Biology subjects

Heavens, D.

Publications and source records attributed to Heavens, D..

At least 19 recordsLinked to original sources

bioRxiv2026

City life: airborne DNA metagenomic biodiversity monitoring reveals dynamic changes across time and space

Airborne environmental DNA can capture biodiversity across the tree of life, but low sample biomass makes rapid, untargeted detection technically challenging. We combined 45-min air collection, nanopore sequencing and real-time taxonomic analysis in a shotgun metagenomic workflow capable of producing results within 3 hours. Across 77 samples from 13 London sites, including a year of weekly sampling at the Natural History Museum Wildlife Garden, we detected 1,916 species spanning bacteria, fungi, plants and animals. Communities varied spatially and seasonally, shifting from plant dominance in spring to ascomycete dominance in summer and basidiomycete dominance in late autumn and winter. Plant read abundance increased with upwind vegetation, linking airborne signals to surrounding habitat. Detection of catalogued garden plants depended on reference availability, dispersal biology, plant size and proximity to the collector. Together, these findings establish airborne shotgun metagenomics as a platform for rapid, repeated and scalable biodiversity assessment across space and time.

ecology↗

bioRxiv2026

Enriching the Human Stool Microeukaryotes for Shotgun Sequencing

The human gut microbiome harbours a diverse community of microeukaryotes, predominantly fungi, which may potentially play important roles in gut ecology and homeostasis. Despite their potential, the study of gut microeukaryotes has been hampered by the limited sensitivity of standard sequencing approaches, which struggle to capture DNA from low-abundance microorganisms against the overwhelming background of bacterial biomass. To address this, we developed a method to selectively enrich for microeukaryotic cells in human faecal samples by depleting bacterial cells prior to metagenomic sequencing. Through systematic comparison and optimisation at each processing step, we established a robust standard operating procedure (SOP) for microeukaryotic cell enrichment. By benchmarking this SOP across eight human faecal samples with three technical replicates each, we showed that it consistently increased microeukaryote representation in metagenomic libraries, greater microeukaryotic taxonomic diversity, and a reduced proportion of unclassified taxa. Together, these improvements enabled substantially deeper characterisation of the microeukaryotic fraction of the human gut microbiome.

microbiology↗

bioRxiv2025

Decoding the microbiome and resistome of advanced chronic liver disease through long-read metagenomics

IntroductionPatients with advanced chronic liver disease (ACLD) and underlying cirrhosis frequently require repeated courses of antimicrobial therapy, with both the frequency and spectrum of antimicrobial exposure increasing alongside disease progression. In this population, impaired immune function and increased intestinal barrier dysfunction contribute to a heightened susceptibility of multidrug-resistant bacterial infections. ObjectiveTo comprehensively characterise the gastrointestinal microbiome and antimicrobial resistance gene (ARG) landscape across the clinical spectrum of ACLD, and to identify microbial and resistome signatures associated with disease severity. DesignWe employed long-read metagenomic sequencing (Oxford Nanopore Technologies) to profile the gastrointestinal microbiome and resistome across distinct ACLD stages: acute-on-chronic liver failure (ACLF), decompensated cirrhosis (DC), and stable cirrhosis, compared to healthy controls. ResultsACLF patients had pronounced levels of Enterococcus faecium, with six samples out of 28 showing over 95% relative abundance, suggesting its potential as a bacterial biomarker for advanced cirrhosis. We reconstructed 28 high-quality MAGs of E. faecium from cirrhosis patients, 17 of which originated from ACLF cases. This dominance of E. faecium correlated with substantially reduced microbial diversity and a marked depletion of key commensal taxa, including Blautia, Akkermansia, Faecalibacterium, and Bifidobacterium. Resistome analysis revealed significant enrichment of clinically relevant ARGs in DC and ACLF, including those conferring resistance to aminoglycosides, beta-lactams, and glycopeptides, correlating with prior antimicrobial exposure. ConclusionLong-read metagenomics enables high-resolution characterisation of microbial and resistome dynamics across ACLD severities. By capturing taxonomic shifts, functional potential, and ARG enrichment, this approach provides valuable insights into microbiome trajectories linked with disease severity, informing mechanistic research and potential clinical interventions. Impact statementChronic liver disease is a major global health burden, responsible for approximately 2 million deaths each year. Advanced chronic liver disease profoundly disrupts the gut microbiome, often exacerbated by repeated antibiotic exposure, promoting the persistence of antimicrobial-resistant organisms. Leveraging Oxford Nanopore Technologies long-read metagenomic sequencing, this study delivers high-resolution insights into the gut microbiome and resistome across progressive stages of cirrhosis. We reveal Enterococcus faecium dominance as a defining feature of cirrhosis, accompanied by severe loss of commensal diversity and enrichment of clinically significant resistance genes. These findings underscore the clinical utility of culture-independent metagenomic profiling for detecting pathogenic taxa and resistance determinants within the gut ecosystem of high-risk patients. Our work highlights the translational potential of long-read metagenomics as an accessible tool for pathogen surveillance, antimicrobial stewardship, and precision infection management in advanced liver disease.

