TP53 somatic mutations are associated with somatic mitogenome substitutions but not indels in colorectal cancer cells

BACKGROUND

p53 is a tumour suppressor protein that is involved in many cancer-related processes. Growing evidence suggests that p53 also plays an important role in mitochondrial (mtDNA) maintenance. Somatic mitogenome mutations are frequently observed in colorectal cancer (CC) cells. Thus, it was important to determine whether somatic mtDNA changes are associated with TP53 mutational status.

METHODS

In the present study, we analysed the TP53 gene in 67 CC patients, for whom mitogenome haplotypes were previously described. In total, 134 TP53 sequences (of cancer and matched normal specimens) were determined using the dideoxy method.

RESULTS

Nine hereditary polymorphisms in the TP53 gene were detected in normal colon cells. None of them (neither alleles, nor genotypes) was associated with somatic mitogenome mutations in CC cells. Moreover, 42 somatic TP53 mutations were found in approximately 36% of CC tissues. These somatic changes were significantly more frequent in CC cells with somatic mtDNA mutations (p = 0.0069). Furthermore, we show that only mitochondrial somatic substitutions (p = 0.0017), but not indels (p > 0.05), were associated with somatic TP53 mutations.

CONCLUSIONS

The results of the present study suggest that changes in TP53 may modify p53 properties, which may result in the accumulation of somatic substitutions in CC mitogenomes.

Comparative mitochondrial genomics reveals a possible role of a recent duplication of NADH dehydrogenase subunit 5 in gene regulation

Mitochondrial genome (mtDNA) carries not only well-conserved protein coding, tRNA and rRNA genes, but also highly variable non-coding regions (NCRs). However, the NCRs show poor conservation across species, making their function and evolution elusive. Identification and functional characterization of NCRs across species would be critical for addressing these questions. To this end, we devised a computational pipeline and performed de novo assembly and annotation of mtDNA from 19 Caenorhabditis species using next-generation sequencing (NGS) data. The mtDNAs for 14 out of the 19 species are reported for the first time. Comparison of the 19 genomes reveals species-specific sampling of partial displacement-loop (D-loop) sequence as a novel NCR inserted into a unique tRNA cluster, suggesting an important role of the D-loop and the tRNA cluster in shaping NCR evolution. Intriguingly, RNA-Seq analysis suggests that a novel NCR resulting from a recent duplication of NADH dehydrogenase subunit 5 (ND5) could be utilized as a 3' UTR for up-regulation of its upstream gene. The expression analysis shows a species- and sex-specific expression of mitochondrial genes encoded by mtDNA and nucleus, respectively. Our analyses provide important insights into the function and evolution of mitochondrial NCRs and pave the way for further studying the function and evolution of mitochondrial genome.

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.

Mitochondrial disease genetics update: recent insights into the molecular diagnosis and expanding phenotype of primary mitochondrial disease

PURPOSE OF REVIEW

Primary mitochondrial disease (PMD) is a genetically and phenotypically diverse group of inherited energy deficiency disorders caused by impaired mitochondrial oxidative phosphorylation (OXPHOS) capacity. Mutations in more than 350 genes in both mitochondrial and nuclear genomes are now recognized to cause primary mitochondrial disease following every inheritance pattern. Next-generation sequencing technologies have dramatically accelerated mitochondrial disease gene discovery and diagnostic yield. Here, we provide an up-to-date review of recently identified, novel mitochondrial disease genes and/or pathogenic variants that directly impair mitochondrial structure, dynamics, and/or function.

RECENT FINDINGS

A review of PubMed publications was performed from the past 12 months that identified 16 new PMD genes and/or pathogenic variants, and recognition of expanded phenotypes for a wide variety of mitochondrial disease genes.

SUMMARY

Broad-based exome sequencing has become the standard first-line diagnostic approach for PMD. This has facilitated more rapid and accurate disease identification, and greatly expanded understanding of the wide spectrum of potential clinical phenotypes. A comprehensive dual-genome sequencing approach to PMD diagnosis continues to improve diagnostic yield, advance understanding of mitochondrial physiology, and provide strong potential to develop precision therapeutics targeted to diverse aspects of mitochondrial disease pathophysiology.

