The atypical organization of the luxI/R family genes in AHL-driven quorum-sensing circuits.

Quorum sensing (QS) is an elaborate regulatory mechanism associated with virulence and bacterial adaptation to the changing environment. QS is widespread in Proteobacteria and acts primarily through N-acylhomoserine lactone (AHL) signals. At the core of the AHL-driven QS systems are the AHL synthase gene (luxI family) and its cognate transcriptional regulator gene (luxR family). Several QS systems display one or more genes intervening between the luxI and luxR, in which gene arrangements are notably different due to the relative position and the transcriptional orientation between the essential luxI/R and the genes of location correlation. These adjacent genes may exert a regulatory impact on the primary QS genes or contribute toward an extension of QS regulatory control. In this review, we describe the organization of AHL-driven QS genes based on previous research and specific genome databases and provide new insights into these atypical QS gene arrangements.

The complete mitochondrial genome of Ogmocotyle ailuri: gene content, composition and rearrangement and phylogenetic implications.

Trematodes of the genus Ogmocotyle are intestinal flukes that can infect a variety of definitive hosts, resulting in significant economic losses worldwide. However, there are few studies on molecular data of these trematodes. In this study, the mitochondrial (mt) genome of Ogmocotyle ailuri isolated from red panda (Ailurus fulgens) was determined and compared with those from Pronocephalata to investigate the mt genome content, genetic distance, gene rearrangements and phylogeny. The complete mt genome of O. ailuri is a typical closed circular molecule of 14 642 base pairs, comprising 12 protein-coding genes (PCGs), 22 transfer RNA genes, 2 ribosomal RNA genes and 2 non-coding regions. All genes are transcribed in the same direction. In addition, 23 intergenic spacers and 2 locations with gene overlaps were determined. Sequence identities and sliding window analysis indicated that cox1 is the most conserved gene among 12 PCGs in O. ailuri mt genome. The sequenced mt genomes of the 48 Plagiorchiida trematodes showed 5 types of gene arrangement based on all mt genome genes, with the gene arrangement of O. ailuri being type I. Phylogenetic analysis using concatenated amino acid sequences of 12 PCGs revealed that O. ailuri was closer to Ogmocotyle sikae than to Notocotylus intestinalis. These data enhance the Ogmocotyle mt genome database and provide molecular resources for further studies of Pronocephalata taxonomy, population genetics and systematics.

Phylogenetic position of Bopyroides hippolytes, with comments on the rearrangement of the mitochondrial genome in isopods (Isopoda: Epicaridea: Bopyridae).

BACKGROUND: Classification of parasitic bopyrids has traditionally been based on morphological characteristics, but phylogenetic relationships have remained elusive due to limited information provided by morphological data and tendency for loss of morphological features as a result of parasitic lifestyle. Subfamily Argeiinae was separated from Bopyrinae based on morphological evidence, although the assignment of all genera has not been phylogenetically evaluated. Bopyroides hippolytes has been traditionally classified in Bopyrinae, but divergent morphological characters make this assignment questionable. To investigate the relationship of bopyrines, we sequenced the complete mitochondrial genome of B. hippolytes and four mitochondrial genes of two other Bopyrinae. RESULTS: The phylogenetic trees based on separate and combined cox1and 18S sequence data recovered Bopyridae as robustly monophyletic, but Bopyrinae as polyphyletic. Bopyroides hippolytes was a close sister to Argeia pugettensis, type species to Argeiinae. Mitochondrial phylogenomics also suggested that B. hippolytes was close to Argeiinae. We also found a novel gene order in B. hippolytes compared to other isopods. CONCLUSIONS: Bopyroides hippolytes should be excluded from the Bopyrinae and has a close affinity with Argeia pugettensis based on molecular and morphological data. The conserved syntenic blocks of mitochondrial gene order have distinctive characteristics at a subordinal level and may be helpful for understanding the higher taxonomic level relationships of Isopoda.

Gene arrangement, phylogeny and divergence time estimation of mitogenomes in Thrips.

