Genome-wide analysis sheds light on the high-altitude adaptation of the buff-throated partridge (Tetraophasis szechenyii)

Modulating vertebrate physiology by genomic fine-tuning of GPCR functions

G protein-coupled receptors (GPCRs) play a crucial role as membrane receptors, facilitating the communication of eukaryotic species with their environment and regulating cellular and organ interactions. Consequently, GPCRs hold immense potential in contributing to adaptation to ecological niches and responding to environmental shifts. Comparative analyses of vertebrate genomes reveal patterns of GPCR gene loss, expansion, and signatures of selection. Integrating these genomic data with insights from functional analyses of gene variants enables the interpretation of genotype-phenotype correlations. This review underscores the involvement of GPCRs in adaptive processes, presenting numerous examples of how alterations in GPCR functionality influence vertebrate physiology or, conversely, how environmental changes impact GPCR functions. The findings demonstrate that modifications in GPCR function contribute to adapting to aquatic, arid, and nocturnal habitats, influencing camouflage strategies, and specializing in particular dietary preferences. Furthermore, the adaptability of GPCR functions provides an effective mechanism in facilitating past, recent, or ongoing adaptations in animal domestication and human evolution and should be considered in therapeutic strategies and drug development.

Coping with alpine habitats: genomic insights into the adaptation strategies of Triplostegia glandulifera (Caprifoliaceae)

How plants find a way to thrive in alpine habitats remains largely unknown. Here we present a chromosome-level genome assembly for an alpine medicinal herb, Triplostegia glandulifera (Caprifoliaceae), and 13 transcriptomes from other species of Dipsacales. We detected a whole-genome duplication event in T. glandulifera that occurred prior to the diversification of Dipsacales. Preferential gene retention after whole-genome duplication was found to contribute to increasing cold-related genes in T. glandulifera. A series of genes putatively associated with alpine adaptation (e.g. CBFs, ERF-VIIs, and RAD51C) exhibited higher expression levels in T. glandulifera than in its low-elevation relative, Lonicera japonica. Comparative genomic analysis among five pairs of high- vs low-elevation species, including a comparison of T. glandulifera and L. japonica, indicated that the gene families related to disease resistance experienced a significantly convergent contraction in alpine plants compared with their lowland relatives. The reduction in gene repertory size was largely concentrated in clades of genes for pathogen recognition (e.g. CNLs, prRLPs, and XII RLKs), while the clades for signal transduction and development remained nearly unchanged. This finding reflects an energy-saving strategy for survival in hostile alpine areas, where there is a tradeoff with less challenge from pathogens and limited resources for growth. We also identified candidate genes for alpine adaptation (e.g. RAD1, DMC1, and MSH3) that were under convergent positive selection or that exhibited a convergent acceleration in evolutionary rate in the investigated alpine plants. Overall, our study provides novel insights into the high-elevation adaptation strategies of this and other alpine plants.

Chromosomal-level reference genome of a wild North American mallard (Anas platyrhynchos)

The mallard (Anas platyrhynchos) is one of the most common, economically, and socially important birds around the world. Mallards were not only an important food source for early humans but eventually becoming intimately linked with people as they were domesticated over the last 2,000 years. To date, mallard genomes are largely reconstructed from samples of domestic or unknown genetic heritage. Here, we report the first high-quality genome assembly and annotation of a genetically vetted wild mallard from North America (NAwild_v1.0). The genome was assembled using a combination of shotgun libraries, proximity ligation Chicago, and Dovetail Hi-C libraries. The final assembly is ∼1.04 Gb in size, with 98.3% of the sequence located in 30 full or nearly full chromosome-level scaffolds, and with a N50/L50 of 79.1 Mb/4 scaffolds. We used a combination of gene prediction and similarity approaches to annotate a total of 23,584 functional genes, of which 19,242 were associated to GO terms. The genome assembly and the set of annotated genes yielded a 95.4% completeness score when compared with the BUSCO aves_odb10 dataset. Next, we aligned 3 previously published mallard genomes to ours, and demonstrate how runs of homozygosity and nucleotide diversity are substantially higher and lower, respectively, to ours and how these artificially changed genomes resulted in profoundly different and biased demographic histories. Our wild mallard assembly not only provides a valuable resource to shed light onto genome evolution, speciation, and other adaptive processes, but also helping with identifying functional genes that have been significantly altered during the domestication process.

