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The model moss species Physcomitrium patens has long been used for studying divergence of land plants spanning from bryophytes to angiosperms. In addition to its phylogenetic relationships, the limited number of differential tissues, and comparable morphology to the earliest embryophytes provide a system to represent basic plant architecture. Based on plant-fungal interactions today, it is hypothesized these kingdoms have a long-standing relationship, predating plant terrestrialization. Mortierellaceae have origins diverging from other land fungi paralleling bryophyte divergence, are related to arbuscular mycorrhizal fungi but are free-living, observed to interact with plants, and can be found in moss microbiomes globally. Due to their parallel origins, we assess here how two Mortierellaceae species, Linnemannia elongata and Benniella erionia, interact with P. patens in coculture. We also assess how Mollicute-related or Burkholderia-related endobacterial symbionts (MRE or BRE) of these fungi impact plant response. Coculture interactions are investigated through high-throughput phenomics, microscopy, RNA-sequencing, differential expression profiling, gene ontology enrichment, and comparisons among 99 other P. patens transcriptomic studies. Here we present new high-throughput approaches for measuring P. patens growth, identify novel expression of over 800 genes that are not expressed on traditional agar media, identify subtle interactions between P. patens and Mortierellaceae, and observe changes to plant-fungal interactions dependent on whether MRE or BRE are present. Our study provides insights into how plants and fungal partners may have interacted based on their communications observed today as well as identifying L. elongata and B. erionia as modern fungal endophytes with P. patens.
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Briófitas , Bryopsida , Micorrizas , Filogenia , Endófitos/metabolismo , Análisis Multinivel , Proteínas de Plantas/metabolismo , Bryopsida/genética , Bryopsida/metabolismo , Briófitas/genética , Briófitas/metabolismo , Micorrizas/metabolismoRESUMEN
BACKGROUND: The colonization of land and the diversification of terrestrial plants is intimately linked to the evolutionary history of their symbiotic fungal partners. Extant representatives of these fungal lineages include mutualistic plant symbionts, the arbuscular mycorrhizal (AM) fungi in Glomeromycota and fine root endophytes in Endogonales (Mucoromycota), as well as fungi with saprotrophic, pathogenic and endophytic lifestyles. These fungal groups separate into three monophyletic lineages but their evolutionary relationships remain enigmatic confounding ancestral reconstructions. Their taxonomic ranks are currently fluid. RESULTS: In this study, we recognize these three monophyletic linages as phyla, and use a balanced taxon sampling and broad taxonomic representation for phylogenomic analysis that rejects a hard polytomy and resolves Glomeromycota as sister to a clade composed of Mucoromycota and Mortierellomycota. Low copy numbers of genes associated with plant cell wall degradation could not be assigned to the transition to a plant symbiotic lifestyle but appears to be an ancestral phylogenetic signal. Both plant symbiotic lineages, Glomeromycota and Endogonales, lack numerous thiamine metabolism genes but the lack of fatty acid synthesis genes is specific to AM fungi. Many genes previously thought to be missing specifically in Glomeromycota are either missing in all analyzed phyla, or in some cases, are actually present in some of the analyzed AM fungal lineages, e.g. the high affinity phosphorus transporter Pho89. CONCLUSION: Based on a broad taxon sampling of fungal genomes we present a well-supported phylogeny for AM fungi and their sister lineages. We show that among these lineages, two independent evolutionary transitions to mutualistic plant symbiosis happened in a genomic background profoundly different from that known from the emergence of ectomycorrhizal fungi in Dikarya. These results call for further reevaluation of genomic signatures associated with plant symbiosis.