BACKGROUND: The metazoan mitogenomes usually display conserved gene arrangement while thrips are known for their extensive gene rearrangement, and duplication of the control region. METHODS AND RESULT: We sequenced complete mitogenomes of eight species of thrips to determine the gene arrangement, phylogeny and divergence time estimation. All contain 37 genes and one control region, (CR) except four species with two CRs. Duplicated tRNAs were detected in Mycterothrips nilgiriensis and Thrips florum. nad4-nad4L were not found adjacent to each other in Phibalothrips peringueyi and Plicothrips apicalis. Both Bayesian and likelihood phylogenetic analyses of thrips mitogenomes supported the monophyly of two suborders (Terebrantia and Tubulifera) and the two largest families (Phlaeothripidae and Thripidae). Out of seven earlier proposed ancestral gene blocks, six are conserved in Panchaetothripinae, three in Thripinae and two in Phlaeothripidae. Additionally, eight Thrips Gene Blocks were identified, of which, three conserved in Tubulifera, four in Terebrantia, and one only in Aeolothripidae. Forty-two gene boundaries (15 from previous study + 27 new) were identified. The molecular divergence time is estimated for the order Thysanoptera and suggested that these insects may have been diversified from hemipterans in the late Permian period. The most recent ancestors belong to family Thripidae and Phlaeothripidae, which were diversified in upper Cretaceous period and showed higher rates of rearrangement from the ancestral gene order. CONCLUSIONS: The current study is the first largest effort to provide the new insights into the mitogenomic features, gene arrangement, phylogeny and divergence time estimation of thrips belonging to the order Thysanoptera.

The complete mitogenome of Orcula dolium (Draparnaud, 1801); ultra-deep sequencing from a single long-range PCR using the Ion-Torrent PGM.

BACKGROUND: With the increasing capacity of present-day next-generation sequencers the field of mitogenomics is rapidly changing. Enrichment of the mitochondrial fraction, is no longer necessary for obtaining mitogenomic data. Despite the benefits, shotgun sequencing approaches also have disadvantages. They do not guarantee obtaining the complete mitogenome, generally require larger amounts of input DNA and coverage is low compared to sequencing with enrichment strategies. If the mitogenome could be amplified in a single amplification, additional time and costs for sample preparation might outweigh these disadvantages. RESULTS: A sequence of the complete mitochondrial genome of the pupilloid landsnail Orcula dolium is presented. The mitogenome was amplified in a single long-range (LR) PCR and sequenced on an Ion Torrent PGM (Life Technologies). The length is 14,063 nt and the average depth of coverage is 1112 X. This is the first published mitogenome for a member of the family Orculidae. It has the typical metazoan makeup of 13 protein coding genes (PCGs), 2 ribosomal RNAs (12S and 16S) and 22 transfer RNAs (tRNAs). Orcula is positioned between Pupilla and the Vertiginidae as the sister-group of Gastrocopta and Vertigo, together. An ancestral gene order reconstruction shows that Orthurethra in contrast to other Stylommatophora, have tRNA-H before tRNA-G and that the gene order in the 'non-achatinoid' clade is identical to that of closely related non-stylommatophoran taxa. CONCLUSIONS: We show it is feasible to ultra-deep sequence a mitogenome from a single LR-PCR. This approach is particularly relevant to studies that have low concentrations of input DNA. It results in a more efficient use of NGS capacity (only the targeted fraction is sequenced) and is an effective selection against nuclear mitochondrial inserts (NUMTS). In contrast to previous studies based in particular on 28S, our results indicate that phylogeny reconstructions based on complete mitogenomes might be more suitable to resolve deep relationships within Stylommatophora. Ancestral gene order reconstructions reveal rearrangements that characterize systematic groups.

Monoplacophoran mitochondrial genomes: convergent gene arrangements and little phylogenetic signal.

