Inhibitory Effect of Sorbus aucuparia Extracts on the Fusarium proliferatum and F. culmorum Growth and Mycotoxin Biosynthesis.

Fungal infections are among the most common diseases of crop plants. Various species of the Fusarium spp. are naturally prevalent and globally cause the qualitative and quantitative losses of farming commodities, mainly cereals, fruits, and vegetables. In addition, Fusarium spp. can synthesize toxic secondary metabolites-mycotoxins under high temperature and humidity conditions. Among the strategies against Fusarium spp. incidence and mycotoxins biosynthesis, the application of biological control, specifically natural plant extracts, has proved to be one of the solutions as an alternative to chemical treatments. Notably, rowanberries taken from Sorbus aucuparia are a rich source of phytochemicals, such as vitamins, carotenoids, flavonoids, and phenolic acids, as well as minerals, including iron, potassium, and magnesium, making them promising candidates for biological control strategies. The study aimed to investigate the effect of rowanberry extracts obtained by supercritical fluid extraction (SFE) under different conditions on the growth of Fusarium (F. culmorum and F. proliferatum) and mycotoxin biosynthesis. The results showed that various extracts had different effects on Fusarium growth as well as ergosterol content and mycotoxin biosynthesis. These findings suggest that rowanberry extracts obtained by the SFE method could be a natural alternative to synthetic fungicides for eradicating Fusarium pathogens in crops, particularly cereal grains. However, more research is necessary to evaluate their efficacy against other Fusarium species and in vivo applications.

Metconazole inhibits fungal growth and toxin production in major Fusarium species that cause rice panicle blight.

Rice panicle blight (RPB) caused by various Fusarium spp. is an emerging disease in the major rice-growing regions of China. Epidemics of this disease cause significant yield loss and reduce grain quality by contaminating panicles with different Fusarium toxins. However, there is currently no registered fungicide for the control of RPB in China. The 14α-demethylation inhibitor (DMI) fungicide metconazole has been shown to be effective against several Fusarium spp. that cause wheat head blight, wheat crown rot and maize ear rot. In this study, we investigated the specific activity of metconazole against six Fusarium spp. that cause RPB. Metconazole significantly inhibited mycelial growth, conidium formation, germination, germ tube elongation and major toxin production in Fusarium strains collected from major rice-growing regions in China, as well as disrupting cell membrane function by inhibiting ergosterol biosynthesis. Greenhouse experiments indicated a significant reduction in blight occurrence and toxin accumulation in rice panicles treated with metconazole. Overall, our study demonstrated the potential of metconazole for managing RPB and toxin contamination, as well as providing insight into its bioactivities and modes of action of metconazole against distinct Fusarium spp.

Nanoencapsulation enhances the antimicrobial and antioxidant stability of cyclic lipopeptides for controlling Fusarium graminearum.

Fusarium graminearum not only causes Fusarium head blight (FHB) on wheat but also produces fungal toxins that pose a serious threat to food safety. Biological control is one of the safe and most effective alternative methods. In this study, cyclic lipopeptides (CLPs) produced from Bacillus mojavensis B1302 were extracted and identified by LC-MS/MS. After preparing mesoporous silica nanoparticles-NH2 (MSNsN) and encapsulating CLPs, the characterization analysis showed that the interaction between CLPs and MSNsN enhanced the crystal structure of CLPs-MSNsN. The antimicrobial activity and antioxidant capacity of CLPs-MSNsN stored at 20 °C and 45 °C were decreased more slowly than those of free CLPs with increasing storage time, indicating the enhancement of the antimicrobial and antioxidant stability of CLPs. Moreover, the field control efficacy of long-term stored CLPs-MSNsN only decreased from 78.66% to 63.2%, but the efficacy of free CLPs decreased significantly from 84.34% to 26.01%. The deoxynivalenol (DON) content of wheat grains in the CLPs-MSNsN treatment group was lower than that in the free CLPs treatment group, which showed that long-term stored CLPs-MSNsN reduced the DON content in wheat grains. Further analysis of the action mechanism of CLPs-MSNsN on F. graminearum showed that CLPs-MSNsN could disrupt mycelial morphology, cause cell apoptosis, lead to the leakage of proteins and nucleic acids, and destroy the cell permeability of mycelia. This work puts a novel insight into the antimicrobial and antioxidant stability enhancement of CLPs-MSNsN through encapsulation and provides a potential fungicide to control F. graminearum, reduce toxins and ensure food safety.

Pyricularia oryzae enhances Streptomyces griseus growth via non-volatile alkaline metabolites.

Chemical compounds that affect microbial interactions have attracted wide interest. In this study, Streptomyces griseus showed enhanced growth when cocultured with the rice blast fungus Pyricularia oryzae on potato dextrose agar (PDA) medium. An improvement in S. griseus growth was observed before contact with P. oryzae, and no growth-promoting effect was observed when the growth medium between the two microorganisms was separated. These results suggested that the chemicals produced by P. oryzae diffused through the medium and were not volatile. A PDA plate supplemented with phenol red showed that the pH of the area surrounding P. oryzae increased. The area with increased pH promoted S. griseus growth, suggesting that the alkaline compounds produced by P. oryzae were involved in this growth stimulation. In contrast, coculture with the soilborne plant pathogen Fusarium oxysporum and entomopathogenic fungus Cordyceps tenuipes did not promote S. griseus growth. Furthermore, DL-α-Difluoromethylornithine, a polyamine biosynthesis inhibitor, prevented the increase in pH and growth promotion of S. griseus by P. oryzae. These results indicated that P. oryzae increased pH by producing a polyamine.