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Genómica , Micorrizas , Filogenia , Simbiosis , Micorrizas/genética , Micorrizas/fisiología , Simbiosis/genética , Genómica/métodos , Evolución Molecular , Genoma Fúngico , Glomeromycota/genética , Glomeromycota/fisiología , Plantas/microbiologíaRESUMEN
Horizontal genetic transfer (HGT) is a common phenomenon in eukaryotic genomes. However, the mechanisms by which HGT-derived genes persist and integrate into other pathways remain unclear. This topic is of significant interest because, over time, the stressors that initially favoured the fixation of HGT may diminish or disappear. Despite this, the foreign genes may continue to exist if they become part of a broader stress response or other pathways. The conventional model suggests that the acquisition of HGT equates to adaptation. However, this model may evolve into more complex interactions between gene products, a concept we refer to as the 'Integrated HGT Model' (IHM). To explore this concept further, we studied specialized HGT-derived genes that encode heavy metal detoxification functions. The recruitment of these genes into other pathways could provide clear examples of IHM. In our study, we exposed two anciently diverged species of polyextremophilic red algae from the Galdieria genus to arsenic and mercury stress in laboratory cultures. We then analysed the transcriptome data using differential and coexpression analysis. Our findings revealed that mercury detoxification follows a 'one gene-one function' model, resulting in an indivisible response. In contrast, the arsH gene in the arsenite response pathway demonstrated a complex pattern of duplication, divergence and potential neofunctionalization, consistent with the IHM. Our research sheds light on the fate and integration of ancient HGTs, providing a novel perspective on the ecology of extremophiles.
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Arsénico , Extremófilos , Transferencia de Gen Horizontal , Rhodophyta , Rhodophyta/genética , Extremófilos/genética , Arsénico/metabolismo , Mercurio/metabolismo , Estrés Fisiológico/genética , Inactivación Metabólica/genética , Evolución MolecularRESUMEN
Schizophyllum commune is a mushroom-forming fungus notable for its distinctive fruiting bodies with split gills. It is used as a model organism to study mushroom development, lignocellulose degradation and mating type loci. It is a hypervariable species with considerable genetic and phenotypic diversity between the strains. In this study, we systematically phenotyped 16 dikaryotic strains for aspects of mushroom development and 18 monokaryotic strains for lignocellulose degradation. There was considerable heterogeneity among the strains regarding these phenotypes. The majority of the strains developed mushrooms with varying morphologies, although some strains only grew vegetatively under the tested conditions. Growth on various carbon sources showed strain-specific profiles. The genomes of seven monokaryotic strains were sequenced and analyzed together with six previously published genome sequences. Moreover, the related species Schizophyllum fasciatum was sequenced. Although there was considerable genetic variation between the genome assemblies, the genes related to mushroom formation and lignocellulose degradation were well conserved. These sequenced genomes, in combination with the high phenotypic diversity, will provide a solid basis for functional genomics analyses of the strains of S. commune.
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Variación Genética , Genoma Fúngico , Genotipo , Lignina , Fenotipo , Schizophyllum , Schizophyllum/genética , Schizophyllum/crecimiento & desarrollo , Schizophyllum/clasificación , Lignina/metabolismo , Genoma Fúngico/genética , Filogenia , Agaricales/genética , Agaricales/crecimiento & desarrollo , Agaricales/clasificación , Análisis de Secuencia de ADNRESUMEN
Given the multitude of extracellular enzymes at their disposal, many of which are designed to degrade nature's polymers (lignin, cutin, cellulose, etc.), fungi are adept at targeting synthetic polyesters with similar chemical composition. Microbial-influenced deterioration of xenobiotic polymeric surfaces is an area of interest for material scientists as these are important for the conservation of the underlying structural materials. Here, we describe the isolation and characterization of the Papiliotrema laurentii 5307AH (P. laurentii) cutinase, Plcut1. P. laurentii is basidiomycete yeast with the ability to disperse Impranil-DLN (Impranil), a colloidal polyester polyurethane, in agar plates. To test whether the fungal factor involved in this clearing was a secreted enzyme, we screened the ability of P. laurentii culture supernatants to disperse Impranil. Using size exclusion chromatography (SEC), we isolated fractions that contained Impranil-clearing activity. These fractions harbored a single ~22 kD band, which was excised and subjected to peptide sequencing. Homology searches using the peptide sequences identified, revealed that the protein Papla1 543643 (Plcut1) displays similarities to serine esterase and cutinase family of proteins. Biochemical assays using recombinant Plcut1 confirmed that this enzyme has the capability to hydrolyze Impranil, soluble esterase substrates, and apple cutin. Finally, we confirmed the presence of the Plcut1 in culture supernatants using a custom antibody that specifically recognizes this protein. The work shown here supports a major role for the Plcut1 in the fungal degradation of natural polyesters and xenobiotic polymer surfaces.IMPORTANCEFungi play a vital role in the execution of a broad range of biological processes that drive ecosystem function through production of a diverse arsenal of enzymes. However, the universal reactivity of these enzymes is a current problem for the built environment and the undesired degradation of polymeric materials in protective coatings. Here, we report the identification and characterization of a hydrolase from Papiliotrema laurentii 5307AH, an aircraft-derived fungal isolate found colonizing a biodeteriorated polymer-coated surface. We show that P. laurentii secretes a cutinase capable of hydrolyzing soluble esters as well as ester-based compounds forming solid surface coatings. These findings indicate that this fungus plays a significant role in biodeterioration through the production of a cutinase adept at degrading ester-based polymers, some of which form the backbone of protective surface coatings. The work shown here provides insights into the mechanisms employed by fungi to degrade xenobiotic polymers.