microbiology↗

bioRxiv2025

Arabidopsis arenosa influences its microbiome as a serpentine soil adaptation strategy

There is growing evidence that microbes can facilitate plant growth in metal-rich soils. However, our current understanding of how plants recruit their microbiomes under abiotic stress remains incomplete. Serpentine soils are elementally skewed, with high concentrations of magnesium and nickel, often accompanied by other heavy metals, which can limit calcium availability and present unique challenges to plant growth. These soils are also nutrient-poor, prone to erosion, and have low water-holding capacity. To date, the mechanisms by which plants adapt to serpentine soils remain poorly understood and the role of plant-associated microbiomes in this process has not been described. Here, we focus on Arabidopsis arenosa populations adapted to serpentine conditions and investigate their bacterial and fungal microbiomes to better understand the role of plant-associated microbes in serpentine adaptation. We show that serpentine soils harbour distinct plant-associated microbiomes across different plant niches and that the plant genetic background plays a key role in shaping microbial community composition. Finally, we identify serpentine-specific bacterial and fungal variants that may contribute to plant adaptation under these challenging soil conditions.

ecology↗

bioRxiv2025

MARTi: a real-time analysis and visualisation tool for nanopore metagenomics

The emergence of nanopore sequencing technology has the potential to transform metagenomics by offering low-cost, portable, and long-read sequencing capabilities. Furthermore, these platforms enable real-time data generation, which could significantly reduce the time from sample collection to result, a crucial factor for point-of-care diagnostics and bio-surveillance. However, the full potential of real-time metagenomics remains largely unfulfilled due to a lack of accessible, open-source bioinformatic tools. We present MARTi (Metagenomic Analysis in Real-Time), an innovative open-source software designed for the real-time analysis, visualisation, and exploration of metagenomic data. MARTi supports various classification methods, including BLAST, Centrifuge, and Kraken2, letting users customise parameters and utilise their own databases for taxonomic classification and antimicrobial resistance analysis. With a user-friendly, browser-based graphical interface, MARTi provides dynamic, real-time updates on community composition and AMR gene identification. MARTis architecture and operational flexibility make it suitable for diverse research applications, ranging from in-field analysis to large-scale metagenomic studies. Using both simulated and real-world data, we demonstrate MARTis performance in read classification, taxon detection, and relative abundance estimation. By bridging the gap between sequencing and actionable insights, MARTi marks a significant advance in the accessibility and functionality of real-time metagenomic analysis.

bioinformatics↗

bioRxiv2024

A Comparison of Nanopore Data Types, Basecalling, and Assembly Algorithms: Whole Plant Genome Assembly and Methylation Analysis from a Single MinION Flow cell

