Biology subjects

Barber, A. E.

Publications and source records attributed to Barber, A. E..

8 recordsLinked to original sources

bioRxiv2026

An Aspergillus lncRNA atlas reveals a novel modulator of aflatoxin biosynthesis

Long non-coding RNAs (lncRNAs) represent a significant fraction of the transcriptome and are vital regulators in eukaryotes, yet their functional landscape in fungi remains largely undefined. Here we present a transcriptomic atlas of 8,553 lncRNAs across four evolutionarily and biotechnologically diverse Aspergillus species. We observed marked diversity in the long non-coding repertoire between species, with only 39% shared between at least two species. However, conserved lncRNAs are expressed at significantly higher levels and across more conditions than species-specific ones, revealing a functional hierarchy within the non-coding transcriptome. We also identify subtelomeres and transposable elements as hotspots for lncRNA innovation in Aspergillus, albeit at the cost of reduced expression. Integrating genomic and transcriptomic data, we show that lncRNAs predominantly exhibit distance-dependent cis-coexpression with neighboring genes and, through guilt-by-association, we identify their participation in global modules governing primary and secondary metabolism. This framework enabled the discovery of aflalinc, a species- and condition-specific lncRNA in A. flavus that plays a role in regulating the aflatoxin biosynthetic gene cluster. Crucially, deletion of this lncRNA severely reduced the production of aflatoxin B, a highly potent agent of acute toxicity and driver of hepatocarcinoma, without affecting growth, conidiation, or sclerotia formation. In addition, examination of an independent dataset confirms the strength of the co-expression networks and uncovers stage-specific functions for lincRNAs in the maturation of A. fumigatus biofilms. Together, these findings establish lncRNAs as integral components of fungal biology and demonstrate that they can modulate mycotoxin production and biofilm formation, with broad implications for controlling fungal threats to food safety and human health.

microbiology↗

bioRxiv2026

The fungal transcription factor SmpR coordinates secondary metabolism and antibacterial defence in Aspergillus fumigatus during interspecies interaction

Aspergillus fumigatus, an opportunistic human fungal pathogen, encodes numerous secondary metabolite biosynthetic gene clusters (BGCs) that are tightly regulated and often remain silent under standard conditions. Co-cultivation with Streptomyces rapamycinicus or treatment with the secondary metabolite from this species, the arginoketide azalomycin F, induce the otherwise silent fumicycline (fcc) BGC of A. fumigatus. To elucidate the underlying regulatory circuitry, we performed transcriptome analyses of A. fumigatus exposed to azalomycin F or co-cultured with S. rapamycinicus. Both conditions triggered a coordinated antibacterial response, characterized by induction of specific secondary metabolites and antibacterial effectors, alongside repression of other BGCs, including those for fusarinine C, pyripyropene A, and fumagillin. Among the most strongly induced genes was a zinc cluster transcription factor, designated SmpR for secondary metabolite multiple pathway regulator, which is conserved within Ascomycota. SmpR expression was selectively induced by azalomycin F, specific Streptomyces species and other bacteria isolated from soil such as Kribbella spp. and Arthrobacter spp.. Functional analyses revealed that SmpR is required for activation of the fumicycline BGC: its deletion reduced, whereas its overexpression enhanced fumicycline production independently of external stimuli. We further demonstrate that SmpR acts upstream of the pathway-specific regulator FccR and additionally controls multiple antibacterial BGCs, including those for hexadehydroastechrome, helvolic acid and xanthocillin. Together, our data identify SmpR as a key regulator coordinating antibacterial secondary metabolism in response to bacterial signals in A. fumigatus.

microbiology↗

bioRxiv2025

Small pangenome of Candida parapsilosis reflects overall low intraspecific diversity

