Cryptic diversity and phylogeography of the Rhabdophis nuchalis group (Squamata: Colubridae).

Previous studies, have found that the rapid uplift of the Tibetan plateau accelerated the diversification of species. However, there are few relevant biogeographic data for the Colubridae in this region. We conducted a comprehensive study of the Rhabdophis nuchalis Group, which presently contains four nominal species, R. nuchalis, R. pentasupralabialis, R. leonardi, and R. chiwen. Building upon previous studies with specimens we have recently examined, greater interspecific and intraspecific diversity has been revealed. Here we address three questions: (1) Do the intraspecific differences represent only geographic variation within lineages, or are there cryptic species? (2) What are the interspecific relationships among members of the R. nuchalis Group? (3) What has been the biogeographic history of this species group? To resolve these questions we used four mitochondrial gene sequences and one nuclear sequence to investigate the molecular phylogenetic and geographic relationships among populations. Our molecular analysis reveals cryptic species diversity within the R. nuchalis Group, and seven clades were identified in the analysis. Ancestral area estimation suggests that the R. nuchalis Group originated in the Hengduan Mountains approximately 6.24 Mya and expanded its range northward to the Qinling-Daba Mountains. The Sichuan Basin appears to have been a barrier to migration. Species divergence seems to have been related to the rapid uplift of the Qinghai-Tibet Plateau.

Characterisation of the gut microbial community of rhesus macaques in high-altitude environments.

BACKGROUND: The mammal intestinal microbiota is involved in various physiological processes and plays a key role in host environment adaption. However, for non-human primates (NHPs), little is known about their gut microbial community in high-altitude environments and even less about their adaption to such habitats. We characterised the gut microbial community of rhesus macaques from multiple high-altitude environments and compared it to those of low-altitude populations. RESULTS: We collected faecal samples of rhesus macaques from four high-altitude populations (above 3000 m) and three low-altitude populations (below 500 m). By calculating the alpha diversity index, we found that high-altitude populations exhibited a higher diversity. Statistical analysis of beta diversity indicated significant differences between high- and low-altitude populations. Significant differences were also detected at the phylum and family levels. At the phylum level, the high-altitude gut microbial community was dominated by Firmicutes (63.42%), while at low altitudes, it was dominated by Bacteroidetes (47.4%). At the family level, the high-altitude population was dominated by Ruminococcaceae (36.2%), while the low-altitude one was dominated by Prevotellaceae (39.6%). Some families, such as Christensenellaceae and Rikenellaceae, were consistently higher abundant in all high-altitude populations. We analysed the overlap of operational taxonomic units (OTUs) in high-altitude populations and determined their core OTUs (shared by all four high-altitude populations). However, when compared with the low-altitude core OTUs, only 65% were shared, suggesting a divergence in core OTUs. Function prediction indicated a significant difference in gene copy number of 35 level-2 pathways between high- and low-altitude populations; 29 of them were higher in high altitudes, especially in membrane transport and carbohydrate metabolism. CONCLUSIONS: The gut microbial community of high-altitude rhesus macaques was significantly distinct from that of low-altitude populations in terms of diversity, composition and function. High-altitude populations were dominated by Firmicutes and Ruminococcace, while in low-altitude populations, Bacteroidetes and Prevotellaceae were dominant. The difference in gut microbiota between these two populations may be caused by differences in host diet, environmental temperature and oxygen pressure. These differentiated gut microbial microorganisms may play a critical role in the adaptive evolution of rhesus macaques to high-altitude environments.

Reconstructing spatial organizations of chromosomes through manifold learning.

Decoding the spatial organizations of chromosomes has crucial implications for studying eukaryotic gene regulation. Recently, chromosomal conformation capture based technologies, such as Hi-C, have been widely used to uncover the interaction frequencies of genomic loci in a high-throughput and genome-wide manner and provide new insights into the folding of three-dimensional (3D) genome structure. In this paper, we develop a novel manifold learning based framework, called GEM (Genomic organization reconstructor based on conformational Energy and Manifold learning), to reconstruct the three-dimensional organizations of chromosomes by integrating Hi-C data with biophysical feasibility. Unlike previous methods, which explicitly assume specific relationships between Hi-C interaction frequencies and spatial distances, our model directly embeds the neighboring affinities from Hi-C space into 3D Euclidean space. Extensive validations demonstrated that GEM not only greatly outperformed other state-of-art modeling methods but also provided a physically and physiologically valid 3D representations of the organizations of chromosomes. Furthermore, we for the first time apply the modeled chromatin structures to recover long-range genomic interactions missing from original Hi-C data.

