Whole genome sequencing of natural populations of social amoebae Dictyostelium discoideum
Ontology highlight
ABSTRACT: Whole genome sequencing of natural strains of D. discoideum from the USA and the world used to uncover the general impact of social conflict on the genome of this species.
INSTRUMENT(S): Illumina HiSeq 2000
ORGANISM(S): Dictyostelium Discoideum
SUBMITTER: Milner Center for Evolution, University of Bath
Project description:Tuberculosis remains one of the most difficult to control infectious diseases in the world. Many different factors contribute to the complexity of this disease. These include the ability of the host to control the infection which may directly relate to nutritional status, presence of co-morbidities and genetic predisposition. Pathogen factors, in particular the ability of different Mycobacterium tuberculosis strains to respond to the harsh environment of the host granuloma, which includes low oxygen and nutrient availability and the presence of damaging radical oxygen and nitrogen species, also play an important role in the success of different strains to cause disease. In this study we evaluate the impact of a naturally occurring 12 gene 15 Kb genomic deletion on the physiology and virulence of M. tuberculosis. The strains denominated ON-A WT (wild type) and ON-A NM (natural mutant) were isolated from a previously reported TB outbreak in an inner city under-housed population in Toronto, Canada. Here we subjected these isogenic strains to transcriptomic (via RNA-seq) and proteomic analyses and identified several gene clusters with differential expression in the natural mutant, including the DosR regulon and the molybdenum cofactor biosynthesis genes, both of which were found in lower abundance in the natural mutant. We also demonstrated lesser virulence of the natural mutant in the guinea pig animal model. Overall, our findings suggest that the ON-A natural mutant is less fit to cause disease, supporting the general idea that even low virulent strains have the potential to cause extended transmission in at risk populations.
Project description:Climate change is one of the main factors shaping the distributions and biodiversity of organisms, among others by greatly altering water availability, thus exposing species and ecosystems to harsh desiccation conditions. Insects are specially threatened by these challenging dry environments, thanks to their small size and thus large surface area to volume ratio. Drosophila melanogaster is a great model to study the response of populations to rapidly changing conditions, because of its southern African origin and recent and fast worldwide spreading. Desiccation stress response is a complex and extensively studied trait, however the natural variation and underlying molecular and physiological mechanisms responsible for the tolerance in natural European D. melanogaster populations has never been studied. Here we subjected to desiccation stress 74 natural D. melanogaster European strains, belonging to five different climate zones. We found that the strains belonging to the cold semi-arid climates are more tolerant compared to the others, and that this tolerance can be explained by the combination of altitude and evaporation. The tolerant strains had a lower level of initial water content and lost less water during desiccation stress. We found that the reduction in the water loss happens through a decrease in the respiration rate in desiccation stress conditions, and by having a less permeable cuticle prior the stress exposure. The decreased rate of respiration in the tolerant strains is a consequence of the down-regulation of genes related to diverse metabolic processes. Moreover, we found that the genes related to response to stimulus and environmental sensing are up-regulated only in the tolerant strains. We also identified four transposable element insertions, which might be responsible for changes in gene expression. Overall, our study for the first time described the physiological and transcriptomic changes underlying the desiccation tolerance of natural European D. melanogaster strains, and generated a list of putative mutations shaping desiccation stress response.
Project description:Identifying when and where environmental change induces molecular responses in natural populations is an important goal in contemporary ecology as it can aid in identifying molecular signatures of populations experiencing stressful conditions and potentially inform if species are approaching the limits of their tolerance niches. Achieving this goal is hampered by our understanding of the influence of environmental variation on the molecular systems of most ecologically relevant species as the pathways underlying fitness-affecting plastic responses have primarily been studied in model organisms under controlled laboratory conditions. To start overcoming this limitation, we establish relationships between protein abundance patterns and the abiotic environment. Profiling the proteomes of 24 natural populations of the putatively cold-adapted species Crunoecia irrorata and subsequently relating these profiles to natural variations in their abiotic freshwater spring habitats shows that protein abundances and networks respond to variation according to the functional roles these proteins have. We provide evidence that geographic and environmental distances affect protein abundances and identifications and that baseline abundances can be determined and used as information rather than noise in comparative field studies. Taking this naturally induced variation into account is a prerequisite if we are to identify the effects environmental change has on natural populations.