BACKGROUND: Although recent studies have greatly advanced understanding of deep molluscan phylogeny, placement of some taxa remains uncertain as different datasets support competing class-relationships. Traditionally, morphologists have placed Monoplacophora, a group of morphologically simple, limpet-like molluscs as sister group to all other conchiferans (shelled molluscs other than Polyplacophora), a grouping that is supported by the latest large-scale phylogenomic study that includes Laevipilina. However, molecular datasets dominated by nuclear ribosomal genes support Monoplacophora + Polyplacophora (Serialia). Here, we evaluate the potential of mitochondrial genome data for resolving placement of Monoplacophora. RESULTS: Two complete (Laevipilina antarctica and Vema ewingi) and one partial (Laevipilina hyalina) mitochondrial genomes were sequenced, assembled, and compared. All three genomes show a highly similar architecture including an unusually high number of non-coding regions. Comparison of monoplacophoran gene order shows a gene arrangement pattern not previously reported; there is an inversion of one large gene cluster. Our reanalyses of recently published polyplacophoran mitogenomes show, however, that this feature is also present in some chiton species. Maximum Likelihood and Bayesian Inference analyses of 13 mitochondrial protein-coding genes failed to robustly place Monoplacophora and hypothesis testing could not reject any of the evaluated placements of Monoplacophora. CONCLUSIONS: Under both serialian or aculiferan-conchiferan scenarios, the observed gene cluster inversion appears to be a convergent evolution of gene arrangements in molluscs. Our phylogenetic results are inconclusive and sensitive to taxon sampling. Aculifera (Polyplacophora + Aplacophora) and Conchifera were never recovered. However, some analyses recovered Serialia (Monoplacophora + Polyplacophora), Diasoma (Bivalvia + Scaphopoda) or Pleistomollusca (Bivalvia + Gastropoda). Although we could not shed light on deep evolutionary traits of Mollusca we found unique patterns of gene arrangements that are common to monoplacophoran and chitonine polyplacophoran species but not to acanthochitonine Polyplacophora. Complete mitochondrial genome of Laevipilina antarctica.

Mitochondrial Phylogenomics of Scoliidae from China, with Evidence to Challenge the Former Placement of the Colpa Group.

Scoliidae, also known as scarab hunters or flower wasps, are important in the biological control of scarabs and for pollination. Mitogenomic and phylogenetic studies are rare for this group. In this study, 10 mitochondrial genomes representing eight genera in two tribes of the family Scoliidae were determined. The general features and rearrangements of the mitochondrial genomes for 15 Scoliidae species representing all genera distributed in China were described and compared and the phylogenetic relationships among them were inferred using MrBayes and IQtree based on four data matrices. Most sequences of Scoliidae have one extra trnM gene. Species belonging to Campsomerini have lower A + T content than all Scoliini species except for Colpa tartara in this study. The AT-skew is positive in 7 out of 15 species. All 15 Scoliidae sequences have similar conserved gene arrangements with the same arrangements of PCGs and rRNA genes, except for Campsomeriella annulata. The tRNA genes have the highest frequency of rearrangement, and C. tartara is always rearranged as in its Scoliini counterparts. Our phylogenetic results support most of the relationships between genera and tribes of Scoliidae in former morphological studies. However, Colpa tartara is proved to be closer to Scoliini according to genome features, phylogenetic analyses and some morphological evidence, which challenges the former attribution of the Colpa group.

The complete mitochondrial genome of the black-breasted thrush Turdus dissimilis (passeriformes: Turdidae).

The Back-breasted Thrush (Turdus dissimilis Blyth 1847), a medium-sized Turdus bird in the Turdidae family, is widely distributed in montane areas from northeastern India and Myanmar to southern China. The mitochondrial DNA of T. dissimilis is packaged in a compact 16,761-basepair (bp) circular molecule with A + T content of 52.50%. It contains 37 typical mitochondrial genes, including 13 protein-coding genes, 2 rRNAs and 22 tRNAs, and 1 noncoding region. We reconstructed a phylogenetic tree based on the mitogenome sequences of 10 Turdidae species and one outgroup. Phylogenetic analysis indicated that T. dissimilis is a sister taxon to T. unicolor. The new mitogenome data would provide useful information for application in conservation.

Complementing aculiferan mitogenomics: comparative characterization of mitochondrial genomes of Solenogastres (Mollusca, Aplacophora).

