The complete nucleotide sequence of the mitochondrial genome (mitogenome) of Geisha distinctissima (Hemiptera: Flatidae) has been determined in this study. The genome is a circular molecule of 15,971 bp with a total A+T content of 75.1%. The gene content, order, and structure are consistent with the Drosophila yakuba genome structure and the hypothesized ancestral arthropod genome arrangement. All 13 protein-coding genes are observed to have a putative, inframe ATR methionine or ATT isoleucine codons as start signals. Canonical TAA and TAG termination codons are found in nine protein-coding genes, and the remaining four (cox1, atp6, cox3, and nad4) have incomplete termination codons. The anticodons of all transfer RNA (tRNAs) are identical to those observed in D. yakuba and Philaenus spumarius, and can be folded in the form of a typical clover-leaf structure except for tRNA(Ser(AGN)). The major non-coding region (the A+T-rich region or putative control region) between the small ribosomal subunit and the tRNA(Ile) gene includes two sets of repeat regions. The first repeat region consists of a direct 152-bp repetitive unit located near the srRNA gene end, and the second repeat region is composed of a direct repeat unit of 19 bp located toward tRNA(Ile) gene. Comparisons of gene variability across the order suggest that the gene content and arrangement of G. distinctissima mitogenome are similar to other hemipteran insects.
Molecular surveys are leading to the discovery of many new cryptic species of marine algae. This is particularly true for red algal intertidal species, which exhibit a high degree of morphological convergence. DNA sequencing of recent collections of Gelidium along the coast of California, USA, identified two morphologically similar entities that differed in DNA sequence from existing species. To characterize the two new species of Gelidium and to determine their evolutionary relationships to other known taxa, phylogenomic, multigene analyses, and morphological observations were performed. Three complete mitogenomes and five plastid genomes were deciphered, including those from the new species candidates and the type materials of two closely related congeners. The mitogenomes contained 45 genes and had similar lengths (24,963-24,964 bp). The plastid genomes contained 232 genes and were roughly similar in size (175,499-177,099 bp). The organellar genomes showed a high level of gene synteny. The two Gelidium species are diminutive, turf-forming, and superficially resemble several long established species from the Pacific Ocean. The phylogenomic analysis, multigene phylogeny, and morphological evidence confirms the recognition and naming of two new species, describe herein as G. gabrielsonii and G. kathyanniae. On the basis of the monophyly of G. coulteri, G. gabrielsonii, G. galapagense, and G. kathyanniae, we suggest that this lineage likely evolved in California. Organellar genomes provide a powerful tool for discovering cryptic intertidal species and they continue to improve our understanding of the evolutionary biology of red algae and the systematics of the Gelidiales.
The complete mitochondrial genome is greatly important for studies on genetic structure and phylogenetic relationship at various taxonomic levels. To obtain information about the evolutionary trends of mtDNA in the Ulvophyceae and also to gain insights into the phylogenetic relationships between ulvophytes and other chlorophytes, we determined the mtDNA sequence of Caulerpa lentillifera (sea grape) using de novo mitochondrial genome sequencing. The complete genomic DNA of C. lentillifera was circular and 209,034 bp in length, and it was the largest green-algal mitochondrial genome sequenced to date, with a low gene density of 65.2%, which is reminiscent of the "expanded" pattern of evolution exhibited by embryophyte mtDNAs. The C. lentillifera mtDNA consisted of a typical set of 17 protein-coding genes (PCGs), 20 transfer RNA (tRNA) genes, three ribosomal RNA (rRNA) genes, 42 putative open reading frames (ORFs) and 29 introns, which had homologs in green-algal mtDNAs displaying an "ancestral" or a "reduced-derived" pattern of evolution. The overall base composition of its mitochondrial genome was 24.19% for A, 24.94% for T, 25.80% for G, 25.07% for C and 50.87% for GC. The mitochondrial genome of C. lentillifera was characterized by numerous small intergenic regions and introns, which was clearly different from other green algae. With the exception of the NADH dehydrogenase subunit 6 (ND6), ND1, ATP and three tRNA genes (tRNA-His, tRNA-Thr and tRNA-Ala), all other mitochondrial genes were encoded on the heavy strand. All of the PCGs had ATG as their start codon and employed TAA, TGA or TAG as their termination codon. To gain insights into the evolutionary trends of mtDNA in the Ulvophyceae, we inferred the complete mtDNA sequence of C. lentillifera, an ulvophyte belonging to a distinct, early-diverging lineage. Taken together, our data offered useful information for the studies on phylogenetic hypotheses and phylogenetic relationships of C. lentillifera within the Chlorophyta.
