Duplicated Control Region Research Articles

Intraspecies mitogenomic variation in the Black-throated Tit (Aegithalos concinnus): conserved structure, concerted evolution of duplicate control regions and multiple distinct evolutionary lineages

The mitochondrial genome is a prominent research topic due to its indispensable role in organisms and its application in many research disciplines. However, few studies have investigated intraspecies mitogenomic variation. In this study, 69 mitogenomes of the Black-throated Tit (Aegithalos concinnus) were assembled and annotated from a large number of short reads generated using high-throughput sequencing technology. Comparative analyses revealed that mitogenomic characteristics such as length, gene and nucleotide composition, codon usage, and duplicated control regions were relatively conserved despite substantial intraspecies morphological changes. Yet, all the individuals from the subspecies A. c. iredalei had one more nucleotide in the 12S rRNA than the other studied subspecies. Phylogenetic analyses showed five distinct lineages based on the complete mitogenomes and the 13 combined protein-coding genes, whereas only four lineages were observed when using the duplicate control regions. Most interestingly, each lineage had both copies of the control regions of the comprising individuals, indicating that the paralogous control regions were more similar than the orthologous sequences from the distinct lineages. This suggested the control regions had undergone concerted evolution. The Black-throated Tit has complex evolutionary history and needs further investigating the taxonomic status of these lineages, as well as the underlying evolutionary processes. Our findings call for more research on intraspecies mitogenomic variation.

Multiple independent origins of duplicated mitochondrial control regions indicate an apomorphy in the Thysanoptera (Insecta).

The mitochondrial genome (mitogenome) of thrips is characterized by the presence of control region (CR) duplication. However, the evolution pattern of duplicated CRs in thrips is still unclear. In this study, the multiple independent origins of duplicated CR indicated that the CR duplication was not an ancestral state for Thysanoptera. The macroevolutionary pattern suggested that the earliest CR duplication event occurred in the middle Cretaceous (94.85 Ma) coincided with rearrangement events forming the ancestors of Aeolothripidae, but much later than that forming the ancestors of the suborder Terebrantia. The mitogenome with duplicated CRs showed a higher rate of gene rearrangement. The sequence similarity of the CR copies and divergence time were negatively correlated, indicating age-related deterioration of mitochondrial function. No significant differences were found in the mitochondrial DNA, the P123 and P4FD between the single and multiple-CR charactered mitogenomes, which suggested that the duplicated CRs may not affect the replication process in thrip mitogenome. The mitogenomes with duplicated CRs (mean: 0.0088 subs/s/my) show a significantly increased evolutionary rate than that with a single one (mean: 0.0058 subs/s/my). However, it seems that this higher evolutionary rate did not have adaptive mechanisms in Terebrantia. We speculated that the duplicated CRs may cause a more intense production of energy by mitochondria, and an accelerated mutation and substitution rate is expected in such mitogenomes. Our study provided new insights into the presence of CR duplications and their evolution in the mitogenomes of thrips.

The complete mitochondrial genome study and phylogenetic analysis of Asiatic Water Snake (Fowlea piscator) using ‘Next-Generation Sequencing’ technology

The first complete mitochondrial genome sequencing of Asiatic Water snake or Checkered Keelback or Fowlea piscator (=Xenochrophis piscator) was carried out using Next-Generation Sequencing technology. The complete mitochondrial genome of Asiatic Water snake is 16,999bp long with a base composition of 33% A, 28% T, 12% G and 27% C, with a GC content of 39%. Like the typical snake mitochondrial genome, F. piscator also shows relatively similar mitogenome arrangement comprising 37 genes including 13 protein-coding genes, 22 tRNA genes, two rRNA genes and two non-coding regions or a duplicated control region (D-Loop) along with an origin of replication. Nine genes including eight tRNAs and NAD6 were encoded on the Light or L-strand. Phylogenetic analyses using the complete mitochondrial genome of F. piscator demonstrate a close relationship with the family Colubridae and sub family Natricinae.

