Biology subjects

Ullrich, K.

Publications and source records attributed to Ullrich, K..

4 recordsLinked to original sources

bioRxiv2024

De novo assembly of the selfish t supergene reveals a deleterious evolutionary trajectory

Supergenes are linked clusters of DNA that are transmitted together due to rare or absent recombination. They undergo co-adaptation, allowing evolution to work on several genes to refine complex phenotypes, giving supergenes a competitive edge. Yet, due to their lack of recombination, supergenes are susceptible to deterioration as they cannot efficiently purge deleterious DNA. Few examples outside of sex chromosomes have been available for study. Here, we present the first assembly of the t haplotype, a 33.4 Mb supergene in house mice that selfishly transmits itself at non-Mendelian frequencies. We characterize the four large non-overlapping inversions that make up the t haplotype. We compare in a t/t individual two different t variants with different recessive lethal phenotypes (age at death). Despite that difference, they differ much less from each other than the rest of the chromosome. However, the differences that they have were much more likely to be deleterious than the differences between the two variants of the rest of the chromosome. We interpret this marked difference as evidence of the accumulation of deleterious variants, a hallmark of deterioration. The t region of chromosome 17 is more distant to the reference than the rest of the chromosome, and has a higher fraction of impactful differences here as well. Thus, we conclude that the t appears as a quickly spreading and deteriorating selfish supergene, a rare example of Mullers ratchet outside of sex chromosomes. Furthermore, we aim for our assembly to provide a resource for comparative work on the t haplotype, such as its evolutionary history.

evolutionary biology↗

bioRxiv2023

Structural genomic variation and migratory behavior in wild songbirds

Structural variants (SVs) are a major source of genetic variation, but accurate descriptions in natural populations and connections with phenotypic traits remain scarce. We integrated advances in genomic sequencing and animal tracking to begin filling this knowledge gap in the Eurasian blackcap. Specifically, we (i) characterized the genome-wide distribution, frequency and overall fitness effects of SVs using haplotype-resolved assemblies for 79 birds, and (ii) used these SVs to study the genetics of seasonal migration. We detected >15K SVs. Many SVs overlapped repetitive regions and exhibited evidence of purifying selection suggesting they have overall deleterious effects on fitness. We used estimates of genomic differentiation to identify SVs exhibiting evidence of selection in blackcaps with different migratory strategies. Insertions and deletions dominated these SVs and were associated with genes that are either directly (e.g., regulatory motifs that maintain circadian rhythms) or indirectly (e.g., through immune response) related to migration. We also broke migration down into individual traits (direction, distance and timing) using existing tracking data and tested if genetic variation at the SVs we identified could account for phenotypic variation at these traits. This was only the case for one trait - direction - and one specific SV (a deletion on chromosome 27) accounted for much of this variation. Our results highlight the evolutionary importance of SVs in natural populations and provide insight into the genetic basis of seasonal migration.

evolutionary biology↗

bioRxiv2017

De Novo Genes are "Frozen Accidents" whichEscaped Rapid Turnover of Pervasively TranscribedORFs

A recent surge of studies suggested that many novel genes arise de novo from previously non-coding DNA and not by duplication. However, since most studies concentrated on longer evolutionary time scales and rarely considered protein structural properties, it remains unclear how these properties are shaped by evolution, depend on genetic mechanisms and influence gene survival. Here we compare open reading frames (ORFs) from high coverage transcriptomes from mouse and another four mammals covering 160 million years of evolution. We find that novel ORFs pervasively emerge from intergenic and intronic regions but are rapidly lost again while relatively fewer arise from duplications but are retained over much longer times. Surprisingly, disorder and other protein properties of young ORFs do not change with gene age. Only length and nucleotide composition change, probably to avoid aggregation. Thus de novo genes resemble frozen accidents of randomly emerged ORFs which survived initial purging, likely because they are functional.

evolutionary biology↗

bioRxiv2017

Ecological plant epigenetics: Evidence from model and non-model species, and the way forward

Growing evidence makes a strong case that epigenetic mechanisms contribute to complex traits, with implications across many fields of biology from dissecting developmental processes to understanding aspects of human health and disease. In ecology, recent studies have merged ecological experimental design with epigenetic analyses to elucidate the contribution of epigenetics to plant phenotypes, stress response, adaptation to habitat, or species range distributions. While there has been some progress in revealing the role of epigenetics in ecological processes, many studies with non-model species have so far been limited to describing broad patterns based on anonymous markers of DNA methylation. In contrast, studies with model species have benefited from powerful genomic resources, which allow for a more mechanistic understanding but have limited ecological realism. To understand the true significance of epigenetics for plant ecology and evolution, we must combine both approaches transferring knowledge and methods from model-species research to genomes of evolutionarily divergent species, and examining responses to complex natural environments at a more mechanistic level. This requires transforming genomics tools specifically for studying non-model species, which is challenging given the large and often polyploid genomes of plants. Collaboration between molecular epigeneticists, ecologists and bioinformaticians promises to enhance our understanding of the mutual links between genome function and ecological processes.

ecology↗