The complete mitochondrial genome of a walnut weevil, Alcidodes juglans Chao (Coleoptera: Curculionidae)

The walnut weevil, Alcidodes juglans Chao (Coleoptera: Curculionidae), is an important agricultural pest and distributed widely in China. The complete mitochondrial genome of A. juglans is 15,638 bp long, and consists of 13 protein-coding genes (PCGs), two ribosomal RNA genes, 21 transfer RNA (tRNA) genes and a putative control region (GenBank accession No. MH819192). The trnI gene has not been observed in the A. juglans mitogenome. The nucleotide composition is significantly biased (A, G, C, and T was 38.35%, 10.02%, 14.96%, and 36.67%, respectively) with A + T contents of 75.02%. All of the 21 tRNAs have the typical cloverleaf structure, with an exception for trnS₁ (AGN). All PCGs are initiated by ATN codons, except for cox1 with AAT instead. Ten PCGs use a common stop codon of TAA or TAG, whereas the remaining three were terminated with a single T. The phylogenetic relationships based on neighbour-joining method showed that A. juglans is closely related to Naupactus xanthographus, which is in accordance with the traditional morphological classification.

Complete mitochondrial genome of the Endangered fish Anabarilius liui yalongensis (Teleostei, Cyprinidae, Cultrinae)

We describe the complete mitochondrial genome of the Endangered fish Anabarilius liui yalongensis. It is a circular molecule of 16,608 bp in size, and all genes show the typical gene arrangement conforming to the vertebrate consensus. The cytochrome c oxidase subunit I (COI) sequence of A. liui yalongensis and other 21 species from 14 genera were used for phylogenetic analysis by Bayesian inference and maximum likelihood methods. The topology demonstrated that the A. liui yalongensis clustered with A. grahami are closely to Hemiculter branch within the subfamily Cultrinae.

Comparative Characterization of the Complete Mitochondrial Genomes of the Three Apple Snails (Gastropoda: Ampullariidae) and the Phylogenetic Analyses

The apple snails Pomacea canaliculata, Pomacea diffusa and Pomacea maculate (Gastropoda: Caenogastropoda: Ampullariidae) are invasive pests causing massive economic losses and ecological damage. We sequenced and characterized the complete mitochondrial genomes of these snails to conduct phylogenetic analyses based on comparisons with the mitochondrial protein coding sequences of 47 Caenogastropoda species. The gene arrangements, distribution and content were canonically identical and consistent with typical Mollusca except for the tRNA-Gln absent in P. diffusa. An identifiable control region (d-loop) was absent. Bayesian phylogenetic analysis indicated that all the Ampullariidae species clustered on the same branch. The genus Pomacea clustered together and then with the genus Marisa. The orders Architaenioglossa and Sorbeoconcha clustered together and then with the order Hypsogastropoda. Furthermore, the intergenic and interspecific taxonomic positions were defined. Unexpectedly, Ceraesignum maximum, Dendropoma gregarium, Eualetes tulipa and Thylacodes squamigerus, traditionally classified in order Hypsogastropoda, were isolated from the order Hypsogastropoda in the most external branch of the Bayesian inference tree. The divergence times of the Caenogastropoda indicated that their evolutionary process covered four geological epochs that included the Quaternary, Neogene, Paleogene and Cretaceous periods. This study will facilitate further investigation of species identification to aid in the implementation of effective management and control strategies of these invasive species.

The complete mitochondrial genome of the sea urchin, Echinometra sp. EZ

The complete mitogenome of Echinometra sp. EZ has been described and fully annotated in this study. Phylogenetic analysis of cytochrome c oxidase subunit I (COI) from six Echinometra species confirms that our sample is E. sp. EZ. The mitogenome is 15,698 bp in length and contains 13 protein-coding genes, 22 tRNAs, 2 rRNAs, and a non-coding region with an identical organization to other Echinoidea. The E. sp. EZ mitogenome shared ∼99.1% identity to the published Echinometra mathaei mitogenome, differing by 147 SNPs. The E. sp. EZ mitogenome will serve as a resource that can be applied to disentangling the Echinometra species complex and to future population genetic studies of this ecologically important sea urchin species.