BackgroundOxford Nanopore Technologies MinION sequencer is a compact, USB-powered device that has been available since 2014. Since the release of the earliest model, the throughput and error rate of the platform have improved dramatically and it has become possible to consider sequencing and assembly of eukaryotic organisms using a single nanopore flow cell. Here, we present MinION sequence data, assembly and methylation analysis for the Columbia (Col-0) accession of the model plant Arabidopsis thaliana. Further, we demonstrate the effect that recent developments (specifically the Q20+ chemistry and basecaller improvements) have had on read accuracy and assembly quality. FindingsDNA extracted from leaves of A. thaliana Col-0 was sequenced on two MinION flow cells, together amounting to 115x coverage of the 135 Mb genome. Reads were assembled and polished using several bioinformatics pipelines for nanopore sequence data. We performed CpG methylation analysis directly from the nanopore data, and this correlated well with a previously published bisulfite dataset. ConclusionsOur results suggest that a single MinION flow cell can generate sufficient data to assemble a genome of 135Mb, indicate functional elements, and unlock genomics for researchers of novel species from $600 in under 5 days. Here we release the full nanopore read sets for both flow cells, together with the nanopore-only assemblies. The data presented here is expected to be of particular interest to those in the Arabidopsis community, designing genome projects (with functional annotations), expanding our understanding of epigenetics across the tree of life, and for designing university or high school practicals teaching genomics and epigenomics. HighlightWe evaluate the effect of recent nanopore chemistry and software improvements on the ability to assemble a complete genome and conduct methylation analysis using data from a single MinION flow cell.

genomics↗

bioRxiv2023

An improved Nicotiana benthamiana bioproduction chassis provides novel insights into nicotine biosynthesis

The model plant Nicotiana benthamiana is an increasingly attractive organism for the production of high-value, biologically active molecules. However, N. benthamiana accumulates high levels of pyridine alkaloids, in particular nicotine, which complicates the downstream purification processes. Here, we report the assembly of an improved N. benthamiana genome as well as the generation of low-nicotine lines by CRISPR/Cas9-based inactivation of berberine bridge enzyme-like proteins (BBLs). Triple as well as quintuple mutants accumulated 3-4 times less nicotine than the respective control lines. The availability of lines without functional BBLs allowed us to probe their catalytic role in nicotine biosynthesis, which has remained obscure. Notably, chiral analysis revealed that the enantiomeric purity of nicotine was fully lost in the quintuple mutants. In addition, precursor feeding experiments showed that these mutants cannot facilitate the specific loss of C6 hydrogen that characterizes natural nicotine biosynthesis. Our work delivers an improved N. benthamiana chassis for bioproduction and opens the possibility that BBLs are the sought-after coupling enzymes in nicotine biosynthesis.

plant biology↗

bioRxiv2022

Disentangling the genomic complexity of the Fragilariopsis cylindrus (CCMP1102) genome

Fragilariopsis cylindrus CCMP1102 is characterised by a complex genome with significant levels of heterozygosity between haplotypes, > 35% repeats, and an unknown karyotype. This complexity hindered prior assemblies, which show coverage discrepancies indicative of incompleteness. Here, we use a k-mer spectra analysis to reveal the coverage signature for a third haplotype. We applied a novel haplotype-specific assembly method to reconstruct the F. cylindrus CCMP1102 genome, producing 10 fully assembled chromosomes capped by telomeres, and a putative chromosome with a single breakpoint. Our analysis shows triploidy, two cases of aneuploidy, and several truncations. We also present evidence that F. cylindrus reproduces sexually. Taken together, our analytical approach is capable of haplotype-resolved assemblies from structurally complex, poly-ploid genomes, making it suitable for complex genomes of non-model organisms, including those with unknown karyotype.

genomics↗

bioRxiv2021

How low can you go? Driving down the DNA input requirements for nanopore sequencing

The requirement for large amounts of purified DNA limits many sequencing experiments, especially when seeking to avoid pre-amplification or when using third generation technology to sequence molecules directly. We wanted to test the limits of current nanopore sequencing input requirements and devised a set of experiments to evaluate extraction and library preparation approaches for low inputs. We found an optimised bead beating approach combined with a magnetic bead protocol, rather than traditional spin columns for DNA extraction, improved both molecule length, integrity score and DNA yield. Through reducing the DNA input to as little as 6.25 % of recommended (25 ng versus 400 ng) and reaction volumes in half, library construction can be completed, and sequencing begun within 20 minutes of sample collection. Applying these approaches, we demonstrated that our pipeline can be used as a cheap and effective method to de novo assemble a genome and identify genes from low quantities and quality of DNA. With our rapid extraction protocol using transportable equipment and low input library construction we were able to generate a de novo assembly from a single insect (Drosophila melanogaster) spanning 125 Mbp / 85 % of the reference genome, over 96.9% complete BUSCO genes, with a contig N50 over 1.2 Mbp, including chromosome arm sized contigs, for a modest consumable cost under {pound}600.

