Mitochondrial Genome Structure Research Articles

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.

Identification of Haemoproteus infection in an imported grey crowned crane (Balearica regulorum) in China

Blood parasites from the order Haemosporida infect many vertebrates and cause malaria-like diseases. In this study, a haemosporidian infection was detected in a sick grey crowned crane imported into China using a combination of morphological and molecular approaches. Blood samples were collected from the jugular vein and processed for morphological identification of infective parasites using stained blood smears and microscopy. No merogony occurs in the blood cells, and sporadic pigment granules were observed. Nested-PCR assays were employed for a molecular examination, which indicated that the cytb gene of this parasite had 94.1–94.9% identity to Haemoproteus antigonis. Subsequently, its mitochondrial genome structure was determined by high-throughput sequencing using the DNBSEQ-T7 platform. The determined structure was confirmed by the Sanger sequencing using amplicons. The mitochondrial genome obtained for this parasite exhibited a low CG content (32.0%) and possessed three protein-coding genes, encoding 1068 amino acids, which constituted 53.7% of the genome. Phylogenetic analysis indicated that this parasite clustered with Haemoproteus sp. is detected in grey crowned cranes from Africa. This parasite was likely acquired during importation of this animal; thus, strict quarantine of imported ornamental animals is required to prevent the entry of new pathogens.

The first report of complete mitogenomes of two endangered species of genus Propomacrus (Coleoptera: Scarabaeidae: Euchirinae) and phylogenetic implications.

To understand the mitochondrial genome structure of two endangered and long-armed scarab beetles, Propomacrus davidi and Propomacrus bimucronatus, their complete mitogenomes were sequenced for the first time in this study. The complete mitogenomes of P. davidi and P. bimucronatus were 18, 042 bp and 18, 104 bp in length, respectively. The gene orders of their mitogenomes were highly consistent with other Coleopteran species, and the typical ATN was used as the start codon in most protein coding genes. The incomplete stop codon T was used in cox1, cox2, and nad5, and TAN was used as a complete stop codon in most protein coding genes. All predicted tRNAs could form a typical cloverleaf secondary structure, except that trnS1 lacked the dihydrouridine arm. Based on the maximum likelihood and the Bayesian inference methods, phylogenetic trees of 50 species were reconstructed. The results showed that P. davidi, P. bimucronatus, Cheirotonus jansoni and Cheirotonus gestroi clustered in the same branch, and were the most closely related. The results supported that subfamily Euchirinae is a monophyletic group of Scarabaeidae, which was consistent with the morphological classification. These molecular data enriched the complete mitogenome database of Euchirinae, and improved our understanding of the phylogenetic relationship and evolutionary characteristics of these two endangered species.

Comparative analysis of the mitochondrial genomes of four Dendrobium species (Orchidaceae) reveals heterogeneity in structure, synteny, intercellular gene transfer, and RNA editing.

The genus Dendrobium, part of the Orchidaceae family, encompasses species of significant medicinal, nutritional, and economic value. However, many Dendrobium species are threatened by environmental stresses, low seed germination rates, and overharvesting. Mitochondria generate the energy necessary for various plant life activities. Despite their importance, research on the mitochondrial genomes of Dendrobium species is currently limited. To address this gap, we performed a comprehensive genetic analysis of four Dendrobium species-D. flexicaule, D. nobile, D. officinale, and D. huoshanense-focusing on their mitochondrial and chloroplast genomes to elucidate their genetic architecture and support conservation efforts. We utilized advanced sequencing technologies, including Illumina for high-throughput sequencing and Nanopore for long-read sequencing capabilities. Our findings revealed the multichromosomal mitochondrial genome structures, with total lengths ranging from 596,506 bp to 772,523 bp. The mitochondrial genomes contained 265 functional genes, including 64-69 protein-coding genes, 23-28 tRNA genes, and 3 rRNA genes. We identified 647 simple sequence repeats (SSRs) and 352 tandem repeats, along with 440 instances of plastid-to-mitochondrial gene transfer. Additionally, we predicted 2,023 RNA editing sites within the mitochondrial protein-coding genes, predominantly characterized by cytosine-to-thymine transitions. Comparative analysis of mitochondrial DNA across the species highlighted 25 conserved genes, with evidence of positive selection in five genes: ccmFC, matR, mttB, rps2, and rps10. Phylogenetic assessments suggested a close sister relationship between D. nobile and D. huoshanense, and a similar proximity between D. officinale and D. flexicaule. This comprehensive genomic study provides a critical foundation for further exploration into the genetic mechanisms and biodiversity of Dendrobium species, contributing valuable insights for their conservation and sustainable utilization.

