Late Pleistocene stickleback environmental genomes reveal the chronology of freshwater adaptation.

Directly observing the chronology and tempo of adaptation in response to ecological change is rarely possible in natural ecosystems. Sedimentary ancient DNA (sedaDNA) has been shown to be a tractable source of genome-scale data of long-dead organisms1,2,3 and to thereby potentially provide an understanding of the evolutionary histories of past populations.4,5 To date, time series of ecosystem biodiversity have been reconstructed from sedaDNA, typically using DNA metabarcoding or shotgun sequence data generated from less than 1 g of sediment.6,7 Here, we maximize sequence coverage by extracting DNA from ∼50× more sediment per sample than the majority of previous studies1,2,3 to achieve genotype resolution. From a time series of Late Pleistocene sediments spanning from a marine to freshwater ecosystem, we compare adaptive genotypes reconstructed from the environmental genomes of three-spined stickleback at key time points of this transition. We find a staggered temporal dynamic in which freshwater alleles at known loci of large effect in marine-freshwater divergence of three-spined stickleback (e.g., EDA)8 were already established during the brackish phase of the formation of the isolation basin. However, marine alleles were still detected across the majority of marine-freshwater divergence-associated loci, even after the complete isolation of the lake from marine ingression. Our retrospective approach to studying adaptation from environmental genomes of three-spined sticklebacks at the end of the last glacial period complements contemporary experimental approaches9,10,11 and highlights the untapped potential for retrospective "evolve and resequence" natural experiments using sedaDNA.

Exploring the microbial diversity of novel misos with metagenomics.

Interest in fermented foods, especially plant-based ones, has increased considerably in the last decade. Miso-a Japanese paste traditionally fermented with soybeans, salt, and koji (Aspergillus oryzae grown on grains or beans)-has gained attention among chefs for its rich flavour and versatility. Some chefs have even been experimenting with making novel misos with untraditional substrates to create new flavours. Such novel fermented foods also offer new scientific opportunities. To explore the microbial diversity of these new traditional foods, we sampled six misos made by the team at a leading restaurant called Noma in Copenhagen (Denmark), using yellow peas (including a nixtamalised treatment), lupin seeds, Swedish Vreta peas, grey peas, and Gotland lentils as substrates. All misos were made with the same recipe and fermented for 3 months at 28 °C. Samples were collected at the end of fermentation for subsequent shotgun metagenomic sequencing and a genome-resolved metagenomic analysis. The taxonomic profile of the samples revealed the presence of koji mould (A. oryzae) and Bacillus amyloliquefaciens in all misos. Various species of the genera Latilactobacillus, Lactiplantibacillus, Pediococcus and Staphylococcus were also detected. The Metagenome-Assembled Genomes (MAGs) revealed genomic sequences belonging to 12 different species and functional analyses of these MAGs were performed. Notably, we detected the presence of Exiguobacterium-the first reported instance of the genus in miso-and Average Nucleotide Identity (ANI) analyses suggest a potentially new species. We hope these results will improve the scientific literature on misos and contribute to developing novel fermented plant-based foods.

Conservation implications of elucidating the Korean wolf taxonomic ambiguity through whole-genome sequencing.

The taxonomic status of the now likely extirpated Korean Peninsula wolf has been extensively debated, with some arguing it represents an independent wolf lineage, Canis coreanus. To investigate the Korean wolf's genetic affiliations and taxonomic status, we sequenced and analysed the genomes of a Korean wolf dated to the beginning of the 20th century, and a captive wolf originally from the Pyongyang Central Zoo. Our results indicated that the Korean wolf bears similar genetic ancestry to other regional East Asian populations, therefore suggesting it is not a distinct taxonomic lineage. We identified regional patterns of wolf population structure and admixture in East Asia with potential conservation consequences in the Korean Peninsula and on a regional scale. We find that the Korean wolf has similar genomic diversity and inbreeding to other East Asian wolves. Finally, we show that, in contrast to the historical sample, the captive wolf is genetically more similar to wolves from the Tibetan Plateau; hence, Korean wolf conservation programmes might not benefit from the inclusion of this specimen.

Intestinal epigenotype of Atlantic salmon (Salmo salar) associates with tenacibaculosis and gut microbiota composition.