genomics↗

bioRxiv2021

Analysis of wild plant pathogen populations reveals a signal of adaptation in genes evolving for survival in agriculture in the beet rust pathogen (Uromyces beticola)

Improvements in crop resistance to pathogens can reduce yield losses and address global malnourishment today. Gene-for-gene -type interactions can identify new sources of resistance but genetic resistance is often short lived. Ultimately an understanding of how pathogens rapidly adapt will allow us to both increase resistance gene durability and more effectively target chemical treatments. Until recently all agricultural pathogens were living on wild hosts. To understand crop pathogen evolution, we compared genetic diversity in agricultural and wild populations. Wild reservoirs may be the source of emergent pathogen lineages, but here we outline a strategy for comparison of wild and agricultural pathogen populations to highlight genes adapting to agriculture. To address this, we have selected and developed the beet rust system (Beta vulgaris, Uromyces beticola, respectively) as our wild-agricultural model. Our hypothesis is that pathogen adaptation to agricultural crops will be evident as divergence in comparisons of wild and agricultural plant pathogen populations. We sampled isolates in both the wild and agriculture, sequenced and assembled and annotated a large fungal genome and analysed genetic diversity in 42 re-sequenced rust isolates. We found population differentiation between isolates in the wild compared to a predominantly agricultural group. Fungal effector genes are co-evolving with host resistance and are important for successful colonisation. We predicted (and found) that these exhibit a greater signal of diversification and adaptation and more importantly displayed increased wild agricultural divergence. Finding a signal of adaptation in these genes highlights this as an important strategy to identify genes which are key to pathogen success, that analysis of agricultural isolates alone cannot. Author SummaryAs quickly as we develop new strategies for crop defence, pathogens evolve to circumvent them. Novel crop pathogen strains emerge periodically and sweep through the agricultural system. However, because of the (often) clonal nature of these crop pathogens it is difficult to identify the trait that is key to their success. In other words, if there is a trait that is key for success in agriculture, all agricultural isolates will have it (or die without it). What we need is a case and control system where we identify genes important to pathogen success in agricultural by comparing them to pathogens that live in the wild. Here we exemplify this strategy by focussing on genes already known to specifically adapt for the successful colonisation of the host, the fungal effector genes. We find that these genes appear to be evolving quickly and that they are more different between the wild and agriculture than other non-effector genes. These differences between wild and agricultural pathogens suggest we are observing adaptation to agriculture. We do this work in the sugar beet rust system because of its tractability to sample but this understanding about how to identify genetic variation that is key to pathogen success in agriculture is applicable to crop systems where pathogen reservoirs exist as well as other pathogen reservoir systems (e.g. zoonoses).

evolutionary biology↗

bioRxiv2021

Nanopore adaptive sampling: a tool for enrichment of low abundance species in metagenomic samples

BackgroundAdaptive sampling is a method of software-controlled enrichment unique to nanopore sequencing platforms recently implemented in Oxford Nanopores own control software. By examining the first few hundred bases of a DNA molecule as it passes through a pore, software can determine if the molecule is sufficiently interesting to sequence in its entirety. If not, the molecule is ejected from the pore by reversing the voltage across it, freeing the pore for a new molecule. User supplied sequences define the targets to be sequenced or ejected. Here we explore the potential of using adaptive sampling for enrichment of rarer species within metagenomic samples. ResultsWe created a synthetic mock community consisting of seven bacterial species at different proportions ranging from 1.2% to 47% and used this as the basis for a series of enrichment and depletion experiments. To investigate the effect of DNA length on adaptive sampling efficiency, we created sequencing libraries with mean read lengths of 1.7 kbp, 4.7 kbp, 10.6 kbp, and 12.8 kbp and enriched or depleted for individual and multiple species over a series of sequencing runs. Across all experiments enrichment ranged from 1.67-fold for the most abundant species with the shortest read length to 13.87-fold for the least abundant species with the longest read length. Factoring in the reduction to sequence output associated with repeatedly rejecting molecules reduces the calculated efficiency of this enrichment to between 0.96-fold and 4.93-fold. We note that reducing ejections due to false negatives (approximately 36%) would significantly increase efficiency. We used the relationship between abundance, molecule length and enrichment factor to produce a mathematical model of enrichment based on molecule length and relative abundance, whose predictions correlated strongly with experimental data. A web application is provided to allow researchers to explore model predictions in advance of performing their own experiments. ConclusionsOur data clearly demonstrates the benefit for enriching low abundant species in adaptive sampling metagenomic experiments, especially with longer molecules, and our mathematical model can be used to determine whether a given experimental DNA sample is suitable for adaptive sampling. Notably, repeated voltage reversals have no effect on pore stability.

