Dataset Information

Genomic analysis of the four ecologically distinct cactus host populations of Drosophila mojavensis.

ABSTRACT:

Background

Relationships between an organism and its environment can be fundamental in the understanding how populations change over time and species arise. Local ecological conditions can shape variation at multiple levels, among these are the evolutionary history and trajectories of coding genes. This study examines the rate of molecular evolution at protein-coding genes throughout the genome in response to host adaptation in the cactophilic Drosophila mojavensis. These insects are intimately associated with cactus necroses, developing as larvae and feeding as adults in these necrotic tissues. Drosophila mojavensis is composed of four isolated populations across the deserts of western North America and each population has adapted to utilize different cacti that are chemically, nutritionally, and structurally distinct.

Results

High coverage Illumina sequencing was performed on three previously unsequenced populations of D. mojavensis. Genomes were assembled using the previously sequenced genome of D. mojavensis from Santa Catalina Island (USA) as a template. Protein coding genes were aligned across all four populations and rates of protein evolution were determined for all loci using a several approaches.

Conclusions

Loci that exhibited elevated rates of molecular evolution tend to be shorter, have fewer exons, low expression, be transcriptionally responsive to cactus host use and have fixed expression differences across the four cactus host populations. Fast evolving genes were involved with metabolism, detoxification, chemosensory reception, reproduction and behavior. Results of this study give insight into the process and the genomic consequences of local ecological adaptation.

SUBMITTER: Allan CW

PROVIDER: S-EPMC6790045 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Publications

Genomic analysis of the four ecologically distinct cactus host populations of Drosophila mojavensis.

Allan Carson W CW Matzkin Luciano M LM

BMC genomics 20191012 1

<h4>Background</h4>Relationships between an organism and its environment can be fundamental in the understanding how populations change over time and species arise. Local ecological conditions can shape variation at multiple levels, among these are the evolutionary history and trajectories of coding genes. This study examines the rate of molecular evolution at protein-coding genes throughout the genome in response to host adaptation in the cactophilic Drosophila mojavensis. These insects are int ...[more]

PMID: 31606030

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Project description:Local adaptation can play a fundamental role in the isolation of populations. While less well-studied than differentiation in sequence variation, changes in transcriptional variation during speciation also are fundamental to the evolutionary process. Drosophila mojavensis offers an unprecedented opportunity to examine the role of transcriptional differentiation in local adaptation. Drosophila mojavensis is a cactophilic fly composed of four ecologically distinct subspecies that inhabit the deserts of western North America. Each of the four subspecies utilizes necrotic tissue of different cactus host species characterized by distinct chemical profiles. The subspecies in Baja California, Mexico uses Stenocereus gummosus (Agria), in mainland Sonora it uses S. thurberi (Organ Pipe), in the Mojave Desert the host is Ferocactus cylindraceus (Red Barrel) and in Santa Catalina Island, USA, Opuntia littoralis (Prickly Pear) is the host. In this chapter we examine how the adaptation to the different environmental conditions across the four subspecies have shaped their transcriptional profiles. Using complete D. mojavensis genome microarrays we examined the transcriptome of third instar larvae from all four subspecies reared in standard laboratory media free of necrotic cactus-derived compounds. This experimental strategy focused on differences between constitutively expressed genes and not genes induced by necrotic cactus-derived compounds. The subspecies exhibited significant differential expression of genes that likely underlie the adaptation to different cactus hosts, such as detoxification genes (Glutathione S-transferases, Cytochrome P450s and UDP-Glycosyltransferases) and chemosensory genes (Odorant Receptors, Gustatory Receptors and Odorant Binding Proteins). Dataset from Matzkin, L. M. and Markow, T.A. Transcriptional differentiation across the four cactus host races of Drosophila mojavensis. In Speciation: Natural Processes, Genetics and Biodiversity. Edited by Michalak, P. Nova Science Publishers, Inc.

