Biology subjects

Werren, J.

Publications and source records attributed to Werren, J..

6 recordsLinked to original sources

bioRxiv2020

Transposable element control disrupted by meiotic drive in a stalk-eyed fly genome

Some stalk-eyed flies in the genus Teleopsis carry selfish genetic elements that induce sex ratio meiotic drive (SR) and impact the fitness of male and female carriers. Here, we produced a chromosome-level genome assembly of the stalk-eyed fly, T. dalmanni, to elucidate patterns of genomic divergence associated with the presence of drive elements. We find evidence for multiple nested inversions along the sex ratio haplotype and widespread differentiation and divergence between XSR and XSR along the entire chromosome. These include a striking XSR-specific expansion of an array of partial copies of JASPer, a gene necessary for maintenance of euchromatin and regulation of transposable element expression (TEs). In addition, the genome contains tens of thousands of TE insertions and hundreds of transcriptionally and insertionally active TE families. Moreover, we find that several TE families are differentially expressed and/or present at a different copy number in SR male testes, suggesting an association between these two categories of selfish genetic elements in this species. We identify T. dalmanni orthologs of genes involved in genome defense via the piRNA pathway, including core members maelstrom, piwi and Argonaute3, that have diverged in sequence, expression or copy number between the SR and standard (ST) X chromosomes, consistent with altered TE regulation in flies carrying a sex ratio X chromosome. Overall, the evidence suggests that this ancient XSR polymorphism has had a variety of impacts on repetitive DNA and its regulation in this species.

evolutionary biology↗

bioRxiv2020

Jekyll or Hyde? The genome (and more) of Nesidiocoris tenuis, a zoophytophagous predatory bug that is both a biological control agent and a pest

Nesidiocoris tenuis (Reuter) is an efficient predatory biological control agent used throughout the Mediterranean Basin in tomato crops but regarded as a pest in northern European countries. Belonging to the family Miridae, it is an economically important insect yet very little is known in terms of genetic information - no published genome, population studies, or RNA transcripts. It is a relatively small and long-lived diploid insect, characteristics that complicate genome sequencing. Here, we circumvent these issues by using a linked-read sequencing strategy on a single female N. tenuis. From this, we assembled the 355 Mbp genome and delivered an ab initio, homology-based, and evidence-based annotation. Along the way, the bacterial "contamination" was removed from the assembly, which also revealed potential symbionts. Additionally, bacterial lateral gene transfer (LGT) candidates were detected in the N. tenuis genome. The complete gene set is composed of 24,688 genes; the associated proteins were compared to other hemipterans (Cimex lectularis, Halyomorpha halys, and Acyrthosiphon pisum), resulting in an initial assessment of unique and shared protein clusters. We visualised the genome using various cytogenetic techniques, such as karyotyping, CGH and GISH, indicating a karyotype of 2n=32 with a male-heterogametic XX/XY system. Additional analyses include the localization of 18S rDNA and unique satellite probes via FISH techniques. Finally, population genomics via pooled sequencing further showed the utility of this genome. This is one of the first mirid genomes to be released and the first of a mirid biological control agent, representing a step forward in integrating genome sequencing strategies with biological control research.

genomics↗

bioRxiv2019

Genome of the parasitoid wasp Diachasma alloeum, an emerging model for ecological speciation and transitions to asexual reproduction

Parasitoid wasps are among the most speciose animals, yet have relatively few available genomic resources. We report a draft genome assembly of the wasp Diachasma alloeum (Hymenoptera: Braconidae), a host-specific parasitoid of the apple maggot fly Rhagoletis pomonella (Diptera: Tephritidae) and a developing model for understanding how ecological speciation can "cascade" across trophic levels. Identification of gene content confirmed the overall quality of the draft genome, and we manually annotated [~]400 genes as part of this study, including those involved in oxidative phosphorylation, chemosensation, and reproduction. Through comparisons to model hymenopterans such as the European honeybee Apis mellifera and parasitoid wasp Nasonia vitripennis, as well as a more closely related braconid parasitoid Microplitis demolitor, we identified a proliferation of transposable elements in the genome, an expansion of chemosensory genes in D. alloeum and other parasitoid wasps, and the maintenance of several key genes with known roles in sexual reproduction and sex determination. The D. alloeum genome will provide a valuable resource for comparative genomics studies in Hymenoptera as well as specific investigations into the genomic changes associated with ecological speciation and transitions to asexuality.

genomics↗

bioRxiv2018

Genome assembly of the A-group Wolbachia in Nasonia oneida and phylogenomic analysis of Wolbachia strains revealed genome evolution and lateral gene transfer

