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Fusarium graminearum is a notorious pathogen that causes Fusarium head blight (FHB) in cereal crops. It produces secondary metabolites, such as deoxynivalenol, diminishing grain quality and leading to lesser crop yield. Many strategies have been developed to combat this pathogenic fungus; however, considering the lack of resistant cultivars and likelihood of environmental hazards upon using chemical pesticides, efforts have shifted toward the biocontrol of plant diseases, which is a sustainable and eco-friendly approach. Fengycin, derived from Bacillus amyloliquefaciens FZB42, was purified from the crude extract by HPLC and further analyzed by MALDI-TOF-MS. Its application resulted in structural deformations in fungal hyphae, as observed via scanning electron microscopy. In planta experiment revealed the ability of fengycin to suppress F. graminearum growth and highlighted its capacity to combat disease incidence. Fengycin significantly suppressed F. graminearum, and also reduced the deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), and zearalenone (ZEN) production in infected grains. To conclude, we report that fengycin produced by B. amyloliquefaciens FZB42 has potential as a biocontrol agent against F. graminearum and can also inhibit the mycotoxins produced by this fungus.

Fusarium graminearum causes Fusarium head blight (FHB), a devastating disease that leads to extensive yield and quality loss of wheat and barley. Bacteria isolated from wheat kernels and plant anthers were screened for antagonistic activity against F. graminearum. Based on its in vitro effectiveness, strain SG6 was selected for characterization and identified as Bacillus subtilis. B. subtilis SG6 exhibited a high antifungal effect on the mycelium growth, sporulation and DON production of F. graminearum with the inhibition rate of 87.9%, 95.6% and 100%, respectively. In order to gain insight into biological control effect in situ, we applied B. subtilis SG6 at anthesis through the soft dough stage of kernel development in field test. It was revealed that B. subtilis SG6 significantly reduced disease incidence (DI), FHB index and DON (P ≤ 0.05). Further, ultrastructural examination shows that B. subtilis SG6 strain induced stripping of F. graminearum hyphal surface by destroying the cellular structure. When hypha cell wall was damaged, the organelles and cytoplasm inside cell would exude, leading to cell death. The antifungal activity of SG6 could be associated with the coproduction of chitinase, fengycins and surfactins.

Controlling toxigenic Fusarium graminearum (FG) is challenging. A bacterial strain (S76-3, identified as Bacillus amyloliquefaciens) that was isolated from diseased wheat spikes in the field displayed strong antifungal activity against FG. Reverse-phase high performance liquid chromatography and electrospray ionization mass spectrometry analyses revealed that S76-3 produced three classes of cyclic lipopeptides including iturin, plipastatin and surfactin. Each class consisted of several different molecules. The iturin and plipastatin fractions strongly inhibited FG; the surfactin fractions did not. The most abundant compound that had antagonistic activity from the iturin fraction was iturin A (m/z 1043.35); the most abundant active compound from the plipastatin fraction was plipastatin A (m/z 1463.90). These compounds were analyzed with collision-induced dissociation mass spectrometry. The two purified compounds displayed strong fungicidal activity, completely killing conidial spores at the minimal inhibitory concentration range of 50 µg/ml (iturin A) and 100 µg/ml (plipastatin A). Optical and fluorescence microscopy analyses revealed severe morphological changes in conidia and substantial distortions in FG hyphae treated with iturin A or plipastatin A. Iturin A caused leakage and/or inactivation of FG cellular contents and plipastatin A caused vacuolation. Time-lapse imaging of dynamic antagonistic processes illustrated that iturin A caused distortion and conglobation along hyphae and inhibited branch formation and growth, while plipastatin A caused conglobation in young hyphae and branch tips. Transmission electron microscopy analyses demonstrated that the cell walls of conidia and hyphae of iturin A and plipastatin A treated FG had large gaps and that their plasma membranes were severely damaged and separated from cell walls.

Lipid droplets (LDs) control lipid metabolism in eukaryotic cells in general. However, the biogenesis regulation and biological functions of LDs are largely unknown in pathogenic fungi. Rapamycin treatment results in a significant increase of LD biogenesis in Fusarium graminearum. Molecular mechanisms of the target of rapamycin (TOR) pathway in regulating LD biogenesis and the functions of LD in virulence of F. graminearum were investigated in depth by combining genetic, cytological and phenotypic strategies. TOR in Fusarium graminearum (FgTOR) inhibition by rapamycin induces LD biogenesis through the FgPpg1/Sit4 signaling branch. FgPpg1 promotes phosphorylation of protein phosphatase FgNem1 by the protein kinase FgCak1. The phosphorylated FgNem1 dephosphorylates the phosphatidate phosphatase FgPah1. Dephosphorylated FgPah1 is active and stimulates LD biogenesis. Moreover, deletion of FgNem1/Spo7 or FgPah1 leads to serious defects in vegetative growth, sexual development and virulence. The results of this study provide novel insights into the regulatory mechanism and biological functions of the LDs in the devastating pathogenic fungus F. graminearum.

