The assembled Banana dihaploid mitochondrial genome is compact with a high number of gene copies

Banana being a major food crop all around the world, attracts various research interests in crop improvement. In banana, complete genome sequences of Musa accuminata and Musa balbisiana are available. However, the mitochondrial genome is not sequenced or assembled. Mitochondrial (mt) genes play an important role in flower and seed development and in Cytoplasmic Male Sterility. Unraveling banana mt genome architecture will be a foundation for understanding inheritance of traits and their evolution. In this study, the complete banana mt genome is assembled from the whole genome sequence data of the Musa acuminata subsp. malaccensis DH-Pahang. The mt genome sequence acquired by this approach was 409574 bp and it contains, 54 genes coding for 25 respiratory complex proteins 15 ribosomal proteins, 12 tRNA genes and two ribosomal RNA gene. Except atpB, rps11 and rps19 other genes are in multiple copies. The copy number is 12 in tRNA genes. In addition, nearly 25% tandem repeats are also present in it. These mt proteins are identical to the mt proteins present in the other members of AA genome and share 98% sequence similarity with M. balbisiana. The C to U RNA editing is profoundly higher (87 vs 13%) in transcripts of M. balbisiana (BB) compared to M. accuminata (AA). The banana AA mitochondrial genome is tightly packed with 233 genes, with less rearrangements and just 5.3% chloroplast DNA in it. The maintenance of high copy number of functional mt genes suggest that they have a crucial role in the evolution of banana.

Assembly and comparative analysis of the first complete mitochondrial genome of Acer truncatum Bunge: a woody oil-tree species producing nervonic acid

Background Acer truncatum (purpleblow maple) is a woody tree species that produces seeds with high levels of valuable fatty acids (especially nervonic acid). The species is admired as a landscape plant with high developmental prospects and scientific research value. The A. truncatum chloroplast genome has recently been reported; however, the mitochondrial genome (mitogenome) is still unexplored. Results We characterized the A. truncatum mitogenome, which was assembled using reads from PacBio and Illumina sequencing platforms, performed a comparative analysis against different species of Acer. The circular mitogenome of A. truncatum has a length of 791,052 bp, with a base composition of 27.11% A, 27.21% T, 22.79% G, and 22.89% C. The A. truncatum mitogenome contains 62 genes, including 35 protein-coding genes, 23 tRNA genes and 4 rRNA genes. We also examined codon usage, sequence repeats, RNA editing and selective pressure in the A. truncatum mitogenome. To determine the evolutionary and taxonomic status of A. truncatum, we conducted a phylogenetic analysis based on the mitogenomes of A. truncatum and 25 other taxa. In addition, the gene migration from chloroplast and nuclear genomes to the mitogenome were analyzed. Finally, we developed a novel NAD1 intron indel marker for distinguishing several Acer species. Conclusions In this study, we assembled and annotated the mitogenome of A. truncatum, a woody oil-tree species producing nervonic acid. The results of our analyses provide comprehensive information on the A. truncatum mitogenome, which would facilitate evolutionary research and molecular barcoding in Acer.

Complete mitochondrial genome of Rhodeus cyanorostris (Teleostei, Cyprinidae): characterization and phylogenetic analysis

Rhodeus cyanorostris Li, Liao & Arai, 2020 is a freshwater fish that is endemic to China and restricted to Chengdu City in Sichuan Province. This study is the first to sequence and characterize the complete mitochondrial genome of R. cyanorostris. The mitogenome of R. cyanorostris is 16580 bp in length, including 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and a control region (D-loop). The base composition of the sequence is 28.5% A, 27.6% C, 26.4% T, and 17.5% G, with a bias toward A+T. The genome structure, nucleotide composition, and codon usage of the mitogenome of R. cyanorostris are consistent with those of other species of Rhodeus. To verify the molecular phylogeny of the genus Rhodeus, we provide new insights to better understand the taxonomic status of R. cyanorostris. The phylogenetic trees present four major clades based on 19 mitogenomic sequences from 16 Rhodeus species. Rhodeus cyanorostris exhibits the closest phylogenetic relationship with R. pseudosericeus, R. amarus, and R. sericeus. This study discloses the complete mitochondrial genome sequence of R. cyanorostris for the first time and provides the most comprehensive phylogenetic reconstruction of the genus Rhodeus based on whole mitochondrial genome sequences. The information obtained in this study will provide new insights for conservation, phylogenetic analysis, and evolutionary biology research.

The mitochondrial genome and phylogenetic analysis of the tick Haemaphysalis qinghaiensis Teng, 1980 (Acari:Ixodidae)

Haemaphysalis qinghaiensis is an endemic species and mainly inhabiting in the northwestern plateau of China, which can transmit many zoonotic pathogens and cause great harm to animals. In this study, the complete mitochondrial genome (mitogenome) of H. qinghaiensis was assembled through the Illumina HiSeq platform. The mitogenome was 14,533 bp in length, consisting of 13 protein-coding genes (PCGs), 22 tRNA genes, 2 rRNA genes and 3 noncoding regions (NCRs). The bias towards a high A+T content with 77.65% in mitogenome of H. qinghaiensis. The rearrangement of mitochondrial genes in H. qinghaiensis was consistent with other hard ticks. The phylogenetic analysis based on the concatenation of 13 PCGs from 65 tick mitogenomes showed that the H. qinghaiensis was clustered into a well-supported clade within the Haemaphysalis genus. This is the first complete mitogenome sequence of H. qinghaiensis, which provides a useful reference for understanding of the taxonomic and genetics of ticks.