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Hidrolasas de Éster Carboxílico , Proteínas Fúngicas , Poliésteres , Proteínas Recombinantes , Hidrolasas de Éster Carboxílico/metabolismo , Hidrolasas de Éster Carboxílico/genética , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Proteínas Fúngicas/química , Proteínas Recombinantes/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/aislamiento & purificación , Poliésteres/metabolismo , HidrólisisRESUMEN
The jasmonic acid (JA) signalling pathway plays an important role in the establishment of the ectomycorrhizal symbiosis. The Laccaria bicolor effector MiSSP7 stabilizes JA corepressor JAZ6, thereby inhibiting the activity of Populus MYC2 transcription factors. Although the role of MYC2 in orchestrating plant defences against pathogens is well established, its exact contribution to ECM symbiosis remains unclear. This information is crucial for understanding the balance between plant immunity and symbiotic relationships. Transgenic poplars overexpressing or silencing for the two paralogues of MYC2 transcription factor (MYC2s) were produced, and their ability to establish ectomycorrhiza was assessed. Transcriptomics and DNA affinity purification sequencing were performed. MYC2s overexpression led to a decrease in fungal colonization, whereas its silencing increased it. The enrichment of terpene synthase genes in the MYC2-regulated gene set suggests a complex interplay between the host monoterpenes and fungal growth. Several root monoterpenes have been identified as inhibitors of fungal growth and ECM symbiosis. Our results highlight the significance of poplar MYC2s and terpenes in mutualistic symbiosis by controlling root fungal colonization. We identified poplar genes which direct or indirect control by MYC2 is required for ECM establishment. These findings deepen our understanding of the molecular mechanisms underlying ECM symbiosis.
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Ciclopentanos , Laccaria , Micorrizas , Oxilipinas , Populus , Micorrizas/genética , Populus/metabolismo , Raíces de Plantas/metabolismo , Simbiosis/genética , Laccaria/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Monoterpenos/metabolismoRESUMEN
Soil fungi belonging to different functional guilds, such as saprotrophs, pathogens, and mycorrhizal symbionts, play key roles in forest ecosystems. To date, no study has compared the actual gene expression of these guilds in different forest soils. We used metatranscriptomics to study the competition for organic resources by these fungal groups in boreal, temperate, and Mediterranean forest soils. Using a dedicated mRNA annotation pipeline combined with the JGI MycoCosm database, we compared the transcripts of these three fungal guilds, targeting enzymes involved in C- and N mobilization from plant and microbial cell walls. Genes encoding enzymes involved in the degradation of plant cell walls were expressed at a higher level in saprotrophic fungi than in ectomycorrhizal and pathogenic fungi. However, ectomycorrhizal and saprotrophic fungi showed similarly high expression levels of genes encoding enzymes involved in fungal cell wall degradation. Transcripts for N-related transporters were more highly expressed in ectomycorrhizal fungi than in other groups. We showed that ectomycorrhizal and saprotrophic fungi compete for N in soil organic matter, suggesting that their interactions could decelerate C cycling. Metatranscriptomics provides a unique tool to test controversial ecological hypotheses and to better understand the underlying ecological processes involved in soil functioning and carbon stabilization.
