Base Composition Of mtDNA Research Articles

Triplex and other DNA motifs show motif-specific associations with mitochondrial DNA deletions and species lifespan

The “theory of resistant biomolecules” posits that long-lived species show resistance to molecular damage at the level of their biomolecules. Here, we test this hypothesis in the context of mitochondrial DNA (mtDNA) as it implies that predicted mutagenic DNA motifs should be inversely correlated with species maximum lifespan (MLS).First, we confirmed that guanine-quadruplex and direct repeat (DR) motifs are mutagenic, as they associate with mtDNA deletions in the human major arc of mtDNA, while also adding mirror repeat (MR) and intramolecular triplex motifs to a growing list of potentially mutagenic features. What is more, triplex motifs showed disease-specific associations with deletions and an apparent interaction with guanine-quadruplex motifs.Surprisingly, even though DR, MR and guanine-quadruplex motifs were associated with mtDNA deletions, their correlation with MLS was explained by the biased base composition of mtDNA. Only triplex motifs negatively correlated with MLS even after adjusting for body mass, phylogeny, mtDNA base composition and effective number of codons.Taken together, our work highlights the importance of base composition for the comparative biogerontology of mtDNA and suggests that future research on mitochondrial triplex motifs is warranted.

Mitochondrial genome of Hylaeus dilatatus (Hymenoptera: Colletidae)

Bees are one of the most well-known and important type of pollinators in agriculture and natural ecosystems, and maintaining their diversity in nature is essential. In this study, we report the complete mitochondrial genome of Hylaeus dilatatus, the first mitochondrial genome of Colletidae. Its complete mtDNA sequence is 15,475 bp in length, which contains 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and one control region. The base composition of mtDNA is 44.27% A, 41.52% T, 8.80% C and 5.41% G. The percentage of A + T is 85.79%. The first complete mitogenome of Colletidae family could be used in studies of molecular systematics, conservation genetics, and stock evaluation.

The complete mitochondrial genome of Eremias przewalskii (Squamata: Lacertidae)

In this paper, the complete mitochondrial genome of Eremias przewalskii (Squamata: Lacertidae) is reported, which is a circular molecule of 18,225 bp in size. The base composition of mtDNA is as follows: 30.3% A, 27.9% T, 27.9% C and 13.9% G. The genome consists of 13 protein coding genes, 22 transfer RNAs, 2 ribosomal RNA genes and one putative control region.

Mitochondrial genome of Emberiza elegans (Emberizidae: Emberiza)

Emberiza elegans is a common bunting with very wide geographical distribution. In this paper, the complete mitochondrial genome of E. elegans (16,779 bp in length) was analyzed for building the database. The results showed that it contained 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and one control region. The base composition of mtDNA was A (29.4%), G (14.7%), C (32.7%), and T (23.2%), therefore, the percentage of A and T (52.6%) was slightly higher than G and C (47.4%). All the genes in E. elegans were distributed on the H-strand, except for the ND6 subunit gene and ten tRNA genes which were encoded on the L-strand.

Mitochondrial genome of the neotropical Parnell's mustached bat Pteronotus parnellii (Pteronotus, Mormoopidae)

We reported complete mitochondrial genome of neotropical Parnell's mustached bat Pteronotus parnellii (16,564 bp in length). Its mitochondrial genome consisted of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 1 control region. The base composition of mtDNA was A (33.1%), G (13.7%), C (27.3%), T (25.9%), and the percentage of A and T (59.0%) was higher than G and C. All the genes in P. parnellii were distributed on the H-strand, except for the ND6 subunit gene and 10 tRNA genes, which were encoded on the L-strand. The new sequenced mitochondrial genome will contribute to our understanding of the systematic evolution in the bats.

The complete mitochondrial genome sequence of the Canada goose (Branta canadensis)

The Canada goose (Branta canadensis) entire mitochondrial genome of a bird from Western Pennsylvania has 16,760 bp (GenBank accession number NC 007011) and has been analyzed for gene locations, length, start codon and stop codons. This genome from a bird harvested during the non-migratory season is the REFSEQ and the haplotype is designated GCC-A. There are two rRNAs, 22 tRNAs, 13 protein-coding regions, and 1 displacement loop region. The base composition of mtDNA was A (30.2%), G (15.1%), C (32.1%), and T (22.6%), so the percentage of A and T (52.8%) was slightly higher than G and C. All genes except ND6 and eight tRNA genes (Gln, Ala, Asn, Cys, Tyr, Ser, Pro and Glu) are encoded on the heavy strand. The gene arrangement is the same as most birds and differs from mammals by an inversion of the mtDNA at the connection between the D-loop and the ND5 junctions.

