Architecture of the dynamic fungal cell wall

Characterization of the Neurospora crassa GH72 family of Laminarin/Lichenin transferases and their roles in cell wall biogenesis

In Neurospora crassa vegetative hyphae, chitin, β-1,3-glucan (laminarin), and a mixed β-1,3-/β-1,4-glucan (lichenin) are the major cell wall polysaccharides. GH72 enzymes have been shown to function as β-1,3-glucanases and glucanosyltransferases and can function in crosslinking β-1,3-glucans together. To characterize the enzymatic activities of the N. crassa enzymes, we expressed GEL-1 with a HIS6 tag in N. crassa. A chimeric maltose binding protein:GEL-2 was produced in E. coli. Purified GEL-1 and GEL-2 were used to characterize their enzymatic activities. We employed thin-layer chromatography (TLC) and polyacrylamide carbohydrate gel electrophoresis (PACE) assays to visualize GEL-1 and GEL-2 hydrolase and transferase activities on lichenin and laminarin substrates. We determined that GEL-1 functions as a laminarinase (β-1,3-glucanase) and as a laminarin transferase. We found that GEL-2 can function as a laminarinase and as a licheninase (β-1,3-/β-1,4-mixed-glucanase) and can crosslink β-1,3-glucans together. We demonstrated that GEL-2 can form enzyme:lichenin intermediates, providing evidence that GEL-2 functions as a lichenin transferase as well as a β-1,3-glucan transferase and crosslinks both types of polysaccharides into the N. crassa cell wall.

Biochemical insights into synergistic Candida biofilm disintegrating ability of p-cymene inclusion complex and miconazole

Phytoactive molecules emerge as a plentiful reservoir of adjuvant and antifungal agents. The resolution of solubility and stability issues has been facilitated by developing molecular complexes or inclusion complexes of phytoactive molecules. Miconazole (MCZ) is a favoured azole with low off-target impact, however, its pharmacological efficacy requires a revamp to enhance its suitability as an antifungal drug. Hence, the present investigation delves into the mechanism of action of the p-cymene/β-cyclodextrin inclusion complex (IC) along with MCZ against Candida albicans and Candidaglabrata biofilms. The synergy between IC and MCZ has been estimated at a concentration of 6.25 μg/mL IC + 0.5 μg/mL MCZ with a FICI of 0.19. The prepared IC + MCZ displayed remarkable antifungal properties against planktonic and sessile growth of Candida species. IC + MCZ exhibited a notable 80% biofilm eradication potential against both species, corroborated by morphological analysis using FE-SEM. The results indicated that IC/IC + MCZ acts by disrupting the biochemical composition of the ECM, altering the surface properties of the cells, reducing ergosterol, enhancing membrane permeability, and inducing oxidative stress. In conclusion, the study highlighted the synergistic antibiofilm activity of p-cymene IC with miconazole against Candida species. In summary, IC + MCZ has been established as a potent antifouling agent against Candida species, warranting further exploration for potential formulation with additional investigations.

Antifungal Performance and Mechanisms of Carbon Quantum Dots in Cellulosic Materials

Cellulosic materials, which are widely utilized in daily life, are highly susceptible to fungal degradation. However, commercial fungicides are usually toxic, posing severe threats to human health and the environment, highlighting the necessity of developing eco-friendly antifungal agents for cellulosic materials. In this work, we synthesized nitrogen-doped carbon quantum dots (CQDs) via a microwave-assisted method. CQDs with proper structure demonstrated significant antifungal effects against both brown-rot (Postia placenta, Pp) and white-decay fungi (Trametes versicolor, Tv) on various cellulosic materials. The underlying antifungal mechanisms of CQDs on cellulosic materials were further elucidated. We found that positively charged nanosized CQDs primarily adhered to and penetrated into fungal cell membranes. This led to fungal metabolism disorder, a significant reduction in enzymatic activities, and ultimately cell death, as confirmed by transcriptome analysis. Additionally, CQDs generated reactive oxygen species (ROS) under light, causing oxidation and dysfunction of the fungal cell wall. Furthermore, CQDs have the ability to chelate Fe3+, which results in the inhibition of the Fenton reaction and the hindering of the nonenzymatic cellulose degradation. These findings suggest that CQDs inhibit fungal degradation of cellulosic materials through integrated mechanisms, with potential implications for sustainable cellulose applications.

Acyltransferases that Modify Cell Surface Polymers Across the Membrane

Cell surface oligosaccharides and related polymers are commonly decorated with acyl esters that alter their structural properties and influence their interactions with other molecules. In many cases, these esters are added to polymers that are already positioned on the extracytoplasmic side of a membrane, presenting cells with a chemical challenge because the high-energy acyl donors used for these modifications are made in the cytoplasm. How activated acyl groups are passed from the cytoplasm to extra-cytoplasmic polymers has been a longstanding question. Recent mechanistic work has shown that many bacterial acyl transfer pathways operate by shuttling acyl groups through two covalent intermediates to their final destination on an extracellular polymer. Key to these and other pathways are cross-membrane acyltransferases─enzymes that catalyze transfer of acyl groups from a donor on one side of the membrane to a recipient on the other side. Here we review what has been learned recently about how cross-membrane acyltransferases in polymer acylation pathways function, highlighting the chemical and biosynthetic logic used by two key protein families, membrane-bound O-acyltransferases (MBOATs) and acyltransferase-3 (AT3) proteins. We also point out outstanding questions and avenues for further exploration.

Chitin estimation in agricultural soils

The present scientific report has been elaborated in the context of the European Commission mandate requesting for an opinion according to Article 23(6) of Regulation (EC) No 1107/2009 regarding the approved plant protection uses of chitosan and chitosan hydrochloride as basic substances. This scientific report focused on estimating the amount of chitin present in an average agricultural soil, aiming to establish a baseline for its natural availability. Understanding the source and concentration of biotic chitin in soil assisted the estimation of chitosan potentially available in the environment, as requested in one of terms of reference of the concerned EC mandate. Chitin in soil was estimated to range from 27 to 280 kg/ha in the first 0-5 cm layer and 99 to 901 kg/ha in the 0-20 cm layer. Fungi are the main chitin producer followed by insects and nematodes. Soil crustaceans could not be considered in the assessment due to the lack of necessary information and the variability of their presence. The development of a polynomial function to estimate the amount of chitin in such biome can also identify the main predictors of chitin content in similar biomes. This estimate was based on the available scientific literature, and it would require additional validation using field measurements and error analysis on different soil types and conditions, to become a generalised model. Lack of information alongside related uncertainties have also been identified.

Characterizing extracellular vesicles of human fungal pathogens

Since their discovery in 2007, there has been growing awareness of the importance of fungal extracellular vesicles (EVs) for fungal physiology, host-pathogen interactions and virulence. Fungal EVs are nanostructures comprising bilayered membranes and molecules of various types that participate in several pathophysiological processes in fungal biology, including secretion, cellular communication, immunopathogenesis and drug resistance. However, many questions remain regarding the classification of EVs, their cellular origin, passage across the cell wall, experimental models for functional and compositional analyses, production in vitro and in vivo and biomarkers for EVs. Here, we discuss gaps in the literature of fungal EVs and identify key questions for the field. We present the history of fungal EV discovery, discuss five major unanswered questions in fungal EV biology and provide future perspectives for fungal EV research. We primarily focus our discussion on human fungal pathogens, but also extend it to include knowledge of other fungi, such as plant pathogens. With this Perspective we hope to stimulate new approaches and expand studies to understand the biology of fungal EVs.

Ecosystems have multiple interacting processes that buffer against co-occurring stressors

There are multiple processes that buffer the effects of anthropogenic stressors. Much is known about how single buffering processes (e.g., biodiversity, adaptation) mitigate the effects of stressors on ecosystem properties and functions, but how multiple buffering processes combine to mitigate the effects of multiple co-occurring stressors is poorly understood. We outline how single processes (e.g., cross-tolerance) can buffer the effects of multiple stressors, whereas multiple buffering processes can act jointly across ecological and temporal scales to reduce the effects of single or multiple stressors. Synergistic interactions between multiple buffering processes can further enhance ecosystem resistance to multiple stressors. A wider awareness of interacting buffering processes in ecosystems will enhance our understanding of ecosystem stability in the face of multiple stressors.