Project description:Climate change is one of the main factors shaping the distribution and biodiversity of organisms, among others by greatly altering water availability, thus exposing species and ecosystems to harsh desiccation conditions. Insects are especially threatened by these challenging dry environments, because of their small size and thus large surface area to volume ratio. Drosophila melanogaster is a great model to study the response of populations to rapidly changing conditions, because of its southern-central African origin and recent worldwide colonization. Desiccation stress response is a complex and extensively studied trait, however the natural variation in tolerance, and the underlying transcriptomic and physiological mechanisms are still not clear. Here we subjected to desiccation stress 74 natural D. melanogaster European strains, belonging to five different climate zones. We found that the strains from cold semi-arid climates are more tolerant compared with the ones from hot summer mediterranean climate zones. Moreover, the variance in the tolerance of the strains correlates with the interaction of altitude and evaporation. We found that the tolerant strains had a lower level of initial water content and lose less water during desiccation stress. The reduction in the water loss is probably due to the decrease in the respiration rate in desiccation stress conditions, and to the cuticular hydrocarbon composition found in tolerant strains. Moreover, we found that the genes related to response to stimulus and environmental sensing are up-regulated only in the tolerant strains. Furthermore, we identified several desiccation candidate genes unique for the tolerant strains that can be targeted by tRNA derived fragments, known to be important in post-transcriptional gene regulation in several stress responses. We also looked for transposable element insertions possibly affecting the expression of genes relevant in desiccation tolerance, however, except for four insertions, there is no clear association between the presence of the TE insertions and the tolerance level of the strains. Overall, our study for the first time described the physiological and transcriptomic changes underlying the desiccation tolerance of natural European D. melanogaster strains and puts tRFs in the scope of desiccation related studies as possible regulators of desiccation tolerance.
Project description:Recent advancements in genome sequencing have facilitated accessing the natural genetic diversity of species, unveiling hidden genetic traits, clarifying gene functions, and the degree to which laboratory studies can be generalized. One notable discovery is the frequent (~20%) aneuploidy - an imbalance in chromosome copy numbers - in natural Saccharomyces cerevisiae (Sc) isolates, despite the significant fitness costs and transient nature reported for lab-engineered yeast aneuploids. To examine this discrepancy, we adapted a high-throughput proteomic platform to analyze the proteome of 800 diverse yeast isolates. Matching these proteomes to the natural isolates’ genomes, transcriptomes, as well as generating ubiquitinome and protein turnover data for selected isolates, we report that natural and lab-generated aneuploids differ specifically at the proteome. While lab-generated aneuploids attenuate specific proteins – mostly protein complex subunits – and do not alter the average gene dosage provided by chromosome duplications, in natural strains, 70% of proteins encoded on aneuploid chromosomes are attenuated, and protein levels are shifted towards the euploid state chromosome-wide. Our data links chromosome-wide dosage compensation in natural strains to i) genome-wide buffering of gene expression changes manifesting in trans on euploid chromosomes, ii) increased expression of structural components of the ubiquitin proteasome system, and iii) increased global rates of protein turnover. Our results encourage the exploitation of natural diversity of species to understand complex biological processes at the molecular level. This submission contains the raw files for the disomics lab engineered strains, the library used for the analysis and the corresponding DIA-NN report and associated files.
Project description:We used RNA-seq to investigate natural variation in gene expression in the Malpighian tubules of three inbred Drosophila melanogaster strains and their F1 hybrids. One of the strains was from a population in the species’ ancestral range (Zambia), while the other two were from a more recently derived population (Sweden).
Project description:Background: Copy number variation is an important component of genetic variation in higher eukaryotes. The extent of natural copy number variation in C. elegans is unknown outside of 2 highly divergent wild isolates and the canonical N2 Bristol strain. Results: We have used array comparative genomic hybridization (aCGH) to detect copy number variation in the genomes of 12 natural isolates of Caenorhabditis elegans. Deletions relative to the canonical N2 strain are more common in these isolates than duplications, and indels are enriched in multigene families on the autosome arms. Among the strains in our study, the Hawaiian and Madeiran strains (CB4856 and JU258) carry the largest number of deletions, followed by the Vancouver strain (KR314). Overall we detected 510 different deletions affecting 1136 genes, or over 5% of the genes in the canonical N2 genome. The indels we identified had a median length of 2.7 kb. Since many deletions are found in multiple isolates, deletion loci were used as markers to derive an unrooted tree to estimate genetic relatedness among the strains. Conclusion: Copy number variation is extensive in C. elegans, affecting over 5% of the genes in the genome. The deletions we have detected in natural isolates of C. elegans contribute significantly to the number of deletion alleles available to researchers. The relationships between strains are complex and different regions of the genome possess different genealogies due to recombination throughout the natural history of the species, which may not be apparent in studies utilizing smaller numbers of genetic markers.