Characterisation of the Complete Mitochondrial Genome of Critically Endangered Mustela lutreola (Carnivora: Mustelidae) and Its Phylogenetic and Conservation Implications

In this paper, a complete mitochondrial genome of the critically endangered European mink Mustela lutreola L., 1761 is reported. The mitogenome was 16,504 bp in length and encoded the typical 13 protein-coding genes, two ribosomal RNA genes and 22 transfer RNA genes, and harboured a putative control region. The A+T content of the entire genome was 60.06% (A > T > C > G), and the AT-skew and GC-skew were 0.093 and −0.308, respectively. The encoding-strand identity of genes and their order were consistent with a collinear gene order characteristic for vertebrate mitogenomes. The start codons of all protein-coding genes were the typical ATN. In eight cases, they were ended by complete stop codons, while five had incomplete termination codons (TA or T). All tRNAs had a typical cloverleaf secondary structure, except tRNASer(AGC) and tRNALys, which lacked the DHU stem and had reduced DHU loop, respectively. Both rRNAs were capable of folding into complex secondary structures, containing unmatched base pairs. Eighty-one single nucleotide variants (substitutions and indels) were identified. Comparative interspecies analyses confirmed the close phylogenetic relationship of the European mink to the so-called ferret group, clustering the European polecat, the steppe polecat and the black-footed ferret. The obtained results are expected to provide useful molecular data, informing and supporting effective conservation measures to save M. lutreola.

Development of Real-time PCR Kit for Detection and Quantitation of Six Common Mutations A3243G, G3380A, A8344G, T8993G, T8993C, G11778A of Human Mitochondrial Genome

A procedure for production of a real-time PCR kit for detection and quantitation of 6 common mitochondrial genome mutations including A3243G, G3380A, A8344G, T8993G, T8993C, G11778A using fluorescent locked nucleic acid (LNA) Taqman probes was reported. The procedure consists of designing of specific primers and LNA probes, selection of master mixture components and real-time PCR thermal conditions. The produced kit had specificity of 100% and sensitivity ≥ 1% and remained fully active after 7 days of storage at 25 oC or 20 days at 4 oC or 6 months at -20 oC. The kit was used to analyze A3243G, G3380A, A8344G, T8993G, T8993C, G11778A mutations from 69 patients tentatively diagnosed with mitochondrial diseases and 3 cases of A3243G carriers (4.34%) was found. In these cases, the A3243G mutation was heteroplasmic, maternally inherited, and the heteroplasmy level was shown to be related to the symptome expression.tome expression.

Fragmentation in mitochondrial genomes in relation to elevated sequence divergence and extreme rearrangements

Background A single circular mitochondrial (mt) genome is a common feature across most metazoans. The mt-genome includes protein-coding genes involved in oxidative phosphorylation, as well as RNAs necessary for translation of mt-RNAs, whose order and number are highly conserved across animal clades, with few known exceptions of alternative mt-gene order or mt-genome architectures. One such exception consists of the fragmented mitochondrial genome, a type of genome architecture where mt-genes are split across two or more mt-chromosomes. However, the origins of mt-genome fragmentation and its effects on mt-genome evolution are unknown. Here, we investigate these origin and potential mechanisms underlying mt-genome fragmentation, focusing on a genus of booklice, Liposcelis, which exhibits elevated sequence divergence, frequent rearrangement of mt-gene order, and fragmentation of the mt genome, and compare them to other Metazoan clades. Results We found this genus Liposcelis exhibits very low conservation of mt-gene order across species, relative to other metazoans. Levels of gene order rearrangement were, however, unrelated to whether or not mt-genomes were fragmented or intact, suggesting mitochondrial genome fragmentation is not affecting mt-gene order directly. We further investigated possible mechanisms underpinning these patterns and revealed very high conservation of non-coding sequences at the edges of multiple recombination regions across populations of one particular Liposcelis species, supportive of a hypothesis that mt-fragmentation arises from recombination errors between mt-genome copies. We propose these errors may arise as a consequence of a heightened mutation rate in clades exhibiting mt-fragmentation. Consistent with this, we observed a striking pattern across three Metazoan phyla (Arthropoda, Nematoda, Cnidaria) characterised by members exhibiting high levels of mt-gene order rearrangement and cases of mt-fragmentation, whereby the mt-genomes of species more closely related to species with fragmented mt-genomes diverge more rapidly despite experiencing strong purifying selection. Conclusions We showed that contrary to expectations, mt-genome fragmentation is not correlated with the increase in mt-genome rearrangements. Furthermore, we present evidence that fragmentation of the mt-genome may be part of a general relaxation of a natural selection on the mt-genome, thus providing new insights into the origins of mt-genome fragmentation and evolution.