The GCN4-Swi6B module mediates low nitrogen-induced cell wall remodeling in Ganoderma lucidum

In natural habitats, microorganisms encounter various unfavorable environmental stresses, including nitrogen deficiency. As the outermost barrier, the cell wall plays a crucial role in the interaction between the cell and the external environment. However, the effect of low nitrogen on cell wall thickness, especially the underlying molecular mechanism, is unclear. Here, we found that compared with those under normal nitrogen conditions, both the cell wall thickness and polysaccharide content of Ganoderma lucidum are increased under low nitrogen conditions. Furthermore, the abundance of SWI6B, a transcription factor that participates in cell wall remodeling, is also increased in low-nitrogen environments. The thickness and polysaccharide content of the cell wall increased in SWI6B-overexpression strains (SWI6B-OEs) but decreased in SWI6-knockdown strains (swi6-kds). Moreover, although the cell wall thickness of all the genotypes increased under nitrogen-limited conditions, the percentage of upregulated swi6-kds was significantly lower than that of the WT, and the percentage of increased SWI6B-OEs was the highest. Moreover, GCN4, a key transcription factor of the low-nitrogen signaling pathway, was found to directly bind to the promoter of SWI6. The transcriptional and translational levels of SWI6B were reduced in GCN4-knockdown strains (gcn4-kds), indicating a positive regulation of SWI6B by GCN4. Consistently, the cell wall thickness of gcn4-kds was also lower than that of the wild type. Taken together, our results revealed that the GCN4-Swi6B module regulates cell wall remodeling in G. lucidum under nitrogen deficiency conditions.

IMPORTANCE

To survive in stressful environments, fungi initiate cell wall remodeling pathways to adaptively modify the cell wall composition and structure. Here, we found that nitrogen deficiency upregulated the cell wall polysaccharide content and cell wall thickness through the GCN4-SWI6B signaling pathway. Our findings provide valuable insights into the environmental adaptation of fungal cell walls, contributing to a deeper understanding of fungal responses to environmental stress.

Control of Fungal Spores on Surfaces with UV-C Exposure Necessitates Complete Inactivation to Prevent Mycorrhizal Network Establishment

Mold infestations on surfaces present significant challenges to public health. Germicidal UV-C irradiation effectively inactivates spores suspended in water, yet information on surface spore mitigation is surprisingly absent. We show the effectiveness of 265-275 nm UV-C light to mitigateAspergillus nigeron nutrient-rich surfaces. UV-C mitigation of surface molds differs from inactivating spores suspended in water due to the unique characteristics of mycelial structures. Complete preinactivation of all viable cells during UV-C exposure is crucial to prevent mycelia formation; otherwise, even a single spore can gradually spread, covering surfaces by producing a progressive mycelial structure. A UV-C dose of 144 mJ/cm2 from 265 nm LEDs achieved complete preinactivation at lower concentrations (100-1000 CFU/plate), while higher concentrations required increased UV-C doses. Intermittent duty cycling of light delivery (10 min ON then 50 min OFF) at 275 nm delivered from side-emitting optical fibers achieved comparable mitigation to continuous irradiation. Insufficient UV-C exposure induced more resistant mycelial structures that shielded live spores beneath. This study highlights complete preinactivation of viable molds, or sustained inhibition by UV-C light, is more effective than UV-C posttreatment. Mycelial alteration triggered by sublethal stress helps spores to persist in unfavorable environments, where microbial control is the goal.

Toward nanoscale structural and chemical analysis of microbial surfaces

Microbial surfaces play a critical role in various biological processes, including cell adhesion and biofilm formation. Understanding these surfaces at the nanoscale is essential for both fundamental and applied microbiology. This review explores recent advancements in nanoscale structural and chemical analyses of microbial surfaces, with a focus on vibrational spectroscopy, such as Raman spectroscopy, infrared spectroscopy, and atomic force microscopy. The review also discusses current challenges of these techniques, including variability in sample preparation and the reproducibility of data, and highlights future directions in nanoscale analysis that could lead to new insights in microbial physiology, antimicrobial resistance, and biofilm research.

Sustainable disease management in tomatoes: Fe3O4 nanoparticles as an eco-friendly alternative to conventional fungicides for Fusarium wilt control

BACKGROUND

Fusarium wilt disease caused by the soil pathogen Fusarium oxysporum f. sp. lycopersici significantly impacts global tomato production. While conventional fungicides remain the primary control method, their high application volumes and environmental persistence necessitate alternative approaches. We hypothesize that magnetite nanoparticles (NPs) suppress fungal growth through a tripartite mechanism that disrupts membrane integrity at the nano-bio interface, generation of reactive oxygen species through iron-mediated catalysis, and perturbation of fungal iron homeostasis pathways.

RESULTS

In vitro studies demonstrated that 5 nm magnetite NPs exhibited superior antifungal activity with an EC₅₀ of 8.84 mg/L compared to Ningnanomycin at 84.77 mg/L. Comparative disease control efficacy under greenhouse conditions showed that magnetite NPs at 0.5 mg/L achieved 65% pathogen suppression versus Ningnanomycin at 71.4%, while requiring significantly lower application volumes of 180-360 g per hectare versus 4500-5850 mL per hectare. The NP treatment reduced disease index by 35.42%, alleviated root rot symptoms by 19.33%, and enhanced plant defense mechanisms through elevated reactive oxygen species accumulation and increased root iron content of 92.15%.

CONCLUSION

This study demonstrates that magnetite NPs provide competitive disease control efficacy against Fusarium wilt through multiple mechanistic pathways while reducing total chemical input. The dual functionality of direct pathogen suppression and enhanced plant defense activation, combined with lower application volumes, establishes these nanoparticles as a promising alternative to ecofriendly fungicides in tomato production systems. © 2025 Society of Chemical Industry.

A polyene macrolide targeting phospholipids in the fungal cell membrane

The global spread of multidrug-resistant pathogenic fungi presents a serious threat to human health, necessitating the discovery of antifungals with unique modes of action1. However, conventional activity-based screening for previously undescribed antibiotics has been hampered by the high-frequency rediscovery of known compounds and the lack of new antifungal targets2. Here we report the discovery of a polyene antifungal antibiotic, mandimycin, using a phylogeny-guided natural-product discovery platform. Mandimycin is biosynthesized by the mand gene cluster, has evolved in a distinct manner from known polyene macrolide antibiotics and is modified with three deoxy sugars. It has demonstrated potent and broad-spectrum fungicidal activity against a wide range of multidrug-resistant fungal pathogens in both in vitro and in vivo settings. In contrast to known polyene macrolide antibiotics that target ergosterol, mandimycin has a unique mode of action that involves targeting various phospholipids in fungal cell membranes, resulting in the release of essential ions from fungal cells. This unique ability to bind multiple targets gives it robust fungicidal activity as well as the capability to evade resistance. The identification of mandimycin using the phylogeny-guided natural-product discovery strategy represents an important advancement in uncovering antimicrobial compounds with distinct modes of action, which could be developed to combat multidrug-resistant fungal pathogens.

Solid-state NMR observation of chitin in whole cells by indirect 15N detection with NC, NCC, CNC and CNCC polarization transfers

Chitin is the most important nitrogen-containing polysaccharide found on Earth. This polysaccharide is a polymer of an N-acetylglucosamine and it is a crucial structural component of fungal cell walls and crustaceans. Magic-angle spinning solid-state NMR is emerging as a powerful analytical approach to study polysaccharides in the context of intact cell walls and whole cells. The presence of an acetamido group in chitin is attractive for 15N solid-state NMR. Here we investigate the use of various multi-step polarization transfer experiments incorporating indirect 15N detection at moderate spinning frequency, adapted from pulse sequences commonly employed for residue resonance assignment in biosolid proteins. The 13C,15N chitin spin topology slightly differs from amino acids, and we discussed the use of frequency-selective 15N-13C cross-polarization transfers followed by broadband or frequency-selective homonuclear 13C-13C transfers to detect chitin resonances. Demonstrated here for chitin found in the cell wall of the fungus Aspergillus fumigatus, the use of indirect 15N detection through multi-step polarization transfers could be advantageous to investigate more complex nitrogen-containing polysaccharides found in whole cells and peptidoglycan samples.

