The complete mitochondrial genome of Metasepia tullbergi (Cephalopoda: Sepiidae).
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ABSTRACT:
SUBMITTER: Lee HT
PROVIDER: S-EPMC8008933 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundMitochondria contain small genomes that are physically separate from those of nuclei. Their comparison serves as a model system for understanding the processes of genome evolution. Although complete mitochondrial genome sequences have been reported for more than 600 animals, the taxonomic sampling is highly biased toward vertebrates and arthropods, leaving much of the diversity yet uncharacterized.ResultsThe mitochondrial genome of the bellybutton nautilus, Nautilus macromphalus, a cephalopod mollusk, is 16,258 nts in length and 59.5% A+T, both values that are typical of animal mitochondrial genomes. It contains the 37 genes that are almost universally found in animal mtDNAs, with 15 on one DNA strand and 22 on the other. The arrangement of these genes can be derived from that of the distantly related Katharina tunicata (Mollusca: Polyplacophora) by a switch in position of two large blocks of genes and transpositions of four tRNA genes. There is strong skew in the distribution of nucleotides between the two strands, and analysis of this yields insight into modes of transcription and replication. There is an unusual number of non-coding regions and their function, if any, is not known; however, several of these demark abrupt shifts in nucleotide skew, and there are several identical sequence elements at these junctions, suggesting that they may play roles in transcription and/or replication. One of the non-coding regions contains multiple repeats of a tRNA-like sequence. Some of the tRNA genes appear to overlap on the same strand, but this could be resolved if the polycistron were cleaved at the beginning of the downstream gene, followed by polyadenylation of the product of the upstream gene to form a fully paired structure.ConclusionNautilus macromphalus mtDNA contains an expected gene content that has experienced few rearrangements since the evolutionary split between cephalopods and polyplacophorans. It contains an unusual number of non-coding regions, especially considering that these otherwise often are generated by the same processes that produce gene rearrangements. The skew in nucleotide composition between the two strands is strong and associated with the direction of transcription in various parts of the genomes, but a comparison with K. tunicata implies that mutational bias during replication also plays a role. This appears to be yet another case where polyadenylation of mitochondrial tRNAs restores what would otherwise be an incomplete structure.
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Project description:The complete sequence of honeybee (Apis mellifera) mitochondrial DNA is reported being 16,343 bp long in the strain sequenced. Relative to their positions in the Drosophila map, 11 of the tRNA genes are in altered positions, but the other genes and regions are in the same relative positions. Comparisons of the predicted protein sequences indicate that the honeybee mitochondrial genetic code is the same as that for Drosophila; but the anticodons of two tRNAs differ between these two insects. The base composition shows extreme bias, being 84.9% AT (cf. 78.6% in Drosophila yakuba). In protein-encoding genes, the AT bias is strongest at the third codon positions (which in some cases lack guanines altogether), and least in second codon positions. Multiple stepwise regression analysis of the predicted products of the protein-encoding genes shows a significant association between the numbers of occurrences of amino acids and %T in codon family, but not with the number of codons per codon family or other parameters associated with codon family base composition. Differences in amino acid abundances are apparent between the predicted Apis and Drosophila proteins, with a relative abundance in the Apis proteins of lysine and a relative deficiency of alanine. Drosophila alanine residues are as often replaced by serine as conserved in Apis. The differences in abundances between Drosophila and Apis are associated with %AT in the codon families, and the degree of divergence in amino acid composition between proteins correlates with the divergence in %AT at the second codon positions. Overall, transversions are about twice as abundant as transitions when comparing Drosophila and Apis protein-encoding genes, but this ratio varies between codon positions. Marked excesses of transitions over chance expectation are seen for the third positions of protein-coding genes and for the gene for the small subunit of ribosomal RNA. For the third codon positions the excess of transitions is adequately explained as due to the restriction of observable substitutions to transitions for conserved amino acids with two-codon families; the excess of transitions over expectation for the small ribosomal subunit suggests that the conservation of nucleotide size is favored by selection.
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Project description:The complete mitochondrial DNA genome of Triplophysa nasobarbatula was sequenced and characterized. Triplophysa nasobarbatula revealed that the complete length of its mitochondrial genome was 16,316 bp, composed of A (29.71%), C (24.79%), G (17.22%), T (28.29%), A + T (57.99%), and C + G (42.01%). Its genetic constitution and arrangement were consistent with the taxon of the Teleost, including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 2 main non-coding regions, D-loop region and OL region. All genes were encoded by the H-strand, except for 1 protein-coding gene (ND6) and 8 tRNA genes (tRNA-Gln, tRNA-Ala, tRNA-Cys, tRNA-Asn, tRNA-Tyr, tRNA-Ser, tRNA-Glu and tRNA-Pro) are encoded by the L-strand. Our mitochondrial genome data may provide information for taxonomic resolution, taxonomic resolution, and other studies about this genus of Triplophysa.