Project description:Although the importance of host plant chemistry in plant-insect interactions is widely accepted, the genetic basis of adaptation to host plants is poorly understood. Here, we investigate transcriptional changes associated with a host plant shift in Drosophila mettleri. While D. mettleri is distributed mainly throughout the Sonoran Desert where it specializes on columnar cacti (Carnegiea gigantea and Pachycereus pringleii), a population on Santa Catalina Island has shifted to coastal prickly pear cactus (Opuntia littoralis). We compared gene expression of larvae from the Sonoran Desert and Santa Catalina Island when reared on saguaro (C. gigantea), coastal prickly pear, and laboratory food. Consistent with expectations based on the complexity and toxicity of cactus relative to laboratory food, within population comparisons between larvae reared on these food sources revealed transcriptional differences in detoxification and other metabolic pathways. The majority of transcriptional differences between populations on the cactus hosts were independent of the rearing environment, and included a disproportionate number of genes involved in processes relevant to host plant adaptation (e.g. detoxification, central metabolism, and chemosensory pathways). Comparisons of transcriptional reaction norms between the two populations revealed extensive shared plasticity that likely allowed colonization of coastal prickly pear on Santa Catalina Island. We also found that while plasticity may have facilitated subsequent adaptive divergence in gene expression between populations, the majority of genes that differed in expression on the novel host were not transcriptionally plastic in the presumed ancestral state. mRNA profiles of third instar larvae from two different populations reared on three food types was sequenced on two lanes of an Illumina HiSeq 2000 Please note that the de novo assembly gives names to transcripts with the following convention: compXXX_cX_seqX. The first two identifiers (compXX_cX) are equivalent to a gene while the 'seq' identifier might refer to different isoforms or splice variants, etc. Therefore, for example, a gene might be comp123_c0, and this could have multiple sequences corresponding to different isoforms or splice variants. Since the analysis was carried out at the gene level, the program internally merged the multiple sequences together for each gene to generate the count matrix (AllGenesint.counts.matrix.txt) (i.e. it only includes comp123_c0), while the file from the assembly (i.e. Trinity.fasta) also include the individual sequences with the 'seq' identifier.

Project description:Background and objectivesAmong placental mammals, females undergo immunological shifts during pregnancy to accommodate the fetus (i.e. fetal tolerance). Fetal tolerance has primarily been characterized within post-industrial populations experiencing evolutionarily novel conditions (e.g. reduced pathogen exposure), which may shape maternal response to fetal antigens. This study investigates how ecological conditions affect maternal immune status during pregnancy by comparing the direction and magnitude of immunological changes associated with each trimester among the Tsimane (a subsistence population subjected to high pathogen load) and women in the USA.MethodologyData from the Tsimane Health and Life History Project (N = 935) and the National Health and Nutrition Examination Survey (N = 1395) were used to estimate population-specific effects of trimester on differential leukocyte count and C-reactive protein (CRP), a marker of systemic inflammation.ResultsIn both populations, pregnancy was associated with increased neutrophil prevalence, reduced lymphocyte and eosinophil count and elevated CRP. Compared to their US counterparts, pregnant Tsimane women exhibited elevated lymphocyte and eosinophil counts, fewer neutrophils and monocytes and lower CRP. Total leukocyte count remained high and unchanged among pregnant Tsimane women while pregnant US women exhibited substantially elevated counts, resulting in overlapping leukocyte prevalence among all third-trimester individuals.Conclusions and implicationsOur findings indicate that ecological conditions shape non-pregnant immune baselines and the magnitude of immunological shifts during pregnancy via developmental constraints and current trade-offs. Future research should investigate how such flexibility impacts maternal health and disease susceptibility, particularly the degree to which chronic pathogen exposure might dampen inflammatory response to fetal antigens.Lay summaryThis study compares immunological changes associated with pregnancy between the Tsimane (an Amazonian subsistence population) and individuals in the USA. Results suggest that while pregnancy enhances non-specific defenses and dampens both antigen-specific immunity and parasite/allergy response, ecological conditions strongly influence immune baselines and the magnitude of shifts during gestation.

Dataset Information

Genomic analysis of the four ecologically distinct cactus host populations of Drosophila mojavensis.

Background

Results

Conclusions

Publications

Genomic analysis of the four ecologically distinct cactus host populations of Drosophila mojavensis.

Similar Datasets

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