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Bosques , Hongos , Microbiología del Suelo , Transcriptoma , Hongos/genética , Hongos/fisiología , Transcriptoma/genética , Micorrizas/fisiología , Micorrizas/genética , Perfilación de la Expresión Génica , Regulación Fúngica de la Expresión Génica , Nitrógeno/metabolismo , Suelo/química , Ecosistema , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Nidulariaceae, also known as bird's nest fungi, is an understudied group of mushroom-forming fungi. The common name is derived from their nest-like morphology. Bird's nest fungi are ubiquitous wood decomposers or saprobes on dung. Recent studies showed that species in the Nidulariaceae form a monophyletic group with five sub-clades. However, phylogenetic relationships among genera and placement of Nidulariaceae are still unclear. We present phylogenomic analyses of bird's nest fungi and related Agaricales fungi to gain insight into the evolution of Nidulariaceae. A species tree with 17 newly generated genomes of bird's nest fungi and representatives from all major clades of Agaricales was constructed using 1044 single-copy genes to explore the intergeneric relationships and pinpoint the placement of Nidulariaceae within Agaricales. We corroborated the hypothesis that bird's nest fungi are sister to Squamanitaceae, which includes mushroom-shaped fungi with a stipe and pileus that are saprobes and mycoparasites. Lastly, stochastic character mapping of discrete traits on phylogenies (SIMMAP) suggests that the ancestor of bird's nest fungi likely possessed an evanescent, globose peridium without strings attaching to the spore packets (funiculi). This analysis suggests that the funiculus was gained twice and that the persistent, cupulate peridium form was gained at least four times and lost once. However, alternative coding schemes and datasets with a wider array of Agaricales produced conflicting results during ancestral state reconstruction, indicating that there is some uncertainty in the number of peridium transitions and that taxon sampling may significantly alter ancestral state reconstructions. Overall, our results suggest that several key morphological characters of Nidulariaceae have been subject to homoplasy.
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Cyathus , Animales , Filogenia , AvesRESUMEN
BACKGROUND: Among the non-traditional antibacterial agents in development, only a few targets critical Gram-negative bacteria such as carbapenem-resistant Pseudomonas aeruginosa, Acinetobacter baumannii or cephalosporin-resistant Enterobacteriaceae. Endolysins and their genetically modified versions meet the World Health Organization criteria for innovation, have a novel mode of antibacterial action, no known bacterial cross-resistance, and are being intensively studied for application against Gram-negative pathogens. METHODS: The study presents a multidisciplinary approach, including genetic engineering of LysECD7-SMAP and production of recombinant endolysin, its analysis by crystal structure solution following molecular dynamics simulations and evaluation of antibacterial properties. Two types of antimicrobial dosage forms were formulated, resulting in lyophilized powder for injection and hydroxyethylcellulose gel for topical administration. Their efficacy was estimated in the treatment of sepsis, and pneumonia models in BALB/c mice, diabetes-associated wound infection in the leptin receptor-deficient db/db mice and infected burn wounds in rats. RESULTS: In this work, we investigate the application strategies of the engineered endolysin LysECD7-SMAP and its dosage forms evaluated in preclinical studies. The catalytic domain of the enzyme shares the conserved structure of endopeptidases containing a putative antimicrobial peptide at the C-terminus of polypeptide chain. The activity of endolysins has been demonstrated against a range of pathogens, such as Klebsiella pneumoniae, A. baumannii, P. aeruginosa, Staphylococcus haemolyticus, Achromobacter spp, Burkholderia cepacia complex and Haemophylus influenzae, including those with multidrug resistance. The efficacy of candidate dosage forms has been confirmed in in vivo studies. Some aspects of the interaction of LysECD7-SMAP with cell wall molecular targets are also discussed. CONCLUSIONS: Our studies demonstrate the potential of LysECD7-SMAP therapeutics for the systemic or topical treatment of infectious diseases caused by susceptible Gram-negative bacterial species and are critical to proceed LysECD7-SMAP-based antimicrobials trials to advanced stages.