BACKGROUND: With the advances in high-throughput sequencing and bioinformatic pipelines, mitochondrial genomes have become increasingly popular for phylogenetic analyses across different clades of invertebrates. Despite the vast rise in available mitogenomic datasets of molluscs, one class of aplacophoran molluscs - Solenogastres (or Neomeniomorpha) - is still neglected. RESULTS: Here, we present six new mitochondrial genomes from five families of Solenogastres (Amphimeniidae, Gymnomeniidae, Proneomeniidae, Pruvotinidae, Simrothiellidae), including the first complete mitogenomes, thereby now representing three of the four traditional orders. Solenogaster mitogenomes are variable in size (ranging from approximately 15,000 bp to over 17,000 bp). The gene order of the 13 protein coding genes and two rRNA genes is conserved in three blocks, but considerable variation occurs in the order of the 22 tRNA genes. Based on phylogenetic analyses and reconstruction of ancestral mitochondrial genomes of Aculifera, the position of (1) trnD gene between atp8 and atp6, (2) trnT and P genes between atp6 and nad5, and (3) trnL1 gene between G and E, resulting in a 'MCYWQGL1E'-block of tRNA genes, are all three considered synapomorphies for Solenogastres. The tRNA gene block 'KARNI' present in Polyplacophora and several conchiferan taxa is dissolved in Solenogastres. CONCLUSION: Our study shows that mitogenomes are suitable to resolve the phylogenetic relationships among Aculifera and within Solenogastres, thus presenting a cost and time efficient compromise to approach evolutionary history in these clades.

Climate-driven mitochondrial selection in lacertid lizards.

The mitochondrion, which is an intracellular organelle responsible for most of the energy-producing pathways, can have its genome targeted for climate-driven selection. However, climate-driven mitochondrial selection remains a sparsely studied area in reptiles. Here, we reported the complete mitochondrial genome sequence of a lacertid lizard (Takydromus intermedius) and used mitogenomes from 54 species of lacertid lizards to study their phylogenetic relationships and to identify the mitochondrial genes under positive selection by climate. The length of the complete mitochondrial genome sequence of T. intermedius was 17,713 bp, which was within the range of lengths (17,224-18,943) ever reported for Takydromus species. The arrangement of mitochondrial genes in T. intermedius was the same as in other congeneric species. The 54 lacertid species could be divided into three geographically and climatically different clades. We identified three mitochondrial genes (ATP6, ATP8, and ND3) under positive selection by climate, and found that isothermality, temperature seasonality, precipitation of wettest month, and precipitation seasonality were the most important climatic variables contributing to the gene selection.

The complete mitochondrial genomes of deep-sea squid (Bathyteuthis abyssicola), bob-tail squid (Semirossia patagonica) and four giant cuttlefish (Sepia apama, S. latimanus, S. lycidas and S. pharaonis), and their application to the phylogenetic analysis of Decapodiformes.

We determined the complete mitochondrial (mt) genomes of the deep-sea squid (Bathyteuthis abyssicola; supperfamily Bathyteuthoidea), the bob-tail squid (Semirossia patagonica; order Sepiolida) and four giant cuttlefish (Sepia apama, S. latimanus, S. lycidas and S. pharaonis; order Sepiida). The unique structures of the mt genomes of Bathyteuthis and Semirossia provide new information about the evolution of decapodiform mt genomes. We show that the mt genome of B. abyssicola, like those of other oegopsids studied so far, has two long duplicated regions that include seven genes (COX1-3, ATP6 and ATP8, tRNA(Asn), and either ND2 or ND3) and that one of the duplicated COX3 genes has lost its function. The mt genome of S. patagonica is unlike any other decapodiforms and, like Nautilus, its ATP6 and ATP8 genes are not adjacent to each other. The four giant cuttlefish have identical mt gene order to other cuttlefish determined to date. Molecular phylogenetic analyses using maximum likelihood and Bayesian methods suggest that traditional order Sepioidea (Sepiolida+Sepiida) is paraphyletic and Sepia (cuttlefish) has the sister-relationship with all other decapodiforms. Taking both the phylogenetic analyses and the mt gene order analyses into account, it is likely that the octopus-type mt genome is an ancestral state and that it had maintained from at least the Cephalopoda ancestor to the common ancestor of Oegopsida, Myopsida and Sepiolida.

Gene Arrangements in Expression Vector Affect 3-Hydroxypropionic Acid Production in Klebsiella pneumoniae.