Proton-Detected Solid-State NMR for Deciphering Structural Polymorphism and Dynamic Heterogeneity of Cellular Carbohydrates in Pathogenic Fungi

Carbohydrate polymers in their cellular context display highly polymorphic structures and dynamics essential to their diverse functions, yet they are challenging to analyze biochemically. Proton-detection solid-state NMR spectroscopy offers high isotopic abundance and sensitivity, enabling rapid and high-resolution structural characterization of biomolecules. Here, an array of 2D/3D 1 H-detection solid-state NMR techniques are tailored to investigate polysaccharides in fully protonated or partially deuterated cells of three prevalent pathogenic fungi: Rhizopus delemar , Aspergillus fumigatus , and Candida albicans , representing filamentous species and yeast forms. Selective detection of acetylated carbohydrates reveals fifteen forms of N-acetylglucosamine units in R. delemar chitin, which coexists with chitosan as separate domains or polymers and associates with proteins only at limited sites. This is supported by distinct order parameters and effective correlation times of their motions, analyzed through relaxation measurements and model-free analysis. Five forms of α-1,3-glucan with distinct structural origins and dynamics were identified in A. fumigatus , important for this buffering polysaccharide to perform diverse roles of supporting wall mechanics and regenerating soft matrix under antifungal stress. Eight α-1,2-mannan sidechain variants in C. albicans were resolved, highlighting the crucial role of mannan sidechains in maintaining interactions with other cell wall polymers to preserve structural integrity. These methodologies provide novel insights into the functional structures of key fungal polysaccharides and create new opportunities for exploring carbohydrate biosynthesis and modifications across diverse organisms.

The therapeutic effect and mechanism of carnosic acid in Aspergillus fumigatus keratitis

Fungal keratitis is a vision-threatening corneal infectious disease. However, clinically therapeutic medicines cannot attain ideal efficacy due to limited control of fungal virulence and excessive inflammatory response. Carnosic acid (CA) is a phenolic diterpene, which has been reported to have multiple abilities including antibacterial, anti-inflammatory and antioxidant. The therapeutic efficacy and potential mechanism of CA in fungal keratitis remain unknown. This study aimed to confirm the therapeutic role and potential mechanism of CA in Aspergillus fumigatus (A. fumigatus)-caused keratitis. In this study, we demonstrated that CA markedly suppressed the growth of A. fumigatus hyphae, the generation of biofilms and the integrity of the hyphal membrane. A. fumigatus-related genes (RodA, RodB, FKs, Rho1, CshA-C and Cyp51A-B) levels were suppressed under CA treatment. CA at 5 μg/mL and 10 μg/mL obviously promoted cell proliferation. In A. fumigatus-infected mice cornea, CA relieved the severity of corneal impairment, inhibited neutrophil recruitment and fungal load. Compared with inactivated hyphae, CA down-regulated the mRNA and protein levels of inflammatory cytokines, Dectin-1, NLRP3, cleaved caspase-1, IL-18 and IL-1β. Moreover, Curdlan (a specific agonist of Dectin-1) stimulation could promote the expression of NLRP3, cleaved caspase-1, IL-18 and IL-1β, which could be down-regulated by CA treatment. In conclusion, CA displays antifungal function on A. fumigatus. CA ameliorates the prognosis of keratomycosis by suppressing inflammatory cytokines production, which is regulated by Dectin-1 and pyroptosis.

Solid-State NMR Analysis of Schizosaccharomyces pombe Reveals Role of α -Amylase Family Enzymes in Cell Wall Structure and Function

The fission yeast Schizosaccharomyces pombe is a widely employed model organism for studying the eukaryotic cell cycle. Like plants and bacteria, S. pombe must build a cell wall in concert with its cell cycle, but how cell wall-synthesizing and remodeling enzymes mediate this process remains unclear. Here we characterize the functions of Aah1 and Aah3, two related S. pombe α-amylases that are putative members of this evolutionarily conserved family of cell wall-modifying proteins. We found that unlike rod-shaped wildtype S. pombe cells, aah1 Δ aah3 Δ cells are nearly spherical, grow slowly, have thickened cell walls, and have severe defects in cell separation following cytokinesis. Solid-state NMR spectroscopy analyses of intact wildtype and aah1 Δ aah3 Δ cells revealed that aah1 Δ aah3 Δ cell walls are rigidified with a significant reduction in the α-glucan matrix, characterized by reduced amounts of the major α-1,3-glucan and the minor α-1,4-glucan within the rigid and mobile phases; this reduction was compensated for by a two-fold increase in β-glucan content. Indeed, viability of aah1 Δ aah3 Δ cells depended on β-glucan upregulation and the cell wall integrity pathway that mediates it. While aah1 Δ aah3 Δ cells resemble cells with impaired function of the transglycosylation domain of α-glucan synthase 1 (Ags1), increased expression of Aah3 does not compensate for impaired Ags1 function or vice-versa. Overall, our data suggest that Aah1 and Aah3 are required in addition to Ags1, likely downstream, for the transglycosylation of α-glucan chains to generate fibers of appropriate dimensions to support proper cell morphology, growth, and division.

Significance Statement

This study utilized a range of imaging techniques and high-resolution solid-state NMR spectroscopy of intact S. pombe cells to refine our understanding of S. pombe cell wall composition. This study also determined that two related GPI-anchored α-amylase family proteins, Aah1 and Aah3, likely act as transglycosylases non-redundantly with an α-glucan synthase in the synthesis of α-glucan chains of appropriate content and size to support polarized growth and cell division. Our results also highlight the anti-fungal therapeutic potential of GPI-anchored enzymes acting in concert with glucan synthases.

Structure-function insights of natural Ganoderma polysaccharides: advances in biosynthesis and functional food applications

Ganoderma polysaccharides (GPs), derived from various species of the Ganoderma genus, exhibit diverse bioactivities, including immune modulation, anti-tumor effects, and gut microbiota regulation. These properties position GPs as dual-purpose agents for medicinal and functional food development. This review comprehensively explores the structural complexity of six key GPs and their specific mechanisms of action, such as TLR signaling in immune modulation, apoptosis pathways in anti-tumor activity, and their prebiotic effects on gut microbiota. Additionally, the structure-activity relationships (SARs) of GPs are highlighted to elucidate their biological efficacy. Advances in green extraction techniques, including ultrasonic-assisted and enzymatic methods, are discussed for their roles in enhancing yield and aligning with sustainable production principles. Furthermore, the review addresses biotechnological innovations in polysaccharide biosynthesis, improving production efficiency and making large-scale production feasible. These insights, combined with ongoing research into their bioactivity, provide a solid foundation for developing health-promoting functional food products that incorporate GPs. Furthermore, future research directions are suggested to optimize biosynthesis pathways and fully harness the health benefits of these polysaccharides.

From glycans to green biotechnology: exploring cell wall dynamics and phytobiota impact in plant glycopathology

Filamentous plant pathogens, including fungi and oomycetes, pose significant threats to cultivated crops, impacting agricultural productivity, quality and sustainability. Traditionally, disease control heavily relied on fungicides, but concerns about their negative impacts motivated stakeholders and government agencies to seek alternative solutions. Biocontrol agents (BCAs) have been developed as promising alternatives to minimize fungicide use. However, BCAs often exhibit inconsistent performances, undermining their efficacy as plant protection alternatives. The eukaryotic cell wall of plants and filamentous pathogens contributes significantly to their interaction with the environment and competitors. This highly adaptable and modular carbohydrate armor serves as the primary interface for communication, and the intricate interplay within this compartment is often mediated by carbohydrate-active enzymes (CAZymes) responsible for cell wall degradation and remodeling. These processes play a crucial role in the pathogenesis of plant diseases and contribute significantly to establishing both beneficial and detrimental microbiota. This review explores the interplay between cell wall dynamics and glycan interactions in the phytobiome scenario, providing holistic insights for efficiently exploiting microbial traits potentially involved in plant disease mitigation. Within this framework, the incorporation of glycobiology-related functional traits into the resident phytobiome can significantly enhance the plant's resilience to biotic stresses. Therefore, in the rational engineering of future beneficial consortia, it is imperative to recognize and leverage the understanding of cell wall interactions and the role of the glycome as an essential tool for the effective management of plant diseases.

Dual function of Candida auris mannosyltransferase, MNT5, in biofilm community protection from antifungal therapy and the host

Screen of mutants from a mannosyltransferase family identified the importance of MNT5 for C. auris biofilm drug resistance and neutrophil evasion. Biochemical analysis of the mnt5∆ mutant matrix and cell wall identified alterations in the mannan structures. Resistance and matrix for mnt5∆ were restored with delivery of wild-type matrix via extracellular vesicles. Analysis of the mnt5∆ cell wall revealed a reduction in mannan and compensatory increase in cell surface glucan and chitin, suggesting a role for MNT5 in mannan masking of pathogen-associated molecular patterns.