A de novo assembled genome of the Tibetan Partridge (Perdix hodgsoniae) and its high-altitude adaptation

The Tibetan Partridge (Perdix hodgsoniae) is an endemic species distributed in high-altitude areas of 3600-5600 m on the Qinghai-Tibet Plateau. To explore how the species is adapted to the high elevation environment, we assembled a draft genome based on both the Illumina and PacBio sequencing platforms with its population genetics and genomics analysis. In total, 134.74 Gb short reads and 30.81 Gb long reads raw data were generated. The 1.05-Gb assembled genome had a contig N50 of 4.56 Mb, with 91.94% complete BUSCOs. The 17 457 genes were annotated, and 11.35% of the genome was composed of repeat sequences. The phylogenetic tree showed that P. hodgsoniae was located at the basal position of the clade, including Golden Pheasant (Chrysolophus pictus), Common Pheasant (Phasianus colchicus), and Mikado Pheasant (Syrmaticus mikado). We found that 1014, 2595, and 2732 of the 6641 one-to-one orthologous genes were under positive selection in P. hodgsoniae, detected using PAML, BUSTED, and aBSREL programs, respectively, of which 965 genes were common under positive selection with 3 different programs. Several positively selected genes and immunity pathways relevant to high-altitude adaptation were detected. Gene family evolution showed that 99 gene families experienced significant expansion events, while 6 gene families were under contraction. The total number of olfactory receptor genes was relatively low in P. hodgsoniae. Genomic data provide an important resource for a further study on the evolutionary history of P. hodgsoniae, which provides a new insight into its high-altitude adaptation mechanisms.

Integrative analysis identifies potential ferroptosis-related genes of hypoxia adaptation in yak

There are studies on the hypoxia adaptation in yak, but there are few studies on the regulation of ferroptosis by hypoxia. This study was the first time to explore ferroptosis-related genes about hypoxia in yak. In this study, the oviduct epithelial cells between yak and bovine are performed by integrative analysis for functions, regulating network and hub genes. The results showed 29 up-regulated ferroptosis genes and 67 down-regulated ferroptosis genes, and GO-KEGG analysis showed that up-regulated differentially expressed genes (DEGs) were significantly enriched in ribosome pathway and oxidative phosphorylation pathway. Down-regulated DEGs were significantly enriched in longevity regulating pathway-mammal pathway. Mitophagy-Animal Pathway was a significant enrichment pathway for the up-regulated differentially expressed ferroptosis genes (DE-FRGs). HIF-1 signaling pathway is a significant pathway for the down-regulated DE-FRGs. By constructing DE-FRGs protein-protein interaction (PPI) network, 10 hub DE-FRGs (Jun, STAT3, SP1, HIF1A, Mapk1, Mapk3, Rela, Ulk1, CDKN1A, EPAS1) were obtained. The bta-mir-21-5p, bta-mir-10a and bta-mir-17-5p related to STAT3 were predicted. The results of this study indicated the important genes and pathways of the hypoxia in yak, and it was the first time to study ferroptosis genes and pathways related to the hypoxia adaptation by bulk-seq in yak. This study provided sufficient transcriptome datas for hypoxia adaptation.

Comparative Genomics and Evolution of Avian Specialized Traits

Genomic data are important for understanding the origin and evolution of traits. Under the context of rapidly developing of sequencing technologies and more widely available genome sequences, researchers are able to study evolutionary mechanisms of traits via comparative genomic methods. Compared with other vertebrates, bird genomes are relatively small and exhibit conserved synteny with few repetitive elements, which makes them suitable for evolutionary studies. Increasing genomic progress has been reported on the evolution of powered flight, body size variation, beak morphology, plumage colouration, high-elevation colonization, migration, and vocalization. By summarizing previous studies, we demonstrate the genetic bases of trait evolution, highlighting the roles of small-scale sequence variation, genomic structural variation, and changes in gene interaction networks. We suggest that future studies should focus on improving the quality of reference genomes, exploring the evolution of regulatory elements and networks, and combining genomic data with morphological, ecological, behavioural, and developmental biology data.

Evolutionary dynamics of the elevational diversity gradient in passerine birds

Low-elevation regions harbour the majority of the world's species diversity compared to high-elevation areas. This global gradient suggests that lowland species have had more time to diversify, or that net diversification rates have been higher in the lowlands. However, highlands seem to be cradles of diversity as they contain many young endemics, suggesting that their rates of speciation are exceptionally fast. Here we use a phylogenetic diversification model that accounts for the dispersal of species between different elevations to examine the evolutionary dynamics of the elevational diversity gradient in passerine birds, a group that has radiated globally to occupy almost all elevations and latitudes. We find strong support for a model in which passerines diversify at the same rate in the highlands and the lowlands but in which the per-capita rate of dispersal from high to low elevations is more than twice as fast as that in the reverse direction. This suggests that while there is no consistent trend in diversification across elevations, part of the diversity generated by highland regions migrates into the lowlands, thus setting up the observed gradient in passerine diversity. We find that this process drives tropical regions but for temperate areas, the analysis could be hampered by their lower richness. Despite their lower diversity, highland regions are disproportionally important for maintaining diversity in the adjacent lowlands.