Assembly of a Complete Mitogenome of Chrysanthemum nankingense Using Oxford Nanopore Long Reads and the Diversity and Evolution of Asteraceae Mitogenomes

Diversity in structure and organization is one of the main features of angiosperm mitochondrial genomes (mitogenomes). The ultra-long reads of Oxford Nanopore Technology (ONT) provide an opportunity to obtain a complete mitogenome and investigate the structural variation in unprecedented detail. In this study, we compared mitogenome assembly methods using Illumina and/or ONT sequencing data and obtained the complete mitogenome (208 kb) of Chrysanthemum nankingense based on the hybrid assembly method. The mitogenome encoded 19 transfer RNA genes, three ribosomal RNA genes, and 34 protein-coding genes with 21 group II introns disrupting eight intron-contained genes. A total of seven medium repeats were related to homologous recombination at different frequencies as supported by the long ONT reads. Subsequently, we investigated the variations in gene content and constitution of 28 near-complete mitogenomes from Asteraceae. A total of six protein-coding genes were missing in all Asteraceae mitogenomes, while four other genes were not detected in some lineages. The core fragments (~88 kb) of the Asteraceae mitogenomes had a higher GC content (~46.7%) than the variable and specific fragments. The phylogenetic topology based on the core fragments of the Asteraceae mitogenomes was highly consistent with the topologies obtained from the corresponding plastid datasets. Our results highlighted the advantages of the complete assembly of the C. nankingense mitogenome and the investigation of its structural variation based on ONT sequencing data. Moreover, the method based on local collinear blocks of the mitogenomes could achieve the alignment of highly rearrangeable and variable plant mitogenomes as well as construct a robust phylogenetic topology.

eKLIPse: a sensitive tool for the detection and quantification of mitochondrial DNA deletions from next-generation sequencing data

PURPOSE

Accurate detection of mitochondrial DNA (mtDNA) alterations is essential for the diagnosis of mitochondrial diseases. The development of high-throughput sequencing technologies has enhanced the detection sensitivity of mtDNA pathogenic variants, but the detection of mtDNA rearrangements, especially multiple deletions, is still poorly processed. Here, we present eKLIPse, a sensitive and specific tool allowing the detection and quantification of large mtDNA rearrangements from single and paired-end sequencing data.

METHODS

The methodology was first validated using a set of simulated data to assess the detection sensitivity and specificity, and second with a series of sequencing data from mitochondrial disease patients carrying either single or multiple deletions, related to pathogenic variants in nuclear genes involved in mtDNA maintenance.

RESULTS

eKLIPse provides the precise breakpoint positions and the cumulated percentage of mtDNA rearrangements at a given gene location with a detection sensitivity lower than 0.5% mutant. eKLIPse software is available either as a script to be integrated in a bioinformatics pipeline, or as user-friendly graphical interface to visualize the results through a Circos representation ( https://github.com/dooguypapua/eKLIPse ).

CONCLUSION

Thus, eKLIPse represents a useful resource to study the causes and consequences of mtDNA rearrangements, for further genotype/phenotype correlations in mitochondrial disorders.

The Mitochondrial Genomes of Phytophagous Scarab Beetles and Systematic Implications

In this study, we newly sequenced five mitogenomes of representatives of phytophagous scarab beetles (Coleoptera: Scarabaeidae) by using next-generation sequencing technology. Two species have complete (or nearly complete) mitogenome sequences, namely Popillia mutans Newman (Coleoptera: Scarabaeidae) and Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae). The remaining three species have the partial mitogenomes, and the missing genes are mainly located adjacent to the control region. The complete (or nearly complete) mitogenomes have the same genome structure as most of the existing Scarabaeidae mitogenomes. We conducted phylogenetic analyses together with 24 published mitogenomes of Scarabaeoidea. The results supported a basal split of coprophagous and phytophagous Scarabaeidae. The subfamily Sericinae was recovered as sister to all other phytophagous scarab beetles. All analyses supported a non-monophyletic Melolonthinae, which included two different non-sister clades. The Cetoniinae was recovered as sister to a clade including Rutelinae and Dynastinae. Although the Rutelinae was rendered paraphyletic by Dynastinae in the Bayesian trees inferred under the site-heterogeneous CAT-GTR or CAT-MTART model, discordant patterns were given in some of ML trees estimated using the homogeneous GTR model.

