplasmic variants in MT-COI and MT-TL2 genes may play a role in the pathophysiology of glucose metabolism in humans.

Variability of the mitochondrial genome in young Yakut patients with breast cancer

Background. The Sakha (Yakutia) population, the indigenous population of Siberia living in Yakutia, has one of the lowest rates of breast cancer (BC) incidence worldwide. The low BC incidence among the indigenous population of Yakutia has been reported by several authors, but to date the reasons for this phenomenon have not been fully elucidated. It should be noted that the study of factors that reduce the risk of BC is important for its prevention. In several studies, no hereditary BC was found in the Yakuts, and no pathogenic variants of the BRCA1/2 genes associated with hereditary syndromes of breast and ovarian cancers were found. In this regard, we decided to shift the focus to studying the mitochondrial genome of Sakha BC patients using the sequencing method.The purpose of the study was to identify BC-associated mitochondrial genome variants in Sakha patients.Material and Methods. The study included 14 Sakha patients diagnosed with BC. The median age of the patients was 49 years. DNA isolation was performed using phenol-chloroform extraction. DNA libraries were prepared using the Nextera Flex kit (Illumina, USA).Whole-genome sequencing of the mitochondrial genome was performed on a MiSeq instrument (Illuminа, USA). in the Shared Use Centre of the Research Institute of Medical Genetics, Tomsk National Research Centre of the Russian Academy of Sciences. The results obtained in BC patients were compared with those of control subjects.Results. In Sakha women with BC, 159 mitochondrial genome variants that differed from the human mitochondrial DNA (mtDNA) reference sequence (rCRS) were identified. Likely pathogenic variants m.3736G>A of the MT-ND1 gene and m.7279T>C of the MT-CO1 gene were shown to be associated with BC. For the first time, variants predisposing to BC (m.10398A>G; m.14783T>C; m.15043G>A; m.15301G>A) were identified. A distinctive feature of the mitochondrial genome of populations with a low BC incidence is a high level of mtDNA variants with changes in the length of the polycytosine region in the D310 locus.Conclusion. For the first time, mtDNA variants with changes in the length of the polycytosine tract in the D310 locus and likely pathogenic variants m.3736G>A of the MT-ND1 gene and m.7279T>C of the MT-CO1 gene were identified in Sakha BC women. The data obtained indicate that further studies on the role of the identified mtDNA variants in the development of BC using a larger sample of Sakha patients are required.

Diversity and evolution of mitochondrial translation apparatus

The evolution of mitochondria proceeded independently in different eukaryotic lines, reflected in the diversity of mitochondrial genomes and mechanisms of their expression observed in different eukaryotic species. Mitochondria lost most of the genes of their bacterial ancestor, partially transferred them to the nucleus or completely eliminated. However, the mitochondria of almost all eukaryotic cells retain relatively small genomes, as well as their replication, transcription, and translation apparatuses. Dependence on the nuclear genome, features of mitochondrial transcripts, and the necessity to synthesize highly hydrophobic membrane proteins led to a number of significant changes in translation apparatus derived from the bacterial ancestor. It retained the basic structure necessary for protein synthesis but became more specialized and labile. In this review, we consider what changes take place during the initiation of mitochondrial translation, and how the evolution of mitochondria affected the functions of the main factors initiating protein biosynthesis in these organelles.

Whole mitogenome sequencing uncovers a relation between mitochondrial heteroplasmy and leprosy severity

