Transposon accumulation at xenobiotic gene family loci in aphids.

The evolution of resistance is a major challenge for the sustainable control of pests and pathogens. Thus, a deeper understanding of the evolutionary and genomic mechanisms underpinning resistance evolution is required to safeguard health and food production. Several studies have implicated transposable elements (TEs) in xenobiotic-resistance evolution in insects. However, analyses are generally restricted to one insect species and/or one or a few xenobiotic gene families (XGFs). We examine evidence for TE accumulation at XGFs by performing a comparative genomic analysis across 20 aphid genomes, considering major subsets of XGFs involved in metabolic resistance to insecticides: cytochrome P450s, glutathione S-transferases, esterases, UDP-glucuronosyltransferases, and ABC transporters. We find that TEs are significantly enriched at XGFs compared with other genes. XGFs show similar levels of TE enrichment to those of housekeeping genes. But unlike housekeeping genes, XGFs are not constitutively expressed in germline cells, supporting the selective enrichment of TEs at XGFs rather than enrichment owing to chromatin availability. Hotspots of extreme TE enrichment occur around certain XGFs. We find, in aphids of agricultural importance, particular enrichment of TEs around cytochrome P450 genes with known functions in the detoxification of synthetic insecticides. Our results provide evidence supporting a general role for TEs as a source of genomic variation at host XGFs and highlight the existence of considerable variability in TE content across XGFs and host species. These findings show the need for detailed functional verification analyses to clarify the significance of individual TE insertions and elucidate underlying mechanisms at TE-XGF hotspots.

Earl Grey: A Fully Automated User-Friendly Transposable Element Annotation and Analysis Pipeline.

Transposable elements (TEs) are major components of eukaryotic genomes and are implicated in a range of evolutionary processes. Yet, TE annotation and characterization remain challenging, particularly for nonspecialists, since existing pipelines are typically complicated to install, run, and extract data from. Current methods of automated TE annotation are also subject to issues that reduce overall quality, particularly (i) fragmented and overlapping TE annotations, leading to erroneous estimates of TE count and coverage, and (ii) repeat models represented by short sections of total TE length, with poor capture of 5' and 3' ends. To address these issues, we present Earl Grey, a fully automated TE annotation pipeline designed for user-friendly curation and annotation of TEs in eukaryotic genome assemblies. Using nine simulated genomes and an annotation of Drosophila melanogaster, we show that Earl Grey outperforms current widely used TE annotation methodologies in ameliorating the issues mentioned above while scoring highly in benchmarking for TE annotation and classification and being robust across genomic contexts. Earl Grey provides a comprehensive and fully automated TE annotation toolkit that provides researchers with paper-ready summary figures and outputs in standard formats compatible with other bioinformatics tools. Earl Grey has a modular format, with great scope for the inclusion of additional modules focused on further quality control and tailored analyses in future releases.

Chromosome Fissions and Fusions Act as Barriers to Gene Flow between Brenthis Fritillary Butterflies.

Chromosome rearrangements are thought to promote reproductive isolation between incipient species. However, it is unclear how often, and under what conditions, fission and fusion rearrangements act as barriers to gene flow. Here we investigate speciation between two largely sympatric fritillary butterflies, Brenthis daphne and Brenthis ino. We use a composite likelihood approach to infer the demographic history of these species from whole-genome sequence data. We then compare chromosome-level genome assemblies of individuals from each species and identify a total of nine chromosome fissions and fusions. Finally, we fit a demographic model where effective population sizes and effective migration rate vary across the genome, allowing us to quantify the effects of chromosome rearrangements on reproductive isolation. We show that chromosomes involved in rearrangements experienced less effective migration since the onset of species divergence and that genomic regions near rearrangement points have a further reduction in effective migration rate. Our results suggest that the evolution of multiple rearrangements in the B. daphne and B. ino populations, including alternative fusions of the same chromosomes, have resulted in a reduction in gene flow. Although fission and fusion of chromosomes are unlikely to be the only processes that have led to speciation between these butterflies, this study shows that these rearrangements can directly promote reproductive isolation and may be involved in speciation when karyotypes evolve quickly.

Transposon-mediated insertional mutagenesis unmasks recessive insecticide resistance in the aphid Myzus persicae.

The evolution of resistance to insecticides threatens the sustainable control of many of the world's most damaging insect crop pests and disease vectors. To effectively combat resistance, it is important to understand its underlying genetic architecture, including the type and number of genetic variants affecting resistance and their interactions with each other and the environment. While significant progress has been made in characterizing the individual genes or mutations leading to resistance, our understanding of how genetic variants interact to influence its phenotypic expression remains poor. Here, we uncover a mechanism of insecticide resistance resulting from transposon-mediated insertional mutagenesis of a genetically dominant but insecticide-susceptible allele that enables the adaptive potential of a previously unavailable recessive resistance allele to be unlocked. Specifically, we identify clones of the aphid pest Myzus persicae that carry a resistant allele of the essential voltage-gated sodium channel (VGSC) gene with the recessive M918T and L1014F resistance mutations, in combination with an allele lacking these mutations but carrying a Mutator-like element transposon insertion that disrupts the coding sequence of the VGSC. This results in the down-regulation of the dominant susceptible allele and monoallelic expression of the recessive resistant allele, rendering the clones resistant to the insecticide bifenthrin. These findings are a powerful example of how transposable elements can provide a source of evolutionary potential that can be revealed by environmental and genetic perturbation, with applied implications for the control of highly damaging insect pests.