Biosynthesis of 3-hydroxypropionic acid (3-HP) typically involves two sequential reactions catalyzed by glycerol dehydratase (DhaB) and aldehyde dehydrogenase (AldH). Although plasmid-dependent over-expression of the two enzymes is common, systematic investigation of gene arrangement in vector has not been reported. Here we show that gene arrangements have a noticeable influence on 3-HP production. Using Klebsiella pneumoniae as a host, three AldH-coding genes: ald4 from Saccharomyces cerevisiae, aldh from Escherichia coli, and puuC from host K. pneumoniae, were respectively ligated to dhaB. The recombinant Kp/pET-pk-ald4-dhaB (Kp refers to as K. pneumoniae, pk is a native promoter) produced the highest yield of 3-HP in comparison to both Kp/pET-pk-dhaB-ald4 and Kp/pET-pk-dhaB-pk-ald4, suggesting that the preferential expression of AldH can increase 3-HP production. Additionally, when different AldH-coding genes were respectively ligated downstream of dhaB, the recombinant Kp/pET-pk-dhaB-puuC produced more 3-HP than that by Kp/pET-pk-dhaB-aldh or Kp/pET-pk-dhaB-ald4, implying the intrinsic compatibility of native gene puuC with its host. These findings indicate the applicability of native AldH-coding gene and provide insights into strategies for metabolic engineering of multiple genes.

Characterization and Comparison of the Two Mitochondrial Genomes in the Genus Rana.

The mitochondrial genome (mitogenome) possesses several invaluable attributes, including limited recombination, maternal inheritance, a fast evolutionary rate, compact size, and relatively conserved gene arrangement, all of which make it particularly useful for applications in phylogenetic reconstruction, population genetics, and evolutionary research. In this study, we aimed to determine the complete mitogenomes of two morphologically similar Rana species (Rana hanluica and Rana longicrus) using next-generation sequencing. The entire circular mitogenome was successfully identified, with a length of 19,395 bp for R. hanluica and 17,833 bp for R. longicrus. The mitogenomes of both species contained 37 genes, including 13 protein-coding genes (PCGs), two ribosomal RNA genes, 22 transfer RNA genes, and one control region; mitogenome size varied predominantly with the length of the control region. The two synonymous codon usages in 13 PCGs showed that T and A were used more frequently than G and C. The ratios of non-synonymous to synonymous substitutions of all 13 PCGs were <1 in the Rana species, indicating that the PCGs were under purifying selection. Finally, phylogenetic relationship analyses suggested that R. hanluica and R. longicrus were classified in the R. japonica group. Our study provides valuable reference material for the taxonomy of the genus Rana.

Comparative Mitogenomics of Jumping Spiders with First Complete Mitochondrial Genomes of Euophryini (Araneae: Salticidae).

Salticidae is the most species-rich family of spiders with diverse morphology, ecology and behavior. However, the characteristics of the mitogenomes within this group are poorly understood with relatively few well-characterized complete mitochondrial genomes. In this study, we provide completely annotated mitogenomes for Corythalia opima and Parabathippus shelfordi, which represent the first complete mitogenomes of the tribe Euophryini of Salticidae. The features and characteristics of the mitochondrial genomes are elucidated for Salticidae by thoroughly comparing the known well-characterized mitogenomes. The gene rearrangement between trnL2 and trnN was found in two jumping spider species, Corythalia opima and Heliophanus lineiventris Simon, 1868. Additionally, the rearrangement of nad1 to between trnE and trnF found in Asemonea sichuanensis Song & Chai, 1992 is the first protein-coding gene rearrangement in Salticidae, which may have an important phylogenetic implication for the family. Tandem repeats of various copy numbers and lengths were discovered in three jumping spider species. The codon usage analyses showed that the evolution of codon usage bias in salticid mitogenomes was affected by both selection and mutational pressure, but selection may have played a more important role. The phylogenetic analyses provided insight into the taxonomy of Colopsus longipalpis (Zabka, 1985). The data presented in this study will improve our understanding of the evolution of mitochondrial genomes within Salticidae.

Comparative analysis of the mitochondrial genomes of the family Mactridae (Mollusca: Venerida) and their phylogenetic implications.

