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Browsing by Author "Rashkovetsky, Eugenia"

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    Genomic divergence and adaptive convergence in Drosophila simulans from Evolution Canyon, Israel
    Kang, Lin; Rashkovetsky, Eugenia; Michalak, Katarzyna; Garner, Harold R.; Mahaney, James E.; Rzigalinski, Beverly A.; Korol, Abraham B.; Nevo, Eviatar; Michalak, Pawel (2019-06-11)
    Biodiversity refugia formed by unique features of the Mediterranean arid landscape, such as the dramatic ecological contrast of "Evolution Canyon," provide a natural laboratory in which local adaptations to divergent microclimate conditions can be investigated. Significant insights have been provided by studies of Drosophila melanogaster diversifying along the thermal gradient in Evolution Canyon, but a comparative framework to survey adaptive convergence across sister species at the site has been lacking. To fill this void, we present an analysis of genomic polymorphism and evolutionary divergence of Drosophila simulans, a close relative of Drosophila melanogaster with which it co-occurs on both slopes of the canyon. Our results show even deeper interslope divergence in D. simulans than in D. melanogaster, with extensive signatures of selective sweeps present in flies from both slopes but enhanced in the population from the hotter and drier south-facing slope. Interslope divergence was enriched for genes related to electrochemical balance and transmembrane transport, likely in response to increased selection for dehydration resistance on the hotter slope. Both species shared genomic regions that underwent major selective sweeps, but the overall level of adaptive convergence was low, demonstrating no shortage of alternative genomic solutions to cope with the challenges of the microclimate contrast. Mobile elements were a major source of genetic polymorphism and divergence, affecting all parts of the genome, including coding sequences of mating behavior-related genes.
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    Rapid genomic changes in Drosophila melanogaster adapting to desiccation stress in an experimental evolution system
    Kang, Lin; Aggarwal, Dau Dayal; Rashkovetsky, Eugenia; Korol, Abraham B.; Michalak, Pawel (BMC, 2016-03-15)
    Background Experimental evolution studies, coupled with whole genome resequencing and advances in bioinformatics, have become a powerful tool for exploring how populations respond to selection at the genome-wide level, complementary to genome-wide association studies (GWASs) and linkage mapping experiments as strategies to connect genotype and phenotype. In this experiment, we analyzed genomes of Drosophila melanogaster from lines evolving under long-term directional selection for increased desiccation resistance in comparison with control (no-selection) lines. Results We demonstrate that adaptive responses to desiccation stress have exerted extensive footprints on the genomes, manifested through a high degree of fixation of alleles in surrounding neighborhoods of eroded heterozygosity. These patterns were highly convergent across replicates, consistent with signatures of ‘soft’ selective sweeps, where multiple alleles present as standing genetic variation become beneficial and sweep through the replicate populations at the same time. Albeit much less frequent, we also observed line-unique sweep regions with zero or near-zero heterozygosity, consistent with classic, or ‘hard’, sweeps, where novel rather than pre-existing adaptive mutations may have been driven to fixation. Genes responsible for cuticle and protein deubiquitination seemed to be central to these selective sweeps. High divergence within coding sequences between selected and control lines was also reflected by significant results of the McDonald-Kreitman and Ka/Ks tests, showing that as many as 347 genes may have been under positive selection. Conclusions Desiccation stress, a common challenge to many organisms inhabiting dry environments, proves to be a very potent selecting factor having a big impact on genome diversity.
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    Regulation of gene expression and RNA editing in Drosophila adapting to divergent microclimates
    Yablonovitch, Arielle L.; Fu, Jeremy; Li, Kexin; Mahato, Simpla; Kang, Lin; Rashkovetsky, Eugenia; Korol, Abraham B.; Tang, Hua; Michalak, Pawel; Zelhof, Andrew C.; Nevo, Eviatar; Li, Jin Billy (Springer Nature, 2017-11-17)
    Determining the mechanisms by which a species adapts to its environment is a key endeavor in the study of evolution. In particular, relatively little is known about how transcriptional processes are fine-tuned to adjust to different environmental conditions. Here we study Drosophila melanogaster from 'Evolution Canyon' in Israel, which consists of two opposing slopes with divergent microclimates. We identify several hundred differentially expressed genes and dozens of differentially edited sites between flies from each slope, correlate these changes with genetic differences, and use CRISPR mutagenesis to validate that an intronic SNP in prominin regulates its editing levels. We also demonstrate that while temperature affects editing levels at more sites than genetic differences, genetically regulated sites tend to be less affected by temperature. This work shows the extent to which gene expression and RNA editing differ between flies from different microclimates, and provides insights into the regulation responsible for these differences.