Transcriptome-wide N 6 -methyladenosine methylome profiling of porcine muscle and adipose tissues reveals a potential mechanism for transcriptional regulation and differential methylation pattern.

BACKGROUND: N 6 -methyladenosine (m6A) is the most prevalent internal form of modification in messenger RNA in higher eukaryotes and potential regulatory functions of reversible m6A methylation on mRNA have been revealed by mapping of m6A methylomes in several species. m6A modification in active gene regulation manifests itself as altered methylation profiles in a tissue-specific manner or in response to changing cellular or species living environment. However, up to date, there has no data on m6A porcine transcriptome-wide map and its potential biological roles in adipose deposition and muscle growth. METHODS: In this work, we used methylated RNA immunoprecipitation with next-generation sequencing (MeRIP-Seq) technique to acquire the first ever m6A porcine transcriptome-wide map. Transcriptomes of muscle and adipose tissues from three different pig breeds, the wild boar, Landrace, and Rongchang pig, were used to generate these maps. RESULTS: Our findings show that there were 5,872 and 2,826 m6A peaks respectively, in the porcine muscle and adipose tissue transcriptomes. Stop codons, 3'-untranslated regions, and coding regions were found to be mainly enriched for m6A peaks. Gene ontology analysis revealed that common m6A peaks in nuclear genes are associated with transcriptional factors, suggestive of a relationship between m6A mRNA methylation and nuclear genome transcription. Some genes showed tissue- and breed-differential methylation, and have novel biological functions. We also found a relationship between the m6A methylation extent and the transcript level, suggesting a regulatory role for m6A in gene expression. CONCLUSION: This comprehensive map provides a solid basis for the determination of potential functional roles for RNA m6A modification in adipose deposition and muscle growth.

A new species of the genus Rhabdophis Fitzinger, 1843 (Squamata: Colubridae) from Guangdong Province, southern China.

A new species, Rhabdophis guangdongensis sp. nov., is described from the Guangdong Province, China. It can be easily distinguished from other known congeners by cyt b and c-mos sequences, and by the following combination of morphological characters: body size small; head distinct from the neck; 20 maxillary teeth, the three most posterior teeth strongly enlarged, and not separated by diastemata from other teeth; six supralabials, the third and fourth touching the eye; seven infralabials, the first four in contact with anterior chin shields; dorsal scales in 15 rows throughout the body, weakly keeled, the outer row smooth; 126 ventrals; 39 paired subcaudals; anal scale divided; 44 pairs of narrow dorsolateral black cross-bars on body and 15 pairs on tail; body and tail with two dorsolateral longitudinal brownish-red lines, respectively with a series of white spots in cross-bars. The description of this new species brings the total number of described species of this genus to 21 and represents the tenth known Rhabdophis species in China.

A time-course transcriptome analysis revealing the potential molecular mechanism of early gonadal differentiation in the Chinese giant salamander.

The Chinese giant salamander (CGS) Andrias davidianus is the largest extant amphibian and has recently become an important species for aquaculture with high economic value. Meanwhile, its wild populations and diversity are in urgent need of protection. Exploring the mechanism of its early gonadal differentiation will contribute to the development of CGS aquaculture and the recovery of its wild population. In this study, transcriptomic and phenotypic research was conducted on the critical time points of early gonadal differentiation of CGS. The results indicate that around 210 days post-hatching (dph) is the critical window for female CGS's gonadal differentiation, while 270 dph is that of male CGS. Besides, the TRPM1 gene may be the crucial gene among many candidates determining the sex of CGS. More importantly, in our study, key genes involved in CGS's gonadal differentiation and development are identified and their potential pathways and regulatory models at early stage are outlined. This is an initial exploration of the molecular mechanisms of CGS's early gonadal differentiation at multiple time points, providing essential theoretical foundations for its captive breeding and offering unique insights into the conservation of genetic diversity in wild populations from the perspective of sex development.

Identity of the holotype and type locality of Rhabdophis leonardi (Wall, 1923) (Colubridae: Natricinae), with notes on the morphology and natural history of the species in southwestern China.