Genome-wide transcriptomic changes reveal the genetic pathways involved in insect migration.

Insects are capable of extraordinary feats of long-distance movement that have profound impacts on the function of terrestrial ecosystems. The ability to undertake these movements arose multiple times through the evolution of a suite of traits that make up the migratory syndrome, however the underlying genetic pathways involved remain poorly understood. Migratory hoverflies (Diptera: Syrphidae) are an emerging model group for studies of migration. They undertake seasonal movements in huge numbers across large parts of the globe and are important pollinators, biological control agents and decomposers. Here, we assembled a high-quality draft genome of the marmalade hoverfly (Episyrphus balteatus). We leveraged this genomic resource to undertake a genome-wide transcriptomic comparison of actively migrating Episyrphus, captured from a high mountain pass as they flew south to overwinter, with the transcriptomes of summer forms which were non-migratory. We identified 1543 genes with very strong evidence for differential expression. Interrogation of this gene set reveals a remarkable range of roles in metabolism, muscle structure and function, hormonal regulation, immunity, stress resistance, flight and feeding behaviour, longevity, reproductive diapause and sensory perception. These features of the migrant phenotype have arisen by the integration and modification of pathways such as insulin signalling for diapause and longevity, JAK/SAT for immunity, and those leading to octopamine production and fuelling to boost flight capabilities. Our results provide a powerful genomic resource for future research, and paint a comprehensive picture of global expression changes in an actively migrating insect, identifying key genomic components involved in this important life-history strategy.

Melanism: Cryptic control by non-coding RNAs.

Melanism drives both crypsis and mimicry in butterflies and moths. To date, melanism has been mapped to a structural gene called cortex, but now more detailed work shows that in fact it is controlled by non-coding RNAs at the same locus.

The genome sequence of the Lulworth Skipper, Thymelicus acteon (Rottemburg, 1775).

We present a genome assembly from an individual male Thymelicus acteon (the Lulworth Skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence is 537.0 megabases in span. Most of the assembly is scaffolded into 28 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genome has also been assembled and is 17.08 kilobases in length. Gene annotation of this assembly on Ensembl identified 12,813 protein-coding genes.

The genome sequence of the Essex Skipper butterfly, Thymelicus lineola (Ochsenheimer, 1808).

We present a genome assembly from an individual female Essex Skipper butterfly, Thymelicus lineola (Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence spans 511.80 megabases. Most of the assembly is scaffolded into 30 chromosomal pseudomolecules, including the Z and W sex chromosomes. The mitochondrial genome has also been assembled and is 17.24 kilobases in length.

The genome sequence of the Chalkhill Blue, Lysandra coridon (Poda, 1761).

We present a genome assembly from an individual male Lysandra coridon (the Chalkhill Blue; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequence is 541 megabases in span. Most of the assembly is scaffolded into 90 chromosomal pseudomolecules, including the assembled Z sex chromosome. The mitochondrial genome has also been assembled and is 15.4 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,334 protein coding genes.

The genome sequence of the Large Skipper, Ochlodes sylvanus, (Esper, 1777).

We present a genome assembly from an individual female Ochlodes sylvanus, the Large Skipper (Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence is 380 megabases in span. Most of the assembly (99.97%) is scaffolded into 30 chromosomal pseudomolecules, including the assembled W and Z sex chromosomes. The mitochondrial genome has also been assembled and is 17.1 kilobases in length. Gene annotation of this assembly on Ensembl identified 13,451 protein coding genes.

The genome sequence of the Mazarine Blue, Cyaniris semiargus (Rottemburg, 1775).

We present a genome assembly from an individual male Cyaniris semiargus (the Mazarine Blue; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequence is 441.5 megabases in span. Most of the assembly is scaffolded into 24 chromosomal pseudomolecules, including the assembled Z sex chromosome. The mitochondrial genome has also been assembled and is 15.4 kilobases in length. Gene annotation of this assembly on Ensembl identified 16,408 protein coding genes.

The genome sequence of the Brown Argus, Aricia agestis (Denis & Schiffermüller, 1775).

We present genome assemblies from two male Aricia agestis specimens (the Brown Argus; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequences are 435.3 and 437.4 megabases in span. Each assembly is scaffolded into 23 chromosomal pseudomolecules, including the Z sex chromosome. The mitochondrial genomes were assembled and are 15.47 and 15.45 kilobases in length. Gene annotation of these assemblies on Ensembl identified 12,688 and 12,654 protein coding genes.