Project description:Streptomyces has the largest repertoire of natural product biosynthetic gene clusters (BGCs), yet developing a universal engineering strategy for each Streptomyces species is challenging. Given that some Streptomyces species have larger BGC repertoires than others, we hypothesized that a set of genes co-evolved with BGCs to support biosynthetic proficiency must exist in those strains, and that their identification may provide universal strategies to improve the productivity of other strains. We show here that genes co-evolved with natural product BGCs in Streptomyces can be identified by phylogenomics analysis. Among the 597 genes that co-evolved with polyketide BGCs, 11 genes in the “coenzyme” category have been examined, including a gene cluster encoding for the co-factor pyrroloquinoline quinone (PQQ). When the pqq gene cluster was engineered into 11 Streptomyces strains, it enhanced production of 16,385 metabolites, including 36 known natural products with up to 40-fold improvement and several activated silent gene clusters. This study provides a new engineering strategy for improving polyketide production and discovering new biosynthetic gene clusters.
Project description:Background: Copy number variation is an important component of genetic variation in higher eukaryotes. The extent of natural copy number variation in C. elegans is unknown outside of 2 highly divergent wild isolates and the canonical N2 Bristol strain. Results: We have used array comparative genomic hybridization (aCGH) to detect copy number variation in the genomes of 12 natural isolates of Caenorhabditis elegans. Deletions relative to the canonical N2 strain are more common in these isolates than duplications, and indels are enriched in multigene families on the autosome arms. Among the strains in our study, the Hawaiian and Madeiran strains (CB4856 and JU258) carry the largest number of deletions, followed by the Vancouver strain (KR314). Overall we detected 510 different deletions affecting 1136 genes, or over 5% of the genes in the canonical N2 genome. The indels we identified had a median length of 2.7 kb. Since many deletions are found in multiple isolates, deletion loci were used as markers to derive an unrooted tree to estimate genetic relatedness among the strains. Conclusion: Copy number variation is extensive in C. elegans, affecting over 5% of the genes in the genome. The deletions we have detected in natural isolates of C. elegans contribute significantly to the number of deletion alleles available to researchers. The relationships between strains are complex and different regions of the genome possess different genealogies due to recombination throughout the natural history of the species, which may not be apparent in studies utilizing smaller numbers of genetic markers. Twelve C. elegans natural isolate samples were studied. There were no replicates or dye-swap hybridizations.
Project description:In marine Vibrio species, chitin-induced natural transformation enables bacteria to take up DNA from the external environment and integrate it into their genome via homologous recombination. Expression of the master competence regulator TfoX bypasses the need for chitin induction and drives expression of the genes required for competence in several Vibrio species. Here, we show that TfoX expression in two Vibrio campbellii strains, DS40M4 and NBRC 15631, enables high frequencies of natural transformation. Conversely, transformation was not achieved in the model quorum-sensing strain V. campbellii BB120 (previously classified as Vibrio harveyi). Surprisingly, we find that quorum sensing is not required for transformation in V. campbellii DS40M4. This result is in contrast to Vibrio cholerae that requires the quorum-sensing regulator HapR to activate the competence regulator QstR. However, similar to V. cholerae, QstR is necessary for transformation in DS40M4. To investigate the difference in transformation frequencies between BB120 and DS40M4, we used previously studied V. cholerae competence genes to inform a comparative genomics analysis coupled with transcriptomics. BB120 encodes homologs of all known competence genes, but most of these genes were not induced by ectopic expression of TfoX, which likely accounts for the non-functional natural transformation in this strain. Comparison of transformation frequencies among Vibrio species indicates a wide disparity among even closely related strains, with Vibrio vulnificus having the lowest functional transformation frequency. We show that ectopic expression of both TfoX and QstR is sufficient to produce a significant increase in transformation frequency in Vibrio vulnificus.