The first complete mitochondrial genome of the Mariana Trench Freyastera benthophila (Asteroidea: Brisingida: Brisingidae) allows insights into the deep-sea adaptive evolution of Brisingida

Starfish (phylum Echinodermata) are ecologically important and diverse members of marine ecosystems in all of the world's oceans, from the shallow water to the hadal zone. The deep sea is recognized as an extremely harsh environment on earth. In this study, we present the mitochondrial genome sequence of Mariana Trench starfish Freyastera benthophila, and this study is the first to explore in detail the mitochondrial genome of a deep-sea member of the order Brisingida. Similar to other starfish, it contained 13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes (duplication of two tRNAs: trnL and trnS). Twenty-two of these genes are encoded on the positive strand, while the other 15 are encoded on the negative strand. The gene arrangement was identical to those of sequenced starfish. Phylogenetic analysis showed the deep-sea Brisingida as a sister taxon to the traditional members of the Asteriidae. Positive selection analysis indicated that five residues (8 N and 16 I in atp8, 47 D and 196 V in nad2, 599 N in nad5) were positively selected sites with high posterior probabilities. Compared these features with shallow sea starfish, we predict that variation specifically in atp8, nad2, and nad5 may play an important role in F. benthophila's adaptation to deep-sea environment.

Maternal age effects on fecundity and offspring egg-to-adult viability are not affected by mitochondrial haplotype

While numerous studies have demonstrated that mitochondrial genetic variation can shape organismal phenotype, the level of contribution the mitochondrial genotype makes to life-history phenotype across the life course remains unknown. Furthermore, a clear technical bias has emerged in studies of mitochondrial effects on reproduction, with many studies conducted on males, but few on females. Here, we apply a classic prediction of the evolutionary theory of aging to the mitochondrial genome, predicting the declining force of natural selection with age will have facilitated the accumulation of mtDNA mutations that confer late-life effects on female reproductive performance. This should lead to increased levels of mitochondrial genetic variation on reproduction at later-life stages. We tested this hypothesis using thirteen strains of Drosophila melanogaster that each possessed a different mitochondrial haplotype in an otherwise standard nuclear genetic background. We measured fecundity and egg-to-adult viability of females over five different age classes ranging from early to late life and quantified the survival of females throughout this time period. We found no significant variation across mitochondrial haplotypes for the reproductive traits, and no mitochondrial effect on the slope of decline in these traits with increasing age. However, we observed that flies that died earlier in the experiment experienced steeper declines in the reproductive traits prior to death, and we also identified maternal and grandparental age effects on the measured traits. These results suggest the mitochondrial variation does not make a key contribution to shaping the reproductive performance of females.

Characterization of the complete mitochondrial genome of band-rumped Storm-petrel, Hydrobates castro

In this study, the complete mitochondrial genome of band-rumped Storm-petrel, Hydrobates castro, was determined through sequencing of PCR fragments. The complete mitochondrial genome of H. castro was 17,065 bp in length and encoded 13 protein-coding genes, 22 transfer RNA (tRNA) genes, and two ribosomal RNA genes. The overall nucleotide composition is: 30.4% A, 24.5% T, 30.9% C, and 14.2% G, with a total G + C content of 45.1%. By phylogenetic analysis using Bayes method, H. castro showed the closest relationship with the white-faced storm petrel (Pelagodroma marina).

Complete Mitochondrial Genome of the Chagas Disease Vector, Triatoma rubrofasciata

Triatoma rubrofasciata is a wide-spread vector of Chagas disease in Americas. In this study, we completed the mitochondrial genome sequencing of T. rubrofasciata. The total length of T. rubrofasciata mitochondrial genome was 17,150 bp with the base composition of 40.4% A, 11.6% G, 29.4% T and 18.6% C. It included 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and one control region. We constructed a phylogenetic tree on the 13 protein-coding genes of T. rubrofasciata and other 13 closely related species to show their phylogenic relationship. The determination of T. rubrofasciata mitogenome would play an important role in understanding the genetic diversity and evolution of triatomine bugs.