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Endopeptidasas , Bacterias Gramnegativas , Infecciones por Bacterias Gramnegativas , Ratones Endogámicos BALB C , Animales , Infecciones por Bacterias Gramnegativas/tratamiento farmacológico , Ratones , Endopeptidasas/farmacología , Endopeptidasas/administración & dosificación , Bacterias Gramnegativas/efectos de los fármacos , Antibacterianos/farmacología , Antibacterianos/administración & dosificación , Ratas , Masculino , Ingeniería de Proteínas/métodosRESUMEN
Despite various plans to rationalize antibiotic use, antibiotic resistance in environmental bacteria is increasing due to the accumulation of antibiotic residues in the environment. This study aimed to test the ability of basidiomycete fungal strains to biotransform the antibiotic levofloxacin, a widely-used third-generation broad-spectrum fluoroquinolone, and to propose enzyme targets potentially involved in this biotransformation. The biotransformation process was performed using fungal strains. Levofloxacin biotransformation reached 100% after 9 days of culture with Porostereum spadiceum BS34. Using genomics and proteomics analyses coupled with activity tests, we showed that P. spadiceum produces several heme-peroxidases together with H2O2-producing enzymes that could be involved in the antibiotic biotransformation process. Using UV and high-resolution mass spectrometry, we were able to detect five levofloxacin degradation products. Their putative identity based on their MS2 fragmentation patterns led to the conclusion that the piperazine moiety was the main target of oxidative modification of levofloxacin by P. spadiceum, leading to a decrease in antibiotic activity.
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Peróxido de Hidrógeno , Levofloxacino , Polyporales , Antibacterianos/química , Fluoroquinolonas/química , Hongos/metabolismoRESUMEN
The ability of most opportunistic bacteria to form biofilms, coupled with antimicrobial resistance, hinder the efforts to control widespread infections, resulting in high risks of negative outcomes and economic costs. Endolysins are promising compounds that efficiently combat bacteria, including multidrug-resistant strains and biofilms, without a low probability of subsequent emergence of stable endolysin-resistant phenotypes. However, the details of antibiofilm effects of these enzymes are poorly understood. To elucidate the interactions of bacteriophage endolysins LysAm24, LysAp22, LysECD7, and LysSi3 with bacterial films formed by Gram-negative species, we estimated their composition and assessed the endolysins' effects on the most abundant exopolymers in vitro. The obtained data suggests a pronounced efficiency of these lysins against biofilms with high (Klebsiella pneumoniae) and low (Acinetobacter baumannii) matrix contents, or dual-species biofilms, resulting in at least a twofold loss of the biomass. These peptidoglycan hydrolases interacted diversely with protective compounds of biofilms such as extracellular DNA and polyanionic carbohydrates, indicating a spectrum of biofilm-disrupting effects for bacteriolytic phage enzymes. Specifically, we detected disruption of acid exopolysaccharides by LysAp22, strong DNA-binding capacity of LysAm24, both of these interactions for LysECD7, and neither of them for LysSi3.
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Bacteriófagos , Biopelículas , Endopeptidasas , Biopelículas/efectos de los fármacos , Biopelículas/crecimiento & desarrollo , Endopeptidasas/metabolismo , Endopeptidasas/farmacología , Endopeptidasas/química , Bacteriófagos/enzimología , Acinetobacter baumannii/efectos de los fármacos , Klebsiella pneumoniae/efectos de los fármacos , Proteínas Virales/metabolismo , Antibacterianos/farmacología , Antibacterianos/química , N-Acetil Muramoil-L-Alanina Amidasa/metabolismo , N-Acetil Muramoil-L-Alanina Amidasa/químicaRESUMEN
Functional traits influence the assembly of microbial communities, but identifying these traits in the environment has remained challenging. We studied ectomycorrhizal fungal (EMF) communities inhabiting Populus trichocarpa roots distributed across a precipitation gradient in the Pacific Northwest, USA. We profiled these communities using taxonomic (meta-barcoding) and functional (metagenomic) approaches. We hypothesized that genes involved in fungal drought-stress tolerance and fungal mediated plant water uptake would be most abundant in drier soils. We were unable to detect support for this hypothesis; instead, the abundance of genes involved in melanin synthesis, hydrophobins, aquaporins, trehalose-synthases, and other gene families exhibited no significant shifts across the gradient. Finally, we studied variation in sequence homology for certain genes, finding that fungal communities in dry soils are composed of distinct aquaporin and hydrophobin gene sequences. Altogether, our results suggest that while EMF communities exhibit significant compositional shifts across this gradient, coupled functional turnover, at least as inferred using community metagenomics is limited. Accordingly, the consequences of these distinct EMF communities on plant water uptake remain critically unknown, and future studies targeting the expression of genes involved in drought stress tolerance are required.