Complete Mitogenomes of Polypedates Tree Frogs Unveil Gene Rearrangement and Concerted Evolution within Rhacophoridae.

Simple SummaryDuplicated control regions have been reported several times in the tree frog family Rhacophoridae, and previous studies have mostly relied on sequence analysis to reconstruct their evolution. This is the first study to employ a phylogenetic method to demonstrate the existence of concerted and parallel evolution succinctly and intuitively in the duplicated control regions of the family Rhacophoridae. Phylogenetic relationships were also used to illustrate the parallel evolution of ATP8 loss of function in the genus Polypedates. In general, this study elucidated the evolutionary patterns and pathways of mitochondrial gene rearrangement of the family Rhacophoridae from a phylogenetic perspective, which aids in understanding the evolutionary history of this fascinating tree frog taxon from a molecular evolution standpoint.New developments in sequencing technology and nucleotide analysis have allowed us to make great advances in reconstructing anuran phylogeny. As a clade of representative amphibians that have radiated from aquatic to arboreal habitats, our understanding of the systematic status and molecular biology of rhacophorid tree frogs is still limited. We determined two new mitogenomes for the genus Polypedates (Rhacophoridae): P. impresus and P. mutus. We conducted comparative and phylogenetic analyses using our data and seven other rhacophorid mitogenomes. The mitogenomes of the genera Polypedates, Buergeria, and Zhangixalus were almost identical, except that the ATP8 gene in Polypedates had become a non-coding region; Buergeria maintained the legacy “LTPF” tRNA gene cluster compared to the novel “TLPF” order in the other two genera; and B. buergeri and Z. dennysi had no control region (CR) duplication. The resulting phylogenetic relationship supporting the above gene rearrangement pathway suggested parallel evolution of ATP8 gene loss of function (LoF) in Polypedates and CR duplication with concerted evolution of paralogous CRs in rhacophorids. Finally, conflicting topologies in the phylograms of 185 species reflected the advantages of phylogenetic analyses using multiple loci.

Evolution of the Noncoding Features of Sea Snake Mitochondrial Genomes within Elapidae.

Mitochondrial genomes of four elapid snakes (three marine species [Emydocephalus ijimae, Hydrophis ornatus, and Hydrophis melanocephalus], and one terrestrial species [Sinomicrurus japonicus]) were completely sequenced by a combination of Sanger sequencing, next-generation sequencing and Nanopore sequencing. Nanopore sequencing was especially effective in accurately reading through long tandem repeats in these genomes. This led us to show that major noncoding regions in the mitochondrial genomes of those three sea snakes contain considerably long tandem duplications, unlike the mitochondrial genomes previously reported for same and other sea snake species. We also found a transposition of the light-strand replication origin within a tRNA gene cluster for the three sea snakes. This change can be explained by the Tandem Duplication—Random Loss model, which was further supported by remnant intervening sequences between tRNA genes. Mitochondrial genomes of true snakes (Alethinophidia) have been shown to contain duplicate major noncoding regions, each of which includes the control region necessary for regulating the heavy-strand replication and transcription from both strands. However, the control region completely disappeared from one of the two major noncoding regions for two Hydrophis sea snakes, posing evolutionary questions on the roles of duplicate control regions in snake mitochondrial genomes. The timing and molecular mechanisms for these changes are discussed based on the elapid phylogeny.

Concerted and Independent Evolution of Control Regions 1 and 2 of Water Monitor Lizards (Varanus salvator macromaculatus) and Different Phylogenetic Informative Markers.