BackgroundIn recent years, the mitochondria/immune system interaction has been proposed, so that variants of mitochondrial genome and levels of heteroplasmy might deregulate important metabolic processes in fighting infections, such as leprosy.MethodsWe sequenced the whole mitochondrial genome to investigate variants and heteroplasmy levels, considering patients with different clinical forms of leprosy and household contacts. After sequencing, a specific pipeline was used for preparation and bioinformatics analysis to select heteroplasmic variants.ResultsWe found 116 variants in at least two of the subtypes of the case group (Borderline Tuberculoid, Borderline Lepromatous, Lepromatous), suggesting a possible clinical significance to these variants. Notably, 15 variants were exclusively found in these three clinical forms, of which five variants stand out for being missense (m.3791T > C in MT-ND1, m.5317C > A in MT-ND2, m.8545G > A in MT-ATP8, m.9044T > C in MT-ATP6 and m.15837T > C in MT-CYB). In addition, we found 26 variants shared only by leprosy poles, of which two are characterized as missense (m.4248T > C in MT-ND1 and m.8027G > A in MT-CO2).ConclusionWe found a significant number of variants and heteroplasmy levels in the leprosy patients from our cohort, as well as six genes that may influence leprosy susceptibility, suggesting for the first time that the mitogenome might be involved with the leprosy process, distinction of clinical forms and severity. Thus, future studies are needed to help understand the genetic consequences of these variants.

Using machine learning of neuroimaging patterns combined with mitochondrial genomics to predict maternal inheritance of Alzheimer’s disease

AbstractBackgroundMaternal family history (FHm) contributes increased risk for developing Alzheimer’s disease (AD) compared to paternal. Family history is often unknown, making it difficult to identify these higher‐risk patients. Atrophy patterns indicative of AD relate to parent‐of‐origin effects. Risk factors may also include mitochondrial variation (mtDNA). Machine learning (ML) approaches could identify predictive traits for FHm, helping detect higher‐risk patients with unknown family history. We aimed to determine if structural MRI variables and mitochondrial haplogroups could classify FHm.MethodUsing data from the National Alzheimer’s Coordinating Center and NIA Genetics of Disease Storage Site, we determined if a feature set, comprised of structural MRI variables and mitochondrial haplogroups, could accurately predict FHm. Haplogroups were called with HaploGrep v2.4.0 based on the PT17‐FU1 reference. Two‐thirds of the dataset was used for training and one‐third for testing. For hyper‐parameter tuning and optimization of model performance, we used 4‐fold cross‐validation. To identify traits that aid in predicting FHm, feature importance was calculated for the best performing model (selected based on accuracy and AUC).ResultML models were initially trained on imaging variables for 961 individuals (60% female) with confirmed positive (69%) or negative (31%) FHm. Average age at MRI was 68±11 years old. XGboost emerged as the best method (Accuracy = 0.62, AUC = 0.56). Feature importance calculations indicated precuneus was the most important. Including haplogroups significantly reduced the sample size (n = 602) and model performance. Most of the dataset (87%) were assigned to mitochondrial haplogroups within the R branch. Notably, although model performance was reduced, precuneus remained one of the most important variables.ConclusionThis analysis was among the first to explore if structural or genomic traits predicted FH. Although performance for the initial models showed moderate accuracy, we are currently testing additional ML approaches to enhance predictivity. We identified the precuneus as a key‐AD‐vulnerable region associated with FHm. Our study contributes to a growing literature showing structural, neurodegenerative, cerebral metabolic and increased amyloid‐β burden in the precuneus of individuals with FHm. Analyses aimed at more comprehensive evaluation of mitochondrial genomic variation that expands upon haplogroup classification are ongoing to clarify the role mtDNA plays in maternally inherited AD.

Complete Mitochondrial DNA Genome Variation in the Swedish Population.

The development of complete mitochondrial genome (mitogenome) reference data for inclusion in publicly available population databases is currently underway, and the generation of more high-quality mitogenomes will only enhance the statistical power of this forensically useful locus. To characterize mitogenome variation in Sweden, the mitochondrial DNA (mtDNA) reads from the SweGen whole genome sequencing (WGS) dataset were analyzed. To overcome the interference from low-frequency nuclear mtDNA segments (NUMTs), a 10% variant frequency threshold was applied for the analysis. In total, 934 forensic-quality mitogenome haplotypes were characterized. Almost 45% of the SweGen haplotypes belonged to haplogroup H. Nearly all mitogenome haplotypes (99.1%) were assigned to European haplogroups, which was expected based on previous mtDNA studies of the Swedish population. There were signature northern Swedish and Finnish haplogroups observed in the dataset (e.g., U5b1, W1a), consistent with the nuclear DNA analyses of the SweGen data. The complete mitogenome analysis resulted in high haplotype diversity (0.9996) with a random match probability of 0.15%. Overall, the SweGen mitogenomes provide a large mtDNA reference dataset for the Swedish population and also contribute to the effort to estimate global mitogenome haplotype frequencies.

