Complete mitochondrial genome of Penicillidia dufourii (Diptera: Hippoboscoidea: Nycteribiidae) and phylogenetic relationship.

Penicillidia dufourii (Westwood 1834) is a specialized parasite categorized under family Nycteribiidae that prefers to parasitize the body surface of various bats under the genus Myotis. Many species of the family Nycteribiidae are carriers of various pathogens; however, research on P. dufourii remains scarce, and studies on its molecular identification and population genetic structure are still lacking. In this study, the complete mitochondrial genome of P. dufourii was elucidated for the first time using Illumina sequencing. The mitochondrial genome is 15,354 bp in size and encodes approximately 37 genes, including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 1 control region. Analysis of 13 protein-coding genes revealed that UUA, UCA, CGA, and GGA were the most common codons, while nad4L had the fastest evolutionary rate and cox1 the slowest. Phylogenetic analysis based on the mitochondrial genome indicated that P. dufourii is clustered with other species of the family Nycteribiidae and is most closely related to Nycteribia parvula and Phthiridium szechuanum.

New taxonomic insights for Brazilian Syrbatus Reitter (Coleoptera: Staphylinidae: Pselaphinae), including three new species and their mitochondrial genomes.

Here we present a taxonomic treatment for the Brazilian species of Syrbatus (Reitter, 1882), including the description of three new species (Syrbatus moustache Asenjo & Valois sp. nov., Syrbatus obsidian Asenjo & Valois sp. nov. and Syrbatus superciliata Asenjo & Valois sp. nov.) from the Quadrilátero Ferrífero (Minas Gerais, Brazil). In addition, we designated lectotypes for the Brazilian species of species-group 2, Syrbatus centralis (Raffray, 1898), Syrbatus hetschkoi (Reitter, 1888), Syrbatus hiatusus (Reitter, 1888), Syrbatus transversalis (Raffray, 1898), and Syrbatus trinodulus (Schaufuss, 1887), besides recognizing the holotype for Syrbatus brevispinus (Reitter, 1882), Syrbatus bubalus (Raffray, 1898), and Syrbatus grouvellei (Raffray, 1898). The mitochondrial genomes (mitogenomes) of the three new species are presented, for which we present the phylogenetic placement among Staphylinidae with previously published data.

The first mitogenome of the subfamily Stenoponiinae (Siphonaptera: Ctenophthalmidae) and implications for its phylogenetic position.

Fleas are the most important insect vectors that parasitize warm-blooded animals and are known vectors of zoonotic pathogens. A recent study showed that Stenoponia polyspina parasitizing Eospalax baileyi in Zoige County have carried Bartonella spp. and Spotted fever group Rickettsia (SFGR). Accurate identification and differentiation of fleas are essential for prevention and control of zoonotic pathogens. To understand phylogenetic relationship of the subfamily Stenoponiinae, we described morphological characteristics of S. polyspina and sequenced its mitogenome with 14,933 bp in size and high A + T content (~ 79%). The S. polyspina mitogenome retained the ancestral pattern of mitochondrial gene arrangement of arthropods without rearrangement. The start codons of 13 protein-coding genes (PCGs) are traditional ATN and the stop codons are TAA or TAG. Anticodon loops of all tRNA genes were 7 bp except for trnL2 and trnD had anticodon loops with 9 bp and the abnormal anticodon loops may be associated with frameshifting mutation. Genetic distance and Ka/Ks ratios indicated that all 13 PCGs of S. polyspina were subjected to purifying selection, with cox1 at the slowest rate and atp8 at the fastest rate. The mitogenomes of 24 species representing 7 families in the order Siphonaptera were selected to reconstruct phylogenetic tree based on concatenated nucleotide sequences of two datasets (PCGRNA matrix and PCG12RNA matrix) using Bayesian inference (BI) and Maximum likelihood (ML) methods. Phylogenetic tree supported that the superfamilies Ceratophylloidea, Vermipsylloidea, Pulicoidea were monophyletic and the superfamily Hystrichopsylloidea was paraphyletic. The family Ctenophthalmidae was monophyletic in PCGRNA-ML (codon partition) and paraphyletic in the remain trees. S. polyspina belongs to the subfamily Stenoponiinae was closely more related to the subfamily Rhadinopsyllinae. This paper explored phylogenetic position of diverse clades within the order Siphonaptera based on morphological and mitogenome data of S. polyspina. Our research enriched NCBI database of the order Siphonaptera.