The genome sequence of the Adonis blue, Lysandra bellargus (Rottemburg, 1775).

We present a genome assembly from an individual female Lysandra bellargus (the Adonis blue; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequence is 529 megabases in span. The majority of the assembly (99.93%) is scaffolded into 46 chromosomal pseudomolecules with the W and Z sex chromosomes assembled. The complete mitochondrial genome was also assembled and is 15.6 kilobases in length. Gene annotation of this assembly on Ensembl has identified 13,249 protein coding genes.

The genome sequence of the marbled white butterfly, Melanargia galathea (Linnaeus, 1758).

We present a genome assembly from an individual female Melanargia galathea (the marbled white; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 606 megabases in span. The majority (99.97%) of the assembly is scaffolded into 25 chromosomal pseudomolecules, with the W and Z sex chromosomes assembled.

The genome sequence of the grizzled skipper, Pyrgus malvae (Linnaeus, 1758).

We present a genome assembly from an individual male Pyrgus malvae (the grizzled skipper; Arthropoda; Insecta; Lepidoptera; Hesperiidae). The genome sequence is 725 megabases in span. The majority (99.97%) of the assembly is scaffolded into 31 chromosomal pseudomolecules, with the Z sex chromosome assembled.

The genome sequence of the high brown fritillary, Fabriciana adippe (Dennis & Schiffermüller, 1775).

We present a genome assembly from an individual female Fabriciana adippe (the high brown fritillary; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 485 megabases in span. Most of the assembly (99.98%) is scaffolded into 29 chromosomal pseudomolecules with the Z sex chromosome assembled. The complete mitochondrial genome was also assembled and is 15.1 kilobases in length. Gene annotation of this assembly in Ensembl identified 13,536 protein coding genes.

The genome sequence of the Arran brown, Erebia ligea (Linnaeus, 1758).

We present a genome assembly from an individual male Erebia ligea (Arran brown; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 506 megabases in span. The majority (99.92%) of the assembly is scaffolded into 29 chromosomal pseudomolecules, with the Z sex chromosome assembled. The complete mitochondrial genome was also assembled and is 15.2 kilobases in length.

The genome sequence of the white admiral, Limenitis camilla (Linnaeus, 1764).

We present a genome assembly from an individual female Limenitis camilla (the white admiral; Arthropoda; Insecta; Lepidoptera; Nymphalidae). The genome sequence is 435 megabases in span. Most of the assembly (99.97%) is scaffolded into 31 chromosomal pseudomolecules, corresponding to 29 autosomes plus the W and Z sex chromosomes. The complete mitochondrial genome was also assembled and is 15.2 kilobases in length. Gene annotation of this assembly on Ensembl identified 12,489 protein coding genes.

The genome sequence of the silver-studded blue, Plebejus argus (Linnaeus, 1758).

We present a genome assembly from an individual male Plebejus argus (silver-studded blue; Arthropoda; Insecta; Lepidoptera; Lycaenidae). The genome sequence is 382 megabases in span. The entire assembly (100%) is scaffolded into 23 chromosomal pseudomolecules with the Z sex chromosome assembled. The complete mitochondrial genome was also assembled and is 27.4 kilobases in length. Gene annotation of this assembly on Ensembl identified 12,693 protein coding genes.

Bacterial colonisation dynamics of household plastics in a coastal environment.

Accumulation of plastics in the marine environment has widespread detrimental consequences for ecosystems and wildlife. Marine plastics are rapidly colonised by a wide diversity of bacteria, including human pathogens, posing potential risks to health. Here, we investigate the effect of polymer type, residence time and estuarine location on bacterial colonisation of common household plastics, including pathogenic bacteria. We submerged five main household plastic types: low-density PE (LDPE), high-density PE (HDPE), polypropylene (PP), polyvinyl chloride (PVC) and polyethylene terephthalate (PET) at an estuarine site in Cornwall (U.K.) and tracked bacterial colonisation dynamics. Using both culture-dependent and culture-independent approaches, we found that bacteria rapidly colonised plastics irrespective of polymer type, reaching culturable densities of up to 1000 cells cm3 after 7 weeks. Community composition of the biofilms changed over time, but not among polymer types. The presence of pathogenic bacteria, quantified using the insect model Galleria mellonella, increased dramatically over a five-week period, with Galleria mortality increasing from 4% in week one to 65% in week five. No consistent differences in virulence were observed between polymer types. Pathogens isolated from plastic biofilms using Galleria enrichment included Serratia and Enterococcus species and they harboured a wide range of antimicrobial resistance genes. Our findings show that plastics in coastal waters are rapidly colonised by a wide diversity of bacteria independent of polymer type. Further, our results show that marine plastic biofilms become increasingly associated with virulent bacteria over time.