Biology subjects

Grath, S.

Publications and source records attributed to Grath, S..

6 recordsLinked to original sources

bioRxiv2025

Dissecting Cold Tolerance in Drosophila ananassae: A Multi-Phenotypic and Bulk Segregant Analysis

As a major element of the environment, temperature impacts the geographical ranges of insects. Therefore, the worldwide distribution of insects follows adaptation to wide ranges of temperature. A population of Drosophila ananassae from the ancestral region showed variation in cold tolerance levels. The ancestral Bangkok population also differed from the derived Kathmandu population regarding cold tolerance. However, the phenotypic variation was only measured by chill coma assays, and no further characterization of the cold tolerance phenotype was performed. Here, we aimed to further characterize the iso-female lines of Bangkok and Kathmandu populations and the recombinant inbred lines generated from the ancestral population using lethal time and cold shock mortality in addition to chill coma recovery time. We showed that cold tolerance phenotypes differ between sexes, the additional phenotypes do not correlate significantly to chill coma recovery time, and some recombinant inbred lines have extreme phenotypes with higher tolerance than the tolerant founder or lower tolerance than the sensitive founder. We performed bulk segregant analysis using the recombinant inbred lines that exhibited extreme chill coma recovery time to identify genomic regions responsible for the phenotype. We identified 16 regions with significant association with the phenotype and showed that the genes in the putative regions were enriched in muscle development, metabolic processes, and cytoskeletal protein binding. Our results provide further evidence for the need for multiple cold tolerance phenotypes and shed light on the genetic architecture of adaptive phenotypic changes in natural populations of Drosophila.

evolutionary biology↗

bioRxiv2024

Navigating the Cold: Integrative Transcriptome Sequencing Approach Reveals Ionoregulatory and Whole-Body Responses to Cold Acclimation in Drosophila ananassae

Understanding how species adapt to changing environments is a major goal in evolutionary biology and can elucidate the impact of climate change. Climate imposes inevitable effects on the geographical distribution of insects as their body temperature primarily depends on the environment. The vinegar fly Drosophila ananassae expanded from its tropical ancestral range to more temperate regions, which requires adaptation to colder temperatures. Transcriptome and genome-wide association studies focusing on the ancestral-range population identified the targets of selection related to ionoregulatory tissues. However, how cosmopolitan D. ananassae adapted to colder environments, where low temperatures last longer, is still unknown. Here, we present a study on the effect of long-term cold exposure on D. ananassae, examining the gene expression variation in the whole body and the ionoregulatory tissues, namely the hindgut and the Malpighian tubule. To elucidate molecular mechanisms of cold adaptation during species expansion, we included cold-tolerant and cold-sensitive strains from the ancestral species range and cold-tolerant strains from the derived species range. We show that cold acclimation improves cold tolerance and results in differential expression of more than half of the transcriptome in the ionoregulatory tissues and the whole body. Notably, we provide complementary insight into molecular processes at four levels: strains, populations, phenotypes, and tissues. By determining the biochemical pathways of phenotypic plasticity underlying cold tolerance, our results enhance our understanding of how environmental changes affect thermal adaptation in natural populations. SignificanceThe physiological mechanisms underlying cold tolerance of insects are complex. Our study integrates tissue-specific responses with whole-body response to cold and compares these responses in different populations, phenotypes, and strains of the vinegar fly Drosophila ananassae. The study reveals that the response to extended cold in the renal and intestinal tissues are different, that the tissue-specific responses can be masked in the whole body, and that the transcriptomic response to extended cold can depend on population of origin, cold tolerance phenotype, or strain. Overall, this study sheds light on insect cold adaptation in terms of transcriptomic response to cold acclimation in the ionoregulatory tissues and whole bodies.

evolutionary biology↗

bioRxiv2021

Drosophila Evolution over Space and Time (DEST) - A New Population Genomics Resource

Drosophila melanogaster is a leading model in population genetics and genomics, and a growing number of whole-genome datasets from natural populations of this species have been published over the last 20 years. A major challenge is the integration of these disparate datasets, often generated using different sequencing technologies and bioinformatic pipelines, which hampers our ability to address questions about the evolution and population structure of this species. Here we address these issues by developing a bioinformatics pipeline that maps pooled sequencing (Pool-Seq) reads from D. melanogaster to a hologenome consisting of fly and symbiont genomes and estimates allele frequencies using either a heuristic (PoolSNP) or a probabilistic variant caller (SNAPE-pooled). We use this pipeline to generate the largest data repository of genomic data available for D. melanogaster to date, encompassing 271 population samples from over 100 locations in >20 countries on four continents based on a combination of 121 unpublished and 150 previously published genomic datasets. Several of these locations have been sampled at different seasons across multiple years. This dataset, which we call Drosophila Evolution over Space and Time (DEST), is coupled with sampling and environmental meta-data. A web-based genome browser and web portal provide easy access to the SNP dataset. Our aim is to provide this scalable platform as a community resource which can be easily extended via future efforts for an even more extensive cosmopolitan dataset. Our resource will enable population geneticists to analyze spatio-temporal genetic patterns and evolutionary dynamics of D. melanogaster populations in unprecedented detail.