Simple SummaryThe evolutionary patterns and phylogenetic utility of duplicate control regions (CRs) in 72 individuals of Varanus salvator macromaculatus and other varanids have been observed. Divergence of the two CRs from each individual revealed a pattern of independent evolution in CRs of varanid lineage. This study is a first step towards developing new phylogenetic evolutionary models of the varanid lineage, with accurate evolutionary inferences to provide basic insights into the biology of mitogenomes.Duplicate control regions (CRs) have been observed in the mitochondrial genomes (mitogenomes) of most varanids. Duplicate CRs have evolved in either concerted or independent evolution in vertebrates, but whether an evolutionary pattern exists in varanids remains unknown. Therefore, we conducted this study to analyze the evolutionary patterns and phylogenetic utilities of duplicate CRs in 72 individuals of Varanus salvator macromaculatus and other varanids. Sequence analyses and phylogenetic relationships revealed that divergence between orthologous copies from different individuals was lower than in paralogous copies from the same individual, suggesting an independent evolution of the two CRs. Distinct trees and recombination testing derived from CR1 and CR2 suggested that recombination events occurred between CRs during the evolutionary process. A comparison of substitution saturation showed the potential of CR2 as a phylogenetic marker. By contrast, duplicate CRs of the four examined varanids had similar sequences within species, suggesting typical characteristics of concerted evolution. The results provide a better understanding of the molecular evolutionary processes related to the mitogenomes of the varanid lineage.

Conservation and over-representation of G-quadruplex sequences in regulatory regions of mitochondrial DNA across distinct taxonomic sub-groups

G-quadruplexes have important regulatory roles in the nuclear genome but their distribution and potential roles in mitochondrial DNA (mtDNA) are poorly understood. We analysed 11883 mtDNA sequences from 18 taxonomic sub-groups and identified their frequency and location within mtDNA. Large differences in both the frequency and number of putative quadruplex-forming sequences (PQS) were observed amongst all the organisms and PQS frequency was negatively correlated with an increase in evolutionary age. PQS were over-represented in the 3′UTRs, D-loops, replication origins, and stem loops, indicating regulatory roles for quadruplexes in mtDNA. Variations of the G-quadruplex-forming sequence in the conserved sequence block II (CSBII) region of the human D-loop were conserved amongst other mammals, amphibians, birds, reptiles, and fishes. This D-loop PQS was conserved in the duplicated control regions of some birds and reptiles, indicating its importance to mitochondrial function. The guanine tracts in these PQS also displayed significant length heterogeneity and the length of these guanine tracts were generally longest in bird mtDNA. This information provides further insights into how G4s may contribute to the regulation and function of mtDNA and acts as a database of information for future studies investigating mitochondrial G4s in organisms other than humans.

Mitogenomes of Accipitriformes and Cathartiformes Were Subjected to Ancestral and Recent Duplications Followed by Gradual Degeneration.

The rearrangement of 37 genes with one control region, firstly identified in Gallus gallus mitogenome, is believed to be ancestral for all Aves. However, mitogenomic sequences obtained in recent years revealed that many avian mitogenomes contain duplicated regions that were omitted in previous genomic versions. Their evolution and mechanism of duplication are still poorly understood. The order of Accipitriformes is especially interesting in this context because its representatives contain a duplicated control region in various stages of degeneration. Therefore, we applied an appropriate PCR strategy to look for duplications within the mitogenomes of the early diverged species Sagittarius serpentarius and Cathartiformes, which is a sister order to Accipitriformes. The analyses revealed the same duplicated gene order in all examined taxa and the common ancestor of these groups. The duplicated regions were subjected to gradual degeneration and homogenization during concerted evolution. The latter process occurred recently in the species of Cathartiformes as well as in the early diverged lineages of Accipitriformes, that is, Sagittarius serpentarius and Pandion haliaetus. However, in other lineages, that is, Pernis ptilorhynchus, as well as representatives of Aegypiinae, Aquilinae, and five related subfamilies of Accipitriformes (Accipitrinae, Circinae, Buteoninae, Haliaeetinae, and Milvinae), the duplications were evolving independently for at least 14–47 Myr. Different portions of control regions in Cathartiformes showed conflicting phylogenetic signals indicating that some sections of these regions were homogenized at a frequency higher than the rate of speciation, whereas others have still evolved separately.

