Mitochondrial 16S Research Articles

Phylogenetic placement and description of Ngaliadessus humphreysi gen. et sp. nov., Watts & Villastrigo (Coleoptera: Dytiscidae), a subterranean diving beetle from the Ngalia Basin in central Australia

AbstractThe largest diversity in the world of subterranean diving beetles (Dytiscidae) has been discovered in underground waters of the Australian arid zone. The majority of species are from the Dytiscidae genera Limbodessus Guignot, 1939 (Bidessini) and Paroster Sharp, 1882 (Hydroporini) and are distributed within two major regions: calcrete islands of central Western Australia and the Ngalia Basin of the Northern Territory. Here, we use an integrative approach based on morphological and molecular analyses to describe Ngaliadessus humphreysi gen. et sp. nov. Watts & Villastrigo representing a new genus and species of stygobiotic Bidessini collected from a single well in the Ngalia Basin. Phylogenetic analyses using whole mitochondrial genome, Histone 3 and 18S rRNA data, representing a comprehensive coverage of Bidessini genera, support the distinction of the genus and species as a separate evolutionary lineage sister to the Australasian genus Limbodessus and the widely distributed genus Allodessus Guignot, 1953. Our study further confirms that the Ngalia Basin, containing 13 subterranean dytiscid species from four distinct genera, is one of the most speciose areas within the world's most diverse hotspot of subterranean diving beetles.

DNA metabarcoding of mock communities highlights potential biases when assessing Neotropical fish diversity

AbstractDespite the increasing popularity of DNA metabarcoding in the assessment of aquatic ecosystems using fish eDNA or ichthyoplankton, challenges have hampered its broader application in the Neotropical freshwaters. Using five mock communities composed of fish species from two Neotropical River basins, we evaluated the influence of DNA concentration and choice of mitochondrial 12S molecular markers (MiFish, NeoFish, and Teleo) on species detection and relative read abundance (RRA) using DNA metabarcoding. Of the three 12S markers analyzed, only MiFish detected all species from all mock communities. The performance of a taxonomy‐free approach using ASV/MOTUs was not as precise as assigning DNA reads to species using a curated 12S library that includes approximately 100 fish species since more than one ASV/MOTU was observed for the same specimen. Thus, here we showcase the importance of a custom reference database to allow precise assignment of Neotropical fish species in metabarcoding studies and that the RRA is dependent on community composition, marker, and DNA concentration. We highlight the importance of controlled experiments using known species communities before large investments are made in assessing biodiversity using non‐invasive methods that apply DNA metabarcoding.

A massive infestation of the long-legged buzzard, Buteo rufinus (Cretzschmar), by Hyalomma marginatum Koch (Acari: Ixodidae) ticks in Türkiye

Ticks are obligate blood-sucking ectoparasites of vertebrate animals, including mammals, birds, reptiles, and even amphibians. As a suitable host, birds may carry and spread ticks and serve as reservoirs for some tick-borne pathogens. The present study reports an impressive tick infestation on a long-legged buzzard, Buteo rufinus (Cretzschmar), in Türkiye. One hundred fifty-nine engorged nymphal ticks were removed with tweezers from a B. rufinus in the Wildlife Rescue Rehabilitation, Training, Practice, and Research Center (AKUREM), Afyon Kocatepe University, Afyonkarahisar province, Türkiye. All ticks were morphologically identified as the Hyalomma marginatum group. For accurate species identification, a molecular study on randomly selected two engorged nymphs was performed through Polymerase Chain Reaction (PCR) amplification of a ~460 bp fragment of the mitochondrial 16S rRNA gene. Comparing our mitochondrial 16S rRNA sequences with those from the NCBI Genbank database showed that our ticks have a significant genetic similarity over 99% with Hyalomma marginatum Koch. Further, the extracted tick DNAs were also screened for the presence of Rickettsia, Borrelia and Bartonella bacteria targeting the rickettsial citrate synthase (gltA, ~750 bp), flagellin B (flaB, ~659 bp), NADH dehydrogenase gamma subunit (nuoG, ~346) genes, respectively; but samples were negative for these bacteria. To our knowledge, this is the first report of H. marginatum infesting B. rufinus in Türkiye and the first observation of the massive infestation of H. marginatum on B. rufinus.

Integrative revision of the Blommersia wittei complex, with description of a new species of frog from western and north-western Madagascar.