The Complete Mitogenome of Apostasia fujianica Y.Li & S.Lan and Comparative Analysis of Mitogenomes across Orchidaceae.

Apostasia fujianica belongs to the genus Apostasia and is part of the basal lineage in the phylogenetic tree of the Orchidaceae. Currently, there are only ten reported complete mitochondrial genomes in orchids, which greatly hinders the understanding of mitochondrial evolution in Orchidaceae. Therefore, we assembled and annotated the mitochondrial genome of A. fujianica, which has a length of 573,612 bp and a GC content of 44.5%. We annotated a total of 44 genes, including 30 protein-coding genes, 12 tRNA genes, and two rRNA genes. We also performed relative synonymous codon usage (RSCU) analysis, repeat sequence analysis, intergenomic transfer (IGT) analysis, and Ka/Ks analysis for A. fujianica and conducted RNA editing site analysis on the mitochondrial genomes of eight orchid species. We found that most protein-coding genes are under purifying selection, but nad6 is under positive selection, with a Ka/Ks value of 1.35. During the IGT event in A. fujianica's mitogenome, the trnN-GUU, trnD-GUC, trnW-CCA, trnP-UGG, and psaJ genes were identified as having transferred from the plastid to the mitochondrion. Compared to other monocots, the family Orchidaceae appears to have lost the rpl10, rpl14, sdh3, and sdh4 genes. Additionally, to further elucidate the evolutionary relationships among monocots, we constructed a phylogenetic tree based on the complete mitogenomes of monocots. Our study results provide valuable data on the mitogenome of A. fujianica and lay the groundwork for future research on genetic variation, evolutionary relationships, and breeding of Orchidaceae.

Complete mitochondrial genomes of three vulnerable cave bat species and their phylogenetic relationships within the order Chiroptera.

The IUCN Red List of Threatened Species contains 175 Brazilian bat species that are threatened by extinction in some degree. From this perspective, it is essential to expand the knowledge about the genetic diversity of vulnerable bats. Genomic sequencing can be useful to generate robust and informative genetic references, increasing resolution when analyzing relationships among populations, species, or higher taxonomic levels. In this study, we sequenced and characterized in detail the first complete mitochondrial genomes of Furipterus horrens, Lonchorhina aurita, and Natalus macrourus, and investigated their phylogenetic position based on amino acid sequences of protein-coding genes (PCGs). The mitogenomes of these species are 16,516, 16,697, and 16,668 bp in length, respectively, and each comprises 13 PCGs, 22 tRNA genes, two rRNA genes, and a putative control region (CR). In the three species, genes were arranged similarly to all other previously described bat mitogenomes, and nucleotide composition was also consistent with the reported range. The length and arrangement of rrnS and rrnL were also consistent with those of other bat species, showing a positive AT-skew and a negative GC-skew. Except for trnS1, for which we did not observe the DHU arm, all other tRNAs showed the cloverleaf secondary structure in the three species. In addition, the mitogenomes showed minor differences in start and stop codons, and in all PCGs, codons ending in adenine were more common compared to those ending in guanine. We found that PCGs of the three species use multiple codons to encode each amino acid, following the previously documented pattern. Furthermore, all PCGs are under purifying selection, with atp8 experiencing the most relaxed purifying selection. Considering the phylogenetic reconstruction, F. horrens was recovered as sister to Noctilio leporinus, L. aurita and Tonatia bidens shared a node within Phyllostomidae, and N. macrourus appeared as sister to Molossidae and Vespertilionidae.

Museomics allows comparative analyses of mitochondrial genomes in the family Gryllidae (Insecta, Orthoptera) and confirms its phylogenetic relationships.

Background: Next-generation sequencing technology can now be used to sequence historical specimens from natural history collections, an approach referred to as museomics. The museomics allows obtaining molecular data from old museum-preserved specimens, a resource of biomolecules largely underexploited despite the fact that these specimens are often unique samples of nomenclatural types that can be crucial for resolving scientific questions. Despite recent technical progress, cricket mitogenomes are still scarce in the databases, with only a handful of new ones generated each year from freshly collected material. Methods: In this study, we used the genome skimming method to sequence and assemble three new complete mitogenomes representing two tribes of the cricket subfamily Eneopterinae: two were obtained from old, historical type material of Xenogryllus lamottei (68 years old) and X. maniema (80 years old), the third one from a freshly collected specimen of Nisitrus vittatus. We compared their genome organization and base composition, and reconstructed the molecular phylogeny of the family Gryllidae. Results: Our study not only confirmed that the genome skimming method used by next generation sequencing allows us to efficiently obtain the whole mitogenome from dry-pinned historical specimens, but we also confirmed how promising it is for large-scale comparative studies of mitogenomes using resources from natural history collections. Used in a phylogenetic context the new mitogenomes attest that the mitogenomic data contain valuable information and also strongly support phylogenetic relationships at multiple time scales.