Characterization and Comparative Analysis of Complete Mitogenomes of Three Cacatua Parrots (Psittaciformes: Cacatuidae)

Cacatua alba, Cacatua galerita, and Cacatua goffiniana are parrots of the family Cacatuidae. Wild populations of these species are declining with C. alba listed by the International Union for the Conservation of Nature and Natural Resources (IUCN) as Endangered. In this study, complete mitogenomes were sequenced for a comparative analysis among the Cacatua species, and a detailed analysis of the control region. Mitogenome lengths of C. alba, C. galerita, and C. goffiniana were 18,894, 18,900, and 19,084 bp, respectively. They included 13 protein coding genes, two ribosomal RNA genes, 24 transfer RNA genes, three degenerated genes, and two control regions. Ten conserved motifs were found in three domains within each of the two control regions. For an evolution of duplicated control regions of Cacatua, domain I and the 3′ end of domain III experienced an independent evolution, while domain II and most of the regions of domain III was subjected to a concerted evolution. Based on a phylogenetic analysis of 37 mitochondrial genes, the genus Cacatua formed a well-supported, monophyletic, crown group within the Cacatuidae. Molecular dating results showed that Cacatua diverged from other genera of Cacatuinae in the middle of Miocene.

Novel gene rearrangement in the mitochondrial genome of Muraenesox cinereus and the phylogenetic relationship of Anguilliformes

The structure and gene sequence of the fish mitochondrial genome are generally considered to be conservative. However, two types of gene arrangements are found in the mitochondrial genome of Anguilliformes. In this paper, we report a complete mitogenome of Muraenesox cinereus (Anguilliformes: Muraenesocidae) with rearrangement phenomenon. The total length of the M. cinereus mitogenome was 17,673 bp, and it contained 13 protein-coding genes, two ribosomal RNAs, 22 transfer RNA genes, and two identical control regions (CRs). The mitochondrial genome of M. cinereus was obviously rearranged compared with the mitochondria of typical vertebrates. The genes ND6 and the conjoint trnE were translocated to the location between trnT and trnP, and one of the duplicated CR was translocated to the upstream of the ND6. The tandem duplication and random loss is most suitable for explaining this mitochondrial gene rearrangement. The Anguilliformes phylogenetic tree constructed based on the whole mitochondrial genome well supports Congridae non-monophyly. These results provide a basis for the future Anguilliformes mitochondrial gene arrangement characteristics and further phylogenetic research.

New view on the organization and evolution of Palaeognathae mitogenomes poses the question on the ancestral gene rearrangement in Aves

BackgroundBird mitogenomes differ from other vertebrates in gene rearrangement. The most common avian gene order, identified first in Gallus gallus, is considered ancestral for all Aves. However, other rearrangements including a duplicated control region and neighboring genes have been reported in many representatives of avian orders. The repeated regions can be easily overlooked due to inappropriate DNA amplification or genome sequencing. This raises a question about the actual prevalence of mitogenomic duplications and the validity of the current view on the avian mitogenome evolution. In this context, Palaeognathae is especially interesting because is sister to all other living birds, i.e. Neognathae. So far, a unique duplicated region has been found in one palaeognath mitogenome, that of Eudromia elegans.ResultsTherefore, we applied an appropriate PCR strategy to look for omitted duplications in other palaeognaths. The analyses revealed the duplicated control regions with adjacent genes in Crypturellus, Rhea and Struthio as well as ND6 pseudogene in three moas. The copies are very similar and were subjected to concerted evolution. Mapping the presence and absence of duplication onto the Palaeognathae phylogeny indicates that the duplication was an ancestral state for this avian group. This feature was inherited by early diverged lineages and lost two times in others. Comparison of incongruent phylogenetic trees based on mitochondrial and nuclear sequences showed that two variants of mitogenomes could exist in the evolution of palaeognaths. Data collected for other avian mitogenomes revealed that the last common ancestor of all birds and early diverging lineages of Neoaves could also possess the mitogenomic duplication.ConclusionsThe duplicated control regions with adjacent genes are more common in avian mitochondrial genomes than it was previously thought. These two regions could increase effectiveness of replication and transcription as well as the number of replicating mitogenomes per organelle. In consequence, energy production by mitochondria may be also more efficient. However, further physiological and molecular analyses are necessary to assess the potential selective advantages of the mitogenome duplications.