IMPORTANCE

C. auris recalcitrance is linked to biofilm drug resistance and immune evasion. The mannosyltransferase encoded by MNT5 is necessary for both phenotypes and may serve as a useful therapeutic target.

The curtain model as an alternative and complementary to the classic turgor concept of filamentous fungi

Turgor pressure is critically important for all organisms with the cell wall. In fungi, turgor is involved in the apical growth of hyphae, affects cell size, provides tension to the plasma membrane, creates the necessary rigidity for hyphae to penetrate the substrate, and has many other functions. However, there is increasing evidence that turgor pressure is not always the sole or main factor influencing some of these processes. This review characterizes the curtain model, previously proposed to describe the regulation of plasma membrane tension in the hyphae of basidiomycetes. The current understanding of the four main components of the model is outlined: the driving actin cytoskeleton, the elastic cell wall, tight adhesion of the plasma membrane to the cell wall, and macroinvaginations of the plasma membrane. All four elements, as a single model, complement or replace some physiological functions of turgor and allow us to understand how a non-apical fungal cell maintains its physiological functionality under changing environmental conditions. Further experimental confirmation of this model is fundamentally important for mycology and applied sciences.

Expression of endochitinase and exochitinase in lettuce chloroplasts increases plant biomass and kills fungal pathogen Candida albicans

Lettuce (Lactuca sativa) is a popular leafy vegetable with global production of ~28 million Mt, cultivated >1 million hectares, with a market value of US$ 4 billion in 2022. However, lettuce is highly susceptible to fungal pathogens that drastically reduce biomass and quality due to spoilage/rot. Therefore, in this study, we investigated the expression of chitinase genes via the lettuce chloroplast genome to enhance biomass and disease resistance. Site-specific integration of the expression cassette into chloroplast genomes was confirmed using two sets of PCR primers. Homoplasmy in transplastomic lines was confirmed in Southern blots by the absence of untransformed genomes. Maternal inheritance of transgenes was confirmed by the lack of segregation when seedlings were germinated in the selection medium. Chitinases expressed in chloroplasts are active in a broad range of pH (5-9) and temperatures (20-50 °C). Exochitinase expression significantly increased the number of leaves, root or shoot length and biomass throughout the growth cycle. Endochitinase expression reduced root/shoot biomass at early stages but recovered in older plants. Plant extracts expressing endochitinase/exochitinase showed activities as high as purified commercial enzymes. Antifungal activity in Candida albicans cultures inhibited growth up to 87%. A novel Carbotrace 680™ Optotracer binding to the ß-1,4 linkages of chitin, evaluated for the first time in plant systems, is highly sensitive to measure chitinase activity. To the best of our knowledge, this is the first report of chitinase expression via the chloroplast genomes of an edible plant, to confer desired agronomic traits or for biomedical applications.

Uncovering the transcriptional landscape of Fomes fomentarius during fungal-based material production through gene co-expression network analysis

BACKGROUND

Fungal-based composites have emerged as renewable, high-performance biomaterials that are produced on lignocellulosic residual streams from forestry and agriculture. Production at an industrial scale promises to revolutionize the world humans inhabit by generating sustainable, low emission, non-toxic and biodegradable construction, packaging, textile, and other materials. The polypore Fomes fomentarius is one of the basidiomycete species used for biomaterial production, yet nothing is known about the transcriptional basis of substrate decomposition, nutrient uptake, or fungal growth during composite formation. Co-expression network analysis based on RNA-Seq profiling has enabled remarkable insights into a range of fungi, and we thus aimed to develop such resources for F. fomentarius.

RESULTS

We analysed gene expression from a wide range of laboratory cultures (n = 9) or biomaterial formation (n = 18) to determine the transcriptional landscape of F. fomentarius during substrate decomposition and to identify genes important for (i) the enzymatic degradation of lignocellulose and other plant-based substrates, (ii) the uptake of their carbon monomers, and (iii) genes guiding mycelium formation through hyphal growth and cell wall biosynthesis. Simple scripts for co-expression network construction were generated and tested, and harnessed to identify a fungal-specific transcription factor named CacA strongly co-expressed with multiple chitin and glucan biosynthetic genes or Rho GTPase encoding genes, suggesting this protein is a high-priority target for engineering adhesion and branching during composite growth. We then updated carbohydrate activated enzymes (CAZymes) encoding gene annotation, used phylogenetics to assign putative uptake systems, and applied network analysis to predict repressing/activating transcription factors for lignocellulose degradation. Finally, we identified entirely new types of co-expressed contiguous clusters not previously described in fungi, including genes predicted to encode CAZymes, hydrophobins, kinases, lipases, F-box domains, chitin synthases, amongst others.

CONCLUSION

The systems biology data generated in this study will enable us to understand the genetic basis of F. fomentarius biomaterial formation in unprecedented detail. We provided proof-of-principle for accurate network-derived predictions of gene function in F. fomentarius and generated the necessary data and scripts for analysis by any end user. Entirely new classes of contiguous co-expressed gene clusters were discovered, and multiple transcription factor encoding genes which are high-priority targets for genetic engineering were identified.

Sdd3 regulates the biofilm formation of Candida albicans via the Rho1-PKC-MAPK pathway

Candida albicans, the most frequently isolated fungal pathogen in humans, forms biofilms that enhance resistance to antifungal drugs and host immunity, leading to frequent treatment failure. Understanding the molecular mechanisms governing biofilm formation is crucial for developing anti-biofilm therapies. In this study, we conducted a genetic screen to identify novel genes that regulate biofilm formation in C. albicans. One identified gene is ORF19.6693, a homolog of the Saccharomyces cerevisiae SDD3 gene. The sdd3∆/∆ mutant exhibited severe defects in biofilm formation and significantly reduced chitin content in the cell wall. Overexpression of the constitutively active version of the Rho1 GTPase Rho1G18V, an upstream activator of the protein kinase C (PKC)-mitogen-activated protein kinase (MAPK) cell-wall integrity pathway, rescued these defects. Affinity purification, mass spectrometry, and co-immunoprecipitation revealed Sdd3's physical interaction with Bem2, the GTPase-activating protein of Rho1. Deletion of SDD3 significantly reduced the amount of the active GTP-bound form of Rho1, thereby diminishing PKC-MAPK signaling and downregulating chitin synthase genes CHS2 and CHS8. Taken together, our studies identify a new biofilm regulator, Sdd3, in C. albicans that modulates Rho1 activity through its inhibitory interaction with Bem2, thereby regulating the PKC-MAPK pathway to control chitin biosynthesis, which is critical for biofilm formation. As an upstream component of the pathway and lacking a homolog in mammals, Sdd3 has the potential to serve as an antifungal target for biofilm infections.IMPORTANCEThe human fungal pathogen Candida albicans is categorized as a critical priority pathogen on the World Health Organization's Fungal Priority Pathogens List. A key virulence attribute of this pathogen is its ability to form biofilms on the surfaces of indwelling medical devices. Fungal cells in biofilms are highly resistant to antifungal drugs and host immunity, leading to treatment failure. This study conducted a genetic screen to discover novel genes that regulate biofilm formation. We found that deletion of the SDD3 gene caused severe biofilm defects. Sdd3 negatively regulates the Rho1 GTPase, an upstream activator of the protein kinase C-mitogen-activated protein kinase pathway, through direct interaction with Bem2, the GTPase-activating protein of Rho1, resulting in a significant decrease in chitin content in the fungal cell wall. This chitin synthesis defect leads to biofilm formation failure. Given its essential role in biofilm formation, Sdd3 could serve as an antifungal target for biofilm infections.

A pioneering review on Ganoderma lucidum-derived leather: taking a step towards a cruelty-free leather manufacturing

Ganoderma lucidum-derived leather presents a sustainable alternative to traditional leather, addressing ethical, environmental, and socio-economic concerns in the fashion industry. This study explores the advantages of G. lucidum-derived leather, including its cruelty-free nature, eco-friendly characteristics, and positive social and economic implications. By eliminating the need for animal exploitation, G. lucidum-derived leather aligns with ethical consumer preferences and promotes compassion towards animals. Additionally, its production process is environmentally friendly, utilizing organic substrates and avoiding toxic chemicals, thereby reducing pollution and minimizing ecological footprints. Furthermore, G. lucidum-derived leather offers significant social and economic benefits, enhancing brand reputation and attracting socially conscious consumers. Its cultivation creates economic opportunities in rural communities, stimulating local economies and providing jobs in mushroom cultivation and leather manufacturing. However, challenges remain, such as the need for further research on its mechanical properties and biodegradability. G. lucidum-derived leather represents a promising solution to the challenges facing the fashion industry, offering a sustainable and ethical alternative that meets the demands of conscious consumers and promotes environmental stewardship.

