Biology subjects

Duncan, S.

Publications and source records attributed to Duncan, S..

17 recordsLinked to original sources

bioRxiv2026

Development and evaluation of a pan-fungal lateral flow device for the rapid identification of pathogen class in microbial keratitis

PurposeTo develop a pan-fungal lateral flow device (LFD); evaluating device performance with samples obtained from ex vivo porcine cornea infection models. MethodsFungal {beta}-glucan (PF1), human CLEC7A/Dectin-1/CLECSF12 protein (Fc Tag; PF2), and fungal melanin (PF3) antibodies were evaluated for binding to clinically relevant fungal and bacterial species (Aspergillus flavus, Fusarium keratoplasticum, Candida albicans, Pseudomonas aeruginosa, Staphylococcus aureus) by immunofluorescence staining. PF1 and PF2 were evaluated in proof-of-concept, in-house LFD strips using cultured pathogens and ex vivo porcine corneal infection samples. The lead antibody (PF1) was validated in a commercially-developed prototype LFD. ResultsPF1 and PF2 discriminated target fungi from bacteria by immunofluorescence microscopy and in-house LFD strips. The lead candidate PF1 demonstrated good sensitivity (0.75) and specificity (0.94) with cultured fungal hyphae. Samples obtained from infected ex vivo cornea by clinically relevant methods confirmed excellent sensitivity (scrapes: 1.00, swabs: 0.94) and specificity (scrapes: 1.00, swabs: 0.83). The commercially-developed PF1-LFD prototype achieved perfect sensitivity (1.00) and specificity (1.00) when detecting and discriminating fungi from non-fungal ex vivo corneal swab samples. ConclusionsFeasibility of pan-fungal LFD application in microbial keratitis diagnosis was demonstrated - using {beta}-glucan as a pan-fungal target and a clinically relevant microbial keratitis ex vivo model. LFDs were able to differentiate fungal from bacterial samples, detect antigen present in corneal swabs, and provide a read-out within 20 minutes. Sensitivity and specificity values are comparable to currently used diagnostic tests. Translational RelevanceEarly discrimination of fungal keratitis cases is important to adapt treatment, and improve patient outcome.

microbiology↗

bioRxiv2025

Co-transcriptional splicing changes combine with reduced productive transcription initiation for cold-induced repression of FLC

The Arabidopsis floral repressor locus FLC is epigenetically silenced during winter cold to align flowering with spring. During weeks of cold exposure, FLC transcription is progressively reduced both by transcriptional repression mediated by FLC antisense transcription, and epigenetic silencing implemented through a Polycomb-mediated epigenetic switch. In the warm, FLC is transcriptionally repressed by coordinated changes in transcription initiation and RNA PolII speed in a mechanism involving proximal termination. Whether similar mechanisms contribute to the cold-induced FLC transcriptional repression is unknown. Here, we combine mathematical modelling and transcription profiling to investigate FLC transcriptional changes during the cold. We find different dynamics of spliced and unspliced transcripts during cold exposure with only a small change in PolII speed. We also show that, unlike short-term cold, long-term cold temperatures drive an increase in splicing rates while simultaneously reducing productive transcription at FLC. This process is influenced by antisense COOLAIR transcription but does not rely on proximal COOLAIR termination. Cold-induced transcriptional repression of FLC thus involves a decoupling of changes in productive transcription initiation from PolII speed and rates of co-transcriptional splicing, a different mechanism to that repressing FLC in the warm.

molecular biology↗

bioRxiv2025

Life-history trade-offs explain local adaptation in Arabidopsis thaliana

Local adaptation has been demonstrated in many organisms, but the traits involved, and the temporal and spatial scales at which selection acts are generally unknown. We carried out a multi-year study of 200 accessions (natural inbred lines) of Swedish Arabidopsis thaliana using local field sites and a combination of common-garden experiments that measured adult survival and fecundity, and selection experiments that measured fitness over the full life cycle. We found evidence of strong and variable selection, with particular genotypes favored more than five-fold in certain years and locations. Fecundity showed evidence of classical local adaptation, with accessions generally performing better closer to their home. However, relative to other accessions, southern ones usually had the highest fecundity---but were far more sensitive to harsh winters and slug herbivory, which strongly decreased both survival and fecundity. Furthermore, accessions originally sampled on beaches had low fecundity in all common-garden experiments, but massively outperformed all other accessions in the selection experiments, presumably due to an advantage during seedling establishment associated with their very large seeds. We conclude that local adaptation in A. thaliana reflects strong temporally and spatially varying selection on multiple traits, generally involving trade-offs and different life-history strategies, making fitness difficult to predict and measure.