Turdoides affinis mitogenome reveals the translational efficiency and importance of NADH dehydrogenase complex-I in the Leiothrichidae family

Mitochondrial genome provides useful information about species concerning its evolution and phylogenetics. We have taken the advantage of high throughput next-generation sequencing technique to sequence the complete mitogenome of Yellow-billed babbler (Turdoides affinis), a species endemic to Peninsular India and Sri Lanka. Both, reference-based and de-novo assemblies of mitogenome were performed and observed that de-novo assembled mitogenome was most appropriate. The complete mitogenome of yellow-billed babbler (assembled de-novo) was 17,672 bp in length with 53.2% AT composition. Thirteen protein-coding genes along with two rRNAs and 22 tRNAs were detected. The arrangement pattern of these genes was found conserved among Leiothrichidae family mitogenomes. Duplicated control regions were found in the newly sequenced mitogenome. Downstream bioinformatics analysis revealed the effect of translational efficiency and purifying selection pressure over thirteen protein-coding genes in yellow-billed babbler mitogenome. Ka/Ks analysis indicated the highest synonymous substitution rate in the nad6 gene. Evolutionary analysis revealed the conserved nature of all the protein-coding genes across Leiothrichidae family mitogenomes. Our limited phylogeny results placed T. affinis in a separate group, a sister group of Garrulax. Overall, our results provide a useful information for future studies on the evolutionary and adaptive mechanisms of birds belong to the Leiothrichidae family.

Rearrangement and evolution of mitochondrial genomes in Thysanoptera (Insecta)

Prior to this study, complete mitochondrial genomes from Order Thysanoptera were restricted to a single family, the Thripidae, resulting in a biased view of their evolution. Here we present the sequences for the mitochondrial genomes of four additional thrips species, adding three extra families and an additional subfamily, thus greatly improving taxonomic coverage. Thrips mitochondrial genomes are marked by high rates of gene rearrangement, duplications of the control region and tRNA mutations. Derived features of mitochondrial tRNAs in thrips include gene duplications, anticodon mutations, loss of secondary structures and high gene translocation rates. Duplicated control regions are found in the Aeolothripidae and the ‘core’ Thripinae clade but do not appear to promote gene rearrangement as previously proposed. Phylogenetic analysis of thrips mitochondrial sequence data supports the monophyly of two suborders, a sister-group relationship between Stenurothripidae and Thripidae, and suggests a novel set of relationships between thripid genera. Ancestral state reconstructions indicate that genome rearrangements are common, with just eight gene blocks conserved between any thrips species and the ancestral insect mitochondrial genome. Conversely, 71 derived rearrangements are shared between at least two species, and 24 of these are unambiguous synapomorphies for clades identified by phylogenetic analysis. While the reconstructed sequence of genome rearrangements among the protein-coding and ribosomal RNA genes could be inferred across the phylogeny, direct inference of phylogeny from rearrangement data in MLGO resulted in a highly discordant set of relationships inconsistent with both sequence-based phylogenies and previous morphological analysis. Given the demonstrated rates of genomic evolution within thrips, extensive sampling is needed to fully understand these phenomena across the order.

Resolving Phylogenetic Relationships within Passeriformes Based on Mitochondrial Genes and Inferring the Evolution of Their Mitogenomes in Terms of Duplications.