Frogs of the Blommersia wittei complex are widespread in western and northern Madagascar, and are one of two clades of the family Mantellidae that have colonized the Comoran island of Mayotte. Based on a comprehensive set of DNA sequences of the mitochondrial 16S rRNA gene and the nuclear-encoded RAG1 and SACS genes, integrated with morphological and bioacoustic data, we here analyze the genetic differentiation of populations of this complex across Madagascar. We confirm that a candidate species named B. sp. Ca5 in previous studies represents a genetically well-defined evolutionary lineage distributed over much of western Madagascar, which we describe herein as Blommeria bara sp. nov. based on its molecular and bioacoustic differentiation. Blommersia wittei occurs across northern Madagascar but its type locality Ambanja, at the lower Sambirano river, is very close to the range of another, newly discovered microendemic lineage that was only found at two sites along the upper Sambirano river (here named as candidate species B. sp. Ca12). The B. wittei complex thus provides an example of a clade of closely related Malagasy frogs that contains species widespread over hundreds of kilometers, as well as extreme microendemics. For a full resolution of this species complex, more data need to be collected on the geographical contact among these two lineages, on the morphology and bioacoustics of B. sp. Ca12, and on the north-eastern populations of B. wittei at Sambava, which are weakly differentiated in mitochondrial genes but differ in bioacoustics and possibly in the extent of foot webbing.

Description of a New Species of Hua (Gastropoda: Semisulcospiridae) from Guizhou, China, Based on Morphology and Molecular Evidence.

A new species of Hua, Hua qiannanensis sp. nov., is described from Guizhou Province, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: the smooth shell, only three smaller cusps of lateral teeth on the inner side, outer marginal teeth with eight flattened and rounded denticles, an ovipositor pore in females, and BW/H ≥ 80%, B/H = 76.8-82.3%. Molecular analysis based on partial mitochondrial COI and 16S rDNA also supports the systematic position of the new taxon.

Cancer-cell-secreted extracellular vesicles target p53 to impair mitochondrial function in muscle.

Skeletal muscle loss and weakness are associated with bad prognosis and poorer quality of life in cancer patients. Tumor-derived factors have been implicated in muscle dysregulation by inducing cachexia and apoptosis. Here, we show that extracellular vesicles secreted by breast cancer cells impair mitochondrial homeostasis and function in skeletal muscle, leading to decreased mitochondrial content and energy production and increased oxidative stress. Mechanistically, miR-122-5p in cancer-cell-secreted EVs is transferred to myocytes, where it targets the tumor suppressor TP53 to decrease the expression of TP53 target genes involved in mitochondrial regulation, including Tfam, Pgc-1α, Sco2, and 16S rRNA. Restoration of Tp53 in muscle abolishes mitochondrial myopathology in mice carrying breast tumors and partially rescues their impaired running capacity without significantly affecting muscle mass. We conclude that extracellular vesicles from breast cancer cells mediate skeletal muscle mitochondrial dysfunction in cancer and may contribute to muscle weakness in some cancer patients.

Results of combined newborn hearing and deafness gene screening in Yuncheng area of Shanxi Province

To analyze the clinical significance of combined newborn hearing and deafness gene screening in Yuncheng area of Shanxi Province. Results of audiological examinations, including transient evoked otoacoustic emission and automatic discriminative auditory brainstem evoked potentials, for 6 723 newborns born in Yuncheng area from January 1, 2021 to December 31, 2021, were retrospectively analyzed. Those who failed one of the tests were considered to have failed the examination. A deafness-related gene testing kit was used to detect 15 hot spot variants of common deafness-associated genes in China including GJB2, SLC26A4, GJB3, and mtDNA12S rRNA. Neonates who had passed the audiological examinations and those who had not were compared using a chi-square test. Among the 6 723 neonates, 363 (5.40%) were found to carry variants. These have included 166 cases (2.47%) with GJB2 gene variants, 136 cases (2.03%) with SLC26A4 gene variants, 26 cases (0.39%) with mitochondrial 12S rRNA gene variants, and 33 cases (0.49%) with GJB3 gene variants. Among the 6 723 neonates, 267 had failed initial hearing screening, among which 244 had accepted a re-examination, for which 14 cases (5.73%) had failed again. This has yielded an approximate prevalence of hearing disorder of 0.21% (14/6 723). Among 230 newborns who had passed the re-examination, 10 (4.34%) were found to have carried a variant. By contrast, 4 out of the 14 neonates (28.57%) who had failed the re-examination had carried a variant, and there was a significant difference between the two groups (P < 0.05). Genetic screening can provide an effective supplement to newborn hearing screening, and the combined screening can provide a best model for the prevention of hearing loss, which can enable early detection of deafness risks, targeted prevention measures, and genetic counseling to provide accurate prognosis for the newborns.