Genome-wide identification of the MYB gene family and FfMYB13 regulation analysis in cell wall synthesis underlying tissue toughening process of yellow Flammulina filiformis stipes

MYB transcription factors (TFs) play important roles in fungal growth, development, stress response, and secondary metabolism. Cell wall glycan remodeling induced by oxidative damage levels is vital for stipe quality during mature stage of yellow Flammulina filiformis fruiting bodies. In this study, we identified 15 F. filiformis MYB (FfMYB) that are ranging from 28.43 kDa-172.3 kDa, with an average of 73.51 kDa. These FfMYB genes were unevenly distributed among six chromosomes. Phylogenetic analysis indicated that 15 FfMYBs were closely related to existing model fungi, while they were more distant from Arabidopsis thaliana. Based on expression analysis, a MYB TF termed FfMYB13 were isolated and identified as a potential regulator binding the promoter of Ff-FeSOD1, which was negatively correlated with tissue toughening of yellow F. filiformis stipes. The data of DAP-seq analysis suggested that the downstream target genes of FfMYB13 were significantly enriched in cell wall metabolism. The result of EMSA and dual luciferase report experiments demonstrated that FfMYB13 served as an upstream transcriptional regulatory factor that activates four cell wall synthesis metabolism related genes, FfKRE6, Ffgas1, FfHYD-1, and FfGFA1. Moreover, FfMYB13 might negatively influence tissue toughening in the inhibition of oxidative damage by activating Ff-FeSOD1.

Fungal β-1, 3-glucanosyltransferases: A comprehensive review on classification, catalytic mechanism and functional role

β-1,3-Glucans form the major carbohydrate component of fungal cell walls, playing a vital role in cell viability, stress response, virulence, and even healthy functions such as immuno-enhancement. The elongation and branching of β-1,3-glucans is a mystery. More evidence proved the β-1, 3-glucantransferases belonging to GH72 or GH17 family to branch and remodel the synthesized linear β-1, 3-glucan chain by cleaving its internal β-1, 3-linkage and transfer the cleaved fragment to the nonreducing end of another β-1, 3-glucan acceptor. The present review summarized the comprehensive advances of β-1, 3-glucantransferases including their structures such as catalytic and non-catalytic protein domains, catalytic mechanisms and roles in cell wall formation, cell separation and cell viability to provide the references for understanding and guiding the biosynthesis and production regulation of functional β-1, 3-glucans with high-branched or elongated structures.

Protein kinases MpkA and SepH transduce crosstalk between CWI and SIN pathways to activate protective hyphal septation under echinocandin cell wall stress

This study investigates a previously unreported stress signal transduced as crosstalk between the cell wall integrity (CWI) pathway and the septation initiation network (SIN). Echinocandins, which target cell wall synthesis, are widely used to treat mycoses. Their efficacy, however, is species specific. Our findings suggest that this is due largely to CWI-SIN crosstalk and the ability of filamentous species to fortify with septa in response to echinocandin stress. To better understand this crosstalk, we used a microscopy-based assay to measure septum density, aiming to understand the septation response to cell wall stress. The echinocandin micafungin, an inhibitor of β-(1,3)-glucan synthase, was employed to induce this stress. We observed a strong positive correlation between micafungin treatment and septum density in wild-type strains. This finding suggests that CWI activates SIN under cell wall stress, increasing septum density to protect against cell wall failure. More detailed investigations, with targeted knockouts of CWI and SIN signaling proteins, enabled us to identify crosstalk occurring between the CWI kinase, MpkA, and the SIN kinase, SepH. This discovery of the previously unknown crosstalk between the CWI and SIN pathways not only reshapes our understanding of fungal stress responses, but also unveils a promising new target pathway for the development of novel antifungal strategies.

IMPORTANCE

Echinocandin-resistant species pose a major challenge in clinical mycology by rendering one of only four lines of treatment, notably one of the two that are well-tolerated, ineffective in treating systemic mycoses of these species. Previous studies have demonstrated that echinocandins fail against highly polarized fungi because they target only apical septal compartments. It is known that many filamentous species respond to cell wall stress with hyperseptation. In this work, we show that echinocandin resistance hinges on this dynamic response, rather than on innate septation alone. We also describe, for the first time, the signaling pathway used to deploy the hyperseptation response. By disabling this pathway, we were able to render mycelia susceptible to echinocandin stress. This work enhances our microbiological understanding of filamentous fungi and introduces a potential target to overcome echinocandin-resistant species.

Molecular Insights into the Role of the MET30 Protein and Its WD40 Domain in Colletotrichum gloeosporioides Growth and Virulence

Colletotrichum gloeosporioides is a major phytopathogen responsible for anthracnose in Capsicum annuum (pepper) which leads to significant yield losses. At present, the molecular mechanism of C. gloeosporioides pathogenesis is not very clear. In this study, we focused on the MET30 protein and its key WD40 domain, with an emphasis on its role in the biological functions of C. gloeosporioides. Bioinformatics analysis revealed that the MET30 protein contains a conserved F-box domain and multiple WD40 repeats, which interact with other proteins to participate in various cellular processes, including nutrient acquisition, stress responses, and pathogenicity. Gene knockout and complementation experiments demonstrated that deleting the MET30 protein or its WD40 domain significantly reduced the rates of spore production and hyphal growth while increasing tolerance to environmental stresses such as high salinity and oxidative stress. Furthermore, pathogenicity assays revealed that the WD40 domain of the MET30 protein is crucial for regulating fungal pathogenicity, as mutants lacking WD40 domains presented increased virulence on pepper leaves. These findings suggest that the WD40 domain, in synergy with the MET30 protein, regulates the pathogenicity and stress response of C. gloeosporioides, provides new insights into the molecular mechanisms of anthracnose, and offers potential strategies for effective disease control.

A microbial natural product fractionation library screen with HRMS/MS dereplication identifies new lipopeptaibiotics against Candida auris

The rise of drug-resistant fungal pathogens, including Candida auris, highlights the urgent need for novel antifungal therapies. We developed a cost-effective platform combining microbial extract prefractionation with rapid MS/MS-bioinformatics-based dereplication to efficiently prioritize new antifungal scaffolds. Screening C. auris and C. albicans revealed novel lipopeptaibiotics, coniotins, from Coniochaeta hoffmannii WAC11161, which were undetectable in crude extracts. Coniotins exhibited potent activity against critical fungal pathogens on the WHO Fungal Priority Pathogens List, including C. albicans, C. neoformans, multidrug-resistant C. auris, and Aspergillus fumigatus, with high selectivity and low resistance potential. Coniotin A targets β-glucan, compromising fungal cell wall integrity, remodelling, and sensitizing C. auris to caspofungin. Identification of a PKS-NRPS biosynthetic gene cluster further enables the discovery of related clusters encoding potential novel lipopeptaibiotics. This study demonstrates the power of natural product prefractionation in uncovering bioactive scaffolds and introduces coniotins as promising candidates for combating multidrug-resistant fungal pathogens.

Comparative analysis of polysaccharide and cell wall structure in Aspergillus nidulans and Aspergillus fumigatus by solid-state NMR

Invasive aspergillosis poses a significant threat to immunocompromised patients, leading to high mortality rates associated with these infections. Targeting the biosynthesis of cell wall carbohydrates is a promising strategy for antifungal drug development and will be advanced by a molecular-level understanding of the native structures of polysaccharides within their cellular context. Solid-state NMR spectroscopy has recently provided detailed insights into the cell wall organization of Aspergillus fumigatus, but genetic and biochemical evidence highlights species-specific differences among Aspergillus species. In this study, we employed a combination of 13C, 15N, and 1H-detection solid-state NMR, supplemented by Dynamic Nuclear Polarization (DNP), to compare the structural organization of cell wall polymers and their assembly in the cell walls of A. fumigatus and A. nidulans, both of which are key model organisms and human pathogens. The two species exhibited a similar rigid core architecture, consisting of chitin, α-glucan, and β-glucan, which contributed to comparable cell wall properties, including polymer dynamics, water retention, and supramolecular organization. However, differences were observed in the chitin, galactosaminogalactan, protein, and lipid content, as well as in the dynamics of galactomannan and the structure of the glucan matrix.