Mitochondrial genes are placed on one molecule, which implies that they should carry consistent phylogenetic information. Following this advantage, we present a well-supported phylogeny based on mitochondrial genomes from almost 300 representatives of Passeriformes, the most numerous and differentiated Aves order. The analyses resolved the phylogenetic position of paraphyletic Basal and Transitional Oscines. Passerida occurred divided into two groups, one containing Paroidea and Sylvioidea, whereas the other, Passeroidea and Muscicapoidea. Analyses of mitogenomes showed four types of rearrangements including a duplicated control region (CR) with adjacent genes. Mapping the presence and absence of duplications onto the phylogenetic tree revealed that the duplication was the ancestral state for passerines and was maintained in early diverged lineages. Next, the duplication could be lost and occurred independently at least four times according to the most parsimonious scenario. In some lineages, two CR copies have been inherited from an ancient duplication and highly diverged, whereas in others, the second copy became similar to the first one due to concerted evolution. The second CR copies accumulated over twice as many substitutions as the first ones. However, the second CRs were not completely eliminated and were retained for a long time, which suggests that both regions can fulfill an important role in mitogenomes. Phylogenetic analyses based on CR sequences subjected to the complex evolution can produce tree topologies inconsistent with real evolutionary relationships between species. Passerines with two CRs showed a higher metabolic rate in relation to their body mass.

The revised complete mitogenome sequence of the tree frog Polypedatesmegacephalus (Anura, Rhacophoridae) by next-generation sequencing and phylogenetic analysis.

The mitochondrial genome (mitogenome) sequence of the tree frog Polypedates megacephalus (16,473 bp) was previously reported as having the unusual characteristic of lacking the ND5 gene. In this study, a new mitogenome of P. megacephalus (19,952 bp) was resequenced using the next-generation sequencing (NGS) and standard Sanger sequencing technologies. It was discovered that the ND5 gene was not lost but translocated to the control region (CR) from its canonical location between the ND4 and ND6 genes. In addition, a duplicated control region was found in the new mitogenome of this species. Conservative region identification of the ND5 gene and phylogenetic analysis confirmed that the ND5 gene was located between two control regions. The phylogenetic relationship among 20 related species of anura revealed a rearrangement of the ND5 gene during the evolutionary process. These results also highlighted the advantages of next-generation sequencing. It will not only decrease the time and cost of sequencing, but also will eliminate the errors in published mitogenome databases.

Complete mitochondrial genome of Ophichthus brevicaudatus reveals novel gene order and phylogenetic relationships of Anguilliformes

Generally, a teleostean group possesses only one type or a set of similar mitochondrial gene arrangement. However, two types of gene arrangement have been identified in the mitochondrial genomes (mitogenomes) of Anguilliformes. Here, a newly sequenced mitogenome of Ophichthus brevicaudatus (Anguilliformes; Ophichthidae) was presented. The total length of the O. brevicaudatus mitogenome was 17,773 bp, and it contained 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), 22 transfer RNA (tRNA) genes, and two identical control regions (CRs). The gene order differed from that of the typical vertebrate mitogenomes. The genes ND6 and the conjoint trnE were translocated to the location between trnT and trnP, and one of the duplicated CR was translocated to the upstream of the ND6. The duplication-random loss model was adopted to explain the gene rearrangement events in this mitogenome. The most comprehensive phylogenetic trees of Anguilliformes based on complete mitogenome was constructed. The non-monophyly of Congridae was well supported, whereas the non-monophyly of Derichthyidae and Chlopsidae was not supported. These results provide insight into gene arrangement features of anguilliform mitogenomes and lay the foundation for further phylogenetic studies on Anguilliformes.

New Insight into Parrots' Mitogenomes Indicates That Their Ancestor Contained a Duplicated Region.

Mitochondrial genomes of vertebrates are generally thought to evolve under strong selection for size reduction and gene order conservation. Therefore, a growing number of mitogenomes with duplicated regions changes our view on the genome evolution. Among Aves, order Psittaciformes (parrots) is especially noteworthy because of its large morphological, ecological, and taxonomical diversity, which offers an opportunity to study genome evolution in various aspects. Former analyses showed that tandem duplications comprising the control region with adjacent genes are restricted to several lineages in which the duplication occurred independently. However, using an appropriate polymerase chain reaction strategy, we demonstrate that early diverged parrot groups contain mitogenomes with the duplicated region. These findings together with mapping duplication data from other mitogenomes onto parrot phylogeny indicate that the duplication was an ancestral state for Psittaciformes. The state was inherited by main parrot groups and was lost several times in some lineages. The duplicated regions were subjected to concerted evolution with a frequency higher than the rate of speciation. The duplicated control regions may provide a selective advantage due to a more efficient initiation of replication or transcription and a larger number of replicating genomes per organelle, which may lead to a more effective energy production by mitochondria. The mitogenomic duplications were associated with phenotypic features and parrots with the duplicated region can live longer, show larger body mass as well as predispositions to a more active flight. The results have wider implications on the presence of duplications and their evolution in mitogenomes of other avian groups.