genomics↗

bioRxiv2020

The discovery, distribution and diversity of DNA viruses associated with Drosophila melanogaster in Europe

Drosophila melanogaster is an important model for antiviral immunity in arthropods, but very few DNA viruses have been described from the family Drosophilidae. This deficiency limits our opportunity to use natural host-pathogen combinations in experimental studies, and may bias our understanding of the Drosophila virome. Here we report fourteen DNA viruses detected in a metagenomic analysis of approximately 6500 pool-sequenced Drosophila, sampled from 47 European locations between 2014 and 2016. These include three new Nudiviruses, a new and divergent Entomopox virus, a virus related to Leptopilina boulardi filamentous virus, and a virus related to Musca domestica salivary gland hypertrophy virus. We also find an endogenous genomic copy of Galbut virus, a dsRNA Partitivirus, segregating at very low frequency. Remarkably, we find that Drosophila Vesanto virus, a small DNA virus previously described as a Bidnavirus, may be composed of up to 12 segments and represent a new lineage of segmented DNA viruses. Two of the DNA viruses, Drosophila Kallithea nudivirus and Drosophila Vesanto virus are relatively common, found in 2% or more of wild flies. The others are rare, with many likely to be represented by a single infected fly. We find that virus prevalence in Europe reflects the prevalence seen in publicly-available datasets, with Drosophila Kallithea nudivirus and Drosophila Vesanto virus the only ones commonly detectable in public data from wild-caught flies and large population cages, and the other viruses being rare or absent. These analyses suggest that DNA viruses are at lower prevalence than RNA viruses in D. melanogaster, and may be less likely to persist in laboratory cultures. Our findings go some way to redressing an earlier bias toward RNA virus studies in Drosophila, and lay the foundation needed to harness the power of Drosophila as a model system for the study of DNA viruses.

microbiology↗

bioRxiv2019

Three quantitative trait loci explain more than 60% of phenotypic variation for chill coma recovery time in Drosophila ananassae

Ectothermic species such as insects are particularly vulnerable to climatic fluctuations. Nevertheless, many insects that evolved and diversified in the tropics have successfully colonized temperate regions all over the globe. To shed light on the genetic basis of cold tolerance in such species, we conducted a quantitative trait locus (QTL) mapping experiment for chill coma recovery time (CCRT) in Drosophila ananassae, a cosmopolitan species that has expanded its range from tropical to temperate regions.\n\nWe created a mapping population of recombinant inbred advanced intercross lines (RIAILs) from two founder strains with diverging CCRT phenotypes. The RIAILs were phenotyped for their CCRT and, together with the founder strains, genotyped for polymorphic markers with double-digest restriction site-associated DNA (ddRAD) sequencing. Using a hierarchical mapping approach that combined standard interval mapping and a multiple-QTL model, we mapped three QTL which altogether explained 64% of the phenotypic variance. For two of the identified QTL, we found evidence of epistasis. To narrow down the list of cold tolerance candidate genes, we cross-referenced the QTL intervals with genes that we previously identified as differentially expressed in response to cold in D. ananassae, and with thermotolerance candidate genes of D. melanogaster. Among the 58 differentially expressed genes that were contained within the QTL, GF15058 showed a significant interaction of the CCRT phenotype and gene expression. Further, we identified the orthologs of four D. melanogaster thermotolerance candidate genes, MtnA, klarsicht, CG5246 (D.ana/GF17132) and CG10383 (D.ana/GF14829) as candidates for cold tolerance in D. ananassae.

evolutionary biology↗

bioRxiv2018

Genomic analysis of European Drosophila melanogaster populations on a dense spatial scale reveals longitudinal population structure and continent-wide selection

Genetic variation is the fuel of evolution, with standing genetic variation especially important for short-term evolution and local adaptation. To date, studies of spatio-temporal patterns of genetic variation in natural populations have been challenging, as comprehensive sampling is logistically difficult, and sequencing of entire populations costly. Here, we address these issues using a collaborative approach, sequencing 48 pooled population samples from 32 locations, and perform the first continent-wide genomic analysis of genetic variation in European Drosophila melanogaster. Our analyses uncover longitudinal population structure, provide evidence for continent-wide selective sweeps, identify candidate genes for local climate adaptation, and document clines in chromosomal inversion and transposable element frequencies. We also characterise variation among populations in the composition of the fly microbiome, and identify five new DNA viruses in our samples.

evolutionary biology↗