Wolbachia are obligate intracellular bacteria which commonly infect various nematode and arthropod species. Based on depth differences, we assembled the genome of Wolbachia in the parasitoid jewel wasp species Nasonia oneida (wOne), using 10X Genomics Chromium linked-read technology. The final draft assembly consists of 1,293,406 bp in 47 scaffolds with 1,114 coding genes and 97.01% genome completeness assessed by checkM. wOne is the A1 strain previously reported in N. oneida, and pyrosequencing confirms that the wasp strain lacks A2 and B types, which were likely lost during laboratory culturing. Polymorphisms identified in the wOneA1 genome have elevated read depths, indicating recent gene duplications rather that strain variation. These polymorphisms are enriched in nonsynonymous changes in 27 coding genes, including phase baseplate assembly proteins and transporter activity related genes. wOneA1 is more closely grouped with A-Wolbachia in the Drosophila simulans (wHa) than A-Wolbachia found in wasps. Genome variation was next evaluated in 34 published Wolbachia genomes for 211 single ortholog genes, and revealed six supergroup discordant trees, indicating recombination events not only between A and B supergroups, but also between A and E supergroups. Comparisons of strain divergence using the five genes of the Multi Locus Strain Typing (MLST) system show a high correlation (rho=0.98) between MLST and whole genome divergences, indicating that MLST is a reliable method for identifying related strains when whole genome data are not available. Assembling bacterial genomes from host genome projects can provide an effective method for sequencing Wolbachia genomes and characterizing their diversity.\n\nAuthor SummaryMore than half of the arthropod species are infected by the obligated intracellular bacteria Wolbachia. As one of the most widespread parasitic microbes, Wolbachia mediate important biological processes such as cytoplasmic incompatibility and lateral gene transfer in insects. Their evolutionary relationship has been characterize using five protein-coding and 16S rRNA genes. In this work, we identified 211 conserved single copies genes in 34 genome sequenced Wolbachia strains, and we discovered that they maintain the supergroup relationship classified previously based on selected genes. We constructed phylogenetic trees for individual genes and found only six genes display discordant tree structure between supergroups, due to lateral gene transfer and homologous recombination events. But these events are not common (3%) in Wolbachia genomes, at least in these conserved single copy genes. In addition to known lateral gene transfer events between A and B supergroups, we identified transfers between A and E supergroups for the first time. Selective maintenance of such transfers suggests possible roles in Wolbachia infection related functions. We also found enriched nonsynonymous polymorphisms in Nasonia oneida Wobachia genome, and their differences are more likely to result from gene duplications within the strain, rather than strain variation within the parasitoid.

evolutionary biology↗

bioRxiv2018

Evolutionary rate coevolution between mitochondria and mitochondria-associated nuclear-encoded proteins in insects

The mitochondrion is a pivotal organelle for energy production, and includes components encoded by both the mitochondrial and nuclear genomes. How these two genomes coevolve is a long-standing question in evolutionary biology. Here we initially investigate the evolutionary rates of mitochondrial components (oxidative phosphorylation (OXPHOS) proteins and ribosomal RNAs) and nuclear-encoded proteins associated with mitochondria, across the major orders of holometabolous insects. There are significant evolutionary rate correlations (ERCs) between mitochondria and mitochondria-associated nuclear-encoded proteins, which is likely driven by different rates of mitochondrial sequence evolution and compensatory changes in the interacting nuclear-encoded proteins. The pattern holds after correction for phylogenetic relationships and considering protein conservation levels. Correlations are stronger for nuclear-encoded OXPHOS proteins in contact with mitochondrial-encoded OXPHOS proteins and nuclear-encoded mitochondrial ribosomal amino acids directly contacting the mitochondrial rRNA. Mitochondrial-associated proteins show apparent rate acceleration over evolutionary time, but we suspect this pattern to be due to artifacts (e.g. rate estimation or calibration bias). We find that ERC between mitochondrial and nuclear proteins is a strong predictor of nuclear proteins known to interact with mitochondria, and therefore ERCs can be used to predict new candidate nuclear proteins with mitochondrial function. Using this approach, we detect proteins with high ERCs but not with known mitochondrial function based on gene ontology (GO). Manual screening of the literature revealed potential mitochondrial function for some of these proteins in humans or yeast. Their holometabolous ERCs therefore indicate these proteins may have phylogenetically conserved mitochondrial function. Twenty three additional candidates warrant further study for mitochondrial function based on this approach, including ERC evidence that proteins in the minichromosome maintenance helicase (MCM) complex interact with mitochondria. We conclude that the ERC method shows promise for identifying new candidate proteins with mitochondrial function.

evolutionary biology↗

bioRxiv2017

The house spider genome reveals an ancient whole-genome duplication during arachnid evolution

The duplication of genes can occur through various mechanisms and is thought to make a major contribution to the evolutionary diversification of organisms. There is increasing evidence for a large-scale duplication of genes in some chelicerate lineages including two rounds of whole genome duplication (WGD) in horseshoe crabs. To investigate this further we sequenced and analyzed the genome of the common house spider Parasteatoda tepidariorum. We found pervasive duplication of both coding and non-coding genes in this spider, including two clusters of Hox genes. Analysis of synteny conservation across the P. tepidariorum genome suggests that there has been an ancient WGD in spiders. Comparison with the genomes of other chelicerates, including that of the newly sequenced bark scorpion Centruroides sculpturatus, suggests that this event occurred in the common ancestor of spiders and scorpions and is probably independent of the WGDs in horseshoe crabs. Furthermore, characterization of the sequence and expression of the Hox paralogs in P. tepidariorum suggests that many have been subject to neofunctionalization and/or subfunctionalization since their duplication, and therefore may have contributed to the diversification of spiders and other pulmonate arachnids.

genomics↗