Insights into Fungal Mitochondrial Genomes and Inheritance Based on Current Findings from Yeast-like Fungi.

The primary functions of mitochondria are to produce energy and participate in the apoptosis of cells, with them being highly conserved among eukaryotes. However, the composition of mitochondrial genomes, mitochondrial DNA (mtDNA) replication, and mitochondrial inheritance varies significantly among animals, plants, and fungi. Especially in fungi, there exists a rich diversity of mitochondrial genomes, as well as various replication and inheritance mechanisms. Therefore, a comprehensive understanding of fungal mitochondria is crucial for unraveling the evolutionary history of mitochondria in eukaryotes. In this review, we have organized existing reports to systematically describe and summarize the composition of yeast-like fungal mitochondrial genomes from three perspectives: mitochondrial genome structure, encoded genes, and mobile elements. We have also provided a systematic overview of the mechanisms in mtDNA replication and mitochondrial inheritance during bisexual mating. Additionally, we have discussed and proposed open questions that require further investigation for clarification.

Insights into structure, codon usage, repeats, and RNA editing of the complete mitochondrial genome of Perilla frutescens (Lamiaceae)

Perilla frutescens (L.) Britton, a member of the Lamiaceae family, stands out as a versatile plant highly valued for its unique aroma and medicinal properties. Additionally, P. frutescens seeds are rich in Îś-linolenic acid, holding substantial economic importance. While the nuclear and chloroplast genomes of P. frutescens have already been documented, the complete mitochondrial genome sequence remains unreported. To this end, the sequencing, annotation, and assembly of the entire Mitochondrial genome of P. frutescens were hereby conducted using a combination of Illumina and PacBio data. The assembled P. frutescens mitochondrial genome spanned 299,551 bp and exhibited a typical circular structure, involving a GC content of 45.23%. Within the genome, a total of 59 unique genes were identified, encompassing 37 protein-coding genes, 20 tRNA genes, and 2 rRNA genes. Additionally, 18 introns were observed in 8 protein-coding genes. Notably, the codons of the P. frutescens mitochondrial genome displayed a notable A/T bias. The analysis also revealed 293 dispersed repeat sequences, 77 simple sequence repeats (SSRs), and 6 tandem repeat sequences. Moreover, RNA editing sites preferentially produced leucine at amino acid editing sites. Furthermore, 70 sequence fragments (12,680 bp) having been transferred from the chloroplast to the mitochondrial genome were identified, accounting for 4.23% of the entire mitochondrial genome. Phylogenetic analysis indicated that among Lamiaceae plants, P. frutescens is most closely related to Salviamiltiorrhiza and Platostoma chinense. Meanwhile, inter-species Ka/Ks results suggested that Ka/Ks <1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$<1$$\\end{document} for 28 PCGs, indicating that these genes were evolving under purifying selection. Overall, this study enriches the mitochondrial genome data for P. frutescens and forges a theoretical foundation for future molecular breeding research.