Characterization of the complete mitochondrial genome of a newly discovered torrent catfish, Liobagrus geumgangensis, and their phylogenetic relationships.

BACKGROUND: A new Liobagrus fish was reported from the Korean Peninsula, but research on this taxon is lacking. Moreover, existing research on the mitogenome of the genus Liobagrus in Korea is very limited, and no studies have been conducted on structural characteristics of transfer RNA (tRNA) or gene order comparisons between taxa; instead, research has been restricted to basic phylogeny. OBJECTIVE: The complete mitochondrial genome of Liobagrus geumgangensis was analyzed for the first time. We then aimed to reconstruct the phylogenetic relationships of the genus Liobagrus and estimate the divergence time of speciation events. METHODS: We used a dissected fin clip from an adult of Liobagrus geumgangensis. Genomic DNA was extracted and analyzed with whole genome sequencing (WGS) and assembled by the NOVOPlasty method. The mitogenome sequence was annotated, and a genome map, tRNA structure, and phylogenetic tree were constructed using maximum likelihood analysis. In addition, divergence time was estimated. RESULTS: The mitochondrial genome was 16,522 bp in length and comprised 37 genes. The overall base composition was 30.5% A, 25.5% T, 28.4% C, and 15.7% G. Most tRNAs exhibited the typical clover leaf shape, except trnS1. Phylogenetic analysis revealed that Liobagrus geumgangensis clustered within a clade with four other Liobagrus species exclusive to the southern region of the Korean Peninsula. Its divergence was estimated to have occurred during the late Miocene. CONCLUSION: Characteristics of Liobagrus geumgangensis mitogenome were consistent with those of other torrent catfish species. Time scale estimation revealed distinct groupings, with some distributed across mainland Asia and others in the southern region of the Korean Peninsula. Notably, the Korean Peninsula group was identified as its own lineage, comprising entirely endemic species.

The Phylogenetic Relationships of Major Lizard Families Using Mitochondrial Genomes and Selection Pressure Analyses in Anguimorpha.

Anguimorpha, within the order Squamata, represents a group with distinct morphological and behavioral characteristics in different ecological niches among lizards. Within Anguimorpha, there is a group characterized by limb loss, occupying lower ecological niches, concentrated within the subfamily Anguinae. Lizards with limbs and those without exhibit distinct locomotor abilities when adapting to their habitats, which in turn necessitate varying degrees of energy expenditure. Mitochondria, known as the metabolic powerhouses of cells, play a crucial role in providing approximately 95% of an organism's energy. Functionally, mitogenomes (mitochondrial genomes) can serve as a valuable tool for investigating potential adaptive evolutionary selection behind limb loss in reptiles. Due to the variation of mitogenome structures among each species, as well as its simple genetic structure, maternal inheritance, and high evolutionary rate, the mitogenome is increasingly utilized to reconstruct phylogenetic relationships of squamate animals. In this study, we sequenced the mitogenomes of two species within Anguimorpha as well as the mitogenomes of two species in Gekkota and four species in Scincoidea. We compared these data with the mitogenome content and evolutionary history of related species. Within Anguimorpha, between the mitogenomes of limbless and limbed lizards, a branch-site model analysis supported the presence of 10 positively selected sites: Cytb protein (at sites 183 and 187), ND2 protein (at sites 90, 155, and 198), ND3 protein (at site 21), ND5 protein (at sites 12 and 267), and ND6 protein (at sites 72 and 119). These findings suggested that positive selection of mitogenome in limbless lizards may be associated with the energy requirements for their locomotion. Additionally, we acquired data from 205 mitogenomes from the NCBI database. Bayesian inference (BI) and Maximum Likelihood (ML) trees were constructed using the 13 mitochondrial protein-coding genes (PCGs) and two rRNAs (12S rRNA and 16S rRNA) from 213 mitogenomes. Our phylogenetic tree and the divergence time estimates for Squamata based on mitogenome data are consistent with results from previous studies. Gekkota was placed at the root of Squamata in both BI and ML trees. However, within the Toxicofera clade, due to long-branch attraction, Anguimorpha and (Pleurodonta + (Serpentes + Acrodonta)) were closely related groupings, which might indicate errors and also demonstrate that mitogenome-based phylogenetic trees may not effectively resolve long-branch attraction issues. Additionally, we reviewed the origin and diversification of Squamata throughout the Mesozoic era, suggesting that Squamata originated in the Late Triassic (206.05 Mya), with the diversification of various superfamilies occurring during the Cretaceous period. Future improvements in constructing squamate phylogenetic relationships using mitogenomes will rely on identifying snake and acrodont species with slower evolutionary rates, ensuring comprehensive taxonomic coverage of squamate diversity, and increasing the number of genes analyzed.