LAMP assay for the detection of the Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psylloidea: Psyllidae)

Diaphorina citri Kuwayama, also known as the Asian citrus psyllid (ACP), can vector the bacterium Candidatus Liberibacter asiaticus (CLas), agent of Huanglongbing (HLB): an incurable disease affecting citrus trees worldwide. In citrus growing regions where ACP and HLB are absent, such as Australia, the risk of an incursion and consequent economic damage to citrus industries make this psyllid one of the top-priority pests. Due to ACP’s small dimensions and the generally poorly studied native psylloid fauna worldwide, morphological identification of this insect to distinguish it from harmless species is challenging, especially in the field, and with immature, partial or damaged specimens. To allow rapid and efficient detection of ACP in the field, we designed and optimised a new Loop-mediated isothermal amplification (LAMP) assay for the detection of D. citri based on the mitochondrial 16S locus. The optimised ACP 16S LAMP assay produced amplification from D. citri samples within 13.3 ± 3.6 min, with an anneal derivative of ~ 78.5 °C. A synthetic gBlock gene fragment was also developed to be used as positive control for the new LAMP assay with a different anneal derivative of ~ 83 °C. An existing commercially available LAMP assay for detection of the bacterium CLas was also tested in this study on ACP DNA. The ACP 16S LAMP assay we developed and tested here provides a valuable new in-field compatible tool that can allow early detections of ACP, enabling a quick biosecurity response, and could potentially be adopted by a wide range of users, from farmers to agronomists and from researchers to industry.

The first case of Echinococcus canadensis found in a moose in Norway: What does it entail?

The first case of Echinococcus canadensis found in a moose in Norway: What does it entail?

Exploration of Multi-Gene DNA Barcode Markers to Reveal the Broad Genetic Diversity of Field Ticks (Acari: Ixodidae) in a Tropical Environment of Hainan Island, China

Ticks are hematophagous arthropods and obligate ectoparasites of humans and other animals. This study focused on the molecular discrimination of ticks in the tropical environment of Hainan according to multi-gene DNA barcode markers with the expectation of accurately distinguishing species. A total of 420 ticks, including 49 adult ticks, 203 nymphal ticks, and 168 larval ticks, were collected in the field, and the 49 adult ticks were identified as Rhipicephalus turanicus, Dermacentor marginatus, and Haemaphysalis longicornis. The mitochondrial 16S rRNA, ribosomal 28S rRNA D2, and ribosomal internal transcribed spacer 2 (ITS2) regions were used as DNA barcode markers to discriminate species. According to basic local alignment search tool analysis against the GenBank database, 16S rRNA positively identified ticks in the Rhipicephalus, Dermacentor, and Haemaphysalis genera; the 28S rRNA D2 region identified ticks in the Rhipicephalus and Dermacentor genera; and ITS2 identified ticks as D. marginatus. Pairwise sequence comparisons based on these three regions were visualized with a Sequence Demarcation Tool matrix. Substitution saturation tests using data analysis and molecular biology and evolution revealed little substitution saturation (Iss < Iss.c, p < 0.05) in the 16S rRNA region for the Haemaphysalis genus; 28S rRNA D2 region for the Rhipicephalus, Dermacentor, and Haemaphysalis genera; and ITS2 region for the Rhipicephalus and Dermacentor genera. Distinctive sequences for which it is difficult to obtain good matches with the sequences available in GenBank exist in the ticks of Hainan. Future studies should obtain complementary sequences to refine and update the database for the molecular characterization of ticks.

A new species of Homonota (Squamata: Phyllodactylidae) from the Uruguayan Savanna

AbstractCryptic diversity is frequent among lizards from the Neotropical region. In particular, geckos belonging to the genus Homonota exhibit high levels of phenotypic and ecological conservatism. Homonota uruguayensis is endemic to rocky outcrops in the Uruguayan Savanna, and a previous study based on mitochondrial DNA (mtDNA) revealed a highly divergent clade in an isolated population. In this study, we used a set of two mitochondrial (Cytb and 12S) and six autosomal (DMLX, MXRA, PRLR, SNCAIP, H19B and H30B) genetic markers to evaluate the taxonomic status of different populations of H. uruguayensis. We then used morphological data to further check the favoured coalescent model of species delimitation. A careful re‐evaluation of meristic and continuous morphological traits within the H. uruguayensis complex indicated that the new species can be morphologically distinguished. The species tree confirmed the deep divergence times associated with the new species previously reported for mtDNA and indicated congruence among independent gene trees. Overall, the results clearly support the recognition of a new species, based on deep genetic divergence and morphological differentiation. While the full geographic range of the new species has not been thoroughly characterized, the localized endemism in a patch of rocky outcrops surrounded by intense silviculture activity strongly suggest that the new species should be considered to be under some degree of threat.