The Complete Mitogenomes of Two Species of Snakehead Fish (Perciformes: Channidae): Genome Characterization and Phylogenetic Analysis

Channidae (snakehead fish) is a family of medium-to-large freshwater carnivorous fish and contain the genus, Channa. Here, the complete mitogenomes of two Channa fish were determined and comparatively analyzed with the mitogenomes of 16 other Channidae fish species. The two newly sequenced complete mitogenomes were circular DNA molecules with sizes of 16,953 bp (Channa burmanica; OP954106) and 16,897 bp (Channa aurantimaculata; OQ134162). The mitogenomes were composed of 37 genes and one D-loop region. Positive AT skews and negative GC skews were found in the mitogenomes. Most protein-coding genes (PCGs) started with the conventional start codon, ATG; however, the sequence of the stop codon was variable. There was no obvious difference in relative synonymous codon usage among the two mitogenomes, and the two species shared a similar number of codon usage of mitogenomic PCGs, which was also similar to the mean values for the other 15 species of Channa. All Ka/Ks values were &lt;1; cox1 had the lowest value, and atp8 had the highest. All of the tRNAs were typical clover structures, except trnS1. Phylogenetic analysis showed that C. burmanica and C. aurantimaculata shared a close relationship and that they were also closely related to C. gachua. These findings enrich the gene database of Channidae species, clarify the mitochondrial genome structure of the two species, and provide basic data for invasive biological surveillance in the future.

The rearrangement features and phylogenetic signals of mitochondrial genomes of gall midge subfamily Cecidomyiinae (Diptera: Cecidomyiidae) with first complete mitogenome of an economically important mango gall midge pest, Procontarina fructiculi from Guangxi, China

ABSTRACT In this study, we obtained the first complete mitochondrial genome of Procontarina fructiculi, an important mango gall midge pest from Guangxi, China. The mitogenome of P. fructiculi was sequenced and annotated for the first time, and compared with all the published and annotated data of Cecidomyiidae species to summarise the gall midge organisation and rearrangement features of mitochondrial genomes with phylogenetic analysis. The comparison of gall midge mitochondrial genome structure shows that the rearrangement of the mitochondrial gene structure is very common, and most rearrangements are embodied in rearrangement in the order of tRNAs. The phylogenetic results based on the maximum likelihood (ML) and Bayesian inference (BI) methods both highly supported the monophyly of Cecidomyiinae. Cecidomyiinae can be divided into two distinct clades (except Cecidomyiidae sp. 3): A: (Mayetiola destructor + Rhopalomyia pomum) and B: (Asphondylia rosetta + ((Procontarinia fructiculi + Orseolia oryzae) + ((Cecidomyiidae sp. 1 + Aphidoletes aphidimyza) + Cecidomyiidae sp. 2))). Based on the above results, some phylogenetic signals in rearrangement have been found in the mitochondrial genome structure of Cecidomyiinae for the first time.

Complete mitochondrial genomes of edible mushrooms: features, evolution, and phylogeny.

Edible mushrooms are an important food source with high nutritional and medicinal value. They are a useful source for studying phylogenetic evolution and species divergence. The exploration of the evolutionary relationships among these species conventionally involves analyzing sequence variations within their complete mitochondrial genomes, which range from 31,854 bp (Cordyceps militaris) to 197,486 bp (Grifolia frondosa). The study of the complete mitochondrial genomes of edible mushrooms has emerged as a critical field of research, providing important insights into fungal genetic makeup, evolution, and phylogenetic relationships. This review explores the mitochondrial genome structures of various edible mushroom species, highlighting their unique features and evolutionary adaptations. By analyzing these genomes, robust phylogenetic frameworks are constructed to elucidate mushrooms lineage relationships. Furthermore, the exploration of different variations of mitochondrial DNA presents novel opportunities for enhancing mushroom cultivation biotechnology and medicinal applications. The mitochondrial genomic features are essential for improving agricultural practices and ensuring food security through improved crop productivity, disease resistance, and nutritional qualities. The current knowledge about the mitochondrial genomes of edible mushrooms is summarized in this review, emphasising their significance in both scientific research and practical applications in bioinformatics and medicine.

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.

