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At least 19 recordsLinked to original sources

Genomic signatures of the Arctic-adapted North American gray wolf ecotype.

The Arctic Circle is one of Earth's most extreme environments. It features cold temperatures, resource shortages, and near-complete winter darkness. Here, we generated a chromosome-level genome assembly of a male wolf from the Arctic Archipelago (Canis lupus arctos). Our assembly and that of the related C. l. orion from Greenland was used to identify candidate genic and regulatory features of Arctic-adapted polar wolves, ranging from selection acting on standing variation and amino acid changes in genes to conserved non-exonic elements (CNEEs) that may regulate gene expression. We identified genes and nearby CNEEs associated with thermoregulation (e.g., APOB), coat color and patterning (e.g., GOLGB1), and DNA damage response (e.g., POLQ). In vitro assays supported changes in polar wolf gene (POLQ and TRPV2 amino acid substitutions) and CNEE function. Our report offers insights into the genetic mechanisms underlying polar wolf adaptations, laying a foundation for future studies on Arctic canines.

Amino acid substitutions

Complex and Dynamic Gene-by-Age and Gene-by-Environment Interactions Underlie Functional Morphological Variation in Adaptive Divergence in Arctic Charr (Salvelinus alpinus).

The evolution of adaptive phenotypic divergence requires heritable genetic variation. However, it is underappreciated that trait heritability is molded by developmental processes interacting with the environment. We hypothesized that the genetic architecture of divergent functional traits was dependent on age and foraging environment. Thus, we induced plasticity in full-sib families of Arctic charr (Salvelinus alpinus) morphs from two Icelandic lakes by mimicking prey variation in the wild. We characterized variation in body shape and size at two ages and investigated their genetic architecture with quantitative trait locus (QTL) analysis. Age had a greater effect on body shape than diet in most families, suggesting that development strongly influences phenotypic variation available for selection. Consistent with our hypothesis, multiple QTL were detected for all traits and their location depended on age and diet. Many of the genome-wide QTL were located within a subset of duplicated chromosomal regions suggesting that ancestral whole genome duplication events have played a role in the genetic control of functional morphological variation in the species. Moreover, the detection of two body shape QTL after controlling for the effects of age provides additional evidence for genetic variation in the plastic response of morphological traits to environmental variation. Thus, functional morphological traits involved in phenotypic divergence are molded by complex genetic interactions with development and environment.

Animals

Primary angle-closure glaucoma. Oculometry, epidemiology, and genetics in a high risk population.

The ocular dimensions in patients suffering from primary angle-closure glaucoma (a.c.g.) have been studied in several clinical series, chiefly in Caucasians. The epidemiology and aetiology of a.c.g. are less well known although genetic factors seem to be involved. Eskimos have recently been shown to constitute a high risk population with respect to a.c.g. Consequently, a series of oculometric, epidemiologic, and genetic studies among Greenland Eskimos was undertaken. Besides the immediate purpose, prevention of blindness in this population, the survey had important general aspects and the following main results were obtained: 1a) Ocular dimensions, as well as clinical symptoms, in Eskimo a.c.g. patients correspond closely to those of a.c.g. reports from other ethnic groups and 1b) ocular dimensions of the anterior segment in the general Eskimo population deviate conspicuously towards the low level characteristic of all samples of a.c.g. patients. 2) A.c.g. prevalence rates were estimated at 1.6% in males and 5.1% in females of the general population aged 40 years or more. The epidemiology of a.c.g. seems to reflect closely the variations of axial anterior chamber depth (ACD) according to race (Eskimo, Caucasian), sex and age. Empirical a.c.g. risk estimates, depending on the ACD value, were obtained in elderly females. 3) A relatively shallow chamber was found in 1st and 2nd degree relatives of a.c.g. patients, in close agreement with an earlier study in Caucasians (Törnquist 1953). However, also in the general Eskimo population a pronounced familial resemblance with respect to ACD and corneal diameter was found. Thus the family studies indicate that the size of the anterior chamber shows a mainly genetic determination, which probably constitutes the genetic basis of a.c.g. as well. With this background a hypothesis is discussed, which interprets the small anterior chambers in Eskimos as a result of genetic adaptation to arctic environment. Corneal protection may have been the significant advantage and the a.c.g. load in elderly persons a relatively less important cost.