Complete mitochondrial genome of the spiny rock crab Thalamita crenata (rüppell, 1830) (Crustacea: Decapoda: Portunidae) from China coast and its phylogeny

To understand the evolution of the swimming crab Thalamita crenata, the complete mitochondrial genome of T. crenata from China was sequenced and analyzed. The circular mitogenome sequence was 15,787 bp in length, made up of 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and a control region. The overall mitogenome composition was 34.40% for A, 11.55% for G, 35.31% for T, and 18.74% for C, respectively, with a high A + T content of 69.71%. Phylogenetic analysis showed that T. crenata was closest to the genus Charybdis.

The complete mitochondrial genome of the Basidiomycete edible fungus Hypsizygus marmoreus

The complete mitochondrial genome of the edible fungus Hypsizygus marmoreus was published in this paper. It was determined using Pacbio and Illumina sequencing. The complete mitochondrial DNA (mtDNA) is 106,417 bp in length with a GC content of 31.74%, which was the fourth large mitogenome in Agaricales. The circular mitogenome encoded 67 protein-coding genes and one ribosomal RNAs (rns). Among these genes, 13 conserved protein-coding genes were determined in the genome, including 6 subunits of NAD dehydrogenase (nad1-4, 4L and 6), three cytochrome oxidases (cox1-3), one apocytochrome b (cob) and three ATP synthases (atp6, apt 8 and apt 9). The phylogenic analysis confirmed that H. marmoreus (Lyophyllaceae) clustered together with Tricholoma matsutake (Tricholomataceae).

The complete mitochondrial genome of Schisandra sphenanthera (Schisandraceae)

Schisandra sphenanthera (Austrobaileyales) is a famous traditional Chinese medicine being long-history used, is also one of early-diverging angiosperms and important links to uncover the early evolution of angiosperms. Here the complete mitochondrial genome of S. sphenanthera was obtained for the first time. It is 1,106,521 bp in length with 46.4% GC content. It contains 58 genes, including 41 protein coding genes, three ribosomal RNA genes and 14 transfer RNA genes. Phylogenetic analysis indicated that S. sphenanthera was placed in the basal angiosperm just after Amborella and Nuphar. The mitogenome of S. sphenanthera would provide a reliable genetic and evolutionary resource.

Complete mitochondrial genome of the Salangid icefish Neosalanx taihuensis (Actinopterygii: Osmeriformes: Salangidae)

The complete mitochondrial DNA genome of the Salangid icefish (Neosalanx taihuensis) was sequenced by the primer walking sequence method. The entire mitochondrial genome of this species is 17,035 bp in length, making it the longest among the reported mitochondrial genomes of Osmeriformes. It contains 13 protein-coding genes, 2 ribosomal RNA (rRNA) genes, 22 transfer RNA (tRNA) genes, and one control region (CR). The gene arrangement, nucleotide composition, and codon usage pattern of the mitochondrial genome are similar to those of other teleosts except for two long tandem repeats in the CR. A 486 bp tandem repeat fragment was identified that comprises 2 copies of 243 bp motif and accounts approximately 35.5% of the CR. The 243 bp tandem repeat motif can be folded into a stem-loop secondary structure. Phylogenetic analysis based on 12 concatenated protein-coding genes of the heavy strand shows the genus Neosalanx diverged most recently and clustered with Protosalanx hyalocranius as a clade.

The complete mitochondrial genome of Fea's muntjac (Muntiacus feae Thomas and Doria, 1889) with phylogenetic analysis†

The complete mitochondrial genome (mitogenome) of the rare Fea's muntjac (Muntiacus feae) was sequenced (GenBank accession nos. MG857662-MG857664). The mitogenome was found to be 16,355 bp in length with base compositions of 33.16% A, 24.59% C, 13.46% G, and 28.78% T and a GC content of 38.06%. The genome is comprised of 13 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes, and a control region (D-loop). Phylogenetic analysis revealed that Fea's muntjac is more closely related to Black muntjac (M. cronifrons) than to Red muntjac (M. muntjak). These data will be useful for further studies on the genetic diversity and molecular phylogenetic relationship of the genus Muntiacus.