Genetic confirmation of Octopus insularis (Leite and Haimovici, 2008) in South Florida, United States using physical features and de novo genome assembly.

The distribution of octopuses within the Octopus vulgaris species complex remains inadequately understood. Species determination can be complex and involves characterizing a specimen's physical features and comparing its genetic makeup to other populations. In this study, we present the first genetic confirmation of Octopus insularis (Leite and Haimovici, 2008) inhabiting the coastal waters of the Florida Keys, United States. We employed visual observations to identify species-specific body patterns of three wild-caught octopuses and used de novo genome assembly to confirm their species. All three specimens exhibited a red/white reticulated pattern on their ventral arm surface. Two specimens displayed body pattern components of deimatic display (white eye encircled by a light ring, with darkening around the eye). All visual observations were consistent with distinguishing features of O. insularis. We then compared mitochondrial subunits COI, COIII, and 16S in these specimens across all available annotated octopod sequences, including Sepia apama (Hotaling et al., 2021) as a control outgroup taxon. For species exhibiting intraspecific genomic variation, we included multiple sequences from geographically distinct populations. Laboratory specimens consistently clustered into a single taxonomic node with O. insularis. These findings confirm O. insularis presence in South Florida and suggest a more extensive northern distribution than previously assumed. Whole genome Illumina sequencing of multiple specimens enabled taxonomic identification with well-established DNA barcodes while also generating the first de novo full assembly of O. insularis. Furthermore, constructing and comparing phylogenetic trees for multiple conserved genes is essential for confirming the presence and delineation of cryptic species in the Caribbean.

VertU: universal multilocus primer sets for eDNA metabarcoding of vertebrate diversity, evaluated by both artificial and natural cases

Environmental DNA (eDNA) metabarcoding is a powerful tool for monitoring biodiversity in natural ecosystems. The accuracy of eDNA metabarcoding relies heavily on the PCR primers that amplify target sequences. For vertebrates, most available primers are designed for particular groups. There have been inadequate attempts to design “universal” primers applicable to all vertebrates. Here, we developed three new universal primer sets (V12S-U, V16S-U, and VCOI-U) targeting mitochondrial 12S, 16S, and COI genes, respectively. They work for all vertebrate groups, with amplification length of 200-250 bp, facilitating the use of short-read sequencing platforms. We evaluated and compared the species detection ability of our primer sets and seven previously published ones through bothin-silicoPCR and experiment tests with mock DNA and zoo eDNA. The species detection success of the new primer sets is over 90%, showing better performance than previously published primer sets. We also tested our new primers with water eDNA samples of natural environments, and detected a total of 895 vertebrate OTUs (BLAST identity ≥ 0.95), comprising 182 species, 195 genera, and 94 families. Our results indicated that utilizing multiple markers can achieve better species detection than using only a single marker, which is especially important for monitoring large biological communities like vertebrates. The new primer sets enable researchers to detect the presence of species of different vertebrate groups in one eDNA metabarcoding survey, which simplifies the workflow and reduces the cost. It has the potential to serve as an alternative/complementary tool for future eDNA metabarcoding studies targeting vertebrates.

A historical and integrative taxonomic account of mangrove oyster species native to the Atlantic American coast: A re-evaluation of Brazilian Crassostrea species