Comparative mitochondrial genome analysis provides new insights into the classification of Modiolinae.

BACKGROUND: Mitochondrial genomes have become a powerful tool for studying molecular genetics and phylogeny of mollusks. Currently, the position of Modiolinae within Mytilidae and the taxonomic and phylogenetic relationships within Modiolinae were still controversial. This study focuses on the complete mitochondrial genomes of two species: Modiolus modulaides (Röding, 1798) and Modiolus auriculatus Krauss, 1848, which have not been sequenced before. METHODS AND RESULTS: We assembled and characterized the mitochondrial genomes of M. modulaides and M. auriculatus and then analyzed the phylogenetic relationships. The mitochondrial genomes of M. modulaides and M. auriculatus were 15,422 bp and 16,027 bp, respectively. Both of them were composed of 36 functional genes, including 12 protein-coding genes, 22 transfer RNAs, and 2 ribosomal RNAs. All protein-coding genes showed A + T bias, positive GC skews, and negative AT skews in nucleotide composition. Phylogenetic analysis based on the mitochondrial genomes showed that Modiolinae and Bathymodiolinae clustered together to form a sister relationship. Seven Modiolinae species were divided into two clades: L1 (M. modulaides, M. auriculatus and Modiolus philippinarum Hanley, 1843) and L2 [Modiolus modiolus (Linnaeus, 1758), Modiolus kurilensis Bernard, 1983, Modiolus nipponicus (Oyama, 1950), and Modiolus comptus (Sowerby III, 1915)]. The divergence time of the two clades was approximately 105.75 Ma. Furthermore, the transfer RNA gene rearrangement, longer genetic distance, and greater genetic differentiation were confirmed between the L1 and L2 clades, as well as differences in the external characteristics of the shells of the two clades. CONCLUSIONS: Based on the molecular data, it was speculated that species from the L1 clade might belong to other genera or new genera. This study provides molecular information for further taxonomic and phylogenetic studies of Mytilidae.

Deciphering tissue-specific expression profiles of mitochondrial genome-encoded tRNAs and rRNAs through transcriptomic profiling in buffalo.

BACKGROUND: Mitochondria, essential for cellular energy production through oxidative phosphorylation (OXPHOS), integrate mt-DNA and nuclear-encoded genes. This cooperation extends to the mitochondrial translation machinery, involving crucial mtDNA-encoded RNAs: 22 tRNAs (mt-tRNAs) as adapters and two rRNAs (mt-rRNAs) for ribosomal assembly, enabling mitochondrial-encoded mRNA translation. Disruptions in mitochondrial gene expression can strongly impact energy generation and overall animal health. Our study investigates the tissue-specific expression patterns of mt-tRNAs and mt-rRNAs in buffalo. MATERIAL AND METHODS: To investigate the expression patterns of mt-tRNAs and mt-rRNAs in different tissues and gain a better understanding of tissue-specific variations, RNA-seq was performed on various tissues, such as the kidney, heart, brain, and ovary, from post-pubertal female buffaloes. Subsequently, we identified transcripts that were differentially expressed in various tissue comparisons. RESULTS: The findings reveal distinct expression patterns among specific mt-tRNA and mt-rRNA genes across various tissues, with some exhibiting significant upregulation and others demonstrating marked downregulation in specific tissue contexts. These identified variations reflect tissue-specific physiological roles, underscoring their significance in meeting the unique energy demands of each tissue. Notably, the brain exhibits the highest mtDNA copy numbers and an abundance of mitochondrial mRNAs of our earlier findings, potentially linked to the significant upregulation of mt-tRNAs in brain. This suggests a plausible association between mtDNA replication and the regulation of mtDNA gene expression. CONCLUSION: Overall, our study unveils the tissue-specific expression of mitochondrial-encoded non-coding RNAs in buffalo. As we proceed, our further investigations into tissue-specific mitochondrial proteomics and microRNA studies aim to elucidate the intricate mechanisms within mitochondria, contributing to tissue-specific mitochondrial attributes. This research holds promise to elucidate the critical role of mitochondria in animal health and disease.