genomics↗

bioRxiv2020

An accessible, efficient and global approach for the large-scale sequencing of bacterial genomes

We have developed an efficient and inexpensive pipeline for streamlining large-scale collection and genome sequencing of bacterial isolates. Evaluation of this method involved a worldwide research collaboration focused on the model organism Salmonella enterica, the 10KSG consortium. By optimising a logistics pipeline that collected isolates as thermolysates, permitting shipment in ambient conditions, the project assembled a diverse collection of 10,419 clinical and environmental isolates from low- and middle-income countries in less than one year. The bacteria were obtained from 51 countries/territories dating from 1949 to 2017, with a focus on Africa and Latin-America. All isolates were collected in barcoded tubes and genome sequenced using an optimised DNA extraction method and the LITE pipeline for library construction. After Illumina sequencing, the total reagent cost was less than USD$10 per genome. Our method can be applied to genome-sequence other large bacterial collections at a relatively low cost, within a limited timeframe, to support global collaborations.

microbiology↗

bioRxiv2020

A low-cost pipeline for soil microbiome profiling

BackgroundCommon bottlenecks in environmental microbiome studies are the consumable and personnel costs necessary for genomic DNA extraction and sequencing library construction. This is harder for challenging environmental samples such as soil, which is rich in PCR inhibitors. To address this, we have established a low-cost genomic DNA extraction method for inhibitor rich samples alongside an Illumina-compatible 16S and ITS rRNA gene amplicon library preparation workflow that uses common laboratory equipment. We evaluated the performance of our genomic DNA extraction method against two leading commercial soil genomic DNA kits (MoBio PowerSoil(R) and MP Biomedicals FastDNA SPIN) and a recently published non-commercial extraction method by Zou et al. (2017). Our benchmarking experiment used four different soil types (coniferous, broad leafed, and mixed forest plus a standardised cereal crop compost mix) assessing the quality and quantity of the extracted genomic DNA by analysing sequence variants of 16S V4 and ITS rRNA amplicons. ResultsWe found that our genomic DNA extraction method compares well to both commercially available genomic DNA extraction kits in DNA quality and quantity. The MoBio PowerSoil(R) kit, which relies on silica column-based DNA extraction with extensive washing delivered the cleanest genomic DNA e.g. best A260:A280 and A260:A230 absorbance ratios. The MP Biomedicals FastDNA SPIN kit, which uses a large amount of binding material, yielded the most genomic DNA. Our method fits between the two commercial kits, producing both good yields and clean genomic DNA with fragment sizes of approximately 10 kb. Comparative analysis of detected amplicon sequence variants shows that our method correlates well with the two commercial kits. ConclusionHere we present a low-cost genomic DNA extraction method for inhibitor rich sample types such as soil that can be coupled to an Illumina-compatible simple two step amplicon library construction workflow for 16S V4 and ITS marker genes. Our method delivers high quality genomic DNA at a fraction of the cost of commercial kits and enables cost-effective, large scale amplicon sequencing projects. Notably our extracted gDNA molecules are long enough to be suitable for downstream techniques such as full gene sequencing or even metagenomics shotgun approaches using long reads (PacBio or Nanopore), 10x Genomics linked reads, Dovetail genomics etc.