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Contamination of genomes is an increasingly recognized problem affecting several downstream applications, from comparative evolutionary genomics to metagenomics. Here we introduce ContScout, a precise tool for eliminating foreign sequences from annotated genomes. It achieves high specificity and sensitivity on synthetic benchmark data even when the contaminant is a closely related species, outperforms competing tools, and can distinguish horizontal gene transfer from contamination. A screen of 844 eukaryotic genomes for contamination identified bacteria as the most common source, followed by fungi and plants. Furthermore, we show that contaminants in ancestral genome reconstructions lead to erroneous early origins of genes and inflate gene loss rates, leading to a false notion of complex ancestral genomes. Taken together, we offer here a tool for sensitive removal of foreign proteins, identify and remove contaminants from diverse eukaryotic genomes and evaluate their impact on phylogenomic analyses.
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Genoma , Genómica , Filogenia , Evolución Biológica , Metagenómica , Evolución MolecularRESUMEN
Geothermal springs house unicellular red algae in the class Cyanidiophyceae that dominate the microbial biomass at these sites. Little is known about host-virus interactions in these environments. We analyzed the virus community associated with red algal mats in three neighboring habitats (creek, endolithic, soil) at Lemonade Creek, Yellowstone National Park (YNP), USA. We find that despite proximity, each habitat houses a unique collection of viruses, with the giant viruses, Megaviricetes, dominant in all three. The early branching phylogenetic position of genes encoded on metagenome assembled virus genomes (vMAGs) suggests that the YNP lineages are of ancient origin and not due to multiple invasions from mesophilic habitats. The existence of genomic footprints of adaptation to thermophily in the vMAGs is consistent with this idea. The Cyanidiophyceae at geothermal sites originated ca. 1.5 Bya and are therefore relevant to understanding biotic interactions on the early Earth.
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Manantiales de Aguas Termales , Rhodophyta , Filogenia , Parques Recreativos , Ecosistema , Biomasa , Rhodophyta/genéticaRESUMEN
Fusarium oxysporum is a cross-kingdom pathogen. While some strains cause disseminated fusariosis and blinding corneal infections in humans, others are responsible for devastating vascular wilt diseases in plants. To better understand the distinct adaptations of F. oxysporum to animal or plant hosts, we conducted a comparative phenotypic and genetic analysis of two strains: MRL8996 (isolated from a keratitis patient) and Fol4287 (isolated from a wilted tomato [Solanum lycopersicum]). In vivo infection of mouse corneas and tomato plants revealed that, while both strains cause symptoms in both hosts, MRL8996 caused more severe corneal ulceration and perforation in mice, whereas Fol4287 induced more pronounced wilting symptoms in tomato. In vitro assays using abiotic stress treatments revealed that the human pathogen MRL8996 was better adapted to elevated temperatures, whereas the plant pathogen Fol4287 was more tolerant of osmotic and cell wall stresses. Both strains displayed broad resistance to antifungal treatment, with MRL8996 exhibiting the paradoxical effect of increased tolerance to higher concentrations of the antifungal caspofungin. We identified a set of accessory chromosomes (ACs) and protein-encoding genes with distinct transposon profiles and functions, respectively, between MRL8996 and Fol4287. Interestingly, ACs from both genomes also encode proteins with shared functions, such as chromatin remodeling and post-translational protein modifications. Our phenotypic assays and comparative genomics analyses lay the foundation for future studies correlating genotype with phenotype and for developing targeted antifungals for agricultural and clinical uses.
