Wujiao Li

First insights into the giant panda (Ailuropoda melanoleuca) blood transcriptome: a resource for novel gene loci and immunogenetics

The giant panda (Ailuropoda melanoleuca) is one of the most famous flagship species for conservation, and its draft genome has recently been assembled. However, the transcriptome is not yet available. In this study, the blood transcriptomes of three pandas were characterized and about 160 million sequencing reads were generated using Illumina HiSeq 2000 paired‐end sequencing technology. The assembly yielded 92 598 transcripts with an average length of 1626 bp and N50 length of 2842 bp. Based on a sequence similarity search against nonredundant (nr) protein database, a total of 38 522 (41.6%) transcripts were annotated. Of these annotated transcripts, 25 142 and 8272 transcripts were assigned to gene ontology terms and clusters of orthologous group, respectively. A search against the Kyoto Encyclopedia of Genes and Genomes Pathway database (KEGG) indicated that 9098 (9.83%) transcripts mapped to 324 KEGG pathways, and the best represented functional categories of pathways were signal transduction and immune system. We have also identified 23 460 microsatellites, 43 560 SNPs as well as 21 456 alternative splicing events in the assembly. Additionally, a total of 24 341 complete open reading frames (ORFs) were detected from the assembly where 1492 ORFs were found to be novel gene loci as these have not been annotated so far in any public database.

Phylogenomics and Evolutionary Dynamics of the Family Actinomycetaceae

The family Actinomycetaceae comprises several important pathogens that impose serious threat to human health and cause substantial infections of economically important animals. However, the phylogeny and evolutionary dynamic of this family are poorly characterized. Here, we provide detailed description of the genome characteristics of Trueperella pyogenes, a prevalent opportunistic bacterium that belongs to the family Actinomycetaceae, and the results of comparative genomics analyses suggested that T. pyogenes was a more versatile pathogen than Arcanobacterium haemolyticum in adapting various environments. We then performed phylogenetic analyses at the genomic level and showed that, on the whole, the established members of the family Actinomycetaceae were clearly separated with high bootstrap values but confused with the dominant genus Actinomyces, because the species of genus Actinomyces were divided into three main groups with different G+C content. Although T. pyogenes and A. haemolyticum were found to share the same branch as previously determined, our results of single nucleotide polymorphism tree and genome clustering as well as predicted intercellular metabolic analyses provide evidence that they are phylogenetic neighbors. Finally, we found that the gene gain/loss events occurring in each species may play an important role during the evolution of Actinomycetaceae from free-living to a specific lifestyle.

Distinct patterns of simple sequence repeats and GC distribution in intragenic and intergenic regions of primate genomes.

As the first systematic examination of simple sequence repeats (SSRs) and guanine-cytosine (GC) distribution in intragenic and intergenic regions of ten primates, our study showed that SSRs and GC displayed nonrandom distribution for both intragenic and intergenic regions, suggesting that they have potential roles in transcriptional or translational regulation. Our results suggest that the majority of SSRs are distributed in non-coding regions, such as the introns, TEs, and intergenic regions. In these primates, trinucleotide perfect (P) SSRs were the most abundant repeats type in the 5′UTRs and CDSs, whereas, mononucleotide P-SSRs were the most in the intron, 3′UTRs, TEs, and intergenic regions. The GC-contents varied greatly among different intragenic and intergenic regions: 5′UTRs > CDSs > 3′UTRs > TEs > introns > intergenic regions, and high GC-content was frequently distributed in exon-rich regions. Our results also showed that in the same intragenic and intergenic regions, the distribution of GC-contents were great similarity in the different primates. Tri- and hexanucleotide P-SSRs had the most GC-contents in the 5′UTRs and CDSs, whereas mononucleotide P-SSRs had the least GC-contents in the six genomic regions of these primates. The most frequent motifs for different length varied obviously with the different genomic regions.

Comparative transcriptome analysis of Trueperella pyogenes reveals a novel antimicrobial strategy

Trueperella pyogenes is a prevalent opportunistic bacterium that normally causes diverse suppurative lesions, endometritis and pneumonia in various economically important animals. Although the genomic information of this species has been announced, little is known about its functional profiles. In this study, by performing a comparative transcriptome analysis between the highly and moderately virulent T. pyogenes isolates, we found the expression of a LuxR-type DNA-binding response regulator, PloR, was significantly up-regulated in the highly virulent T. pyogenes. Protein crystal structure prediction and primary functional assessment suggested that, the quorum-sensing signal molecules of Gram-negative bacteria such as Pseudomonas aeruginosa and Escherichia coli could significantly inhibit the growth, biofilm production and hemolysis of T. pyogenes by binding to the upstream sensor histidine kinase, PloS. Therefore, the PloS/PlosR two-component regulatory system might dominate the virulence of T. pyogenes. Our findings provide a major advance in understanding the pathogenesis of T. pyogenes, and may shed new light on the development of novel therapeutic strategies to control T. pyogenes infection.