Soil-borne vascular pathogens pose serious threats to agriculture with complex invasion strategies that remain poorly characterized compared to foliar pathogens. While foliar pathogens like Magnaporthe oryzae employ specialized appressoria to penetrate plant surfaces through a combination of mechanical force and enzymatic degradation, the invasion mechanisms of vascular pathogens that lack classical appressoria have remained largely theoretical. The nanoscale processes governing root penetration and colonization by these pathogens are particularly challenging to visualize due to technical limitations of conventional microscopy. Here we show, using phase-contrast X-ray computed microtomography and advanced microscopy, that Fusarium oxysporum ( Fo ) employs distinct mitogen-activated protein kinase (MAPK) cascades to orchestrate root invasion through unprecedented morphological plasticity. We identify previously undocumented appressoria-like structures that facilitate physical penetration, while demonstrating that Fo exhibits remarkable cellular adaptability, reducing hyphal diameter by more than 20-fold (from 5 μm to 220 nm) to navigate confined plant spaces, a dramatic morphological transition previously thought impossible. By using cellulase-deficient mutants, we demonstrate that cellulolytic activity is dispensable for surface breach and submicrometric hyphal colonization, establishing that mechanical force generation rather than enzymatic degradation is the primary determinant of successful host penetration. Three-dimensional reconstruction reveals a quantitative correlation between fungal proliferation and progressive embolism formation, with distinct MAPK pathways differentially regulating penetration force generation (Fmk1), osmotic adaptation during apoplastic colonization (Hog1), and directional growth toward vascular tissues (Mpk1). These findings provide a mechanistic framework for vascular wilt pathogenesis and reveal potential targets for controlling these economically devastating plant diseases. Using X-ray microtomography, Turrà and colleagues show that Fusarium oxysporum penetrates plant roots via appressoria-like structures through mechanical force. Three MAPK pathways govern force generation, osmoadaptation, and vascular  bundle reach.

MtDef4 is a 47-amino acid cysteine-rich evolutionary conserved defensin from a model legume Medicago truncatula. It is an apoplast-localized plant defense protein that inhibits the growth of the ascomycetous fungal pathogen Fusarium graminearum in vitro at micromolar concentrations. Little is known about the mechanisms by which MtDef4 mediates its antifungal activity. In this study, we show that MtDef4 rapidly permeabilizes fungal plasma membrane and is internalized by the fungal cells where it accumulates in the cytoplasm. Furthermore, analysis of the structure of MtDef4 reveals the presence of a positively charged γ-core motif composed of β2 and β3 strands connected by a positively charged RGFRRR loop. Replacement of the RGFRRR sequence with AAAARR or RGFRAA abolishes the ability of MtDef4 to enter fungal cells, suggesting that the RGFRRR loop is a translocation signal required for the internalization of the protein. MtDef4 binds to phosphatidic acid (PA), a precursor for the biosynthesis of membrane phospholipids and a signaling lipid known to recruit cytosolic proteins to membranes. Amino acid substitutions in the RGFRRR sequence which abolish the ability of MtDef4 to enter fungal cells also impair its ability to bind PA. These findings suggest that MtDef4 is a novel antifungal plant defensin capable of entering into fungal cells and affecting intracellular targets and that these processes are mediated by the highly conserved cationic RGFRRR loop via its interaction with PA.

Multidrug-resistant bacteria such as extended-spectrum beta-lactamase (ESBL), Enterobacteriaceae, and methicillin-resistant (MRSA) pose a challenge to the human health care system. MRSA is among the major causes of hospital-acquired and community infections. Therefore, in the present study, we evaluated the antibacterial activity of silver nanoparticles synthesized by (AgNP ) in combination with simvastatin against reference and multidrug-resistant bacterial strains. Simvastatin showed a minimal inhibitory concentration (MIC) ranging from 0.062 to 0.25 mg mL against MRSA. AgNP with a size of 77.68± 33.95 nm and zeta potential -34.6 ± 12.7 mV showed an MIC of 0.212 mg mL against including MRSA strains. The checkerboard assay and time-kill curves exhibited a synergistic effect of the simvastatin-AgNP combination on antibacterial activity against MRSA strains. The combination of simvastatin and AgNP demonstrated antibacterial activity against producing ESBL. Scanning electron microscopy showed the formation of cell surface protrusions after treatment with AgNP and the formation of a large amorphous mass after treatment with simvastatin, both in MRSA. Our results indicate that the combination of AgNP and simvastatin could be a great future alternative in the control of bacterial infections, where, when combined with simvastatin, smaller doses of AgNP are required, with the same antibacterial activity.