The original description of Natrix leonardi (currently Rhabdophis leonardi) by Frank Wall in 1923, based on a specimen from the "Upper Burma Hills," lacked important morphological details that have complicated the assignment of recently collected material. Furthermore, although the holotype was never lost, its location has been misreported in one important taxonomic reference, leading to further confusion. We report the correct repository of the holotype (Natural History Museum, London), together with its current catalog number. We also describe key features of that specimen that were omitted from the original description, and provide new details on the morphology of the species, including sexual dichromatism unusual for the genus, based upon specimens from southern Sichuan, China. Rhabdophis leonardi is distinguished from its congeners by the following characters: 15 or 17 DSR at midbody and 6 supralabials; distinct annulus around the neck, broad and red in males, and narrow and orange with a black border in females; dorsal ground color light green or olive; some lateral and dorsal scales possessing black edges, the frequency of black edges gradually increasing from anterior to posterior, forming irregular and ill-defined transverse black bands; eye with prominent green iris; black ventral spots with a red edge, most numerous at midbody but extending halfway down the length of the tail. In southwestern China, this species is frequently found at 1730-2230 m elevation. It has been documented to prey upon anuran amphibians, including toads. A recently published phylogenetic analysis showed this species to be deeply nested with the genus Rhabdophis, as a member of the R. nuchalis Group. That analysis also revealed the existence of two closely related but geographically distinct subclades in the molecular analysis, one of which may represent an unnamed taxon.

Mechanisms of Caspases 3/7/8/9 in the Degeneration of External Gills of Chinese Giant Salamanders (Andrias davidianus).

Metamorphosis is a critical stage in the adaptive development of amphibians from aquatic to terrestrial animals. Metamorphosis of the Chinese giant salamander is mainly manifested by the loss of external gills with consequent changes in the respiratory pattern. The loss of the external gill is regulated by the pathway of apoptosis in which caspase genes are the key factors. This study cloned and expressed the caspase 3/7/8/9 genes of the Chinese giant salamander. The main results were as follows: the complete open reading frames (ORFs) were 885 bp, 960 bp, 1461 bp and 1279 bp, respectively; caspase 3/7/8/9 genes all contained the CASc domain, and most of the motifs were located in CASc domain; and caspase 8 possessed two DED structural domains and caspase 9 possessed a CARD structural domain. Furthermore, results from the tissue distribution analysis indicated that caspase 3/7/8/9 genes were all significantly expressed in the external gill, and at 9 and 10 months of age (MOA), which is the peak time for the loss, the EXPRESSION level of caspase 3/7/8/9 genes was obviously high, which was consistent with the histological result. Moreover, the loss of external gills of the Chinese giant salamander may result from activation of both the apoptosis-related death receptor pathway and the mitochondrial pathway. Finally, it was discovered that thyroid hormone (TH) treatment could both advance the time point at which the external gills of the Chinese giant salamander began to degenerate and shorten this process. Interestingly, at the peak of its metamorphosis (9 MOA), the Chinese giant salamander further accelerated the metamorphosis rate of TH treatment, which suggested a promotive effect on the loss of external gills via the superimposition of the exogenous TH and caspase genes. The study of caspase genes in this experiment was conducive to understanding the mechanism of external gill loss in the Chinese giant salamander, as well as improving our understanding of the metamorphosis development of some Caudata species.

The complete mitochondrial genome and phylogenetic analysis of red-and-white giant flying squirrel (Petaurista alborufus).

Red-and-white giant flying squirrel (Petaurista alborufus) is a widely distributed but rarely studied species. Here, we sequenced the complete mitochondrial genome about it, which is a circular genome of 16,511 bp and have a typical structure with mammals. The base composition shows higher composition of A\T. There are 61 variations and eight base deletions between two sequences when compared with the reported sequence (JQ743657). In this study, we obtain a new mitochondrial genome sequence of red-and-white giant flying squirrel, which provide novel molecular information that could prove fundamental to our understanding of diversity research and phylogenetic structure.

Complete mitochondrial genome sequence of a Chinese ferret-badger (Melogale moschata) and phylogenetic analysis.

Ferret-badger (Melogale moschata) is a widely distributed and rarely studied species. Therefore, we sequenced its complete mitochondrial genome, which is circular in shape with 16,511 bp length and have a structure typical to mammals. There is 98.67% similarity when compared with the reported sequence (HM106328). It contained 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and 1 control regions (D-loop). This study can provide novel molecular information and genetic diversity of ferret-badger.

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.

The complete mitochondrial genome sequence and phylogenetic analysis of yellow weasel (Mustela sibirica).