Review on mushroom mycelium-based products and their production process: from upstream to downstream

The global trend toward carbon neutrality and sustainability calls for collaborative efforts in both the basic and applied research sectors to utilize mushroom mycelia as environmentally friendly and sustainable materials. Fungi, along with animals and plants, are one of the major eukaryotic life forms. They have long been utilized in traditional biotechnology sectors, such as food fermentation, antibiotic production, and industrial enzyme production. Some fungi have also been consumed as major food crops, such as the fruiting bodies of various mushrooms. Recently, new trends have emerged, shifting from traditional applications towards the innovative use of mushroom mycelium as eco-friendly bioresources. This approach has gained attention in the development of alternative meats, mycofabrication of biocomposites, and production of mycelial leather and fabrics. These applications aim to replace animal husbandry and recycle agricultural waste for use in construction and electrical materials. This paper reviews current research trends on industrial applications of mushroom mycelia, covering strain improvements and molecular breeding as well as mycelial products and the production processes. Key findings, practical considerations, and valorization are also discussed.

Characterizing phenotype variants of Cercosporidium personatum, causal agent of peanut late leaf spot disease, their morphology, genetics and metabolites

Cercosporidium personatum (CP) causes peanut late leaf spot (LLS) disease with 70% yield losses unless controlled by fungicides. CP grows slowly in culture, exhibiting variable phenotypes. To explain those variations, we analyzed the morphology, genomes, transcriptomes and chemical composition of three morphotypes, herein called RED, TAN, and BROWN. We characterized, for the first time in CP, anthraquinone (AQ) precursors of dothistromin (DOT), including averantin, averufin, norsolorinic acid, versicolorin B, versicolorin A, nidurufin and averufanin. BROWN had the highest AQ and melanin (15 mg/g DW) contents. RED had the highest ergosterol (855 µM FW) and chitin (beta-glucans, 4% DW) contents. RED and TAN had higher resistance to xenobiotics (p ≤ 1.0E-3), including chlorothalonil, tebuconazole and caffeine, compared to CP NRRL 64,463. In RED, TAN, and BROWN, rates of single nucleotide polymorphisms (SNP) (1.4-1.7 nt/kb) and amino acid changes (3k-4k) were higher than in NRRL 64,463. Differential gene expression (p ≤ 1.0E-5) was observed in 47 pathogenicity/virulence genes, 41 carbohydrate-active enzymes (CAZymes), and 23 pigment/mycotoxin biosynthesis genes. We describe the MAT1 locus, and a method to evaluate CP-xenobiotic resistance in 5 days. Chemical profiles indicate each CP morphotype could trigger different immune response in plants, probably hindering development of durable LLS resistance.

Mechanisms of Azole Potentiation: Insights from Drug Repurposing Approaches

The emergence of azole resistance and tolerance in pathogenic fungi has emerged as a significant public health concern, emphasizing the urgency for innovative strategies to bolster the efficacy of azole-based treatments. Drug repurposing stands as a promising and practical avenue for advancing antifungal therapy, with the potential for swift clinical translation. This review offers a comprehensive overview of azole synergistic agents uncovered through drug repurposing strategies, alongside an in-depth exploration of the mechanisms by which these agents augment azole potency. Drawing from these mechanisms, we delineate strategies aimed at enhancing azole effectiveness, such as inhibiting efflux pumps to elevate azole concentrations within fungal cells, intensifying ergosterol synthesis inhibition, mitigating fungal cell resistance to azoles, and disrupting biological processes extending beyond ergosterol synthesis. This review is beneficial for the development of these potentiators, as it meticulously examines instances and provides nuanced discussions on the mechanisms underlying the progression of azole potentiators through drug repurposing strategies.

Recent advances in chemical synthesis of phosphodiester linkages found in fungal mannans

Fungal mannans are located on the exterior of the fungal cell wall, where they interact with the environment and, ultimately, the human host. Mannans play a major role in shaping the innate immune response to fungal pathogens. Understanding the phosphodiester linkage and mannosyl repeat units in the acid-labile portion of mannans is crucial for comprehending their structure/activity relationships and for development of anti-fungal vaccines and immunomodulators. The phosphodiester linkages connect the acid-stable and acid-labile portions of the mannan polymer. Phosphate groups are attached to positions 4 and/or 6 of mannosyl repeat units in the acid-stable portion and to position 1 of mannosyl repeat units in the acid-labile portion. This review focuses on the synthesis of phosphodiester linkages as an approach to the development of mannan glycomimetics, which are based on natural product fungal mannans. Development of successful synthetic strategies for the phosphodiester linkages may enable the production of mannan glycomimetics that elicit anti-fungal immune responses against existing and emerging fungal pathogens, such as Candida albicans and Candida auris.

Cell morphological plasticity in response to substrate availability of a cosmopolitan polymorphic yeast from the open ocean

Polymorphic yeasts can switch between unicellular division and multicellular filamentous growth. Although prevalent in aquatic ecosystems, such as the open ocean, we have a limited understanding of the controlling factors on their morphological variation in an aquatic ecology context. Here we show that substrate concentration regulates cell morphogenesis in a cosmopolitan polymorphic yeast, Aureobasidium pullulans, isolated from the pelagic open ocean and analyzed in liquid batch culture. Filamentous cell development was triggered only under high initial substrate conditions, suggesting that hyphal growth could be more advantageous under eutrophic conditions and may influence pelagic fungal interactions with particulate organic matter. Filamentous growth proportionally declined before the exhaustion of substrate and before budding yeast-type cell division entered stationary phase, possibly modulated by quorum sensing as previously evidenced in other polymorphic yeasts. We also found that budding yeast-type unicells decreased in size and became more elongated in shape in response to substrate depletion, resulting in higher cell surface area to volume ratios, which could affect yeast dispersal and/or provide a nutrient uptake advantage under oligotrophic conditions. Our results demonstrate resource-responsive morphological plasticity in a marine-derived polymorphic yeast, providing mechanistic insight into the ability of fungi to survive fluctuating environmental conditions such as in the open ocean.

Mixed DAMP/MAMP oligosaccharides promote both growth and defense against fungal pathogens of cucumber

Plants recognize a variety of environmental molecules, thereby triggering appropriate responses to biotic or abiotic stresses. Substances containing microbes-associated molecular patterns (MAMPs) and damage-associated molecular patterns (DAMPs) are representative inducers of pathogen resistance and damage repair, thus treatment of healthy plants with such substances can pre-activate plant immunity and cell repair functions. In this study, the effects of DAMP/MAMP oligosaccharides mixture (Oligo-Mix) derived from plant cell wall (cello-oligosaccharide and xylo-oligosaccharide), and fungal cell wall (chitin-oligosaccharide) were examined in cucumber. Treatment of cucumber with Oligo-Mix promoted root germination and plant growth, along with increased chlorophyll contents in the leaves. Oligo-Mix treatment also induced typical defense responses such as MAP kinase activation and callose deposition in leaves. Pretreatment of Oligo-Mix enhanced disease resistance of cucumber leaves against pathogenic fungi Podosphaera xanthii (powdery mildew) and Colletotrichum orbiculare (anthracnose). Oligo-Mix treatment increased the induction of hypersensitive cell death around the infection site of pathogens, which inhibited further infection and the conidial formation of pathogens on the cucumber leaves. RNA-seq analysis revealed that Oligo-Mix treatment upregulated genes associated with plant structural reinforcement, responses to abiotic stresses and plant defense. These results suggested that Oligo-Mix has beneficial effects on growth and disease resistance in cucumber, making it a promising biostimulant for agricultural application.