genetics↗

bioRxiv2025

rTCT: Rodent Triangle Completion Task to facilitate translational study of path integration

Path integration is navigation in the absence of environmental landmarks and is a primary cognitive mechanism underlying spatial memory. Path integration performance is primarily assessed in humans using the Triangle Completion Task (TCT). In humans, TCT has shown promise for the early diagnosis of Alzheimers disease. In rodents, however, path integration is assessed using a wide variety of tasks but none of which currently provide a homologue for the TCT. As rodents are routinely used as preclinical models, homologous path integration tasks that result in comparable performance metrics between species are important. In the present study we developed and tested a novel rodent version of the triangle completion task to enhance cross species comparability of path integration performance. Rats were able to comprehend and perform the task. A group of Alzheimers disease model rats (TgF344-AD) exhibited similar path integration performance to their wild-type littermates; however, analysis of behavioural structure suggests use of differing behavioural strategies. This work establishes a novel rodent homologue of the triangle completion task, facilitating enhanced reverse translational study of human path integration.

neuroscience↗

bioRxiv2024

Quantitative RNA spatial profiling using single-molecule RNA FISH on plant tissue cryosections

Single-molecule fluorescence in situ hybridization (smFISH) has emerged as a powerful tool to study gene expression dynamics with unparalleled precision and spatial resolution in a variety of biological systems. Recent advancements have expanded its application to encompass plant studies, yet a demand persists for a simple and robust smFISH method adapted to plant tissue sections. Here, we present an optimized smFISH protocol (cryo-smFISH) for visualizing and quantifying single mRNA molecules in plant tissue cryosections. This method exhibits remarkable sensitivity, capable of detecting low-expression transcripts, including long non-coding RNAs. Integrating a deep learning-based algorithm in our image analysis pipeline, our method enables us to assign RNA abundance precisely in nuclear and cytoplasmic compartments. Compatibility with Immunofluorescence also allows RNA and endogenous proteins to be visualized and quantified simultaneously. Finally, this study presents for the first time the use of smFISH for single-cell RNA sequencing (scRNA-seq) validation in plants. By extending the smFISH method to plant cryosections, an even broader community of plant scientists will be able to exploit the multiple potentials of quantitative transcript analysis at cellular and subcellular resolutions.

cell biology↗

bioRxiv2024

De novo annotation of the wheat pangenome reveals complexity and diversity of the hexaploid wheat pan-transcriptome

Wheat is the most widely cultivated crop in the world with over 215 million hectares grown annually. However, to meet the demands of a growing global population, breeders face the challenge of increasing wheat production by approximately 60% within the next 40 years. The 10+ Wheat Genomes Project recently sequenced and assembled to chromosome level the genomes of nine wheat cultivars to develop our understanding of genetic diversity and selection within the pan-genome of wheat. Here, we provide a wheat pan-transcriptome with de novo annotation and differential expression analysis for these wheat cultivars, across multiple different tissues and whole seedlings sampled at dusk/dawn. Analysis of these de novo annotations facilitated the discovery of genes absent from the Chinese Spring reference, identified genes specific to particular cultivars and defined the core and dispensable genomes. Expression analysis across cultivars and tissues revealed conservation in expression between a large core set of homeologous genes, but also widespread changes in subgenome homeolog expression bias between cultivars. Co-expression network analysis revealed the impact of divergence of sub-genome homeolog expression and identified cultivar-specific expression profiles. In a case study utilising both the newly constructed wheat pan-genome and pan-transcriptome we demonstrate prevalent variation in the prolamin superfamily and immune-reactive proteins across the pan-cultivars.In summary, this work provides both a valuable resource for the wider wheat community and reveals diversity in gene content and expression patterns between global wheat cultivars.