In this study, we determined the complete mitochondrial genome sequence of the Mustela sibirica. The complete mitogenome of M. sibirica is 16,529 bp in length and consist of 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes, and a D-loop region. The overall base composition of the mitochondrial DNA is 32.88%A, 13.84%G, 27.32%T, and 25.96%C. The phylogenetic tree of the family Mustelidae constructed by using mitogenome sequences from 10 mustelid species of the family Mustelidae. These results provide necessary information for molecular phylogeny and evolutionary analysis of the M. sibirica.

Complete mitochondrial genome sequence of tufted deer (Elaphodus cephalophus) with phylogenetic analysis.

The complete mitochondrial genome of tufted deer (Elaphodus cephalophus) has been described in our research. The sequence of this genome is 16356 bp with a circular structure, and contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA genes, and one control region. When compare with the reference sequence (DQ873526), it shows that there are 262 variations, 4 base deletions and 13 base insertions. In this study we obtain a new complete mitochondrial genome sequence of tufted deer that provide effective molecular information for the diversity research and phylogenetic structure.

Phylogenetic and characterization of the complete mitochondrial genome relationship of Argali sheep (Ovis ammon).

In this study, we sequenced the complete mitochondrial genome of Argali sheep (Ovis ammon). The total length was 16,612 bp, which contained 13 protein-coding genes (PCGs), 22 tRNA genes, 2 rRNA genes, and a control region (D-loop). Eight tRNA genes with one PCG (ND6) encoded on the L-strand, others were encoded on the H-strand. The neighbor-joining analysis shows that Argali sheep has a close relationship with the same genus species of Ovis aries and Ovis orientalis. This study has provided new data for the phylogeny of Argali sheep.

Characterizing the microbiota in gastrointestinal tract segments of Rhabdophis subminiatus: Dynamic changes and functional predictions.

The gut microbiota helps the host to absorb nutrients and generate immune responses that can affect host behavior, development, reproduction, and overall health. However, in most of the previous studies, microbiota was sampled mainly using feces and intestinal contents from mammals but not from wild reptiles. Here, we described the bacterial profile from five different gastrointestinal tract (GIT) segments (esophagus, stomach, small intestine, large intestine, and cloaca) of three wild Rhabdophis subminiatus using 16S rRNA V4 hypervariable amplicon sequencing. Forty-seven bacterial phyla were found in the entire GIT, of which Proteobacteria, Firmicutes, and Bacteroidetes were predominant. The results showed a significant difference in microbial diversity between the upper GIT segments (esophagus and stomach) and lower GIT segments (large intestine and cloaca). An obvious dynamic distribution of Fusobacteria and Bacteroidetes was observed, which mainly existed in the lower GIT segments. Conversely, the distribution of Tenericutes was mainly observed in the upper GIT. We also predicted the microbial functions in the different GIT segments, which showed that microbiota in each segments played an important role in higher membrane transport and carbohydrate and amino acid metabolism. Microbes in the small intestine were also mainly involved in disease-related systems, while in the large intestine, they were associated with membrane transport and carbohydrate metabolism. This is the first study to investigate the distribution of the gut microbiota and to predict the microbial function in R. subminiatus. The composition of the gut microbiota certainly reflects the diet and the living environment of the host. Furthermore, these findings provide vital evidence for the diagnosis and treatment of gut diseases in snakes and offer a direction for a model of energy budget research.

Integrating Hi-C and FISH data for modeling of the 3D organization of chromosomes.

The new advances in various experimental techniques that provide complementary information about the spatial conformations of chromosomes have inspired researchers to develop computational methods to fully exploit the merits of individual data sources and combine them to improve the modeling of chromosome structure. Here we propose GEM-FISH, a method for reconstructing the 3D models of chromosomes through systematically integrating both Hi-C and FISH data with the prior biophysical knowledge of a polymer model. Comprehensive tests on a set of chromosomes, for which both Hi-C and FISH data are available, demonstrate that GEM-FISH can outperform previous chromosome structure modeling methods and accurately capture the higher order spatial features of chromosome conformations. Moreover, our reconstructed 3D models of chromosomes revealed interesting patterns of spatial distributions of super-enhancers which can provide useful insights into understanding the functional roles of these super-enhancers in gene regulation.

Genetic diversity and phylogenetic analyses of 11 cohorts of captive rhesus macaques from Chinese zoos.