Taxonomy and phylogenetic relationships within the family Mactridae have remained debatable because of the plasticity of morphological characteristics and the lack of accurate molecular data, thereby resulting in abundant synonyms and taxa rearrangements. Mitochondrial genomes (mitogenomes) have been widely used as powerful tools to reconstruct phylogenies of various groups of mollusks; however, they have not been used for studying the phylogeny of mactrids specifically. In the present study, mitogenomes of seven Mactridae species, namely Mactra chinensis, Mactra cygnus, Mactra quadrangularis, Mactra cumingii, Mactrinula dolabrata, Raeta pulchella, and Raeta sp., were sequenced by Illumina high-throughput sequencing, and a comparative mitochondrial genomic analysis was conducted. The newly sequenced mitogenomes were double-stranded circular molecules, with all functional genes encoded on the heavy strand. All the new mactrid mitogenomes had two rRNA genes (12S and 16S), 13 protein-coding genes (PCGs) (atp6, cox1, cox2, cox3, cytb, nad1, nad2, nad3, nad4, nad4l, nad5, nad6, and atp8), and 22 tRNAs. The mitogenomes showed considerable variation in AT content, GC skew, and AT skew. The results of the phylogenetic analysis confirmed monophyly of the family Mactridae and suggested that genera Mactrinula, Spisula, Rangia, and Mulinia should not be placed under subfamily Mactrinae. Our results supported that potential cryptic species existed in Mactra antiquata. We also proposed subfamily Kymatoxinae should belong to the family Mactridae rather than Anatinellidae and Mactra alta in China should be Mactra cygnus. Additionally, conservation in functional gene arrangement was found in genera Mactra, Raeta, and Lutraria. But gene orders in S. sachalinensis and S. solida were quite different, questioning their congeneric relationship. Our results further suggested that the taxonomy within the family Mactridae requires an integrative revision.

Novel gene rearrangements in mitochondrial genomes of four families of praying mantises (Insecta, Mantodea) and phylogenetic relationships of Mantodea.

The mitochondrial genome (mitogenome) plays an important role in phylogenetic studies of many species. The mitogenomes of many praying mantis groups have been well-studied, but mitogenomes of special mimic praying mantises, especially Acanthopoidea and Galinthiadoidea species, are still sorely lacking in the NCBI database. The present study analyzes five mitogenomes from four species of Acanthopoidea (Angela sp., Callibia diana, Coptopteryx sp., Raptrix fusca) and one of Galinthiadoidea (Galinthias amoena) that were sequenced by the primer-walking method. Among Angela sp. and Coptopteryx sp., three gene rearrangements were detected in ND3-A-R-N-S-E-F and COX1-L2-COX2 gene regions, two of which were novel. In addition, individual tandem repeats were found in control regions of four mitogenomes (Angela sp., C. diana, Coptopteryx sp., G. amoena). For those, plausible explanations were derived from the tandem duplication-random loss (TDRL) model and the slipped-strand mispairing model. One potential motif was found in Acanthopidae that was seen as a synapomorphy. Several conserved block sequences (CBSs) were detected within Acanthopoidea that paved the way for the design of specific primers. Via BI and ML analysis, based on four datasets (PCG12, PCG12R, PCG123, PCG123R), the merged phylogenetic tree within Mantodea was reconstructed. This showed that the monophyly of Acanthopoidea was supported and that the PCG12R dataset was the most suitable for reconstructing the phylogenetic tree within Mantodea.

Complete mitochondrial genome of Ovalona pulchella (Branchiopoda, Cladocera) as the first representative in the family Chydoridae: Gene rearrangements and phylogenetic analysis of Cladocera.

Chydoridae are phytophilic-benthic microcrustaceans that make up a significant proportion of species diversity and play an important role in the littoral zone of freshwater ecosystems worldwide. Here, we provide the complete mitochondrial genome of Ovalona pulchella (King, 1853), determined by next-generation sequencing. The entire mitochondrial genome is 15,362 bp in length; this is the first sequenced mitochondrial genome in the family Chydoridae. The base composition and codon usage were typical of Cladocera species. The mitochondrial gene arrangement (37 genes) was not consistent with that of other Branchiopoda. Both maximum likelihood and Bayesian analyses supported each suborder and family of Branchiopoda as monophyletic groups. The relationships among the families were as follows: [(Leptestheriidae + Limnadiidae) + (Sididae + (Bosminidae + (Chydoridae + Daphniidae)))] + Triopsidae. The newly sequenced O. pulchella was most closely related to the family Daphniidae. The complete mitochondrial genome of O. pulchella also provides valuable molecular information for further analysis of the phylogeny of the Chydoridae and the taxonomic status of the Branchiopoda.