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Project description:Cheilinus undulatus strain:MITOCHONDRIAL COMPLETE GENOME Genome sequencing and assembly
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Project description:We here report the complete nucleotide sequence of the 47.9 kb mitochondrial (mt) genome from the obligate aerobic yeast Yarrowia lipolytica. It encodes, all on the same strand, seven subunits of NADH: ubiquinone oxidoreductase (ND1-6, ND4L), apocytochrome b (COB), three subunits of cytochrome oxidase (COX1, 2, 3), three subunits of ATP synthetase (ATP6, 8 and 9), small and large ribosomal RNAs and an incomplete set of tRNAs. The Y. lipolytica mt genome is very similar to the Hansenula wingei mt genome, as judged from blocks of conserved gene order and from sequence homology. The extra DNA in the Y. lipolytica mt genome consists of 17 group 1 introns and stretches of A+Trich sequence, interspersed with potentially transposable GC clusters. The usual mould mt genetic code is used. Interestingly, there is no tRNA able to read CGN (arginine) codons. CGN codons could not be found in exonic open reading frames, whereas they do occur in intronic open reading frames. However, several of the intronic open reading frames have accumulated mutations and must be regarded as pseudogenes. We propose that this may have been triggered by the presence of untranslatable CGN codons. This sequence is available under EMBL Accession No. AJ307410.
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Project description:We report here the complete mitochondrial genome sequence of a Rocky Mountain bighorn sheep (Ovis canadensis) in the United States. The circular genome has a size of 16,466?bp and contains 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes.
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Project description:The 13,647-bp complete mitochondrial genome of Mansonella perstans was sequenced and is syntenic to the mitochondrial genome of Mansonella ozzardi Phylogenetic analysis of the mitochondrial genome is consistent with the known phylogeny of ONC5 group filarial nematodes.
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Project description:Chicken mitochondrial DNA is a circular molecule comprising ~16.8 kb. In this study, we used next-generation sequencing to investigate mitochondrial heteroplasmy in the whole chicken mitochondrial genome. Based on heteroplasmic detection thresholds at the 0.5% level, 178 cases of heteroplasmy were identified in the chicken mitochondrial genome, where 83% were due to nucleotide transitions. D-loop regionwas hot spot region for mtDNA heteroplasmy in the chicken since 130 cases of heteroplasmy were located in these regions. Heteroplasmy varied among intraindividual tissues with allele-specific, position-specific, and tissue-specific features. Skeletal muscle had the highest abundance of heteroplasmy. Cases of heteroplasmy at mt.G8682A and mt.G16121A were validated by PCR-restriction fragment length polymorphism analysis, which showed that both had low ratios of heteroplasmy occurrence in five natural breeds. Polymorphic sites were easy to distinguish. Based on NGS data for crureus tissues, mitochondrial mutation/heteroplasmy exhibited clear maternal inheritance features at the whole mitochondrial genomic level. Further investigations of the heterogeneity of the mt.A5694T and mt.T5718G transitions between generations using pyrosequencing based on pedigree information indicated that the degree of heteroplasmy and the occurrence ratio of heteroplasmy decreased greatly from the F0 to F1 generations in the mt.A5694T and mt.T5718G site. Thus, the intergenerational transmission of heteroplasmy in chicken mtDNA exhibited a rapid shift toward homoplasmy within a single generation. Our findings indicate that heteroplasmy is a widespread phenomenon in chicken mitochondrial genome, in which most sites exhibit low heteroplasmy and the allele frequency at heteroplasmic sites changes significantly during transmission events. It suggests that heteroplasmy may be under negative selection to some degree in the chicken.
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Project description:Abstract Dictyostelium intermedium is a member of dictyostelids, the unicellular eukaryotes with a unique life cycle, including a social cycle. Despite the high diversity of dictyostelids, only five species' complete mitochondrial genome sequences were reported. This study aimed to add the D. intermedium mitochondrial genome sequence to the list. The size of this genome is 58,627 bp, with 73.99% A/T, containing 62 genes located on one strand: 41 protein-coding genes, three ribosomal RNA genes, and 18 transfer RNA genes. The 41 protein-coding genes comprised 18 oxidative phosphorylation-related, 16 ribosomal, and seven hypothetical protein-coding genes. The cox1/2 and rnl gene contained introns, similar to other species of Dictyostelium. The phylogenetic tree built based on 34 protein sequences supported the monophyletic clade of Dictyostelium and the dictyostelids' ancestor's position between the two dictyostelids orders: Dictyosteliales and Acytosteliales.
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