Mitochondrial genome structure and composition in 70 fishes: a key resource for fisheries management in the South Atlantic

BackgroundPhylogenetic gaps of public databases of reference sequences are a major obstacle for comparative genomics and management of marine resources, particularly in the Global South, where economically important fisheries and conservation flagship species often lack closely-related references. We applied target-enrichment to obtain complete mitochondrial genomes of marine ichthyofauna from the Brazilian coast selected based on economic significance, conservation status and lack of phylogenetically-close references. These included sardines (Dorosomatidae, Alosidae), mackerels (Scombridae) croakers (Sciaenidae), groupers (Epinephelidae) and snappers (Lutjanidae).ResultsCustom baits were designed to enrich mitochondrial DNA across a broad phylogenetic range of fishes. Sequencing generated approximately 100k reads per sample, which were assembled in a total of 70 complete mitochondrial genomes and include fifty-two new additions to GenBank, including five species with no previous mitochondrial data. Departures from the typical gene content and order occurred in only three taxa and mostly involved tRNA gene duplications. Start-codons for all genes, except Cytochrome C Oxidase subunit I (COI), were consistently ATG, whilst a wide range of stop-codons deviated from the prevailing TAA. Phylogenetic analysis confirmed assembly accuracy and revealed signs of cryptic diversification within the Mullus genus. Lineage delimitation methods using Sardinella aurita and S. brasiliensis mitochondrial genomes support a single Operational Taxonomic Unit.ConclusionsTarget enrichment was highly efficient, providing complete novel mitochondrial genomes with little sequencing effort. These sequences are deposited in public databases to enable subsequent studies in population genetics and adaptation of Latin American fish species and serve as a vital resource for conservation and management programs that rely on molecular data for species and genus-level identification.

Analysis of the Rhodomyrtus tomentosa mitochondrial genome: Insights into repeat-mediated recombination and intra-cellular DNA transfer

Plant mitochondrial genomes participate in encoding proteins crucial to the major producers of ATP in the cell and replication and heredity of their own DNA. The sequences and structure of the plant mitochondrial genomes profoundly impact these fundamental processes, and studies of plant mitochondrial genomes are needed. We reported the complete sequences of the Rhodomyrtus tomentosa mitochondrial genome here, totaling 400,482 bp. Nanopore ONT reads and PCR amplification provided evidence for recombination mediated by the eight repeat pairs for the R. tomentosa mitochondrial genome. Thirty-eight genes were identified in the R. tomentosa mitochondrial genome. Comparative analyses of the mitochondrial genome and plastome and PCR amplification suggest that five fragments of mitochondrial plastid DNA were unfunctional sequences resulting from intracellular gene transfer. Phylogenetic analysis based on each and all of the 27 mitochondrial protein-coding genes of nine Myrtales species revealed that R. tomentosa always clustered with other species of Myrtaceae. This study uncovered the enormous complexity of the R. tomentosa mitochondrial genome, the active repeat-mediated recombinations, the presence of mitochondrial plastid DNAs, and the topological incongruence of Myrtales among the single-gene trees.

The Complete Mitochondrial Genomes of Aelia sibirica and A. fieberi (Hemiptera, Pentatomidae), and Phylogenetic Implications

Species of genus Aelia are important pests of wheat crops in arid areas. In this study, the mitogenomes of A. sibirica and A. fieberi were sequenced using high-throughput sequencing technology. The mitochondrial genome characteristics of both Aelia species were compared and analyzed, and the phylogenetic relationships of Pentatomidae were constructed based on protein-coding genes. In addition, the taxonomic status of the genus Aelia was confirmed. The results showed that the total length of the mitogenome sequences of A. sibirica and A. fieberi were 15,372 bp and 15,450 bp, respectively, including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and a control region. By comparing the mitochondrial genome structure, base composition, codon usage, RNA secondary structure, and other characteristics, it was found that the mitochondrial genome characteristics of the two species were similar. Phylogenetic analysis showed that Phyllocephalinae and Asopinae both formed monophyletic groups, but the relationship between Podopinae and Pentatominae was not resolved. Within the subfamily Pentatominae, (Nezarini + Antestiini), (Aeliini + Carpocorini), and (Strachiini + Pentatoma) formed stable clades. Aelia sibirica and A. fieberi were found to be a stable sibling pair, and the clade was closely related to Dolycoris baccarum.