Candida parapsilosis is an opportunistic yeast pathogen that can cause life-threatening infections in immunocompromised humans. Whole genome sequencing (WGS) studies of the species have demonstrated remarkably low diversity, with strains typically differing by about 1.5 single nucleotide polymorphisms (SNPs) per 10 kb. However, SNP calling alone does not capture the full extent of genetic variation. Here, we define the pangenome of 372 C. parapsilosis isolates to determine variation in gene content. The pangenome consists of 5,859 genes, of which 48 are not found in the genome of the reference strain. This includes 5,791 core genes (present in [≥] 99.5% of isolates). Four genes, including the allantoin permease gene DAL4, were present in all isolates but were truncated in some strains. The truncated DAL4 was classified as a pseudogene in the reference strain CDC317. CRISPR-Cas9 gene editing showed that removing the early stop codon (producing the full-length Dal4 protein) is associated with improved use of allantoin as a sole nitrogen source. We find that the accessory genome of C. parapsilosis consists of 68 homologous clusters. This includes 38 previously annotated genes, 27 novel paralogs of previously annotated genes and 3 uncharacterised ORFs. Approximately one-third of the accessory genome (24/68 genes) is associated with gene fusions between tandem genes in the major facilitator superfamily (MFS). Additionally, we identified two highly divergent C. parapsilosis strains and find that, despite their increased phylogenetic distance ([~]30 SNPs per 10 kb), both strains have similar gene content to the other 372. ImportanceCandida parapsilosis is a human fungal pathogen, listed in the high priority group by the World Health Organisation. It is an increasing cause of hospital-acquired and drug-resistant infection. Here, we studied the genetic diversity of 372 C. parapsilosis isolates, the largest genomic surveillance of this species to date. We show that there is relatively little genetic variation. However, we identified two more distantly-related isolates from Germany, suggesting that even more sampling may yield more diversity. We find that the pangenome (the cumulative gene content of all isolates) is surprisingly small, compared to other fungal species. Many of the non-core genes are involved in transport. We also find that variations in gene content are associated with nitrogen metabolism, which may contribute to the virulence characteristics of this species.

genomics↗

bioRxiv2024

Comparative pan-genomics reveals divergent adaptations in clinically-relevant members of the Fusarium solani species complex

The Fusarium solani species complex (FSSC) is a group of dual-kingdom fungal pathogens capable of causing devastating disease on a wide range of host plants and life-threatening infections in humans that are difficult to treat. In this study, we generate highly contiguous genomes for three clinical isolates of Fusarium keratoplasticum and three clinical isolates of Fusarium petroliphilum and compare them with other genomes of the FSSC from plant and animal sources. We find that human pathogenicity is polyphyletic within the FSSC, including within F. keratoplasticum. Pan-genome analysis revealed extensive gene presence-absence in the complex, with only 41% of genes (11,079/27,068) found in all samples and the presence of accessory chromosomes encoding isolate- and species-specific genes. Definition of long non-coding RNAs (lncRNAs) in F. keratoplasticum and F. petroliphilum demonstrated that they show a similarly high degree of presence-absence variation but are integrated into the transcriptional network to a similar degree as protein-coding genes, suggesting broad and extensive cellular roles. Elucidation of secondary metabolic potential identified many actively transcribed biosynthetic gene clusters with unknown products and identified several lncRNAs as putative regulators of specific metabolite clusters. Finally, examination of the FSSC for Starship gigantic mobile genetic elements revealed that F. keratoplasticum had the largest number with a median of four elements per genome and an overall pattern of Starships in the FSSC that were incongruent with the phylogeny, suggesting multiple horizontal transfer events. This study provides valuable insights into the evolutionary dynamics and genomic architecture of the FSSC, with implications for understanding multi-kingdom virulence, something of increasing relevance as climate change potentially increases the number of fungal species that can grow at human temperatures.

genomics↗

bioRxiv2024

Pathogenicity is associated with population structure in a fungal pathogen of humans

Aspergillus flavus is a clinically and agriculturally important saprotrophic fungus responsible for severe human infections and extensive crop losses. We analyzed genomic data from 250 (95 clinical and 155 environmental) A. flavus isolates from 9 countries, including 70 newly sequenced clinical isolates, to examine population and pan-genome structure and their relationship to pathogenicity. We identified five A. flavus populations, including a new population, D, corresponding to distinct clades in the genome-wide phylogeny. Strikingly, > 75% of clinical isolates were from population D. Accessory genes, including genes within biosynthetic gene clusters, were significantly more common in some populations but rare in others. Population D was enriched for genes associated with zinc ion binding, lipid metabolism, and certain types of hydrolase activity. In contrast to the major human pathogen Aspergillus fumigatus, A. flavus pathogenicity in humans is strongly associated with population structure, making it a great system for investigating how population-specific genes contribute to pathogenicity.

evolutionary biology↗

bioRxiv2022

A Global Survey of Host, Aquatic, and Soil Microbiomes Reveals Ecological Properties Shared between Bacterial and Fungal Generalists