The Whole Mitochondrial Genome Sequence of Dendrobium loddigesii Rolfe, an Endangered Orchid Species in China, Reveals a Complex Multi-Chromosome Structure.

Dendrobium loddigesii is a precious traditional Chinese medicine with high medicinal and ornamental value. However, the characterization of its mitochondrial genome is still pending. Here, we assembled the complete mitochondrial genome of D. loddigesii and discovered that its genome possessed a complex multi-chromosome structure. The mitogenome of D. loddigesii consisted of 17 circular subgenomes, ranging in size from 16,323 bp to 56,781 bp. The total length of the mitogenome was 513,356 bp, with a GC content of 43.41%. The mitogenome contained 70 genes, comprising 36 protein-coding genes (PCGs), 31 tRNA genes, and 3 rRNA genes. Furthermore, we detected 403 repeat sequences as well as identified 482 RNA-editing sites and 8154 codons across all PCGs. Following the sequence similarity analysis, 27 fragments exhibiting homology to both the mitogenome and chloroplast genome were discovered, accounting for 9.86% mitogenome of D. loddigesii. Synteny analysis revealed numerous sequence rearrangements in D. loddigesii and the mitogenomes of related species. Phylogenetic analysis strongly supported that D. loddigesii and D. Amplum formed a single clade with 100% bootstrap support. The outcomes will significantly augment the orchid mitochondrial genome database, offering profound insights into Dendrobium's intricate mitochondrial genome architecture.

Phylogenetic and Comparative Genomics Study of Papilionidae Based on Mitochondrial Genomes.

Most species of Papilionidae are large and beautiful ornamental butterflies. They are recognized as model organisms in ecology, evolutionary biology, genetics, and conservation biology but present numerous unresolved phylogenetic problems. Complete mitochondrial genomes (mitogenomes) have been widely used in phylogenetic studies of butterflies, but mitogenome knowledge within the family Papilionidae is limited, and its phylogeny is far from resolved. In this study, we first report the mitogenome of Byasa confusa from the subfamily Papilioninae of Papilionidae. The mitogenome of B. confusa is 15,135 bp in length and contains 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and an AT-rich control region (CR), closely mirroring the genomic structure observed in related butterfly species. Comparative analysis of 77 Papilionidae mitogenomes shows gene composition and order to be identical to that of an ancestral insect, and the AT bias, Ka/Ks, and relative synonymous codon usage (RSCU) are all consistent with that of other reported butterfly mitogenomes. We conducted phylogenetic analyses using maximum-likelihood (ML) and Bayesian-inference (BI) methods, with 77 Papilionidae species as ingroups and two species of Nymphalidae and Lycaenidae as outgroups. The phylogenetic analysis indicated that B. confusa were clustered within Byasa. The phylogenetic trees show the monophyly of the subfamily Papilioninae and the tribes Leptocircini, Papilionini, and Troidini. The data supported the following relationships in tribe level on Papilioninae: (((Troidini + Papilionini) + Teinopalpini) + Leptocircini). The divergence time analysis suggests that Papilionidae originated in the late Creataceous. Overall, utilizing the largest number of Papilionidae mitogenomes sequenced to date, with the current first exploration in a phylogenetic analysis on Papilionidae (including four subfamilies), this study comprehensively reveals the mitogenome characteristics and mitogenome-based phylogeny, providing information for further studies on the mitogenome, phylogeny, evolution, and taxonomic revision of the Papilionidae family.

Structure, Evolution, and Mitochondrial Genome Analysis of Mussel Species (Bivalvia, Mytilidae).