genomics↗

bioRxiv2020

A draft genome of grass pea (Lathyrus sativus), a resilient diploid legume

We have sequenced the genome of grass pea (Lathyrus sativus), a resilient diploid (2n=14) legume closely related to pea (Pisum sativum). We determined the genome size of the sequenced European accession (LS007) as 6.3 Gbp. We generated two assemblies of this genome, i) EIv1 using Illumina PCR-free paired-end sequencing and assembly followed by long-mate-pair scaffolding and ii) Rbp using Oxford Nanopore Technologies long-read sequencing and assembly followed by polishing with Illumina paired-end data. EIv1 has a total length of 8.12 Gbp (including 1.9 billion Ns) and scaffold N50 59,7 kbp. Annotation has identified 33,819 high confidence genes in the assembly. Rbp has a total length of 6.2 Gbp (with no Ns) and a contig N50 of 155.7 kbp. Gene space assessment using the eukaryote BUSCO database showed completeness scores of 82.8 % and 89.8%, respectively.

genomics↗

bioRxiv2020

A genome assembly of the barley 'transformation reference' cultivar Golden Promise

BackgroundBarley (Hordeum vulgare) is one of the most important crops worldwide and is also considered a research model for the large-genome small grain temperate cereals. Despite genomic resources improving all the time, they are limited for the cv. Golden Promise, the most efficient genotype for genetic transformation. FindingsWe have developed a barley cv. Golden Promise reference assembly integrating Illumina paired-end reads, long mate-pair reads, Dovetail Chicago in vitro proximity ligation libraries and chromosome conformation capture sequencing (Hi-C) libraries into a contiguous reference assembly. The assembled genome of 7 chromosomes and 4.13Gb in size, has a super-scaffold N50 after Chicago libraries of 4.14Mb and contains only 2.2% gaps. Using BUSCO (benchmarking universal single copy orthologous genes) as evaluation the genome assembly contains 95.2% of complete and single copy genes from the plant database. ConclusionsA high-quality Golden Promise reference assembly will be useful and utilised by the whole barley research community but will prove particularly useful for CRISPR-Cas9 experiments.

genomics↗

bioRxiv2019

A novel allele of ASY3 promotes meiotic stability in autotetraploid Arabidopsis lyrata

In this study we performed a genotype-phenotype association analysis of meiotic stability in ten autotetraploid Arabidopsis lyrata and A. lyrata/A. arenosa hybrid populations collected from the Wachau region and East Austrian Forealps. The aim was to determine the effect of eight meiosis genes under extreme selection upon adaptation to whole genome duplication. Individual plants were genotyped by high-throughput sequencing of the eight meiosis genes (ASY1, ASY3, PDS5b, PRD3, REC8, SMC3, ZYP1a/b) implicated in synaptonemal complex formation and phenotyped by assessing meiotic metaphase I chromosome configurations. Our results reveal that meiotic stability varied greatly (20-100%) between individual tetraploid plants and was associated with segregation of a novel allele orthologous to the budding yeast RED1 chromosome axis protein, Asynapsis3 (ASY3), derived from A. lyrata. The adaptive ASY3 protein possesses a putative in-frame tandem duplication (TD) of a serine-rich region upstream of the coiled-coil domain that has arisen at sites of DNA microhomology. The frequency of multivalents observed in plants homozygous for the ASY3 TD haplotype was significantly lower than plants heterozygous for TD/ND (non-duplicated) ASY3 haplotypes. Chiasma distribution was significantly altered in the stable plants compared to the unstable plants with a shift from proximal and interstitial to predominantly distal locations. The number of HEI10 foci at pachtyene that mark class I crossovers was significantly reduced in meiotic nuclei from ASY3 TD homozygous plants compared to ASY3 ND/TD heterozygotes, indicating an adaptive consequence of the ASY3 TD allele. From the ten populations, fifty-eight alleles of these 8 meiosis genes were identified, demonstrating dynamic population variability at these loci which nevertheless exhibit signatures of strong hard selective sweeps. Widespread chimerism between alleles originating from A. lyrata/A. arenosa and diploid/tetraploids indicates that this group of rapidly evolving genes provide precise adaptive control over meiotic recombination in the tetraploids, the very process that gave rise to them. Author summaryWhole genome duplication can promote adaptability, but is a dramatic mutation usually resulting in meiotic catastrophe and genome instability. Here we focus on a case of coordinated stabilization of meiotic recombination in ten autotetraploid Arabidopsis lyrata and A. lyrata/A. arenosa hybrid populations from the Wachau region and East Austrian Forealps. We fuse population genomic data with a genotype-phenotype association study, concentrating on the effects of eight meiosis genes (ASY1, ASY3, PDS5b, PRD3, REC8, SMC3, ZYP1a/b) implicated in synaptonemal complex formation in the tetraploids under extreme selection. Our analysis demonstrates that a novel allele of the meiotic chromosome axis protein Asynapsis3 that contains an in-frame duplication of a serine-rich region is the major determinant of male meiotic stability. This adaptive restabilisation appears to be achieved by a reduction in the number of meiotic crossovers as well as a shift in their positioning towards the chromosome ends. Of the eight genes, fifty-eight alleles were identified, indicating dynamic population variability at these loci under extreme selection. In addition, widespread allelic chimerism between alleles originating from A. lyrata/A. arenosa and diploid/tetraploids indicates that this group of rapidly evolving genes provide precise adaptive control over meiotic recombination in the tetraploids, the very process that gave rise to them.