First report of the complete mitochondrial genome of 3 beetles (Coleoptera: Scarabaeidae) harming Gastrodia elata (Asparagales: Orchidaceae).

Gastrodia elata Blume, a valuable traditional Chinese medicine with significant clinical and nutritional importance, is a fungal heterotrophic orchid. We present the first report of the mitochondrial genome structure and characteristics of 3 Scarabaeidae pests affecting G. elata: Sophrops peronosporus Gu & Zhang, Anomala rufiventris Kollar & Redtenbacher, and Callistethus plagiicollis Fairmaire. Each mitogenome contained 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and a control region, with no gene rearrangements observed. All 21 tRNAs, except trnS1 that lacks a dihydrouridine, had a stable cloverleaf secondary structure. Maximum likelihood and Bayesian inference analyses based on the 13 PCGs produced 2 topologically similar phylogenetic trees, both of with high nodal support. Larvae of these Scarabaeidae pests cause substantial damage by gnawing on the tubers and roots of G. elata, leading to reduced yield and compromised quality. These findings contribute to phylogenetic studies of Scarabaeidae, expand knowledge of G. elata pests, and offer valuable reference materials for their identification and control.

Complete mitochondrial genome and phylogenetic analysis of the marine microalga Symbiochlorum hainanensis (Ulvophyceae, Chlorophyta)

Symbiochlorum hainanensis Gong et al. (2018). is a unicellular green alga belonging to Ulvophyceae, Chlorophyta, and considered as an important species in coral-algae symbiont areas. In this study, we revealed firstly the mitochondrial genome sequence of the S. hainanensis. This mitochondrial genome was a circular DNA molecule of 59,508 bp, including 24 transfer RNA genes, 3 ribosomal RNA genes, and 31 protein-coding genes. The GC content of the genome was 35.4%. The phylogenetic tree suggested that S. hainandiae was a sister to the OUU clade within the class Ulvophyceae. The mitochondrial genome structure and gene content of S. hainanensis supported that S. hainanensis was a new unidentified green alga in Ulvophyceae.

Characterization and phylogenetic analysis of the complete mitochondrial genome of a unique economic plant &lt;i&gt;Lycium barbarum&lt;/i&gt; L.

&lt;i&gt;Lycium barbarum&lt;/i&gt; L. (&lt;i&gt;L. barbarum&lt;/i&gt;), an important medicinal and food crop from the Solanaceae family, is known for excellent tolerance to saline–alkaline and drought stresses. Therefore, it has significant research and application value. The nuclear and chloroplast genomes of &lt;i&gt;L. barbarum&lt;/i&gt; have been previously reported; however, its mitochondrial genome is still unexplored. In this study, mitochondrial DNA sequencing and assembly in &lt;i&gt;L. barbarum&lt;/i&gt; were studied via second- and third-generation sequencing technologies using the anthers collected from the main cultivars “Ningqi No.1” (fertile line) and its male-sterile natural mutant “Ningqi No.5” from Ningxia, China. The results revealed that “Ningqi No.1” and “Ningqi No.5” have the same mitochondrial circular genome structure with a total length of 413,881 bp. In total, 61 genes were annotated, including 35 protein-coding genes, four rRNA genes, 22 tRNA genes, and 2,242 open reading frames with unknown functions. The repeat sequences in mtDNA were analyzed, in which short repeats (30–59 bp) exhibited the highest number. Overall, 23 protein-coding genes in “Ningqi No.1” and “Ningqi No.5” exhibited RNA-editing phenomenon, with different RNA-editing site number and distribution position. Phylogenetic analysis demonstrated that &lt;i&gt;L. barbarum&lt;/i&gt; has the closest relationship with &lt;i&gt;Hyoscyamus niger&lt;/i&gt;. These results provided a basis for a comprehensive understanding of the mitochondrial genome of &lt;i&gt;L. barbarum&lt;/i&gt; and the relevant data for omics studies on &lt;i&gt;L. barbarum&lt;/i&gt;.