genomics↗

bioRxiv2023

Increased flexibility of CA3 memory representations following environmental enrichment

Environmental enrichment (EE) improves memory, particularly under conditions of high memory interference1-6. Here, we investigate the neural mechanisms facilitating improved memory following EE. Using associative recognition memory tasks that model the automatic and integrative nature of episodic memory, we find that EE-dependent improvements in difficult associative memory discriminations are related to increased adult hippocampal neurogenesis and sparser memory representations across the hippocampus. Additionally, by recording CA3 place cells as enriched and standard-housed rats explored the increasingly distinct shapes of a "morph" box, we report for the first time that EE changes the way CA3 place cells discriminate similar contexts. CA3 place cells of enriched rats show greater spatial tuning, increased firing rates, and enhanced remapping to contextual changes. These findings point to more precise and flexible CA3 memory representations in enriched rats. Increased spatial tuning and flexibility might support the well-established EE-dependent improvements in fine memory discrimination. HighlightsO_LIEE improves discrimination of similar associative memories C_LIO_LIEE-dependent memory improvements are related to increased adult neurogenesis C_LIO_LIEE results in sparser hippocampal activity C_LIO_LIEE increases spatial tuning, firing and remapping of CA3 place cells C_LI

neuroscience↗

bioRxiv2023

Monitoring Lake Okeechobee Harmful Algal Bloom populations and dynamics with a long-duration Autonomous Surface Vehicle

This article describes the main findings of a full year of continuous operation of a 2-meter Autonomous Sail and Solar Surface Drone, the Nav2 (Navocean Inc.), as part of a Harmful Algal Bloom (HAB) monitoring program in Lake Okeechobee. The Nav2 was equipped with a set of water quality and atmospheric sensors, that recorded high frequency measurements ({inverted exclamation} 1 min) and transmitted near real-time information to allow reporting through a web portal for assessment and operation responses. Major findings include detection of HABs early in the year through chlorophyll (chl-a) and phycocyanin (phyco) fluorometric measurements, as well as different spatial scales of variability in the algal patches. The 24/7 high resolution monitoring allowed detection of patch motion and discrimination between growth and motion along a transect. Furthermore, the platform can potentially fingerprint specific HAB species based on the relatively fine-scale spatial expression of the phyco to chl-a ratio, which essentially captures the bloom macrostructure (e.g. surface scums versus more uniform sub-surface waves over 0.1 - 1 km scale). Sensor outputs, when converted to concentrations based on calibrated with pure laboratory standards, did not accurately yield true chl-a or phyco values when compared to validation samples, likely due to the high turbidity of the lake. However, routine solid-state validations of fluorometric measurements proved useful for assessing consistency in optical sensors to check for sensor drift (e.g. to due biofouling), which was not significant. Overall this demonstration shows that the Nav2 can uniquely and reliably provide in situ HAB and environmental monitoring capabilities in a large, turbid, shallow lake. We envision that platform as an innovative technology for water resource managers by providing turn-key long-duration baseline environmental data (hands-off waypoint navigation), early warnings of HABs for protecting human health, and for HAB mitigation monitoring.

ecology↗

bioRxiv2022

Data mining and experimental approaches to identify combination of natural herbs against bacterial infections

Various studies have identified that natural herbs can be repurposed to treat infectious and bacterial diseases. The purpose of this study is first to test the medicinal value of five herbs including asafoetida, cumin, fenugreek, neem, and turmeric as single agent and in pairs using the bacterial zone of inhibition assay. Second, we used target and network analyses to predict the best combinations. We found that all the herbs as single agent were effective against bacterial infection in the following descending order of efficacy: cumin > turmeric > neem > fenugreek > asafoetida as compared to vehicle (ethanol) treated control. Among all the tested combinations the turmeric and fenugreek combination had the best efficacy in inhibiting the bacterial growth. Next to understand the mechanism of action and to predict the effective combinations among available herbs, we used a data mining and computational analysis approach. Using NPASS, BindingDB, and pathway analysis tools, we identified the bioactive compounds for each herb, then identified the targets for each bioactive compound, and then identified associated pathways for these targets. Then we measured the target/pathway overlap for each herb and identified that the most effective combinations were those which have non-overlapping targets/pathways. For example, we showed as a proof-of-concept that turmeric and fenugreek have the least overlapping targets/pathways and thus is most effective in inhibiting bacteria growth. Our approach is applicable to treat bacterial infections and other human diseases such as cancer. Overall, the computational prediction along with experimental validation can help identify novel combinations that have significant antibacterial activity and may help prevent drug-resistant microbial diseases in human and plants.

