The complete mitochondrial genome of Rhacophorus dennysi (Anura: Rhacophoridae) and phylogenetic analysis

Two-Fold ND5 Genes, Three-Fold Control Regions, lncRNA, and the "Missing" ATP8 Found in the Mitogenomes of Polypedates megacephalus (Rhacophridae: Polypedates)

In prior research on the mitochondrial genome (mitogenome) of Polypedates megacephalus, the one copy of ND5 gene was translocated to the control region (CR) and the ATP8 gene was not found. Gene loss is uncommon among vertebrates. However, in this study, we resequenced the mitogenomes of P. megacephalus from different regions using a "primer bridging" approach with Sanger sequencing technologies, which revealed the "missing" ATP8 gene in P. megacephalus as well as three other previously published Polypedates. The mitogenome of this species was found to contain two copies of the ND5 genes and three copies of the control regions. Furthermore, multiple tandem repeats were identified in the control regions. Notably, we observed that there was no correlation between genetic divergence and geographic distance. However, using the mitogenome, gene expression analysis was performed via RT-qPCR of liver samples and it was thus determined that COIII, ND2, ND4, and ND6 were reduced to 0.64 ± 0.24, 0.55 ± 0.34, 0.44 ± 0.21 and 0.65 ± 0.17, respectively, under low-temperature stress (8 °C) as compared with controls (p < 0.05). Remarkably, the transcript of long non-coding RNA (lncRNA) between positions 8029 and 8612 decreased significantly with exposure to low-temperature stress (8 °C). Antisense ND6 gene expression showed a downward trend, but this was not significant. These results reveal that modulations of protein-coding mitochondrial genes and lncRNAs of P. megacephalus play a crucial role in the molecular response to cold stress.

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

Simple Summary

Duplicated 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.

Abstract

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.

Complete mitochondrial genome sequence of Japanese forest green tree frog (Rhacophorus arboreus)

We determined the complete mitochondrial genome sequence of the Japanese forest green tree frog (Rhacophorus arboreus). The mitochondrial genome is 22,236 bp in length, which encodes 13 protein-coding genes, 2 rRNA, and 22 tRNA genes, and two control regions (D-loops). The whole gene arrangement of R. arboreus was the same as that of Rhacophorus omeimontis and Rhacophorus schlegelii.

Characterization of complete mitochondrial genome of Hylarana guentheri (Anura: Ranidae) and its phylogenetic implication

The Günther’s frog (Hylarana guentheri) belongs to a member of the family Ranidae. We provide a complete mitogenome of H. guentheri and examine its phylogenetic position with other related species. Its mitogenome is a closed circular molecule 18,698 bp in length including 13 protein coding genes, 22 tRNA coding genes, two rRNA-coding genes, and a control region (CR) that are conserved in most Ranidae mitogenomes. The overall base composition of the H. guentheri mitogenome is 29.27% A, 30.45% T, 26.14% C, and 14.15% G, which is typical for Amphibious animals’ mitochondrial genomes. The alignment of the Ranidae species control regions showed high levels of genetic variation and abundant AT content. Seven tandem repeats were found in the control region. Phylogenetic analysis with Bayesian inference and maximum likelihood based on 13 protein-coding genes indicated that H. guentheri is more closely related to Nidirana okinavana than to Babina subaspera and B. holsti. The complete mitogenome of H. guentheri provides a potentially useful resource for further exploration of the taxonomic status and phylogenetic relationships of Hylarana and related species.

The complete mitochondrial genome of Pyxicephalus adspersus: high gene rearrangement and phylogenetics of one of the world's largest frogs

The family Pyxicephalidae including two subfamilies (Cacosterninae and Pyxicephalinae) is an ecologically important group of frogs distributed in sub-Saharan Africa. However, its phylogenetic position among the Anura has remained uncertain. The present study determined the complete mitochondrial genome sequence of Pyxicephalus adspersus, the first representative mitochondrial genome from the Pyxicephalinae, and reconstructed the phylogenetic relationships within Ranoidae using 10 mitochondrial protein-coding genes of 59 frog species. The P. adspersus mitochondrial genome showed major gene rearrangement and an exceptionally long length that is not shared with other Ranoidae species. The genome is 24,317 bp in length, and contains 15 protein-coding genes (including extra COX3 and Cyt b genes), four rRNA genes (including extra 12S rRNA and 16S rRNA genes), 29 tRNA genes (including extra tRNALeu (UAG), tRNALeu (UUR), tRNAThr , tRNAPro , tRNAPhe , tRNAVal , tRNAGln genes) and two control regions (CRs). The Dimer-Mitogenome and Tandem duplication and random loss models were used to explain these gene arrangements. Finally, both Bayesian inference and maximum likelihood analyses supported the conclusion that Pyxicephalidae was monophyletic and that Pyxicephalidae was the sister clade of (Petropedetidae + Ptychadenidae).

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.

Next-generation sequencing of mixed genomic DNA allows efficient assembly of rearranged mitochondrial genomes in Amolops chunganensis and Quasipaa boulengeri

Recent improvements in next-generation sequencing (NGS) technologies can facilitate the obtainment of mitochondrial genomes. However, it is not clear whether NGS could be effectively used to reconstruct the mitogenome with high gene rearrangement. These high rearrangements would cause amplification failure, and/or assembly and alignment errors. Here, we choose two frogs with rearranged gene order, Amolops chunganensis and Quasipaa boulengeri, to test whether gene rearrangements affect the mitogenome assembly and alignment by using NGS. The mitogenomes with gene rearrangements are sequenced through Illumina MiSeq genomic sequencing and assembled effectively by Trinity v2.1.0 and SOAPdenovo2. Gene order and contents in the mitogenome of A. chunganensis and Q. boulengeri are typical neobatrachian pattern except for rearrangements at the position of "WANCY" tRNA genes cluster. Further, the mitogenome of Q. boulengeri is characterized with a tandem duplication of trnM. Moreover, we utilize 13 protein-coding genes of A. chunganensis, Q. boulengeri and other neobatrachians to reconstruct the phylogenetic tree for evaluating mitochondrial sequence authenticity of A. chunganensis and Q. boulengeri. In this work, we provide nearly complete mitochondrial genomes of A. chunganensis and Q. boulengeri.