Mitochondrial Genome Variation in Polish Elite Athletes.

Energy efficiency is one of the fundamental athletic performance-affecting features of the cell and the organism as a whole. Mitochondrial DNA (mtDNA) variants and haplogroups have been linked to the successful practice of various sports, but despite numerous studies, understanding of the correlation is far from being comprehensive. In this study, the mtDNA sequence and copy number were determined for 99 outstanding Polish male athletes performing in power (n = 52) or endurance sports (n = 47) and 100 controls. The distribution of haplogroups, single nucleotide variant association, heteroplasmy, and mtDNA copy number were analyzed in the blood and saliva. We found no correlation between any haplogroup, single nucleotide variant, especially rare or non-synonymous ones, and athletic performance. Interestingly, heteroplasmy was less frequent in the study group, especially in endurance athletes. We observed a lower mtDNA copy number in both power and endurance athletes compared to controls. This could result from an inactivity of compensatory mechanisms activated by disadvantageous variants present in the general population and indicates a favorable genetic makeup of the athletes. The results emphasize a need for a more comprehensive analysis of the involvement of the mitochondrial genome in physical performance, combining nucleotide and copy number analysis in the context of nuclear gene variants.

Mitochondrial Genetics and Function as Determinants of Bone Phenotype and Aging.

The purpose of this review is to summarize the recently published scientific literature regarding the effects of mitochondrial function and mitochondrial genome mutations on bone phenotype and aging. While aging and sex steroid levels have traditionally been considered the most important risk factors for development of osteoporosis, mitochondrial function and genetics are being increasingly recognized as important determinants of bone health. Recent studies indicate that mitochondrial genome variants found in different human populations determine the risk of complex degenerative diseases. We propose that osteoporosis should be among such diseases. Studies have shown the deleterious effects of mitochondrial DNA mutations and mitochondrial dysfunction on bone homeostasis. Mediators of such effects include oxidative stress, mitochondrial permeability transition, and dysregulation of autophagy. Mitochondrial health plays an important role in bone homeostasis and aging, and understanding underlying mechanisms is critical in leveraging this relationship clinically for therapeutic benefit.

Study on the Mitochondrial Genome of Variants Carrying mt.3243A>G from Type-2 Diabetes Mellitus and Cataract Patients in Indonesia

The association of type-2 diabetes mellitus (T2DM) and cataract with mtDNA mutation has been reported before. Despite the high prevalence of DM and cataract in Indonesia, a study of the mtDNA variants in Indonesia in correlation with the two diseases is still limited. MT.3243A>G is one of the hotspots mutations for mitochondrial diseases, but the explanation for its occurrence in patients with pure cataract is still elusive. Therefore, the objective of this study was to analyze the mitochondrial genome variants from T2DM and cataract patients in Indonesia using the direct sequencing method. The homology analysis of the genome to the Cambridge reference sequence resulted in 86 variants, including 20 variants that cause amino acid substitutions. Based on the Mitomap data, 17 of the 20 variants were novel. Upon comparison with the 12 normal variant genomes, 11 of 17 variants were suggested to be associated with T2DM and cataract diseases since they code the protein in complex-I (ND4L, ND5, and ND6), complex-III (cytb), and complex-V (ATP6) of the respiratory complex. Interestingly, MT.3316G>A, for the first time, is shown in a pure cataract patient. In addition, the novel phenotype of MT.5460G>A and MT.10398A>G were revealed, which are T2DM and cataract in one patient. Based on our study, these diseases might be related to the disruption of the ATP metabolism due to the structure and function changes of proteins involved in the respiratory complex. This discovery is expected to offer an understanding of the origins of gene-level clinical differences, particularly in Indonesia.