Postharvest fungal infections significantly reduce the quality and marketability of papaya fruit, leading to substantial economic losses. Plant-derived essential oils (EOs) have gained attention as eco-friendly alternatives to synthetic fungicides due to their bioactivity and biodegradability. In this study, the antifungal potential of Cymbopogon martinii essential oil (CMEO) was evaluated against two major postharvest pathogens, Colletotrichum gloeosporioides and Fusarium longifundum . Gas chromatography–mass spectrometry (GC–MS) analysis identified 51 compounds representing 98.06% of the total oil, predominantly oxygenated monoterpenes. CMEO exhibited strong concentration-dependent antifungal activity, achieving complete mycelial growth inhibition at 1500 µg/mL for C. gloeosporioides and 1200 µg/mL for F. longifundum . Although its efficacy was lower than that of Bavistin fungicide, CMEO demonstrated significant antifungal potential. Mechanistic investigations revealed disruption of fungal membrane integrity, evidenced by reduced ergosterol content, increased leakage of cellular components (OD 260 ), extracellular acidification, and severe morphological and ultrastructural damage observed through scanning and transmission electron microscopy. Overall, this study highlights the potential of CMEO as a natural antifungal agent and provides mechanistic insights supporting its application for sustainable postharvest disease management of papaya.

A large collection of strains belonging to the Fusarium solani species complex (FSSC) was isolated from soil and perithecia in primary forests in Sri Lanka (from fallen tree bark) and tropical Australia (Queensland, from fallen tree fruits and nuts). Portions of the translation elongation factor 1-alpha (tef1) gene, the nuclear large subunit (NLSU) and internal transcribed spacer regions (ITS) of the nuclear ribosomal RNA genes were sequenced in 52 isolates from soil and perithecia. The FSSC was divided previously into three clades with some biogeographic structure, termed Clades 1, 2 and 3. All Sri Lankan and Australian soil isolates were found to be members of Clade 3, most grouping with the cosmopolitan soil-associated species F. falciforme. All but two Sri Lankan perithecial isolates were associated with a set of five divergent phylogenetic lineages that were associated with Clade 2. Australian perithecial isolates resided in a subclade of Clade 3 where most of the previously defined mating populations of the FSSC reside. Isolates from perithecia and those cultured from soil were always members of different species lineages, even when derived from proximal locations. The previous biogeographic assignment of Clade 2 to South America is now expanded to the worldwide tropics. Sri Lanka appears to be an important center of diversity for the FSSC. Nectria haematococca is epitypified with a collection from the type locality in Sri Lanka; its anamorph is described as a new species, Fusarium haematococcum. Neocosmospora E.F. Smith is adopted as the correct genus for Nectria haematococca. These new species are described: F. kurunegalense/Neo. kurunegalensis, F. rectiphorus/Neo. rectiphora/, F. mahasenii/Neo. mahasenii/, F. kelerajum/Neo. keleraja.

Surface-modified sulfur nanoparticles (SNP) of two different sizes were prepared via a modified liquid-phase precipitation method, using sodium polysulfide and ammonium polysulfide as starting material and polyethylene glycol-400 (PEG-400) as the surface stabilizing agent. Surface topology, size distribution, surface modification of SNPs with PEG-400, quantitative analysis for the presence of sulfur in nanoformulations, and thermal stability of SNPs were determined by atomic force microscopy (AFM), dynamic light scattering (DLS) plus high-resolution transmission electron microscopy (HR-TEM), fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, and thermogravimetric analysis (TGA), respectively. A simultaneous study with micron-sized sulfur (S^sup 0^) and SNPs was carried out to evaluate their fungicidal efficacy against Aspergillus niger and Fusarium oxysporum in terms of radial growth, sporulation, ultrastructural modifications, and phospholipid content of the fungal strains using a modified poisoned food technique, spore-germination slide bioassay, environmental scanning electron microscopy (ESEM), and spectrometry. SNPs expressed promising inhibitory effect on fungal growth and sporulation and also significantly reduced phospholipid content. [PUBLICATION ABSTRACT]