Temperature, rainfall and wind variables underlie environmental adaptation in natural populations of Drosophila melanogaster

While several studies in a diverse set of species have shed light on the genes underlying adaptation, our knowledge on the selective pressures that explain the observed patterns lags behind. Drosophila melanogaster is a valuable organism to study environmental adaptation because this species originated in Southern Africa and has recently expanded worldwide, and also because it has a functionally well-annotated genome. In this study, we aimed to decipher which environmental variables are relevant for adaptation of D. melanogaster natural populations in Europe and North America. We analysed 36 whole-genome pool-seq samples of D. melanogaster natural populations collected in 20 European and 11 North American locations. We used the BayPass software to identify single nucleotide polymorphisms (SNPs) and transposable elements (TEs) showing signature of adaptive differentiation across populations, as well as significant associations with 59 environmental variables related to temperature, rainfall, evaporation, solar radiation, wind, daylight hours, and soil type. We found that in addition to temperature and rainfall, wind related variables are also relevant for D. melanogaster environmental adaptation. Interestingly, 23%-51% of the genes that showed significant associations with environmental variables were not found overly differentiated across populations. In addition to SNPs, we also identified 10 reference transposable element insertions associated with environmental variables. Our results showed that genome-environment association analysis can identify adaptive genetic variants that are undetected by population differentiation analysis while also allowing the identification of candidate environmental drivers of adaptation.

The draft genome of the blood pheasant (Ithaginis cruentus): Phylogeny and high-altitude adaptation

The blood pheasant (Ithaginis cruentus), the only species in the genus Ithaginis, lives in an extremely inhospitable high-altitude environment, coping with hypoxia and ultraviolet (UV) radiation. To further investigate the phylogeny of Phasianidae species based on complete genomes and understand the molecular genetic mechanisms of the high-altitude adaptation of the blood pheasant, we de novo assembled and annotated the complete genome of the blood pheasant. The blood pheasant genome size is 1.04 Gb with scaffold N50 of 10.88 Mb. We identified 109.92 Mb (10.62%) repetitive elements, 279,037 perfect microsatellites, and 17,209 protein-coding genes. The phylogenetic tree of Phasianidae based on whole genomes revealed three highly supported major clades with the blood pheasant included in the "erectile clade." Comparative genomics analysis showed that many genes were positively selected in the blood pheasant, which was associated with response to hypoxia and/or UV radiation. More importantly, among these positively selected genes (PSGs) which were related to high-altitude adaptation, sixteen PSGs had blood pheasant-specific missense mutations. Our data and analysis lay solid foundation to the study of Phasianidae phylogeny and provided new insights into the potential adaptation mechanisms to the high altitude employed by the blood pheasant.

First de novo whole genome sequencing and assembly of the bar-headed goose

Background

The bar-headed goose (Anser indicus) mainly inhabits the plateau wetlands of Asia. As a specialized high-altitude species, bar-headed geese can migrate between South and Central Asia and annually fly twice over the Himalayan mountains along the central Asian flyway. The physiological, biochemical and behavioral adaptations of bar-headed geese to high-altitude living and flying have raised much interest. However, to date, there is still no genome assembly information publicly available for bar-headed geese.

Methods

In this study, we present the first de novo whole genome sequencing and assembly of the bar-headed goose, along with gene prediction and annotation.

Results

10X Genomics sequencing produced a total of 124 Gb sequencing data, which can cover the estimated genome size of bar-headed goose for 103 times (average coverage). The genome assembly comprised 10,528 scaffolds, with a total length of 1.143 Gb and a scaffold N50 of 10.09 Mb. Annotation of the bar-headed goose genome assembly identified a total of 102 Mb (8.9%) of repetitive sequences, 16,428 protein-coding genes, and 282 tRNAs. In total, we determined that there were 63 expanded and 20 contracted gene families in the bar-headed goose compared with the other 15 vertebrates. We also performed a positive selection analysis between the bar-headed goose and the closely related low-altitude goose, swan goose (Anser cygnoides), to uncover its genetic adaptations to the Qinghai-Tibetan Plateau.

Conclusion

We reported the currently most complete genome sequence of the bar-headed goose. Our assembly will provide a valuable resource to enhance further studies of the gene functions of bar-headed goose. The data will also be valuable for facilitating studies of the evolution, population genetics and high-altitude adaptations of the bar-headed geese at the genomic level.