Analysis of the Complete Mitochondrial Genome of Pteronura brasiliensis and Lontra canadensis.

P. brasiliensis and L. canadensis are two otter species, which successfully occupied semi-aquatic habitats and diverged from other Mustelidae. Herein, the full-length mitochondrial genome sequences were constructed for these two otter species for the first time. Comparative mitochondrial genome, selection pressure, and phylogenetic independent contrasts (PICs) analyses were conducted to determine the structure and evolutionary characteristics of their mitochondrial genomes. Phylogenetic analyses were also conducted to confirm these two otter species' phylogenetic position. The results demonstrated that the mitochondrial genome structure of P. brasiliensis and L. canadensis were consistent across Mustelidae. However, selection pressure analyses demonstrated that the evolutionary rates of mitochondrial genome protein-coding genes (PCGs) ND1, ND4, and ND4L were higher in otters than in terrestrial Mustelidae, whereas the evolutionary rates of ND2, ND6, and COX1 were lower in otters. Additionally, PIC analysis demonstrated that the evolutionary rates of ND2, ND4, and ND4L markedly correlated with a niche type. Phylogenetic analysis showed that P. brasiliensis is situated at the base of the evolutionary tree of otters, and then L. canadensis diverged from it. This study suggests a divergent evolutionary pattern of Mustelidae mitochondrial genome PCGs, prompting the otters' adaptation to semi-aquatic habitats.

The mitochondrial genome of the holoparasitic plant Thonningia sanguinea provides insights into the evolution of multi-chromosomal structure.

Multi-chromosomal mitochondrial genome (mitogenome) structures have repeatedly evolved in many lineages of angiosperms. However, the underlying mechanism remains unclear. The mitogenomes of three genera of Balanophoraceae, namely Lophophytum, Ombrophytum and Rhopalocnemis, have already been sequenced and assembled, all showing a highly multi-chromosomal structure, albeit with different genome and chromosome sizes. It is expected that characterization of additional lineages of this family may expand the knowledge of mitogenome diversity and provide insights into the evolution of plant mitogenome structure and size. Here, we assembled and characterized the mitogenome of Thonningia sanguinea, which, together with Balanophora, forms a clade sister to the clade comprising Lophophytum, Ombrophytum and Rhopalocnemis. The mitogenome of T. sanguinea possesses a multi-chromosomal structure of 18 circular chromosomes of 8.7 - 19.2 kb, with a total size of 246,247 bp. There are very limited shared regions and poor chromosomal correspondence between T. sanguinea and other Balanophoraceae species, suggesting frequent rearrangements and rapid sequence turnover. Numerous medium- and small-sized repeats were identified in the T. sanguinea mitogenome, however no repeat-mediated recombination was detected, which was verified by Illumina reads mapping and PCR experiments. Intraspecific mitogenome variations in T. sanguinea are mostly insertions and deletions, some of which can lead to degradation of perfect repeats in one or two accessions. Based on the mitogenome features of T. sanguinea, we propose a mechanism to explain the evolution of a multi-chromosomal mitogenome from a master circle, which involves mutation in organellar DNA replication, recombination and repair genes, decrease of recombination and repeat degradation.

Complete mitochondrial genome of Agrostis stolonifera: insights into structure, Codon usage, repeats, and RNA editing.