Based on the nucleotide sequences of the mitochondrial genome (mitogenome) of specimens taken from two mussel species (Arcuatula senhousia and Mytilus coruscus), an investigation was performed by means of the complex approaches of the genomics, molecular phylogenetics, and evolutionary genetics. The mitogenome structure of studied mussels, like in many other invertebrates, appears to be much more variable than in vertebrates and includes changing gene order, duplications, and deletions, which were most frequent for tRNA genes; the mussel species' mitogenomes also have variable sizes. The results demonstrate some of the very important properties of protein polypeptides, such as hydrophobicity and its determination by the purine and pyrimidine nucleotide ratio. This fact might indirectly indicate the necessity of purifying natural selection for the support of polypeptide functionality. However, in accordance with the widely accepted and logical concept of natural cutoff selection for organisms living in nature, which explains its action against deleterious nucleotide substitutions in the nonsynonymous codons (mutations) and its holding of the active (effective) macromolecules of the polypeptides in a population, we were unable to get unambiguous evidence in favor of this concept in the current paper. Here, the phylogeny and systematics of mussel species from one of the largest taxons of bivalve mollusks are studied, the family known as Mytilidae. The phylogeny for Mytilidae (order Mytilida), which currently has no consensus in terms of systematics, is reconstructed using a data matrix of 26-27 mitogenomes. Initially, a set of 100 sequences from GenBank were downloaded and checked for their gender: whether they were female (F) or male (M) in origin. Our analysis of the new data confirms the known drastic differences between the F/M mitogenome lines in mussels. Phylogenetic reconstructions of the F-lines were performed using the combined set of genetic markers, reconstructing only protein-coding genes (PCGs), only rRNA + tRNA genes, and all genes. Additionally, the analysis includes the usage of nucleotide sequences composed of other data matrices, such as 20-68 mitogenome sequences. The time of divergence from MRCA, estimated via BEAST2, for Mytilidae is close to 293 Mya, suggesting that they originate in the Silurian Period. From all these data, a consensus for the phylogeny of the subfamily of Mytilinae and its systematics is suggested. In particular, the long-debated argument on mussel systematics was resolved as to whether Mytilidae, and the subfamily of Mytilinae, are monophyletic. The topology signal, which was strongly resolved in this paper and in the literature, has refuted the theory regarding the monophyly of Mytilinae.

Detailed characterization of the complete mitochondrial genome of the oceanic whitetip shark Carcharhinus longimanus (Poey, 1861).

BACKGROUND: The oceanic whitetip shark Carcharhinus longimanus (family Carcharhinidae) is one of the largest sharks inhabiting all tropical and subtropical oceanic regions. Due to their life history traits and mortality attributed to pelagic longline fishing practices, this species is experiencing substantial population decline. Currently, C. longimanus is considered by the IUCN Red List of Threatened Species as "vulnerable" throughout its range and "critically endangered" in the western north Atlantic. This study sequences and describes the complete mitochondrial genome of C. longimanus in detail. METHODS AND RESULTS: The mitochondrial genome of C. longimanus was assembled through next-generation sequencing and then analyzed using specialized bioinformatics tools. The circular, double-stranded AT-rich mitogenome of C. longimanus is 16,704 bp long and contains 22 tRNA genes, 2 rRNA genes, 13 protein coding genes and a 1,065 bp long control region (CR). Out of the 22 tRNA genes, only one (tRNA-Ser1) lacked a typical 'cloverleaf' secondary structure. The prevalence of TTA (Leu), ATT (Ile) and CTA (Leu) codons in the PCGs likely contributes to the AT-rich nature of this mitogenome. In the CR, ten microsatellites were detected but no tandem repeats were found. Stem-and-loop secondary structures were common along the entire length of the CR. Ka/Ks values estimated for all PCGs were < 1, indicating that all the PCGs experience purifying selection. A phylomitogenomic analysis based on translated PCGs confirms the sister relationship between C. longimanus and C. obscurus. The analysis did not support the monophyly of the genus Carcharhinus. CONCLUSIONS: The assembled mitochondrial genome of this pelagic shark can provide insight into the phylogenetic relationships in the genus Carcharhinus and aid conservation and management efforts in the Central Pacific Ocean.

Mitochondrial genome of the fluke pond snail, Austropeplea cf. brazieri (Gastropoda: Lymnaeidae).