It remains a challenge to obtain the desired phenotypic traits in aquacultural production of Atlantic salmon, and part of the challenge might come from the effect that host-associated microorganisms have on the fish phenotype. To manipulate the microbiota towards the desired host traits, it is critical to understand the factors that shape it. The bacterial gut microbiota composition can vary greatly among fish, even when reared in the same closed system. While such microbiota differences can be linked to diseases, the molecular effect of disease on host-microbiota interactions and the potential involvement of epigenetic factors remain largely unknown. The aim of this study was to investigate the DNA methylation differences associated with a tenacibaculosis outbreak and microbiota displacement in the gut of Atlantic salmon. Using Whole Genome Bisulfite Sequencing (WGBS) of distal gut tissue from 20 salmon, we compared the genome-wide DNA methylation levels between uninfected individuals and sick fish suffering from tenacibaculosis and microbiota displacement. We discovered >19,000 differentially methylated cytosine sites, often located in differentially methylated regions, and aggregated around genes. The 68 genes connected to the most significant regions had functions related to the ulcerous disease such as epor and slc48a1a but also included prkcda and LOC106590732 whose orthologs are linked to microbiota changes in other species. Although the expression level was not analysed, our epigenetic analysis suggests specific genes potentially involved in host-microbiota interactions and more broadly it highlights the value of considering epigenetic factors in efforts to manipulate the microbiota of farmed fish.

Genomes of Pleistocene Siberian Wolves Uncover Multiple Extinct Wolf Lineages.

Extant Canis lupus genetic diversity can be grouped into three phylogenetically distinct clades: Eurasian and American wolves and domestic dogs.1 Genetic studies have suggested these groups trace their origins to a wolf population that expanded during the last glacial maximum (LGM)1-3 and replaced local wolf populations.4 Moreover, ancient genomes from the Yana basin and the Taimyr peninsula provided evidence of at least one extinct wolf lineage that dwelled in Siberia during the Pleistocene.35 Previous studies have suggested that Pleistocene Siberian canids can be classified into two groups based on cranial morphology. Wolves in the first group are most similar to present-day populations, although those in the second group possess intermediate features between dogs and wolves.67 However, whether this morphological classification represents distinct genetic groups remains unknown. To investigate this question and the relationships between Pleistocene canids, present-day wolves, and dogs, we resequenced the genomes of four Pleistocene canids from Northeast Siberia dated between >50 and 14 ka old, including samples from the two morphological categories. We found these specimens cluster with the two previously sequenced Pleistocene wolves, which are genetically more similar to Eurasian wolves. Our results show that, though the four specimens represent extinct wolf lineages, they do not form a monophyletic group. Instead, each Pleistocene Siberian canid branched off the lineage that gave rise to present-day wolves and dogs. Finally, our results suggest the two previously described morphological groups could represent independent lineages similarly related to present-day wolves and dogs.

The evolutionary history of extinct and living lions.

Lions are one of the world's most iconic megafauna, yet little is known about their temporal and spatial demographic history and population differentiation. We analyzed a genomic dataset of 20 specimens: two ca. 30,000-y-old cave lions (Panthera leo spelaea), 12 historic lions (Panthera leo leo/Panthera leo melanochaita) that lived between the 15th and 20th centuries outside the current geographic distribution of lions, and 6 present-day lions from Africa and India. We found that cave and modern lions shared an ancestor ca. 500,000 y ago and that the 2 lineages likely did not hybridize following their divergence. Within modern lions, we found 2 main lineages that diverged ca. 70,000 y ago, with clear evidence of subsequent gene flow. Our data also reveal a nearly complete absence of genetic diversity within Indian lions, probably due to well-documented extremely low effective population sizes in the recent past. Our results contribute toward the understanding of the evolutionary history of lions and complement conservation efforts to protect the diversity of this vulnerable species.

Photosynthetic and transcriptional responses of the marine diatom Thalassiosira pseudonana to the combined effect of temperature stress and copper exposure.