Rhesus macaques are raised in almost every Chinese zoo due to their likeability and ease in feeding; however, little is yet known about the genetic diversity of rhesus macaques in captivity. In this study, a 475-base pair nucleotide sequence of the mitochondrial DNA control region was obtained from the fecal DNA of 210 rhesus macaque individuals in captivity. A total of 69 haplotypes were defined, 51 of which (73.9%) were newly identified. Of all haplotypes, seven were shared between two zoos, and 62 haplotypes (89.8%) appeared only in a specific zoo, indicating a low rate of animal exchange between Chinese zoos. Moreover, there was a relatively high level of genetic diversity among the rhesus macaques (Hd = 0.0623 ± 0.0009, Pi = 0.979 ± 0.003, K = 28.974). Phylogenetic analysis demonstrated that all haplotypes were clearly clustered into two major haplogroups-Clade A (southeastern China) and Clade B (southwestern China)-and each major clade contained several small sub-haplogroups. The haplotypes of rhesus macaques from the same zoo were not clustered together for the most part, but scattered among several subclades on the phylogenetic tree. This indicates that the rhesus macaques in most Chinese zoos may originat from a diverse collection of geographical areas. Our results demonstrate that zoos play an important role in the conservation of the genetic diversity of rhesus macaques, as well as provide useful information on the genetic management of captive rhesus macaques.

Evolution of nuchal glands, unusual defensive organs of Asian natricine snakes (Serpentes: Colubridae), inferred from a molecular phylogeny.

A large body of evidence indicates that evolutionary innovations of novel organs have facilitated the subsequent diversification of species. Investigation of the evolutionary history of such organs should provide important clues for understanding the basis for species diversification. An Asian natricine snake, Rhabdophis tigrinus, possesses a series of unusual organs, called nuchal glands, which contain cardiotonic steroid toxins known as bufadienolides. Rhabdophis tigrinus sequesters bufadienolides from its toad prey and stores them in the nuchal glands as a defensive mechanism. Among more than 3,500 species of snakes, only 17 Asian natricine species are known to possess nuchal glands or their homologues. These 17 species belong to three nominal genera, Balanophis, Macropisthodon, and Rhabdophis. In Macropisthodon and Rhabdophis, however, species without nuchal glands also exist. To infer the evolutionary history of the nuchal glands, we investigated the molecular phylogenetic relationships among Asian natricine species with and without nuchal glands, based on variations in partial sequences of Mt-CYB, Cmos, and RAG1 (total 2,767 bp). Results show that all species with nuchal glands belong to a single clade (NGC). Therefore, we infer that the common ancestor of this clade possessed nuchal glands with no independent origins of the glands within the members. Our results also imply that some species have secondarily lost the glands. Given the estimated divergence time of related species, the ancestor of the nuchal gland clade emerged 19.18 mya. Our study shows that nuchal glands are fruitful subjects for exploring the evolution of novel organs. In addition, our analysis indicates that reevaluation of the taxonomic status of the genera Balanophis and Macropisthodon is required. We propose to assign all species belonging to the NGC to the genus Rhabdophis, pending further study.

Complete mitochondrial genome of black-shanked douc langurs (Pygathrix nigripes) and its phylogenetic analysis.

In this study, we first characterized the complete mitogenome of Pygathrix nigripes, and analysed its phylogenetic status. The circular mitogenome was 16,534 bp in length, and contained 13 protein-coding genes (PCGs), two rRNA genes, 22 tRNA genes and one non-coding control region (D-loop). These genes except ND6 and 8 tRNA genes were encoded on the H-strand. The phylogenetic analysis exhibited that our sequence formed a sister branch with P. cinereal and P. nemaeus of genus Pygathrix, which showed a closer genetic relationship of the three species. These information contribute to molecular, phylogenetic studies and genetic diversity conservation for this species.

Complete mitochondrial genome and phylogenetic analysis of a Chinese Eurasian lynx (Lynx lynx).

The complete mitochondrial genome of Eurasian lynx (Lynx lynx) from China has been described in this study. It has a circular genome of 16,996 bp with a higher A + T content of 58.65%, and the base composition is A: 32.31%, G: 14.29%, T: 26.35%, C: 27.06%. When compared with the reported individual (KR919624) from China, there are 81 variations and 58 base deletion between the two sequences. The phylogenetic analysis indicated our sequence separated clearly from Eurasian lynx individuals in the previous publications. These results could provide more molecular information for the conservation of Eurasian lynx genetic resources.