We sequenced and annotated the complete mitochondrial genome (mitogenome) of Bactrocera diaphora (Diptera: Tephtitidae), which is an economically important pest in the southwest area of China, India, Sri Lanka, Vietnam and Malaysia. This mitogenome is 15 890 bp in length with an A + T content of 74.103%, and contains 37 typical animal mitochondrial genes that are arranged in the same order as that of the inferred ancestral insects. All protein-coding genes (PCGs) start with a typical ATN codon, except cox1 that begins with TCG. Ten PCGs stop with termination codon TAA or TAG, whereas cox1, nad1 and nad5 have single T-- as the incomplete stop codon. All of the transfer RNA genes present the typical clover leaf secondary structure except trnS1 (AGN) with a looping D-arm. The A + T-rich region is located between rrnS and trnI with a length of 946 bp, and contains a 20 bp poly-T stretch and 22 bp poly-A stretch. Except the control region, the longest intergenic spacer is located between trnR and trnN that is 94 bp long with an excessive high A + T content (95.74%) and a microsatellite-like region (TA)13.
The complete nucleotide sequence of the mitochondrial genome of the white rhinoceros, Ceratotherium simum, was determined. The length of the reported sequence is 16,832 nucleotides. This length can vary, however, due to pronounced heteroplasmy caused by differing numbers of a repetitive motif (5'-CG-CATATACA-3') in the control region. The 16,832 nucleotide sequence presented here is the longest version of the molecule and contains 35 copies of this motif. Comparison between the complete mitochondrial sequences of the white and the Indian (Rhinoceros unicornis) rhinoceroses allowed an estimate of the date of the basal evolutionary divergence among extant rhinoceroses. The calculation suggested that this divergence took place approximately 27 million years before present.
The nucleotide sequence of the mitochondrial DNA (mtDNA) of the harbor seal, Phoca vitulina, was determined. The total length of the molecule was 16,826 bp. The organization of the coding regions of the molecule conforms with that of other mammals, but the control region is unusually long. A considerable portion of the control region is made up of short repeats with the motif GTACAC particularly frequent. The two rRNA genes and the 13 peptide-coding genes of the harbor seal, fin whale, cow, human, mouse, and rat were compared and the relationships between the different species assessed. At ordinal level the 12S rRNA gene and 7 out of the 13 peptide-coding genes yielded a congruent topological tree of the mtDNA relationship between the seal, cow, whale, human, and the rodents. In this tree the whale and the cow join first, and this clade is most closely related to the seal.
The first complete mitochondrial genome sequence for a nemertean, Cephalothrix simula, was determined by conventional and long PCR and sequencing with primer walking methods. This circular genome is 16,296 bp in size and encodes 37 genes (13 protein-coding genes, 2 ribosomal RNAs, and 22 transfer RNAs) typically found in metazoans. All genes are encoded on H-strand except two tRNAs (trnT and trnP). It differs from those reported for other metazoans, but some gene junctions are shared with those of other protostomes. Structure of the mitochondrial genome of C. simula is mostly concordant with the partial mitochondrial genome known for Cephalothrix rufifrons, but notable differences include three large indel events and transposition of 2 tRNAs. Nucleotide composition of the mitochondrial genome of C. simula is highly A+T biased. The compositional skew is strongly reflected in the codon-usage patterns and the amino acid compositions of the mitochondrial proteins. An AT-rich noncoding region with potential to form stem-loop structures may be involved in the initiation of replication or transcription. Gene adjacencies and phylogenetic analysis based on the 12 concatenated amino acid sequences (except atp8) of mitochondrial protein-coding genes show that the nemertean is close to the coelomate lophotrochozoans, rather than the acoelomate platyhelminths.