Adolescent

Temperature and Pressure Shaped the Evolution of Antifreeze Proteins in Polar and Deep Sea Zoarcoid Fishes.

Antifreeze proteins (AFPs) have enabled teleost fishes to repeatedly colonize polar seas. Four AFP types have convergently evolved in several fish lineages. AFPs inhibit ice crystal growth and lower tissue freezing point. In lineages with AFPs, species inhabiting colder environments may possess more AFP copies. Elucidating how differences in AFP copy number evolve is challenging due to the genes' tandem array structure and consequently poor resolution of these repetitive regions. Here, we explore the evolution of type III AFPs (AFP III) in the globally distributed suborder Zoarcoidei, leveraging six new long-read genome assemblies. Zoarcoidei has fewer genomic resources relative to other polar fish clades while it is one of the few groups of fishes adapted to both the Arctic and Southern Oceans. Combining these new assemblies with additional long-read genomes available for Zoarcoidei, we conducted a comprehensive phylogenetic test of AFP III evolution and modeled the effects of thermal habitat and depth on AFP III gene family evolution. We confirm a single origin of AFP III via neofunctionalization of the enzyme sialic acid synthase B. We also show that AFP copy number increased under low temperature but decreased with depth, potentially because pressure lowers freezing point. Associations between the environment and AFP III copy number were driven by duplications of paralogs that were translocated out of the ancestral locus at which AFP III arose. Our results reveal novel environmental effects on AFP evolution and demonstrate the value of high-quality genomic resources for studying how structural genomic variation shapes convergent adaptation.

Animals

Whole Genome Sequencing Reveals How Plasticity and Genetic Differentiation Underlie Sympatric Morphs of Arctic Charr.

Salmonids have a remarkable ability to form sympatric morphs after postglacial colonisation of freshwater lakes. These morphs often differ in morphology, feeding and spawning behaviour. Here, we explored the genetic basis of morph differentiation in Arctic charr (n = 283) by first establishing a high-quality reference genome and then using this in whole genome sequencing of distinct morphs present in two Norwegian and two Icelandic lakes. The four lakes represent the spectrum of genetic differentiation between morphs from one lake with no genetic differentiation between morphs, implying phenotypic plasticity, to two lakes with locus-specific genetic differentiation, implying incomplete reproductive isolation, and one lake with strong genome-wide divergence consistent with complete reproductive isolation. As many as 12 putative inversions ranging from 0.45 to 3.25 Mbp in size segregated among the four morphs present in one lake, Thingvallavatn, and these contributed significantly to the genetic differentiation among morphs. None of the putative inversions were found in any of the other lakes, but there were cases of partial haplotype sharing in similar morph contrasts in other lakes. Our findings are consistent with a highly polygenic basis of morph differentiation with population-specific selection on alleles linked to the development of similar morph phenotypes. The results support a model where morph differentiation is first established through phenotypic plasticity, leading to niche expansion and separation. This may be followed by gradual development of reproductive isolation, locus-specific differentiation and eventually complete reproductive isolation and genome-wide divergence.

Whole Genome Sequencing

Exploring biohydrogen producing potential of Arctic ice and water through metagenomics and dark fermentation kinetics.

Cryospheric ecosystems in the high Arctic harbor largely unexplored microbiomes with significant biotechnological potential. The present study evaluates the biohydrogen production capabilities of the indigenous microbiome of Ny-Ålesund, Svalbard, using glacial ice and surface water samples. Dark fermentation batch assays were performed at 4 °C and 20 °C with 2-bromoethanesulfonate (BES), a methanogenic inhibitor, to track the succession of metabolic and taxonomic diversity. Metagenomic and functional analyses revealed that under 20 °C and BES conditions, psychrotolerant microbial communities maximize biohydrogen production to 85% of the total biogas produced, with an acetate-dominant fermentation pathway, as inferred from volatile fatty acid (VFA) analysis. This evolves into a highly coordinated system utilizing a coupled Rnf-nitrogenase route alongside Formate Hydrogenlyase and [FeFe]-hydrogenase pathways. Kinetic modelling using the Modified Gompertz equation, along with Q10 temperature-sensitivity indices, demonstrated a very high latent catalytic potential in these cold-adapted microbiomes. This study indicates that Arctic microbiomes are highly elastic thermodynamically and could serve as highly efficient, manipulatable biocatalysts for the environmental recovery of bioenergy through engineered low-temperature systems.

Fermentation