Complete characteristics and phylogenetic relationships of the Garrulax albogularis mitochondrial genome (Passeriformes: Timaliidae)

In this study, we sequenced the complete mitochondrial genome of the bird Garrulax albogularis. The mitochondrial genome of G. albogularis was 17,870 bp and contained 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and two control regions. The overall base composition of the mitogenome was biased toward at 53.83%A + T content. ND6 and nine tRNA genes were encoded on the L-strand. The other protein-coding genes (PCGs) and tRNA genes were all distributed on the H-strand.

First report on the complete mitochondrial genome of the deep-water scalpellid barnacle Arcoscalpellum epeeum (Cirripedia, Thoracica, Scalpellidae)

Scalpellids are one of the largest families of Scalpelliformes and reproduce either androdioeciously or dioeciously. Here, we characterized the first mitogenome of a scalpellid barnacle (Arcoscalpellum epeeum), which was 15,593 bp in length with a 71.5% AT content. In comparison with the pollicipedids Capitulum mitella and Pollicipes polymerus, the tRNA genes of A. epeeum were rearranged between ND3 and ND5, between CYTB and ND1, and between 12S rRNA and ND2. On the mitogenomic tree, the Scalpelliformes families Pollicipedidae and Scalpellidae were not monophyletic, which concurs with previous studies.

The complete mitochondrial genome of the apple snail Pomacea maculate (Gastropoda: Ampullariidae)

We present the complete mitochondrial genome of Pomacea maculate in this study. The mitochondrial genome is 15,512 bp in length, containing 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes. Overall nucleotide compositions of the light strand are 41.13% of A, 30.81% of T, 15.25% of C and 12.81% of G. Its gene arrangement and distribution are different from the typical vertebrates. The absence of D-loop is consistent with the Gastropoda, but at least one lengthy non-coding region is essential regulatory element for the initiation of transcription and replication. Phylogenetic tree is constructed by the maximum-likelihood method based on the complete mitochondrial genomes of 15 species of Caenogastropoda, using Helix aspersa as outgroup to assess their actual phylogenetic relationship and evolution. The result provides fundamental data for resolving phylogenetic and genetic problems related to effective management strategies.

The complete mitochondrial genome of Glossaulax reiniana (Littorinimorpha: Naticidae)

In the present study, the complete mitochondrial genome of Glossaulax reiniana was determined using the next-generation sequencing. The circular genome was found to be 15,254 bp in length and had an overall nucleotide composition of 30.6% A, 14.1% C, 15.8% G, and 39.5% T. Similar to the typical caenogastropod mitochondrial genomes, it contained 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes, and a potential control origin. All protein-coding genes started with standard initiation codons (ATA and ATG) and ended by TAA or TAG. The lengths of 12S ribosomal RNA and 16S ribosomal RNA were 948 and 1353 bp, respectively. The largest noncoding region considered to contain the origin of replication was 59 bp in length. The complete mitochondrial genome reported here would provide useful information for molecular phylogeny, genetic conservation, and sustainable management of G. reiniana.

The complete mitochondrial genome of a transitional form in secondary endosymbiotic Cryptophyte algae Guillardia theta strain CCMP2712

The complete mitochondrial genome of Guillardia theta strain CCMP2712 was sequenced, assembled, and annotated in this study. The circular genome is 35,013 bp in size and it contains 36 protein-coding genes (PCGs), 28 transfer RNA genes (tRNA), and 2 ribosomal RNA genes (rRNA). The overall GC contents of the mitochondrial genome are 28.9%. The phylogenetic tree was constructed to validate the taxonomic relationship based on the complete mitogenomes of G. theta strain CCMP2712 through combining with seven Cryptophyta and four Heterokontophyta algae. The complete mitochondrial genome of the Guillardia theta strain CCMP2712 will provide more information for the evolution of secondary endosymbiotic species.