The identification of native mangrove oyster species of the genus Crassostrea in Brazil is a recurring issue for specialists. Studies have recognized the presence of two species in the littoral zone: C. rhizophorae and C. gasar. However, other names may be used, such as C. mangle for C. rhizophorae and C. brasiliana or C. tulipa for C.gasar. As in most oyster taxonomic studies, their identification requires genetic evaluation for the precise determination of taxa. Moreover, previous revisions have proposed some morphological traits by which each species could be precisely identified, leading to a series of debates about the best model for species identity. The aim of this study was to apply an integrative taxonomic approach to native Crassostrea mangrove oyster species on the Brazilian coast to assert the correct species names, delimitations, and concise descriptions. Molecular tracing of cultivated specimens, along with wild specimens of Crassostrea collected from the Brazilian coast, was used to confirm the morphological identity of the taxa. The wild specimens were tentatively identified as either C. gasar or C. rhizophorae based on previous morphological revisions. PCR-RFLP and DNA analyses of the mitochondrial 16S gene mitochondrial rDNA from wild specimens were used to confirm taxa and re-evaluate morphological boundaries and descriptions of the species. We confirmed two patterns in the RFLP and sequence analyses: C. gasar and C. rhizophorae. Conchological and anatomical evaluations of 1006 identified Crassostrea specimens confirmed the inherent polymorphism between the native species, preventing reliable identification of the species by morphology alone. A clear exception, however, is found for specimens whose shell height is greater than 110 mm with internal view of white-colored valves and without an umbonal cavity, fitting the description of C. paraibanensis, which belongs to C. gasar. C. brasiliana and C. mangle are synonyms of C. gasar and C. rhizophorae, respectively. C. tulipa represents a species disconnected from any described mangrove oyster species from Atlantic seas. Conchological and anatomical descriptions of both species were improved to include the variability encountered.

At the edge of the sea: the supralittoral nemertean, Acteonemertes orientalis sp. nov. (Nemertea: Eumonostilifera: Plectonemertidae) from Japan

Ribbon worms (phylum Nemertea) are found in oceans worldwide; however, only a few inhabit terrestrial, semiterrestrial and freshwater environments. In our study, we describe Acteonemertes orientalis sp. nov., a new species of Plectonemertidae Gibson, 1990 and the first plectonemertid discovered in Japan. The species was found in the supralittoral zone, from which nemerteans have rarely been reported and inhabits areas under rocks, wave-dissipating concrete blocks, and fallen leaves and stocks, along the coast of the Sea of Japan. Multi-locus phylogenetic analyses based on two mitochondrial (16S rRNA and cytochrome c oxidase subunit I) and two nuclear gene markers (18S rRNA and 28S rRNA) revealed that A. orientalis sp. nov. formed a clade with Leptonemertes cf. chalicophora collected from Florida. Although the external and internal morphology of A. orientalis sp. nov. is largely consistent with the generic diagnosis, this species differs in having a large proboscis. Based on the molecular and morphological data, we propose to amend the diagnosis of Acteonemertes by excluding proboscis size. ZooBank: urn:lsid:zoobank.org:pub:BBBE9549-5DCE-424F-9A39-930F8243C28B

Molecular and morphological analyses reveal a new hypogean species of amphipod in the genus Crangonyx Bate, 1859 (Crustacea: Crangonyctidae) within the floridanus species complex, from Suwannee County, Florida

ABSTRACT Crangonyx stinei sp. n. is described from Peacock Springs Cave, in Wes Skiles Peacock Springs State Park, Suwannee County, Florida. Crangonyx stinei sp. n. was collected from the cave benthos via SCUBA cave diving techniques. Molecular analyses of the nuclear 18S and 28S rDNA and mitochondrial 16S rDNA reveal significant phylogenetic differences between C. stinei sp. n. and closely related Crangonyx spp. Crangonyx stinei sp. n. is the sixth member of the floridanus species complex in the State of Florida, but only the second to be described from a hypogean habitat. To determine the biogeographic range of C. stinei sp. n., additional collecting in both epigean and hypogean systems is needed. http://www.zoobank.org/urn:lsid:zoobank.org:pub:39692E06-EBAA-492B-91FD-20EBB5D5C242

DNA barcoding of fishes from Zhoushan coastal waters using mitochondrial COI and 12S rRNA genes

DNA barcoding of fishes from Zhoushan coastal waters using mitochondrial COI and 12S rRNA genes

Species limits and diversification of the Dendropsophus rubicundulus subgroup (Anura, Hylidae) in Neotropical savannas