Cell walls, a comparative view of the composition of cell surfaces of plants, algae and microorganisms

While evolutionary studies indicate that the most ancient groups of organisms on Earth likely descended from a common wall-less ancestor, contemporary organisms lacking a carbohydrate-rich cell surface are exceedingly rare. By developing a cell wall to cover the plasma membrane, cells were able to withstand higher osmotic pressures, colonise new habitats and develop complex multicellular structures. This way, the cells of plants, algae and microorganisms are covered by a cell wall, which can generally be defined as a highly complex structure whose main framework is usually composed of carbohydrates. Rather than static structures, they are highly dynamic and serve a multitude of functions that modulate vital cellular processes, such as growth and interactions with neighbouring cells or the surrounding environment. Thus, despite its vital importance for many groups of life, it is striking that there are few comprehensive documents comparing the cell wall composition of these groups. Thus, the aim of this review was to compare the cell walls of plants with those of algae and microorganisms, paying particular attention to their polysaccharide components. It should be highlighted that, despite the important differences in composition, we have also found numerous common aspects and functionalities.

Stressor-Actuated Proximity Labeling for Reporting Cellular Interaction

Cell-cell interactions determine the activation state and function of cells. When host cells are exposed to stressors such as microorganisms, immune defense machinery is activated to release H2O2, providing direct evidence of the relevant cellular physiological processes. Inspired by the fact that peroxidase can catalyze proximity labeling in the presence of exogenous H2O2, a stressor-actuated proximity labeling (SAPL) strategy is developed to report the process information on cell-cell interactions by recording stress levels. The stressors are covalently modified with horseradish peroxidase (HRP) and the H2O2 released by the host cells in response to the stressors triggers HRP-based proximity labeling. Using a fungal mimic or live fungi as stressors, the stress levels of different host cells are compared by in situ imaging of the labeling signals. The ability to accumulate stress signals allows SAPL to more sensitively differentiate between interactions involving different macrophage phenotypes. SAPL is also a powerful tool for real-time, in situ monitoring of the effects of surface modifications on cellular interactions. Thus, the SAPL strategy represents a new perspective in the monitoring of cell-cell interactions using endogenous effector molecules.

β-1,6-Glucan plays a central role in the structure and remodeling of the bilaminate fungal cell wall

The cell wall of human fungal pathogens plays critical roles as an architectural scaffold and as a target and modulator of the host immune response. Although the cell wall of the pathogenic yeast Candida albicans is intensively studied, one of the major fibrillar components in its cell wall, β-1,6-glucan, has been largely neglected. Here, we show that β-1,6-glucan is essential for bilayered cell wall organization, cell wall integrity, and filamentous growth. For the first time, we show that β-1,6-glucan production compensates the defect in mannan elongation in the outer layer of the cell wall. In addition, β-1,6-glucan dynamics are also coordinated by host environmental stimuli and stresses with wall remodeling, where the regulation of β-1,6-glucan structure and chain length is a crucial process. As we point out that β-1,6-glucan is exposed at the yeast surface and modulate immune response, β-1,6-glucan must be considered a key factor in host-pathogen interactions.

Natural SNP Variation in GbOSM1 Promotor Enhances Verticillium Wilt Resistance in Cotton

Osmotin is classified as the pathogenesis-related protein 5 group. However, its molecular mechanism involved in plant disease resistance remains largely unknown. Here, a Verticillium wilt (VW) resistance-related osmotin gene is identified in Gossypium barbadense (Gb), GbOSM1. GbOSM1 is preferentially expressed in the roots of disease-resistant G. barbadense acc. Hai7124 and highly induced by Verticillium dahliae (Vd). Silencing GbOSM1 reduces the VW resistance of Hai7124, while overexpression of GbOSM1 in disease-susceptible G. hirsutum improves tolerance. GbOSM1 predominantly localizes in tonoplasts, while it relocates to the apoplast upon exposure to osmotic stress or Vd infection. GbOSM1 confers VW resistance by hydrolyzing cell wall polysaccharides of Vd and activating plant immune pathways. Natural variation contributes to a differential CCAAT/CCGAT elements in the OSM1 promoter in cotton accessions. All G. hirsutum (Gh) exhibit the CCAAT haplotype, while there are two haplotypes of CCAAT/CCGAT in G. barbadense, with higher expression and stronger VW resistance in CCGAT haplotype. A NFYA5 transcription factor binds to the CCAAT element of GhOSM1 promoter and inhibits its transcription. Silencing GhNFYA5 results in higher GhOSM1 expression and enhances VW resistance. These results broaden the insights into the functional mechanisms of osmotin and provide an effective strategy to breed VW-resistant cotton.

Impact of metal ions on PMS/Cl- disinfection efficacy: Enhancing or impeding microbial inactivation?

Peroxymonosulfate (PMS) is an eco-friendly disinfectant gaining attention. This study examined the influence of metal ions (Co(II), Cu(II), Fe(II)) on PMS disinfection with chloride ions (Cl-) against waterborne microorganisms, encompassing both bacteria and fungal spores. The findings elucidated that metal ions augment the inactivation of bacteria in the PMS/Cl- system while concurrently impeding the inactivation of fungal spores. Specifically, the PMS/Co(II)/Cl- process increased E. coli inactivation rates by 2.25 and 2.75 times compared to PMS/Co(II) and PMS/Cl-, respectively. Conversely, PMS/Me(II)/Cl- generally exhibited a diminished inactivation capacity against the three fungal spores compared to PMS/Cl-, albeit surpassing the efficacy of PMS/Me(II). For instance, the inactivation levels of A. niger by PMS/Cl-, PMS/Cu(II)/Cl-, and PMS/Cu(II) are 4.47-log, 1.92-log, and 0.11-log, respectively. Notably, fungal spores demonstrated a substantially higher resistance to disinfectants compared to bacteria. Differences in microbial susceptibility were linked to cell wall structure, composition, antioxidant defenses, and reactive species generation, such as hydroxyl radicals (•OH), sulfate radicals (SO4•-), and reactive chlorine species (RCS). This study demonstrated the novel and unique phenomenon of metal ions' dual role in modulating the PMS/Cl- disinfection process, which has not been reported before and has important implications for the field of water treatment.

Combating Fungal Infections and Resistance with a Dual-Mechanism Luminogen to Disrupt Membrane Integrity and Induce DNA Damage

Antifungal drug resistance is a critical concern, demanding innovative therapeutic solutions. The dual-targeting mechanism of action (MoA), as an effective strategy to reduce drug resistance, has been validated in the design of antibacterial agents. However, the structural similarities between mammalian and fungal cells complicate the development of such a strategy for antifungal agents as the selectivity can be compromised. Herein, we introduce a dual-targeting strategy addressing fungal infections by selectively introducing DNA binding molecules into fungal nuclei. We incorporate rigid hydrophobic units into a DNA-binding domain to fabricate antifungal luminogens of TPY and TPZ, which exhibit enhanced membrane penetration and DNA-binding capabilities. These compounds exhibit dual-targeting MoA by depolarizing fungal membranes and inducing DNA damage, amplifying their potency against fungal pathogens with undetectable drug resistance. TPY and TPZ demonstrated robust antifungal activity in vitro and exhibited ideal therapeutic efficacy in a murine model of C. albicans-induced vaginitis. This multifaceted approach holds promise for overcoming drug resistance and advancing antifungal therapy.

Dietary Influence on Growth, Physicochemical Stability, and Antimicrobial Mechanisms of Antimicrobial Peptides in Black Soldier Fly Larvae

Safe antibiotic substitutes are needed given the rise in antimicrobial resistance, environmental contamination, and stringent antibiotic regulations. Insect-derived antimicrobial peptides (AMPs) are promising candidates due to their antimicrobial activity, stability, and safety. This study investigates the antimicrobial mechanism of crude AMP extracts and their physicochemical characteristics in black soldier fly larvae (BSFL). The results indicated that BSFL reared on a wheat bran diet exhibited significantly improved growth performance and AMP production when compared to the other three diets. AMP extracts showed enhanced antimicrobial activity and physicochemical stability, including temperatures and metal ions except Cu+. Moreover, AMP extracts disrupted the cell membrane and inhibited the cell cycle of Staphylococcus aureus (S. aureus), thus exhibiting antimicrobial activity. Furthermore, transcriptomic and KEGG enrichment analyses identified 509 differentially expressed genes (DEGs) related to the Toll and IMD signaling pathways. STRING and GeneMANIA analyses confirmed the association of these pathways with immune response and AMP secretion. qRT-PCR results showed elevated expression of immune genes (GNBP3, NFKBIA, GADD45, and Spz) in BSFL following S. aureus immunization, consistent with RNA-seq findings. These findings offer a valuable reference for using AMPs as antibiotic substitutes in animal feeds and highlight the need for further research on AMP purification and the synergistic regulation of protein synthesis and AMP production in BSFL.