A 96-h exposure experiment was conducted to elucidate the toxicity responses of the marine diatom Thalassiosira pseudonana upon exposure to different temperatures and copper (Cu) concentrations. Three Cu treatments (seawater control; 200µg/L Cu, EC50 for the yield at 25°C; and 1000µg/L Cu, EC50 for growth inhibition at 25°C) were conducted against four temperatures (10°C, 15°C, 25°C and 30°C). Growth rate and photosynthetic responses showed a significant interacting thermal-chemical effect with strong synergistic responses observed at 30°C treatments. Expression of heat shock protein (hsp) was positively modulated by increasing temperatures. Hsp 90, hsp90-2 and sit1 (related to silica shell formation) were highly expressed at 30°C under 1000µg/L Cu, while the genes encoding light harvesting proteins (3HfcpA and 3HfcpB) and silaffin precursor sil3 were significantly up-regulated at 15°C under 200µg/L Cu. Our results indicated an increase Cu toxicity to T. pseudonana under high temperature and Cu dose.

De novo transcriptome analysis of Perna viridis highlights tissue-specific patterns for environmental studies.

BACKGROUND: The tropical green-lipped mussel Perna viridis is a common biomonitor throughout the Indo-Pacific region that is used for environmental monitoring and ecotoxicological investigations. However, there is limited molecular data available regarding this species. We sought to establish a global transcriptome database from the tissues of adductor muscle, gills and the hepatopancreas of P. viridis in an effort to advance our understanding of the molecular aspects involved during specific toxicity responses in this sentinel species. RESULTS: Illumina sequencing results yielded 544,272,542 high-quality filtered reads. After de novo assembly using Trinity, 233,257 contigs were generated with an average length of 1,264 bp and an N50 length of 2,868 bp; 192,879 assembled transcripts and 150,111 assembled unigenes were obtained after clustering. A total of 93,668 assembled transcripts (66,692 assembled genes) with putative functions for protein domains were predicted based on InterProScan analysis. Based on similarity searches, 44,713 assembled transcripts and 25,319 assembled unigenes were annotated with at least one BLAST hit. A total of 21,262 assembled transcripts (11,947 assembled genes) were annotated with at least one well-defined Gene Ontology (GO) and 5,131 assembled transcripts (3,181 assembled unigenes) were assigned to 329 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The quantity of assembled unigenes and transcripts obtained from male and female mussels were similar but varied among the three studied tissues, with the highest numbers recorded in the gills, followed by the hepatopancreas, and then the adductor muscle. Multivariate analyses revealed strong tissue-specific patterns among the three different tissues, but not between sexes in terms of expression profiles for annotated genes in various GO terms, and genes associated with stress responses and degradation of xenobiotics. The expression profiles of certain selected genes in each tissue type were further validated using real-time quantitative polymerase chain reaction assays and a similar tissue-specific trend was seen. CONCLUSIONS: The extensive sequence data generated from this study will provide a valuable molecular resource for facilitating environmental studies with P. viridis, and highlight the importance of tissue-specific approaches in the future.

Differential proteomic responses in hepatopancreas and adductor muscles of the green-lipped mussel Perna viridis to stresses induced by cadmium and hydrogen peroxide.

This study aimed to reveal the proteomic responses in the hepatopancreas and adductor muscle of a common biomonitor, Perna viridis after 14-day exposure to two model chemicals, cadmium (Cd; a toxic metal) and hydrogen peroxide (H(2)O(2); a pro-oxidant), using two-dimensional gel electrophoresis coupled with multivariate statistical analyses. Unique sets of tissue-specific protein expression signatures were revealed corresponding to the two treatment groups. In the hepatopancreas, 15 and 2 spots responded to Cd and H(2)O(2) treatments respectively. 6 and 7 spots were differentially expressed in the adductor muscle for Cd and H(2)O(2) treatments, respectively. 15 differentially expressed spots were successfully identified by MALDI-TOF/TOF MS analysis. These proteins are involved in glycolysis, amino acid metabolism, energy homeostasis, oxidative stress response, redox homeostasis and protein folding, heat-shock response, and muscle contraction modulation. This is the first time, to have demonstrated that Cd exposure not only leads to substantial oxidative stress but also results in endoplasmic reticulum stress in hepatopancreas of the mussel. Such notable stress responses may be attributable to high Cd accumulation in this tissue. Our results suggested that investigations on these stress-associated protein changes could be used as a new and complementary approach in pollution monitoring by this popular biomonitor species.