Four new complete mitochondrial genomes (mitogenomes) from the two superfamilies Ocypodoidea and Grapsoidea were sequenced, which represented Uca (Gelasimus) borealis (Ocypodidae: Ucinae), Dotilla wichmani (Dotillidae), Metopograpsus quadridentatus (Grapsidae: Grapsinae), and Gaetice depressus (Varunidae: Gaeticinae). All of the mitogenomes shared the complete set of 37 mitochondrial genes. Mitogenome lengths were 15,659, 15,600, 15,517, and 16,288 bp, respectively, with A + T contents of 69.41%, 68.46%, 70.30%, and 72.96%, respectively. Comparative genomic analyses suggested that they exhibited different genomic rearrangements. In particular, G. depressus shared a major rearrangement pattern present in Eriocheir crabs, while the remainder shared the brachyuran ground genomic rearrangement patterns. Phylomitogenomic inferences provided new evidence for the strongly supported nesting of Thoracotremata within Heterotremata clades. A close phylogenetic relationship was observed between Varunidae and Macrophthalmidae crabs, and between Dotillidae and Grapsidae crabs, which was consistent with mitochondrial genomic rearrangement similarities. Altogether, these results suggest the presence of reciprocal paraphyly for Ocypodoidea and Grapsoidea.
Ceratitis fasciventris is a serious agricultural pest of the Tephritidae family that belongs to the African Ceratitis FAR species complex. Species limits within the FAR complex are obscure and multidisciplinary approaches have attempted to resolve phylogenetic relationships among its members. These studies support the existence of at least three additional species in the complex, C. anonnae, C. rosa and C. quilicii, while they indicate the presence of two structured populations (F1 and F2) within the C. fasciventris species. In the present study we present the mitotic karyotype, polytene chromosome maps, in situ hybridization data and the complete mitochondrial genome sequence of an F2 population of C. fasciventris. This is the first polytene chromosome map and complete mitogenome of a member of the FAR complex and only the second reported for the Ceratitis genus. Both polytene chromosomes and mitochondrial sequence could provide valuable information and be used as reference for comparative analysis among the members of the complex towards the clarification of their phylogenetic relationships.
We analyze mitochondrial genomes to reconstruct a robust phylogenetic framework for caecilian amphibians and use this to investigate life-history evolution within the group. Our study comprises 45 caecilian mitochondrial genomes (19 of them newly reported), representing all families and 27 of 32 currently recognized genera, including some for which molecular data had never been reported. Support for all relationships in the inferred phylogenetic tree is high to maximal, and topology tests reject all investigated alternatives, indicating an exceptionally robust molecular phylogenetic framework of caecilian evolution consistent with current morphology-based supraspecific classification. We used the mitogenomic phylogenetic framework to infer ancestral character states and to assess correlation among three life-history traits (free-living larvae, viviparity, specialized pre-adult or vernal teeth), each of which occurs only in some caecilian species. Our results provide evidence that an ancestor of the Seychelles caecilians abandoned direct development and re-evolved a free-living larval stage. This study yields insights into the concurrent evolution of direct development and of vernal teeth in an ancestor of Teresomata that likely gave rise to skin-feeding (maternal dermatophagy) behavior and subsequently enabled evolution of viviparity, with skin feeding possibly a homologous precursor of oviduct feeding in viviparous caecilians.