microbiology↗

bioRxiv2022

RNA G-quadruplex structure contributes to cold adaptation in plants

Nucleotide composition is suggested to infer gene functionality and ecological adaptation of species to distinct environments. However, the underlying biological function of nucleotide composition dictating environmental adaptations is largely unknown. Here, we systematically analyzed the nucleotide compositions of transcriptomes across 1000 plants (1KP) and their corresponding habitats. Intriguingly, we found that plants growing in cold climates have guanine (G)-enriched transcriptomes, which are prone to forming RNA G-quadruplex structures. Both immunofluorescence detection and in vivo structure profiling revealed that RNA G-quadruplex formation in plants was globally enhanced in response to cold. Cold-responsive RNA G-quadruplexes strongly enhanced mRNA stability, rather than affecting translation. Disruption of individual RNA G-quadruplex promoted mRNA decay in the cold, leading to impaired plant cold response. Therefore, we propose that plants adopted RNA G-quadruplex structure as a molecular marker to facilitate their adaptation to the cold during evolution.

molecular biology↗

bioRxiv2021

Interpreting machine learning models to investigate circadian regulation and facilitate exploration of clock function

The circadian clock is an important adaptation to life on earth. Here, we use machine learning to predict complex temporal circadian gene expression patterns in Arabidopsis. Most significantly, we classify circadian genes using DNA sequence features generated from public genomic resources, with no experimental work or prior knowledge needed. We use model explanation to rank DNA sequence features, observing transcript-specific combinations of potential circadian regulatory elements that discriminate temporal phase of expression. Model interpretation/explanation provides the backbone of our methodological advances, giving insight into biological processes and experimental design. Next, we use model interpretation to optimize sampling strategies when we predict circadian transcripts using reduced numbers of transcriptomic timepoints, saving both time and money. Finally, we predict the circadian time from a single transcriptomic timepoint, deriving novel marker transcripts that are most impactful for accurate prediction, this could facilitate the identification of altered clock function from existing datasets.

genomics↗

bioRxiv2020

Human gut Faecalibacterium prausnitzii deploy a highly efficient conserved system to cross-feed on β-mannan-derived oligosaccharides

{beta}-Mannans are hemicelluloses that are abundant in modern diets as components in seed endosperms and common additives in processed food. Currently, the collective understanding of {beta}-mannan saccharification in the human colon is limited to a few keystone species, which presumably liberate low-molecular-weight mannooligosaccharide fragments that become directly available to the surrounding microbial community. Here we show that a dominant butyrate-producer in the human gut, Faecalibacterium prausnitzii, is able to acquire and degrade various {beta}-mannooligosaccharides ({beta}-MOS), which are derived by the primary mannanolytic activity of neighboring gut microbiota. Detailed biochemical analyses of selected protein components from their two {beta}-mannooligosaccharides ({beta}-MOS) utilization loci (FpMULs) supported a concerted model whereby the imported {beta}-MOS are stepwise disassembled intracellularly by highly adapted enzymes. Coculturing experiments of F. prausnitzii with the primary degrader Bacteroides ovatus on polymeric {beta}-mannan resulted in syntrophic growth and production of butyrate, thus confirming the high efficiency of the FpMULs uptake system. Genomic comparison with human F. prausnitzii strains and analyses of 2441 public human metagenomes revealed that FpMULs are highly conserved and distributed worldwide. Together, our results provide a significant advance in the knowledge of {beta}-mannans metabolism and the degree to which its degradation is mediated by cross-feeding interactions between prominent beneficial microbes in the human gut. ImportanceCommensal butyrate-producing bacteria belonging to the Firmicutes phylum are abundant in the human gut and are crucial for maintaining health. Currently, insight is lacking into how they target otherwise indigestible dietary fibers and into the trophic interactions they establish with other glycan degraders in the competitive gut environment. By combining cultivation, genomic and detailed biochemical analyses this work reveals the mechanism enabling F. prausnitzii, as a model clostridial cluster IV Firmicute, to cross-feed and access {beta}-mannan-derived oligosaccharides released in the gut ecosystem by the action of primary degraders. A comprehensive survey of human gut metagenomes shows that FpMULs are ubiquitous in human populations globally, highlighting the importance of microbial metabolism of {beta}-mannans/{beta}-MOS as a common dietary component. Our findings provide a mechanistic understanding of the {beta}-MOS utilization capability by F. prausnitzii that may be exploited to select dietary formulations specifically boosting this beneficial symbiont, thus butyrate production, in the gut.