Environmental change coupled with alteration in human lifestyles are profoundly impact-ing the microbial communities that play critical roles in the health of the Earth and its inhabitants. To identify bacteria and fungi that are resistant and susceptible to habitat changes respectively, we retrieved paired 16S and ITS rRNA amplicon sequence data from 1,580 host, soil, and aquatic samples and explored the ecological patterns of the thousands of detected bacterial and fungal genera. Through this large-scale analysis, we identified 48 bacterial and 4 fungal genera that were prevalent and abundant across the three biomes, demonstrating their fitness in diverse environmental conditions. The presence of generalists significantly contributed to the alpha diversity of their respective kingdom. Their distri-bution across samples explained a large percentage of the variation in the cross-kingdom community structure. We also found that the genomes of these generalists were larger and encoded more secondary metabolism and antimicrobial resistance genes, illuminating how they can dominate diverse microbial communities. Conversely, 30 bacterial and 19 fungal genera were only found in a single habitat, suggesting they cannot readily adapt to different and changing environments. These findings can contribute to our understanding of microbial niche breadth and its consequences for global diversity loss.

microbiology↗

bioRxiv2022

Functional characterization of the RNA interference pathway in A. fumigatus reveals its potential for antifungal therapy

The RNA interference (RNAi) pathway has evolved numerous functionalities in eukaryotes, with many on display in Kingdom Fungi. RNAi can regulate gene expression, facilitate drug resistance, or even be altogether lost to improve growth potential in some fungal pathogens. In the WHO fungal priority pathogen, Aspergillus fumigatus, the RNAi system is known to be intact and functional. To extend our limited understanding of A. fumigatus RNAi, we first investigated the genetic variation in RNAi-associated genes in a collection of 217 environmental and 83 clinical genomes, where we found that RNAi components are conserved even in clinical strains. Using endogenously expressed inverted-repeat transgenes complementary to a conditionally essential gene (pabA) or a nonessential gene (pksP), we determined that a subset of the RNAi componentry is active in inverted-repeat transgene silencing in conidia and mycelium. Analysis of mRNA-seq data from RNAi double-knockout strains linked the A. fumigatus dicer-like enzymes (DclA/B) and RNA-dependent RNA polymerases (RrpA/B) to regulation of conidial ribosome biogenesis genes; however, surprisingly few endogenous small RNAs were identified in conidia that could explain this broad change. Although RNAi was not clearly linked to growth or stress response defects in the RNAi knockouts, serial passaging of RNAi knockout strains for six generations resulted in lineages with diminished spore production over time, indicating that loss of RNAi can exert a fitness cost on the fungus. Cumulatively, A. fumigatus RNAi appears to play an active role in defense against double-stranded RNA species alongside a previously unappreciated housekeeping function in regulation of conidial ribosomal biogenesis genes.

microbiology↗

bioRxiv2020

Azole use in agriculture reduces Aspergillus fumigatus abundance but does not alter its population structure

Antibiotic resistance is an increasing threat to human health. In the case of Aspergillus fumigatus, which is both an environmental saprobe and an opportunistic human fungal pathogen, resistance is suggested to arise from fungicide use in agriculture, as the azoles used for plant protection are almost identical to the frontline antifungals used clinically. However, limiting azole fungicide use on crop fields to preserve their activity for clinical use could threaten the global food supply via a reduction in yield. In this study we clarify the link between fungicide use on crop fields and resistance in a prototypical human pathogen through systematic soil sampling on farms in Germany and surveying fields before and after azole application. We observed a reduction in the abundance of A. fumigatus on fields following fungicide treatment in 2017--a finding that was not observed on an organic control field applying only natural plant protection agents. However, this finding was less pronounced during our 2018 sampling, indicating that the impact of fungicides on A. fumigatus population size is variable and influenced by additional factors. The overall resistance frequency among agricultural isolates is low, with only 1-3% of isolates from 2016-2018 displaying resistance to medical azoles. Isolates collected after the growing season and azole exposure show a subtle, but consistent decrease in susceptibility to medical and agricultural azoles. Whole genome sequencing indicates that, despite the alterations in antifungal susceptibility, fungicide application does not significantly affect the population structure and genetic diversity of A. fumigatus in fields. Given the low observed resistance rate among agricultural isolates, as well the lack of genomic impact following azole application, we do not find evidence that azole use on crops is significantly driving resistance in A. fumigatus in this context. IMPORTANCEAntibiotic resistance is an increasing threat to human health. In the case of Aspergillus fumigatus, which is an environmental fungus that also causes life-threatening infections in humans, antimicrobial resistance is suggested to arise from fungicide use in agriculture, as the chemicals used for plant protection are almost identical to the antifungals used clinically. However, removing azole fungicides from crop fields threatens the global food supply via a reduction in yield. In this study, we survey crop fields before and after fungicide application. We find a low overall azole resistance rate among agricultural isolates, as well a lack of genomic and population impact following fungicide application, leading us to conclude azole use on crops does not significantly contribute to resistance in A. fumigatus.

microbiology↗