BACKGROUND: Lymnaeid snails of the genus Austropeplea are an important vector of the liver fluke (Fasciola hepatica), contributing to livestock production losses in Australia and New Zealand. However, the species status within Austropeplea is ambiguous due to heavy reliance on morphological analysis and a relative lack of genetic data. This study aimed to characterise the mitochondrial genome of A. cf. brazieri, an intermediate host of liver fluke in eastern Victoria. METHODS: The mitochondrial genome was assembled and annotated from a combination of second- and third-generation sequencing data. For comparative purposes, we performed phylogenetic analyses of the concatenated nucleotide sequences of the mitochondrial protein-coding genes, cytochrome c oxidase subunit 1 and 16S genes. RESULTS: The assembled mt genome was 13,757 base pairs and comprised 37 genes, including 13 protein-coding genes, 22 transfer RNA genes and 2 ribosomal RNA genes. The mt genome length, gene order and nucleotide compositions were similar to related species of lymnaeids. Phylogenetic analyses of the mt nucleotide sequences placed A. cf. brazieri within the same clade as Orientogalba ollula with strong statistical supports. Phylogenies of the cox1 and 16S mt sequences were constructed due to the wide availability of these sequences representing the lymnaeid taxa. As expected in both these phylogenies, A. cf. brazieri clustered with other Austropeplea sequences, but the nodal supports were low. CONCLUSIONS: The representative mt genome of A. cf. brazieri should provide a useful resource for future molecular, epidemiology and parasitological studies of this socio-economically important lymnaeid species.

Comparison and phylogenetic analysis of the mitochondrial genomes of Synodontis eupterus and Synodontis polli.

We aimed to distinguish Synodontis eupterus and Synodontis polli. We performed sequencing and bioinformatic analysis of their mitochondrial genomes and constructed a phylogenetic tree of Mochokidae fish using maximum likelihood and Bayesian methods based on protein-coding gene (PCG) sequences of 14 Mochokidae species. The total length of the S. eupterus mitochondrial genome was 16,579 bp, including 13 (PCGs), 22 tRNA genes, two rRNA genes, and one D-loop, with an AT-biased nucleotide composition (56.0%). The total length of the S. polli mitochondrial genome was 16,544 bp, including 13 PCGs, 22 tRNA genes, two rRNA genes, and one D-loop, with an AT-biased nucleotide composition (55.0%). In both species, except for COI, PCGs use ATG as the starting codon, the vast majority use TAG or TAA as the ending codon, and a few use incomplete codons (T - or TA -) as the ending codon. Phylogenetic analysis showed that S. eupterus and Synodontis clarias converged into one branch, S. polli and Synodontis petricola converged into one branch, Mochokiella paynei, Mochokus brevis, and nine species of the genus Synodontis converged into one branch, and M. paynei clustered with the genus Synodontis. This study lays a foundation for rebuilding a clearer Mochokidae fish classification system.

Molecular phylogenetic position and description of a new genus and species of freshwater Chaetonotidae (Gastrotricha: Chaetonotida: Paucitubulatina), and the annotation of its mitochondrial genome.

Chaetonotidae is the most diversified family of the entire phylum Gastrotricha; it comprises ~430 species distributed across 16 genera. The current classification, established mainly on morphological traits, has been challenged in recent years by phylogenetic studies, indicating that the cuticular ornamentations used to discriminate among species may be misleading when used to identify groupings, which has been the practice until now. Therefore, a consensus is developing toward implementing novel approaches to better define species identity and affiliation at a higher taxonomic ranking. Using an integrative morphological and molecular approach, including annotation of the mitogenome, we report on some freshwater gastrotrichs characterised by a mixture of two types of cuticular scales diagnostic of the genera Aspidiophorus and Heterolepidoderma . Our specimens' overall anatomical characteristics find no correspondence in the taxa of these two genera, calling for their affiliation to a new species. Phylogenetic analyses based on the sequence of the ribosomal RNA genes of 96 taxa consistently found the new species unrelated to Aspidiophorus or Heterolepidoderma but allied with Chaetonotus aff. subtilis, as a subset of a larger clade, including mostly planktonic species. Morphological uniqueness and position along the non-monophyletic Chaetonotidae branch advocate erecting a new genus to accommodate the current specimens; consequently, the name Litigonotus ghinii gen. nov., sp. nov. is proposed. The complete mitochondrial genome of the new taxon resulted in a single circular molecule 14,384 bp long, including 13 protein-coding genes, 17 tRNA genes and 2 rRNAs genes, showing a perfect synteny and collinearity with the only other gastrotrich mitogenome available, a possible hint of a high level of conservation in the mitochondria of Chaetonotidae. ZooBank: urn:lsid:zoobank.org:pub:9803F659-306F-4EC3-A73B-8C704069F24A.

Assembly and evolutionary analysis of the complete mitochondrial genome of Trichosanthes kirilowii, a traditional Chinese medicinal plant.