Understanding the processes that generate and maintain biodiversity at and below the species level is a central goal of evolutionary biology. Here we explore the spatial and temporal drivers of diversification of the treefrog subgroup Dendropsophus rubicundulus, a subgroup of the D. microcephalus species group, over periods of pronounced geological and climatic changes in the Neotropical savannas that they inhabit. This subgroup currently comprises 11 recognized species distributed across the Brazilian and Bolivian savannas, but the taxonomy has been in a state of flux, necessitating reexamination. Using newly generated single nucleotide polymorphism (SNP) data from restriction-site associated DNA sequencing (RADseq) and mitochondrial 16S sequence data for ∼150 specimens, we inferred phylogenetic relationships, tested species limits using a model-based approach, and estimated divergence times to gain insights into the geographic and climatic events that affected the diversification of this subgroup. Our results recognized at least nine species: D. anataliasiasi, D. araguaya, D. cerradensis, D. elianeae, D. jimi, D. rubicundulus, D. tritaeniatus, D. rozenmani, and D. sanborni. Although we did not collect SNP data for the latter two species, they are likely distinct based on mitochondrial data. In addition, we found genetic structure within the widespread species D. rubicundulus, which comprises three allopatric lineages connected by gene flow upon secondary contact. We also found evidence of population structure and perhaps undescribed diversity in D. elianeae, which warrants further study. The D. rubicundulus subgroup is estimated to have originated in the Late Miocene (∼5.45 million years ago), with diversification continuing through the Pliocene and Early Pleistocene, followed by the most recent divergence of D. rubicundulus lineages in the Middle Pleistocene. The epeirogenic uplift followed by erosion and denudation of the central Brazilian plateau throughout the Pliocene and Pleistocene, in combination with the increasing frequency and amplitude of climatic fluctuations during the Pleistocene, was important for generating and structuring diversity at or below the species level in the D. rubicundulus subgroup.

Mt-LAF3 is a pseudouridine synthase ortholog required for mitochondrial rRNA and mRNA gene expression in Trypanosoma brucei

Trypanosoma brucei and related kinetoplastid parasites possess unique RNA processing pathways, including in their mitochondria, that regulate metabolism and development. Altering RNA composition or conformation through nucleotide modifications is one such pathway, and modifications including pseudouridine regulate RNA fate and function in many organisms. We surveyed pseudouridine synthase (PUS) orthologs in trypanosomatids, with a particular interest in mitochondrial enzymes due to their potential importance for mitochondrial function and metabolism. Trypanosoma brucei mitochondrial (mt)-LAF3 is an ortholog of human and yeast mitochondrial PUS enzymes, and a mitoribosome assembly factor, but structural studies differ in their conclusion as to whether it has PUS catalytic activity. Here, we generated T. brucei cells that are conditionally null (CN) for mt-LAF3 expression and showed that mt-LAF3 loss is lethal and disrupts mitochondrial membrane potential (ΔΨm). Addition of a mutant gamma ATP synthase allele to the CN cells permitted ΔΨm maintenance and cell survival, allowing us to assess primary effects on mitochondrial RNAs. As expected, these studies showed that loss of mt-LAF3 dramatically decreases levels of mitochondrial 12S and 9S rRNAs. Notably, we also observed decreases in mitochondrial mRNA levels, including differential effects on edited vs. pre-edited mRNAs, indicating that mt-LAF3 is required for mitochondrial rRNA and mRNA processing, including of edited transcripts. To assess the importance of PUS catalytic activity in mt-LAF3 we mutated a conserved aspartate that is necessary for catalysis in other PUS enzymes and showed it is not essential for cell growth, or maintenance of ΔΨm and mitochondrial RNA levels. Together, these results indicate that mt-LAF3 is required for normal expression of mitochondrial mRNAs in addition to rRNAs, but that PUS catalytic activity is not required for these functions. Instead, our work, combined with previous structural studies, suggests that T. brucei mt-LAF3 acts as a mitochondrial RNA-stabilizing scaffold.

Genetic Diversity and Genetic Structure of Phascolosoma esculenta Populations in Southeastern China Based on 16S rRNA Gene Sequences

Here, we investigated the population genetic structure and genetic diversity of the endemic Chinese oceanic sipuncula Phascolosoma esculenta by using partial mitochondrial DNA 16S rRNA sequences. In total, 80 samples were collected from Xiangshan, Wenling, Ningde, and Zhanjiang, which are four muddy intertidal zones of southeastern China. Results showed that of the 80 16S rRNA gene fragments, 5 were 1010 bp in length, 73 were 1011 bp in length, and 2 were 1012 bp in length. The A+T content (67.7%) was signifi cantly higher than the C+G content (32.3%), thus exhibiting obvious AT biases. In addition, 27 different haplotypes were defi ned by 33 polymorphic sites, giving an overall haplotype diversity of 0.908 and a nucleotide diversity of 0.00247. The topological structure of the haplotype neighbor-joining tree was extremely simple, without any obvious geographical structures within the four groupings. The genetic distances among populations ranged from 0.0022 to 0.0031, and those within populations ranged from 0.002 to 0.0028. The results of AMOVA revealed a low level of genetic differentiation among the four populations. A neutral test and mismatch analysis indicated a recent population expansion for P. esculenta.