Nutrient reduction induced stringent responses promote bacterial quorum-sensing divergence for population fitness

Bacteria use a cell-cell communication system termed quorum-sensing (QS) to adjust population size by coordinating the costly but beneficial cooperative behaviors. It has long been suggested that bacterial social conflict for expensive extracellular products may drive QS divergence and cause the “tragedy of the commons”. However, the underlying molecular mechanism of social divergence and its evolutionary consequences for the bacterial ecology still remain largely unknown. By using the model bacterium Pseudomonas aeruginosa PAO1, here we show that nutrient reduction can promote QS divergence for population fitness during evolution but requiring adequate cell density. Mechanically, decreased nutrient supplies can induce RpoS-directed stringent response and enhance the selection pressure on lasR gene, and lasR mutants are evolved in association with the DNA mismatch repair “switch-off”. The lasR mutants have higher relative fitness than QS-intact individuals due to their energy-saving characteristic under nutrient decreased condition. Furthermore an optimal incorporation of lasR mutants is capable of maximizing the fitness of entire population during in vitro culture and the colonization in mouse lung. Consequently, rather than worsen the population health, QS-coordinated social divergence is an elaborate evolutionary strategy that renders the entire bacterial population more fit in tough times.

Comparison of microsatellite distribution in genomes of Centruroides exilicauda and Mesobuthus martensii.

In this study, we characterized the distribution of microsatellites in the genomes and genes of Centruroides exilicauda and Mesobuthus martensii, carried out Gene Ontology (GO) analysis and GO enrichment analysis of coding sequences (CDSs) with microsatellite (SSR). In addition, over-represented GO functions related to environmental interactions, development process and methylation were identified to develop functional markers and facilitate further analysis of microsatellite function in the genes of scorpions. Location analysis indicated that microsatellites were predominantly concentrated at both ends of genes. Most genes containing microsatellite had the SSR present at only one locus, from which we infer that the number of SSRs per gene is limited even though intragenic tandem repeats can generate functional variability. Lastly, we identified 75 SSRs in 64 genes of 54 expanded gene families and 1 SSR in the toxin gene of Mesobuthus martensii, allowing future studies on the effect of microsatellites on gene function.

The first draft genome of Lophophorus: A step forward for Phasianidae genomic diversity and conservation

The monal genus (Lophophorus) is a branch of Phasianidae and its species inhabit the high-altitude mountains of the Qinghai-Tibet Plateau. The Chinese monal, L. lhuysii, is a threatened endemic bird of China that possesses high-altitude adaptability, diversity of plumage color and potentially low reproductive life history. This is the first study to describe the monal genome using next generation sequencing technology. The Chinese monal genome size is 1.01 Gb, with 16,940 protein-coding genes. Gene annotation yielded 100.93 Mb (9.97%) repeat elements, 785 ncRNA, 5,465,549 bp (0.54%) SSR and 15,550 (92%) genes in public databases. Compared to other birds and mammals, the genome evolution analysis showed numerous expanded gene families and positive selected genes involved in high-altitude adaptation, especially related to the adaptation of low temperature and hypoxia. Consequently, this gene data can be used to investigate the molecular evolution of high-altitude adaptation in future bird research. Our first published genome of the genus Lophophorus will be integral for the study of monal population genetic diversity and conservation, genomic evolution and Galliformes species differentiation in the Qinghai-Tibetan Plateau.

Identification of Triplophysa species from the Qinghai-Tibetan Plateau (QTP) and its adjacent regions through DNA barcodes

The genus Triplophysa is the largest and most difficult to identity morphologically fish group of superfamily Cobitoidea with 140 currently valid species, and is mainly distributed in the Qinghai-Tibetan Plateau (QTP) and adjacent regions. Most species within this genus possess highly similar morphological characteristics for adaption to the highland environment and are very difficult to be identified only based on morphology. The traditional species identification, mainly based on external morphological diagnostic characters, leads to inconsistent results in many cases. Herein, we provided a molecular method based on mitochondrial cytochrome c subunit I (COI) for the identification of Triplophysa fishes. Thirty-three Triplophysa species, 244 individuals, were used to determine whether barcoding was effective in discriminating species for this genus. The mean intraspecific and interspecific K2P distances ranged from 0 to 14.9% (mean, 2.9%) and 0 to 23.4% (mean, 9.7%), respectively. The tree-based analysis displayed most of species formed discrete clusters with strong bootstrap support values (>90%). The results showed that most of Triplophysa species could be identified by DNA barcode and indicated DNA barcode could be used as a molecular marker for these species.

Profile of microRNA in Giant Panda Blood: A Resource for Immune-Related and Novel microRNAs.

The giant panda (Ailuropoda melanoleuca) is one of the world’s most beloved endangered mammals. Although the draft genome of this species had been assembled, little was known about the composition of its microRNAs (miRNAs) or their functional profiles. Recent studies demonstrated that changes in the expression of miRNAs are associated with immunity. In this study, miRNAs were extracted from the blood of four healthy giant pandas and sequenced by Illumina next generation sequencing technology. As determined by miRNA screening, a total of 276 conserved miRNAs and 51 novel putative miRNAs candidates were detected. After differential expression analysis, we noticed that the expressions of 7 miRNAs were significantly up-regulated in young giant pandas compared with that of adults. Moreover, 2 miRNAs were up-regulated in female giant pandas and 1 in the male individuals. Target gene prediction suggested that the miRNAs of giant panda might be relevant to the expressions of 4,602 downstream genes. Subseuqently, the predicted target genes were conducted to KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis and we found that these genes were mainly involved in host immunity, including the Ras signaling pathway, the PI3K-Akt signaling pathway, and the MAPK signaling pathway. In conclusion, our results provide the first miRNA profiles of giant panda blood, and the predicted functional analyses may open an avenue for further study of giant panda immunity.