Mitochondrial genome of the Emberiza pusilla (Emberizidae: Emberiza)

The Emberiza pusilla is a common bunting with very wide geographical range. Here, the complete mitochondrial genome of E. pusilla (16,790 bp in length) has been analyzed for building the database. The results showed that it consisted of 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region. The base composition of mtDNA was A (29.6%), G (14.8%), C (32.8%), and T (22.9%), so the percentage of A and T (52.5%) was slightly higher than G and C. All the genes in E. pusilla were distributed on the H-strand, except for the ND6 subunit gene and 10 tRNA genes, which were encoded on the L-strand.

Molecular phylogeny and evolution of prosimians based on complete sequences of mitochondrial DNAs

Prosimians (tarsiers and strepsirrhini) represent the basal lineages in primates and have a close bearing on the origin of primates. Although major lineages among anthropoidea (humans, apes and monkeys) are well represented by complete mitochondrial DNA (mtDNA) sequence data, only one complete mtDNA sequence from a representative of each of the infraorders in prosimians has been described until quite recently, and therefore we newly determined complete mtDNA sequences from 5 lemurs, 4 lorises, one tarsier and one platyrrhini. These sequences were provided to phylogenetic analyses in combination with the sequences from the 15 primates species reported to the database. The position of tarsiers among primates could not be resolved by the maximum likelihood (ML) and neighbor-joining (NJ) analyses with several data sets. As to the position of tarsiers, any of the three alternative topologies (monophyly of haplorhini, monophyly of prosimians, and tarsiers being basal in primates) was not rejected at the significance level of 5%, neither at the nucleotide nor at the amino acid level. In addition, the significant variations of C and T compositions were observed across primates species. Furthermore, we used AGY data sets for phylogenetic analyses in order to remove the effect of different C/T composition bias across species. The analyses of AGY data sets provided a medium support for the monophyly of haplorhini, which might have been screened by the variation in base composition of mtDNA across species. To estimates the speciation dates within primates, we analyzed the amino acid sequences of mt-proteins with a Bayesian method of Thorne and Kishino. Divergence dates were estimated as follows for the crown groups: about 35.4 million years ago (mya) for lorisiformes, 55.3 mya for lemuriformes, 64.5 mya for strepsirrhini, 70.1 mya for haplorhini and 76.0 mya for primates. Furthermore, we reexamined the biogeographic scenarios which have been proposed for the origin of strepsirrhini (lemuriformes and lorisiformes) and for the dispersal of the lemuriformes and lorisiformes.

Differentiation and gene regulation: Web alert

One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure within a phylum (e.g., Chordata) is generally accepted, although more recent reports show that a considerable number of transpositions are observed also between closely related organisms. Base composition of mtDNA is extremely variable. Genome GC content is often low and, when it increases, the two complementary bases distribute asymmetrically, creating, particularly in vertebrates, a negative GC-skew. In mammals, we have found coding strand base composition and average degree of gene conservation to be related to the asymmetric replication mechanism of mtDNA. A quantitative measurement of mtDNA evolutionary rate has revealed that each of the various components has a different evolutionary rate. Non-synonymous rates are gene specific and fall in a range comparable to that of nuclear genes, whereas synonymous rates are about 22-fold higher in mt than in nuclear genes. tRNA genes are among the most conserved but, when compared to their nuclear counterparts, they evolve 100 times faster. Finally, we describe some molecular phylogenetic reconstructions which have produced unexpected outcomes, and might change our vision of the classification of living organisms.

Evolutionary genomics in Metazoa: the mitochondrial DNA as a model system.

One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure within a phylum (e.g., Chordata) is generally accepted, although more recent reports show that a considerable number of transpositions are observed also between closely related organisms. Base composition of mtDNA is extremely variable. Genome GC content is often low and, when it increases, the two complementary bases distribute asymmetrically, creating, particularly in vertebrates, a negative GC-skew. In mammals, we have found coding strand base composition and average degree of gene conservation to be related to the asymmetric replication mechanism of mtDNA. A quantitative measurement of mtDNA evolutionary rate has revealed that each of the various components has a different evolutionary rate. Non-synonymous rates are gene specific and fall in a range comparable to that of nuclear genes, whereas synonymous rates are about 22-fold higher in mt than in nuclear genes. tRNA genes are among the most conserved but, when compared to their nuclear counterparts, they evolve 100 times faster. Finally, we describe some molecular phylogenetic reconstructions which have produced unexpected outcomes, and might change our vision of the classification of living organisms.

Mitochondrial DNA from Maize Hybrids with Normal and Texas Cytoplasms1

Mitochondrial DNA (mtDNA) was isolated from two hybrids of maize (Zea mays L.), NC232 ✕ T204N (normal cytoplasm) and NC232 ✕ T204 cms T (Texas cytoplasm). No difference was found in the buoyant densities of mtDNA isolated from the two hybrids. The mtDNA had a buoyant density of 1.706 g/cm3 in CsCl and a molar % guanine plus cytosine of 46.9. Therefore, the cytoplasmic dissimilarities with respect to sterility and disease response between the normal and the Texas cytoplasm cannot be accounted for by detectable alterations in the base composition of mtDNA.