Complete Mitochondrial Genomes and Phylogenetic Positions of Two Longicorn Beetles, Anoplophora glabripennis and Demonax pseudonotabilis (Coleoptera: Cerambycidae).

Anoplophora glabripennis (Motschulsky, 1854) and Demonax pseudonotabilis Gressitt & Rondon, 1970 are two commonly found longicorn beetles from China. However, the lack of sufficient molecular data hinders the understanding of their evolution and phylogenetic relationships with other species of Cerambycidae. This study sequenced and assembled the complete mitochondrial genomes of the two species using the next-generation sequencing method. The mitogenomes of A. glabripennis and D. pseudonotabilis are 15,622 bp and 15,527 bp in length, respectively. The mitochondrial gene content and gene order of A. glabripennis and D. pseudonotabilis are highly conserved with other sequenced longicorn beetles. The calculation of nonsynonymous (Ka) and synonymous (Ks) substitution rates in PCGs indicated the existence of purifying selection in the two longicorn beetles. The phylogenetic analysis was conducted using the protein-coding gene sequences from available mitogenomes of Cerambycidae. The two species sequenced in this study are, respectively, grouped with their relatives from the same subfamily. The monophyly of Cerambycinae, Dorcasominae, Lamiinae, and Necydalinae was well-supported, whereas Lepturinae, Prioninae, and Spondylidinae were recovered as paraphyletic.

Comparative Mitogenomics of True Frogs (Ranidae, Anura), and Its Implications for the Phylogeny and Evolutionary History of Rana.

The true frogs of the genus Rana are a complex and diverse group, containing approximately 60 species with wide distribution across Eurasia and the Americas. Recently, many new species have been discovered with the help of molecular markers and morphological traits. However, the evolutionary history in Rana was not well understood and might be limited by the absence of mitogenome information. In this study, we sequenced and annotated the complete mitochondrial genome of R. longicrus and R. zhenhaiensis, containing 22 tRNAs, 13 protein-coding genes, two ribosomal RNAs, and a non-coding region, with 17,502 bp and 18,006 bp in length, respectively. In 13 protein codon genes, the COI was the most conserved, and ATP8 had a fast rate of evolution. The Ka/Ks ratio analysis among Rana indicated the protein-coding genes were suffering purify selection. There were three kinds of gene arrangement patterns found. The mitochondrial gene arrangement was not related to species diversification, and several independent shifts happened in evolutionary history. Climate fluctuation and environmental change may have played an essential role in species diversification in Rana. This study provides mitochondrial genetic information, improving our understanding of mitogenomic structure and evolution, and recognizes the phylogenetic relationship and taxonomy among Rana.

Characterization of the mitochondrial genome of Tetrameres grusi and insights into the phylogeny of Spirurina.

Tetrameres grusi is a significant parasitic nematode of cranes that is classified into suborder Spirurina. However, for more than a century, this classification has been controversial. Mitochondrial genomes are valuable resources for parasite taxonomy, population genetics and systematics studies. Here, the mitochondrial genome of T. grusi was determined and subsequently compared with those from Spirurina species using concatenated datasets of amino acid sequences predicted from mitochondrial protein-coding genes. The complete mitochondrial genome of T. grusi is circular with 13,709 bp, and it contains 12 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes and one non-coding region. All of the protein-coding genes are transcribed in the same direction. There were 18 intergenic spacers of 1-44 bp, and six locations with gene overlaps, ranging from 1 bp to 28 bp, in the mitochondrial genome of T. grusi. The AT content of this mitochondrial genome was 71.56%. This was similar to mitochondrial genomes of other Spirurina species, which also exhibited strong AT content bias, not only in the nucleotide composition but also in codon usage. The sequenced mitogenomes of the 25 Spirurina nematodes showed three classes of gene arrangements based on the 12 protein-coding genes, and the gene arrangement of the T. grusi mitochondrial genome belonged to the Class I. Phylogenetic analyses using mitochondrial genomes of 25 Spirurina nematodes revealed that T. grusi (Habronematoidea) was closer to Gongylonema pulchrum (Spiruroidea) than Spirocerca lupi (Thelazioidea). The availability of the complete mitochondrial genome sequence of T. grusi provides new and useful genetic markers for further studies on Spirurina nematodes.