evolutionary biology↗

bioRxiv2019

Sequencing smart: De novo sequencing and assembly approaches for non-model mammals.

BackgroundWhilst much sequencing effort has focused on key mammalian model organisms such as mouse and human, little is known about the correlation between genome sequencing techniques for non-model mammals and genome assembly quality. This is especially relevant to non-model mammals, where the samples to be sequenced are often degraded and low quality. A key aspect when planning a genome project is the choice of sequencing data to generate. This decision is driven by several factors, including the biological questions being asked, the quality of DNA available, and the availability of funds. Cutting-edge sequencing technologies now make it possible to achieve highly contiguous, chromosome-level genome assemblies, but relies on good quality high-molecular-weight DNA. The funds to generate and combining these data are often only available within large consortiums and sequencing initiatives, and are often not affordable for many independent research groups. For many researchers, value-for-money is a key factor when considering the generation of genomic sequencing data. Here we use a range of different genomic technologies generated from a roadkill European Polecat (Mustela putorius) to assess various assembly techniques on this low-quality sample. We evaluated different approaches for de novo assemblies and discuss their value in relation to biological analyses.\n\nResultsGenerally, assemblies containing more data types achieved better scores in our ranking system. However, when accounting for misassemblies, this was not always the case for Bionano and low-coverage 10x Genomics (for scaffolding only). We also find that the extra cost associated with combining multiple data types is not necessarily associated with better genome assemblies.\n\nConclusionsThe high degree of variability between each de novo assembly method (assessed from the seven key metrics) highlights the importance of carefully devising the sequencing strategy to be able to carry out the desired analysis. Adding more data to genome assemblies not always results in better assemblies so it is important to understand the nuances of genomic data integration explained here, in order to obtain cost-effective value-for-money when sequencing genomes.

genomics↗

bioRxiv2019

Spatially resolved transcriptomics reveals plant host responses to pathogens

BackgroundThorough understanding of complex model systems requires the characterisation of processes in different cell types of an organism. This can be achieved with high-throughput spatial transcriptomics at a large scale. However, for plant model systems this is still challenging as suitable transcriptomics methods are sparsely available. Here we present Grid-seq, an easy to adopt, micro-scale spatial-transcriptomics workflow that allows to study expression profiles across small areas of plant tissue at a fraction of the cost of existing sequencing-based methods.\n\nResultsWe compare the Grid-seq method with widely used library preparation methods (Illumina TruSeq). In spatial experiments we show that the Grid-seq method is sensitive enough to identify expression differences across a plant organ. We further assess the spatial transcriptome response of Arabidopsis thaliana leaves exposed to the bacterial molecule flagellin-22.\n\nConclusionWe show that our method can be used to identify known, rapidly flagellin-22 elicited genes, plant immune response pathways to bacterial attack and spatial expression patterns of genes associated with these pathways.

genomics↗