microbiology↗

bioRxiv2019

RNA G-quadruplex structures exist and function in vivo

Guanine-rich sequences are able to form complex RNA structures termed RNA G-quadruplexes in vitro. Because of their high stability, RNA G-quadruplexes are proposed to exist in vivo and are suggested to be associated with important biological relevance. However, there is a lack of direct evidence for RNA G-quadruplex formation in living cells. Therefore, it is unclear whether any purported functions are associated with the specific sequence content or the formation of an RNA G-quadruplex structure. Here, we profiled the landscape of those guanine-rich regions with the in vitro folding potential in the Arabidopsis transcriptome. We found a global enrichment of RNA G-quadruplexes with two G-quartets whereby the folding potential is strongly influenced by RNA secondary structures. Using in vitro and in vivo RNA chemical structure profiling, we determined that hundreds of RNA G-quadruplex structures are strongly folded in both Arabidopsis and rice, providing direct evidence of RNA G-quadruplex formation in living eukaryotic cells. Subsequent genetic and biochemical analysis showed that RNA G-quadruplex folding was sufficient to regulate translation and modulate plant growth. Our study reveals the existence of RNA G-quadruplex in vivo, and indicates that RNA G-quadruplex structures act as important regulators of plant development and growth.

plant biology↗

bioRxiv2019

The collagen-binding epitopes of Drosophila SPARC are essential for survival and collagen IV distribution and assembly into basement membranes

The assembly of basement membranes (BMs) into tissue-specific morphoregulatory structures requires non-core BM components. Work in Drosophila indicates a principal role of collagen-binding matricellular glycoprotein SPARC (Secreted Protein, Acidic, Rich in Cysteine) in larval fat body BM assembly. We report that SPARC and collagen IV (Col(IV)) first colocalize in the trans-Golgi of hemocytes. Mutating the collagen-binding epitopes of SPARC leads to 2nd instar larval lethality, indicating that SPARC binding to Col(IV) is essential for survival. Analysis of this mutant reveals increased Col(IV) puncta within adipocytes and intense perimeter Col(IV) staining surrounding the fat body as compared to wild-type larvae, reflecting a disruption in chaperone-like activity. In addition, Col(IV) in the wing imaginal disc was absent. Removal of the disulfide bridge in EF-hand2, which is known to enhance Col(IV) binding by SPARC, did not lead to larval lethality; however, a similar but less intense fat body phenotype was observed. Additionally, both SPARC mutants have altered fat body BM pore topography. Wing imaginal disc-derived SPARC did not localize within Col(IV)-rich matrices, indicating a distinct variant. Collectively, these data demonstrate the essential role of Col(IV) chaperone-like activity of SPARC to Drosophila development and indicate tissue-specific variants with differential functions.

developmental biology↗

bioRxiv2019

A high-throughput delayed fluorescence method reveals underling differences in the control of circadian rhythms in Triticum aestivum and Brassica napus