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Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most damaging plant diseases known. Foc race 1 (R1) decimated the Gros Michel-based banana (Musa acuminata) trade, and now Foc tropical race 4 (TR4) threatens global production of its replacement, the Cavendish banana. Here population genomics revealed that all Cavendish banana-infecting Foc race 4 strains share an evolutionary origin distinct from that of R1 strains. Although TR4 lacks accessory chromosomes, it contains accessory genes at the ends of some core chromosomes that are enriched for virulence and mitochondria-related functions. Meta-transcriptomics revealed the unique induction of the entire mitochondrion-localized nitric oxide (NO) biosynthesis pathway upon TR4 infection. Empirically, we confirmed the unique induction of a NO burst in TR4, suggesting that nitrosative pressure may contribute to virulence. Targeted mutagenesis demonstrated the functional importance of fungal NO production and the accessory gene SIX4 as virulence factors.
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Papiliotrema laurentii 5307AH was isolated from an aircraft polymer-coated surface. The genome size is 19,510,785 bp with a G + C content of 56%. The genome harbors genes encoding oxygenases, cutinases, lipases, and enzymes for styrene degradation, all of which could play a critical role in survival on xenobiotic surfaces.
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BACKGROUND: Cost-effective production of biofuels from lignocellulose requires the fermentation of D-xylose. Many yeast species within and closely related to the genera Spathaspora and Scheffersomyces (both of the order Serinales) natively assimilate and ferment xylose. Other species consume xylose inefficiently, leading to extracellular accumulation of xylitol. Xylitol excretion is thought to be due to the different cofactor requirements of the first two steps of xylose metabolism. Xylose reductase (XR) generally uses NADPH to reduce xylose to xylitol, while xylitol dehydrogenase (XDH) generally uses NAD+ to oxidize xylitol to xylulose, creating an imbalanced redox pathway. This imbalance is thought to be particularly consequential in hypoxic or anoxic environments. RESULTS: We screened the growth of xylose-fermenting yeast species in high and moderate aeration and identified both ethanol producers and xylitol producers. Selected species were further characterized for their XR and XDH cofactor preferences by enzyme assays and gene expression patterns by RNA-Seq. Our data revealed that xylose metabolism is more redox balanced in some species, but it is strongly affected by oxygen levels. Under high aeration, most species switched from ethanol production to xylitol accumulation, despite the availability of ample oxygen to accept electrons from NADH. This switch was followed by decreases in enzyme activity and the expression of genes related to xylose metabolism, suggesting that bottlenecks in xylose fermentation are not always due to cofactor preferences. Finally, we expressed XYL genes from multiple Scheffersomyces species in a strain of Saccharomyces cerevisiae. Recombinant S. cerevisiae expressing XYL1 from Scheffersomyces xylosifermentans, which encodes an XR without a cofactor preference, showed improved anaerobic growth on xylose as the primary carbon source compared to S. cerevisiae strain expressing XYL genes from Scheffersomyces stipitis. CONCLUSION: Collectively, our data do not support the hypothesis that xylitol accumulation occurs primarily due to differences in cofactor preferences between xylose reductase and xylitol dehydrogenase; instead, gene expression plays a major role in response to oxygen levels. We have also identified the yeast Sc. xylosifermentans as a potential source for genes that can be engineered into S. cerevisiae to improve xylose fermentation and biofuel production.
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Favolaschia claudopus, a wood-inhabiting basidiomycete of the Mycenaceae family, is considered an invasive species that has recently spread from Oceania to Europe. The CIRM-BRFM 2984 strain of this fungus was originally isolated from a basidiome collected from the fallen limb of a decayed oak tree in Southwest France. The genome sequence of this strain shared characteristics with other Mycenaceae species, including a large genome size and enriched content of protein-coding genes. The genome sequence provided here will facilitate further investigation on the factors that contribute to the successful global dissemination of F. claudopus.