Trichosanthes kirilowii (T. kirilowii) is a valuable plant used for both medicinal and edible purposes. It belongs to the Cucurbitaceae family. However, its phylogenetic position and relatives have been difficult to accurately determine due to the lack of mitochondrial genomic information. This limitation has been an obstacle to the potential applications of T. kirilowii in various fields. To address this issue, Illumina and Nanopore HiFi sequencing were used to assemble the mitogenome of T. kirilowii into two circular molecules with sizes of 245,700 bp and 107,049 bp, forming a unique multi-branched structure. The mitogenome contains 61 genes, including 38 protein-coding genes (PCGs), 20 tRNAs, and three rRNAs. Within the 38 PCGs of the T. kirilowii mitochondrial genome, 518 potential RNA editing sites were identified. The study also revealed the presence of 15 homologous fragments that span both the chloroplast and mitochondrial genomes. The phylogenetic analysis strongly supports that T. kirilowii belongs to the Cucurbitaceae family and is closely related to Luffa. Collinearity analysis of five Cucurbitaceae mitogenomes shows a high degree of structural variability. Interestingly, four genes, namely atp1, ccmFC, ccmFN, and matR, played significant roles in the evolution of T. kirilowii through selection pressure analysis. The comparative analysis of the T. kirilowii mitogenome not only sheds light on its functional and structural features but also provides essential information for genetic studies of the genus of Cucurbitaceae.

Graph-based mitochondrial genomes of three foundation species in the Saccharum genus.

KEY MESSAGE: We reported the graph-based mitochondrial genomes of three foundation species (Saccharum spontaneum, S. robustum and S. officinarum) for the first time. The results revealed pan-structural variation and evolutionary processes in the mitochondrial genomes within Saccharum. Saccharum belongs to the Andropogoneae, and cultivars species in Saccharum contribute nearly 80% of sugar production in the world. To explore the genomic studies in Saccharum, we assembled 15 complete mitochondrial genomes (mitogenome) of three foundation species (Saccharum spontaneum, S. robustum and S. officinarum) using Illumina and Oxford Nanopore Technologies sequencing data. The mitogenomes of the three species were divided into a total of eight types based on contig numbers and linkages. All mitogenomes in the three species encoded 51 unique genes, including 32 protein-coding, 3 ribosomal RNA (rRNA) and 16 transfer RNA (tRNA) genes. The existence of long and short-repeat-mediated recombinations in the mitogenome of S. officinarum and S. robustum was revealed and confirmed through PCR validation. Furthermore, employing comparative genomics and phylogenetic analyses of the organelle genomes, we unveiled the evolutionary relationships and history of the major interspecific lineages in Saccharum genus. Phylogenetic analyses of homologous fragments between S. officinarum and S. robustum showed that S. officinarum and S. robustum are phylogenetically distinct and that they were likely parallel rather than domesticated. The variations between ancient (S. sinense and S. barberi) and modern cultivated species (S. hybrid) possibly resulted from hybridization involving different S. officinarum accessions. Lastly, this project reported the first graph-based mitogenomes of three Saccharum species, and a systematic comparison of the structural organization, evolutionary processes, and pan-structural variation of the Saccharum mitogenomes revealed the differential features of the Saccharum mitogenomes.

Horizontally transferred mitochondrial DNA tracts become circular by microhomology-mediated repair pathways.

The holoparasitic plant Lophophytum mirabile exhibits remarkable levels of mitochondrial horizontal gene transfer (HGT). Gathering comparative data from other individuals and host plants can provide insights into the HGT process. We sequenced the mitochondrial genome (mtDNA) from individuals of two species of Lophophytum and from mimosoid hosts. We applied a stringent phylogenomic approach to elucidate the origin of the whole mtDNAs, estimate the timing of the transfers, and understand the molecular mechanisms involved. Ancestral and recent HGT events replaced and enlarged the multichromosomal mtDNA of Lophophytum spp., with the foreign DNA ascending to 74%. A total of 14 foreign mitochondrial chromosomes originated from continuous regions in the host mtDNA flanked by short direct repeats. These foreign tracts are circularized by microhomology-mediated repair pathways and replicate independently until they are lost or they eventually recombine with other chromosomes. The foreign noncoding chromosomes are variably present in the population and likely evolve by genetic drift. We present the 'circle-mediated HGT' model in which foreign mitochondrial DNA tracts become circular and are maintained as plasmid-like molecules. This model challenges the conventional belief that foreign DNA must be integrated into the recipient genome for successful HGT.