BackgroundA robust circadian clock has been implicated in plant resilience, resource-use efficiency, competitive growth and yield. A huge number of physiological processes are under circadian control in plants including: responses to biotic and abiotic stresses; flowering time; plant metabolism; and mineral uptake. Understanding how the clock functions in crops such as Triticum aestivum (bread wheat) and Brassica napus (oilseed rape) therefore has great agricultural potential. Delayed fluorescence (DF) imaging has been shown to be applicable to a wide range of plant species and requires no genetic transformation. Although DF has been used to measure period length of both mutants and wild ecotypes of Arabidopsis, this assay has never been systematically optimised for crop plants. The physical size of both B. napus and T. aestivum led us to develop a representative sampling strategy which enables high-throughput imaging of these crops.\n\nResultsIn this study, we describe the plant-specific optimisation of DF imaging to obtain reliable circadian phenotypes with the robustness and reproducibility to detect diverging periods between cultivars of the same species. We find that the age of plant material, light regime and temperature conditions all significantly effect DF rhythms and describe the optimal conditions for measuring robust rhythms in each species. We also show that sections of leaf can be used to obtain period estimates with improved throughput for larger sample size experiments.\n\nConclusionsWe present an optimized protocol for high-throughput phenotyping of circadian period specific to two economically valuable crop plants. Application of this method revealed significant differences between the periods of several widely grown elite cultivars. This method also identified intriguing differential responses of circadian rhythms in T. aestivum compared to B. napus; specifically the dramatic change to rhythm robustness when plants were imaged under constant light versus constant darkness. This points towards diverging networks underling circadian control in these two species.

plant biology↗

bioRxiv2018

Harmful algae bloom monitoring via a sustainable, sail-powered mobile platform for in-land and coastal monitoring

Harmful algae blooms (HAB) in coastal marine environments are increasing in number and duration, pressuring local resource managers to implement mitigation solutions to protect human and ecosystem health. However, insufficient spatial and temporal observations create uninformed management decisions. In order to better detect and map blooms, as well as the environmental conditions responsible for their formation, long-term, unattended observation platforms are desired. In this article, we describe a new cost-efficient, autonomous, mobile platform capable of accepting several sensors that can be used to monitor harmful algae blooms in near real-time. The Navocean autonomous sail-powered surface vehicle is deployable by a single person from shore, capable of waypoint navigation in shallow and deep waters, and powered completely by renewable energy. We present results from three surveys of the Florida Red Tide harmful algae bloom (Karenia brevis) of 2017-2018. The vessel made significant progress towards waypoints regardless of wind conditions while underway chl. a measurements revealed HAB bloom patches and CDOM and turbidity provided environmental contextual information. While the autonomous sailboat directly adds to our HAB monitoring capabilities, the boat can also help to ground-truth and thus improve satellite monitoring of HABs. Finally, several other pending and future use cases for coastal and inland monitoring are discussed. To our knowledge, this is the first demonstration of a sail-driven vessel used for coastal HAB monitoring.

ecology↗

bioRxiv2017

Plant genes influence microbial hubs that shape beneficial leaf communities

Although complex interactions between hosts and microbial associates are increasingly well documented, we still know little about how and why hosts shape microbial communities in nature. In addition, host genetic effects on microbial communities vary widely depending on the environment, obscuring conclusions about which microbes are impacted and which plant functions are important. We characterized the leaf microbiota of 200 A. thaliana genotypes in eight field experiments and detected consistent host effects on specific, broadly distributed microbial OTUs. Host genetics disproportionately influenced hubs within the microbial communities, with their impact then percolating through the community, as evidenced by a decline in the heritability of particular OTUs with their distance to the nearest hub. By simultaneously measuring host performance, we found that host genetics associated with microbial hubs explained over 10% of the variation in lifetime seed production among host genotypes across sites and years. We successfully cultured one of these microbial hubs and demonstrated its growth-promoting effects on plants grown in sterile conditions. Finally, genome-wide association mapping identified many putatively causal genes with small effects on the relative abundance of microbial hubs across sites and years, and these genes were enriched for those involved in the synthesis of specialized metabolites, auxins and the immune system. Using untargeted metabolomics, we corroborate the consistent association of variation in specialized metabolites and microbial hubs across field sites. Together, our results reveal that host natural variation impacts the microbial communities in consistent ways across environments and that these effects contribute to fitness variation among host genotypes.

microbiology↗