Plants possess mitochondrial genomes that are large and complex compared to animals. Despite their size, plant mitochondrial genomes do not contain significantly more genes than their animal counterparts. Studies into the sequence and structure of plant mitochondrial genomes heavily imply that the main mechanism driving replication of plant mtDNA, and offer valuable insights into plant evolution, energy production, and environmental adaptation. This study presents the first comprehensive analysis of Agrostis stolonifera's mitochondrial genome, characterized by a branched structure comprising three contiguous chromosomes, totaling 560,800bp with a GC content of 44.07%. Annotations reveal 33 unique protein-coding genes (PCGs), 19 tRNA genes, and 3 rRNA genes. The predominant codons for alanine and glutamine are GCU and CAA, respectively, while cysteine and phenylalanine exhibit weaker codon usage biases. The mitogenome contains 73, 34, and 23 simple sequence repeats (SSRs) on chromosomes 1, 2, and 3, respectively. Chromosome 1 exhibits the most frequent A-repeat monomeric SSR, whereas chromosome 2 displays the most common U-repeat monomeric SSR. DNA transformation analysis identifies 48 homologous fragments between the mitogenome and chloroplast genome, representing 3.41% of the mitogenome's total length. The PREP suite detects 460C-U RNA editing events across 33 mitochondrial PCGs, with the highest count in the ccmFn gene and the lowest in the rps7 gene. Phylogenetic analysis confirms A. stolonifera's placement within the Pooideae subfamily, showing a close relationship to Lolium perenne, consistent with the APG IV classification system. Numerous homologous co-linear blocks are observed in A. stolonifera's mitogenomes and those of related species, while certain regions lack homology. The unique features and complexities of the A. stolonifera mitochondrial genome, along with its similarities and differences to related species, provide valuable insights into plant evolution, energy production, and environmental adaptation. The findings from this study significantly contribute to the growing body of knowledge on plant mitochondrial genomes and their role in plant biology.

Characterization of the complete mitochondrial genome of the longhorn beetle, Batocerahorsfieldi (Coleoptera, Cerambycidae) and its phylogenetic analysis with suitable longhorn beetles.

Mitochondrial genome analysis is an important tool for studying insect phylogenetics. The longhorn beetle, Batocerahorsfieldi, is a significant pest in timber, economic and protection forests. This study determined the mitochondrial genome of B.horsfieldi and compared it with the mitochondrial genomes of other Cerambycidae with the aim of exploring the phylogenetic status of the pest and the evolutionary relationships among some Cerambycidae subgroups. The complete mitochondrial genome of B.horsfieldi was sequenced by the Illumina HiSeq platform. The mitochondrial genome was aligned and compared with the existing mitochondrial genomes of Batoceralineolata and B.rubus in GenBank (MF521888, MW629558, OM161963, respectively). The secondary structure of transfer RNA (tRNA) was predicted using tRNAScan-SE server v.1.21 and MITOS WebSever. Thirteen protein-coding genes (PCGs) and two ribosomal RNA gene sequences of 21 longhorn beetles, including B.horsfieldi, plus two outgroups, Dryopsernesti (Dryopidae) and Heterocerusparallelus (Heteroceridae), were analyzed. The phylogenetic tree was constructed using maximum likelihood and Bayesian inference methods. In this study, we successfully obtained the complete mitochondrial genome of B.horsfieldi for the first time, which is 15 425 bp in length. It contains 37 genes and an A + T-rich region, arranged in the same order as the recognized ancestor of longhorn beetles. The genome of B.horsfieldi is composed of 33.12% A bases, 41.64% T bases, 12.08% C bases, and 13.16% G bases. The structure, nucleotide composition, and codon usage of the new mitochondrial genome are not significantly different from other longhorn mitochondrial genomes. Phylogenetic analyses revealed that Cerambycidae formed a highly supported single clade, and Vesperidae was either clustered with Cerambycidae or formed a separate clade. Interestingly, B.horsfieldi, B.rubus and B.lineolata were clustered with Monochamus and Anoplophora species in both analyses, with high node support. Additionally, the VesperidaeSpiniphilusspinicornis and Vesperussanzi and the 19 Cerambycidae species formed a sister clade in the Bayesian analysis. Our results have produced new complete mitogenomic data, which will provide information for future phylogenetic and taxonomic research, and provide a foundation for future relevant research.