Genetic structural variation in mitochondrial genomes of four species of Gomphidae and their phylogenetic implications

The Gomphids are the most diverse and important group in the (sub)tropics. Currently, research on Gomphids is mainly focused on fieldwork and morphological classification, however, the molecular-based study is still insufficient. Here, complete mitogenomes of Nihonogomphus semanticus (15,368 bp), Nihonogomphus lieftincki (15,342 bp), Asiagomphus septimus (15,334 bp), and Davidius fruhstorferi (15,682 bp) were obtained by high-throughput sequencing. Of the 37 genes conserved in order and orientation, 9 protein-coding genes (PCGs) and 14 tRNA genes were encoded by heavy strand, while the rest were encoded by light strand. The secondary structures of the protein encoded by 13 PCGs showed a general trend of proportion: α helix > random coil > extended strand > β turn. The trnS1 gene lacked a dihydrouridine arm and was thus reduced to a loop. The 3D structures of the protein encoded by 13 PCGs showed moderate to high levels of consistency among species. Phylogenetic analysis showed that Gomphids were well-supported monophyletic group, both BI and ML tree showed clear phylogenetic relationships in known Gomphidae: ((((D. lunatus + D. fruhstorferi) + A. septimus) + ((N. semanticus + N. lieftincki) + Ophiogomphus cecilia)) + Ictinogomphus sp MT 2014). Our study provides insight into the gene or their protein structure features of the family Gomphidae mitogenomes and lays the foundation for further phylogenetic studies.

Mitochondrial genomes – unity and diversity

The emergence of mitochondria was one of the most important events in the history of life on Earth. The engulfed bacterial cell, transformed into a mitochondrion, retained its genome, which then underwent numerous modifications. Through massive loss and numerous gene transfers into the nuclear genome, the autonomous bacterium eventually evolved into the organelle we know today. As a result of changes taking place independently in different evolutionary lineages, we observe a great diversity of mitochondrial genomes with respect to structure and gene content. In most cases, mitochondrial DNA has a circular shape, but linear molecules of mitochondrial DNA are also observed in some eukaryotes. In extreme cases, such as in reduced mitochondrial-derived organelles, the genome has been completely lost. In this article, we discuss the diversity of mitochondrial genome structures within the largest groups of Eukarya.

Mapping mitonuclear epistasis using a novel recombinant yeast population.

Genetic variation in mitochondrial and nuclear genomes can perturb mitonuclear interactions and lead to phenotypic differences between individuals and populations. Despite their importance to most complex traits, it has been difficult to identify the interacting mitonuclear loci. Here, we present a novel advanced intercrossed population of Saccharomyces cerevisiae yeasts, called the Mitonuclear Recombinant Collection (MNRC), designed explicitly for detecting mitonuclear loci contributing to complex traits. For validation, we focused on mapping genes that contribute to the spontaneous loss of mitochondrial DNA (mtDNA) that leads to the petite phenotype in yeast. We found that rates of petite formation in natural populations are variable and influenced by genetic variation in nuclear DNA, mtDNA and mitonuclear interactions. We mapped nuclear and mitonuclear alleles contributing to mtDNA stability using the MNRC by integrating a term for mitonuclear epistasis into a genome-wide association model. We found that the associated mitonuclear loci play roles in mitotic growth most likely responding to retrograde signals from mitochondria, while the associated nuclear loci with main effects are involved in genome replication. We observed a positive correlation between growth rates and petite frequencies, suggesting a fitness tradeoff between mitotic growth and mtDNA stability. We also found that mtDNA stability was correlated with a mobile mitochondrial GC-cluster that is present in certain populations of yeast and that selection for nuclear alleles that stabilize mtDNA may be rapidly occurring. The MNRC provides a powerful tool for identifying mitonuclear interacting loci that will help us to better understand genotype-phenotype relationships and coevolutionary trajectories.