Hyphal swelling induced in the phagosome of macrophages

Macrophages play critical protective roles as sentinels of the innate immune system against fungal infection. It is therefore important to understand the dynamics of the interaction between these phagocytes and their fungal prey. We show here that many of the hyphal apices formed by Candida albicans within the macrophage ceased elongating, and apical and sub-apical hyphal compartments became swollen. Swollen hyphal cell compartments assimilated less Lysotracker-Red than non-swollen compartments, suggesting they had enhanced viability. Staining with florescent dyes suggested that there were higher levels of β-glucan and chitin in internalized fungal filaments compared to non-internalized hyphae, suggesting active cell wall remodelling within macrophages. These observations suggest that the stresses imposed by macrophages upon the fungus lead to changes in cell wall composition, inhibition of polarised growth and the induction of swelling in hyphal compartments, and that this can prevent or delay loss of viability of hyphal cells within the phagocyte.

The pathobiology of human fungal infections

Human fungal infections are a historically neglected area of disease research, yet they cause more than 1.5 million deaths every year. Our understanding of the pathophysiology of these infections has increased considerably over the past decade, through major insights into both the host and pathogen factors that contribute to the phenotype and severity of these diseases. Recent studies are revealing multiple mechanisms by which fungi modify and manipulate the host, escape immune surveillance and generate complex comorbidities. Although the emergence of fungal strains that are less susceptible to antifungal drugs or that rapidly evolve drug resistance is posing new threats, greater understanding of immune mechanisms and host susceptibility factors is beginning to offer novel immunotherapeutic options for the future. In this Review, we provide a broad and comprehensive overview of the pathobiology of human fungal infections, focusing specifically on pathogens that can cause invasive life-threatening infections, highlighting recent discoveries from the pathogen, host and clinical perspectives. We conclude by discussing key future challenges including antifungal drug resistance, the emergence of new pathogens and new developments in modern medicine that are promoting susceptibility to infection.

Bacteria-derived short-chain fatty acids as potential regulators of fungal commensalism and pathogenesis

The human gastrointestinal microbiome encompasses bacteria, fungi, and viruses forming complex bionetworks which, for organismal health, must be in a state of homeostasis. An important homeostatic mechanism derives from microbial competition, which maintains the relative abundance of microbial species in a healthy balance. Microbes compete for nutrients and secrete metabolites that inhibit other microbes. Short-chain fatty acids (SCFAs) are one such class of metabolites made by gut bacteria to very high levels. SCFAs are metabolised by microbes and host cells and have multiple roles in regulating cell physiology. Here, we review the mechanisms by which SCFAs regulate the fungal gut commensal Candida albicans. We discuss SCFA's ability to inhibit fungal growth, limit invasive behaviours and modulate cell surface antigens recognised by immune cells. We review the mechanisms underlying these roles: regulation of gene expression, metabolism, signalling and SCFA-driven post-translational protein modifications by acylation, which contribute to changes in acylome dynamics of C. albicans with potentially large consequences for cell physiology. Given that the gut mycobiome is a reservoir for systemic disease and has also been implicated in inflammatory bowel disease, understanding the mechanisms by which bacterial metabolites, such as SCFAs, control the mycobiome might provide therapeutic avenues.

Advances in molecular enzymology of β-1,3-glucanases: A comprehensive review

β-1,3-Glucanases are essential enzymes involved in the hydrolysis of β-1,3-glucans, with significant biological and industrial relevance. These enzymes are derived from diverse sources, including bacteria, fungi, plants, and animals, each exhibiting unique substrate specificities and biochemical properties. This review provides an in-depth analysis of the natural sources and ecological roles of β-1,3-glucanases, exploring their enzymatic properties such as optimal pH, temperature, molecular weight, isoelectric points, and kinetic parameters, which are crucial for understanding their functionality and stability. Advances in molecular enzymology are discussed, focusing on gene cloning, expression in systems like Escherichia coli and Pichia pastoris, and structural-functional relationships. The reaction mechanisms and the role of non-catalytic carbohydrate-binding modules in enhancing substrate hydrolysis are examined. Industrial applications of β-1,3-glucanases are highlighted, including the production of β-1,3-glucooligosaccharides, uses in the food industry, biological control of plant pathogens, and nutritional roles. This review aims to provide a foundation for future research, improving the efficiency and robustness of β-1,3-glucanases for various industrial applications.

Fgk3, a Glycogen Synthase Kinase, Regulates Chitin Synthesis through the Carbon Catabolite Repressor FgCreA in Fusarium graminearum

The glycogen synthase kinase-3 (GSK3) orthologs are well-conserved in eukaryotic organisms. However, their functions remain poorly characterized in filamentous fungi. In our previous study, we unveiled the function of Fgk3, the GSK3 ortholog, in glycogen metabolism in Fusarium graminearum, the causal agent of Fusarium head blight. Interestingly, the fgk3 mutant was unstable and tended to produce fast-growing suppressors, including secondary suppressors. Using whole-genome sequencing, we identified suppressor mutations in FgCHS5, FgFKS1, FgCREA, FgSSN6, FgRGR1, and FgPP2A in nine primary and four secondary suppressors. Subsequently, we validated that deletion of FgCHS5 or FgCREAΔH253 mutation partially suppressed the defects of fgk3 in vegetative growth and cell wall integrity, suggesting that Fgk3 may regulate the chitin synthesis through FgCreA-mediated transcriptional regulation in F. graminearum. Accordingly, the FGK3 deletion led to hyphal swelling with abnormal chitin deposition, and deletion of FGK3 or FgCREA caused the upregulation of the expression of chitin synthases FgCHS5 and FgCHS6. The interaction between Fgk3 and FgCreA was verified by Yeast two-hybrid and Co-Immunoprecipitation assays. More importantly, we verified that the nuclear localization and protein stability of FgCreA relies on the Fgk3 kinase, while the H253 deletion facilitated the re-localization of FgCreA to the nucleus in the fgk3 mutant background, potentially contributing to the suppression of the fgk3 mutant's defects. Intriguingly, the ΔH253 mutation of FgCreA, identified in suppressor mutant S3, is adjacent to a conserved phosphorylation site, S254, suggesting that this mutation may inhibit the S254 phosphorylation and promote the nuclear localization of FgCreA. Collectively, our findings indicate that the glycogen synthase kinase Fgk3 regulates the chitin synthesis through the carbon catabolite repressor FgCreA in F. graminearum.

Dynamics of interaction and internalisation of the antifungal protein PeAfpA into Penicillium digitatum morphotypes

Antifungal proteins (AFPs) as the highly active PeAfpA from Penicillium expansum or PdAfpB from Penicillium digitatum exert promising antifungal activity, but their mode of action is not fully understood. We characterised the interaction of PeAfpA against P. digitatum, comparing it to the less active PdAfpB. Despite similar effect on conidia germination, PeAfpA did not induce a burst of reactive oxygen species as PdAfpB. Live-cell fluorescence microscopy revealed complex dynamics of interaction and internalisation of both proteins with distinct P. digitatum morphotypes (quiescent conidia, swollen conidia, germlings and hyphae). Labelled PeAfpA co-localised at the cell wall of quiescent conidia, where its localisation was punctate and not uniformly distributed. This pattern changed during germination to a uniform distribution with increased intensity. Conidia from mutants of genes involved in melanin biosynthesis (pksP/alb1 or arp2) showed an altered distribution of PeAfpA but later mimicked the wild type trend of changes during germination. In swollen conidia and germlings, PeAfpA remained attached to the cell wall. In hyphae, PeAfpA was internalised through the growing hyphal tip after binding to the cell wall, in a non-endocytic but energy-dependent process that caused vacuolisation, which preceded cell death. These results may help the development of biofungicides based on AFPs.

Intestinal fungal-host interactions in promoting and maintaining health

The resident microbiota are a key component of a healthy organism. The vast majority of microbiome studies have focused on bacterial members, which constitute a significant portion of resident microbial biomass. Recent studies have demonstrated how the fungal component of the microbiota, or the mycobiome, influences mammalian biology despite its low abundance compared to other microbes. Fungi are known for their pathogenic potential, yet fungi are also prominent colonizers in healthy states, highlighting their duality. We summarize the characteristics that define the gut mycobiome across life, the factors that can impact its composition, and studies that identify mechanisms of how fungi confer health benefits. The goal of this review is to synthesize our knowledge regarding the composition and function of a healthy mycobiome with a view to inspiring future therapeutic advances.