Single-molecule long-read transcriptome profiling of Platysternon megacephalum mitochondrial genome with gene rearrangement and control region duplication

ABSTRACTPlatysternon megacephalum is the sole living representative of the poorly studied turtle lineage Platysternidae. Their mitochondrial genome has been subject to gene rearrangement and control region duplication, resulting in a unique mitochondrial gene order in vertebrates. In this study, we sequenced the first full-length turtle (P. megacephalum) liver transcriptome using single-molecule real-time sequencing to study the transcriptional mechanisms of its mitochondrial genome. ND5 and ND6 anti-sense (ND6AS) forms a single transcript with the same expression in the human mitochondrial genome, but here we demonstrated differential expression of the rearranged ND5 and ND6AS genes in P. megacephalum. And some polycistronic transcripts were also reported in this study. Notably, we detected some novel long non-coding RNAs with alternative polyadenylation from the duplicated control region, and a novel ND6AS transcript composed of a long non-coding sequence, ND6AS, and tRNA-GluAS. These results provide the first description of a mtDNA transcriptome with gene rearrangement and control region duplication. These findings further our understanding of the fundamental concepts of mitochondrial gene transcription and RNA processing, and provide a new insight into the mechanism of transcription regulation of the mitochondrial genome.

Multiple independent structural dynamic events in the evolution of snake mitochondrial genomes

BackgroundMitochondrial DNA sequences have long been used in phylogenetic studies. However, little attention has been paid to the changes in gene arrangement patterns in the snake’s mitogenome. Here, we analyzed the complete mitogenome sequences and structures of 65 snake species from 14 families and examined their structural patterns, organization and evolution. Our purpose was to further investigate the evolutionary implications and possible rearrangement mechanisms of the mitogenome within snakes.ResultsIn total, eleven types of mitochondrial gene arrangement patterns were detected (Type I, II, III, III-A, III-B, III-B1, III-C, III-D, III-E, III-F, III-G), with mitochondrial genome rearrangements being a major trend in snakes, especially in Alethinophidia. In snake mitogenomes, the rearrangements mainly involved three processes, gene loss, translocation and duplication. Within Scolecophidia, the OL was lost several times in Typhlopidae and Leptotyphlopidae, but persisted as a plesiomorphy in the Alethinophidia. Duplication of the control region and translocation of the tRNALeu gene are two visible features in Alethinophidian mitochondrial genomes. Independently and stochastically, the duplication of pseudo-Pro (P*) emerged in seven different lineages of unequal size in three families, indicating that the presence of P* was a polytopic event in the mitogenome.ConclusionsThe WANCY tRNA gene cluster and the control regions and their adjacent segments were hotspots for mitogenome rearrangement. Maintenance of duplicate control regions may be the source for snake mitogenome structural diversity.

Comparative mitogenomic analyses of Amazona parrots and Psittaciformes.

Amazon parrots are long-lived birds with highly developed cognitive skills, including vocal learning. Several parrot mitogenomes have been sequenced, but important aspects of their organization and evolution are not fully understood or have limited experimental support. The main aim of the present study was to describe the mitogenome of the blue-fronted Amazon, Amazona aestiva, and compare it to other mitogenomes from the genus Amazona and the order Psittaciformes. We observed that mitogenomes are highly conserved among Amazon parrots, and a detailed analysis of their duplicated control regions revealed conserved blocks. Population level analyses indicated that the specimen analyzed here seems to be close to A. aestiva individuals from Bahia state. Evolutionary relationships of 41 Psittaciformes species and three outgroups were inferred by BEAST. All relationships were retrieved with high support.