Mitochondrial genomes in the iconic reindeer lichens: Architecture, variation, and synteny across multiple evolutionary scales

ABSTRACT Variation in mitochondrial genome composition across intraspecific, interspecific, and higher taxonomic scales has been little studied in lichen obligate symbioses. Cladonia is one of the most diverse and ecologically important lichen genera, with over 500 species representing an array of unique morphologies and chemical profiles. Here, we assess mitochondrial genome diversity and variation in this flagship genus, with focused sampling of two clades of the “true” reindeer lichens, Cladonia subgenus Cladina, and additional genomes from nine outgroup taxa. We describe composition and architecture at the gene and the genome scale, examining patterns in organellar genome size in larger taxonomic groups in Ascomycota. Mitochondrial genomes of Cladonia, Pilophorus, and Stereocaulon were consistently larger than those of Lepraria and contained more introns, suggesting a selective pressure in asexual morphology in Lepraria driving it toward genomic simplification. Collectively, lichen mitochondrial genomes were larger than most other fungal life strategies, reaffirming the notion that coevolutionary streamlining does not correlate to genome size reductions. Genomes from Cladonia ravenelii and Stereocaulon pileatum exhibited ATP9 duplication, bearing paralogs that may still be functional. Homing endonuclease genes (HEGs), though scarce in Lepraria, were diverse and abundant in Cladonia, exhibiting variable evolutionary histories that were sometimes independent of the mitochondrial evolutionary history. Intraspecific HEG diversity was also high, with C. rangiferina especially bearing a range of HEGs with one unique to the species. This study reveals a rich history of events that have transformed mitochondrial genomes of Cladonia and related genera, allowing future study alongside a wealth of assembled genomes.

A Genetically Heterogeneous Rat Model with Divergent MitochondrialGenomes.

We generated a genetically heterogenous rat model by a 4-way cross strategy using 4 inbred strains (Brown Norway [BN], Fischer 344 [F344], Lewis [LEW], and Wistar Kyoto [KY]) to provide investigators with a highly genetically diverse rat model from commercially available inbred rats. We made reciprocal crosses between males and females from the 2 F1 hybrids to generate genetically heterogeneous rats with mitochondrial genomes from either the BN (OKC-HETB, a.k.a "B" genotype) or WKY (OKC-HETW a.k.a "W" genotype) parental strains. These two mitochondrial genomes differ at 94 nucleotides, more akin to human mitochondrial genome diversity than that available in classical laboratory mouse strains. Body weights of the B and W genotypes were similar. However, mitochondrial genotype antagonistically affected grip strength and treadmill endurance in females only. In addition, mitochondrial genotype significantly affected multiple responses to a high-fat diet (HFD) and treatment with 17α-estradiol. Contrary to findings in mice in which males only are affected by 17α-estradiol supplementation, female rats fed a HFD beneficially responded to 17α-estradiol treatment as evidenced by declines in body mass, adiposity, and liver mass. Male rats, by contrast, differed in a mitochondrial genotype-specific manner, with only B males responding to 17α-estradiol treatment. Mitochondrial genotype and sex differences were also observed in features of brain-specific antioxidant response to a HFD and 17α-estradiol as shown by hippocampal levels of Sod2 acetylation, JNK, and FoxO3a. These results emphasize the importance of mitochondrial genotype in assessing responses to putative interventions in aging processes.

Mitonuclear Interactions and the Origin of Macaque Societies.

In most eukaryotes, aerobic respiration requires interactions between autosomally encoded genes (Ninteract genes) and mitochondrial DNA, RNA, and protein. In species where females are philopatric, contrasting distributions of genetic variation in mitochondrial and nuclear genomes create variation in mitonuclear interactions that may be subject to natural selection. To test this expectation, we turned to a group with extreme female philopatry: the macaque monkeys. We examined four genomic data sets from (1) wild caught and (2) captive populations of rhesus macaque, which is the most widely distributed nonhuman primate, and (3) the stump-tailed macaque and (4) a subspecies of longtail macaque, both of whose mitochondrial DNA is introgressed from a highly diverged ancestor. We identified atypically long runs of homozygosity, low polymorphism, high differentiation, and/or rapid protein evolution associated with Ninteract genes compared with non-Ninteract genes. These metrics suggest a subset of Ninteract genes were independently subject to atypically pervasive natural selection in multiple species. These findings suggest that natural selection on mitonuclear interactions could have influenced several aspects of macaque societies including species diversity, ecological breadth, female-biased adult sex ratio and demography, sexual dimorphism, and mitonuclear phylogenomics.