Unveiling the potential of novel Metschnikowia yeast biosurfactants: triggering oxidative stress for promising antifungal and anticancer activity.

BACKGROUND: Sophorolipids are glycolipid biosurfactants with potential antibacterial, antifungal, and anticancer applications, rendering them promising for research. Therefore, this study hypothesizes that sophorolipids may have a notable impact on disrupting membrane integrity and triggering the production of reactive oxygen species, ultimately resulting in the eradication of pathogenic microbes. RESULTS: The current study resulted in the isolation of two Metschnikowia novel yeast strains. Sophorolipids production from these strains reached maximum yields of 23.24 g/l and 21.75 g/l, respectively, at the bioreactors level. Biosurfactants sophorolipids were characterized using FTIR and LC-MS techniques and found to be a mixture of acidic and lactonic forms with molecular weights of m/z 678 and 700. Our research elucidated sophorolipids' mechanism in disrupting bacterial and fungal membranes through ROS generation, confirmed by transmission electron microscopy and FACS analysis. The results showed that these compounds disrupted the membrane integrity and induced ROS production, leading to cell death in Klebsiella pneumoniae and Fusarium solani. In addition, the anticancer properties of sophorolipids were investigated on the A549 lung cancer cell line and found that sophorolipid-11D (SL-11D) and sophorolipid-11X (SL-11X) disrupted the actin cytoskeleton, as evidenced by immunofluorescence microscopy. The A549 cells were stained with Acridine orange/Ethidium bromide, which showed that they underwent necrosis. This was confirmed by flow cytometric analysis using Annexin/PI staining. The SL-11D and SL-11X molecules exhibited low levels of haemolytic activity and in-vitro cytotoxicity in HEK293, Caco-2, and L929 cell lines. CONCLUSION: In this work, novel yeast species CIG-11DT and CIG-11XT, isolated from the bee's gut, produce significant yields of sophorolipids without needing secondary oil sources, indicating a more economical production method. Our research shows that sophorolipids disrupt bacterial and fungal membranes via ROS production. They suggest they may act as chemo-preventive agents by inducing apoptosis in lung cancer cells, offering the potential for enhancing anticancer therapies.

Identification and antifungal sensitivity of Fusarium species isolated from piscine hosts.

Fusarium is a huge genus of filamentous fungi that has the potential to cause emerging diseases. Members of this genus can cause infections in plants, animals and humans. Here, we report the isolation of F. oxysporum and F. equiseti from 2 important fish species, Oncorhynchus mykiss (rainbow trout) and Tor putitora (golden mahseer), respectively. F. oxysporum has emerged as a significant fungal pathogen causing infection in many fish. However, F. equiseti has been isolated mainly from plants. As far as the available literatures are concerned, this is the first report on the isolation of F. oxysporum and F. equiseti from these hosts. The isolates were identified based on growth morphology and microscopic observation. F. oxysporum produced violet pigmentation on potato dextrose agar, while F. equiseti had yellow colouration. F. oxysporum produced 1- to 2-celled microconidia along with straight or curved macroconidia having 3 to 4 septa. F. equiseti produced abundant macroconidia with 4 or more septa. Species were further confirmed based on the nucleotide sequences of the internal transcribed spacer region. In a molecular phylogeny analysis, F. oxysporum and F. equiseti formed 2 different clades. In an antifungal sensitivity assay, F. oxysporum was found to be susceptible to clotrimazole with a minimum inhibitory concentration of 1.0 µg ml-1, whereas F. equiseti was susceptible to clotrimazole, ketoconazole and fluconazole. Overall, the main findings of this study are the infection of new hosts by Fusarium species and the limited activity of many antifungal drugs against these pathogens.

Enhancing tomato plant immune responses to Fusarium wilt disease by red seaweed Jania sp.

The novelty of this study lies in demonstrating a new approach to control wilt diseases using Jania ethyl acetate extract. In the current investigation, the potential impacts of Jania sp. ethyl acetate extract (JE) on Tomato Fusarium oxysporum wilt (FOW) have been studied. The in vitro antifungal potential of JE against F. oxysporum (FO) was examined. GC-MS investigation of the JE revealed that, the compounds possessing fungicidal action were Phenol,2-methoxy-4-(2-propenyl)-,acetate, Eugenol, Caryophyllene oxide, Isoespintanol, Cadinene, Caryophylla-4(12),8(13)-dien-5à-ol and Copaen. Jania sp. ethyl acetate extract exhibited strong antifungal potential against FO, achieving a 20 mmzone of inhibition. In the experiment, two different methods were applied: soil irrigation (SI) and foliar application (FS) of JE. The results showed that both treatments reduced disease index present DIP by 20.83% and 33.33% respectively. The findings indicated that during FOW, proline, phenolics, and the antioxidant enzymes activity increased, while growth and photosynthetic pigments decreased. The morphological features, photosynthetic pigments, total phenol content, and antioxidant enzyme activity of infected plants improved when JE was applied through soil or foliar methods. It is interesting to note that the application of JE had a substantially less negative effect on the isozymes peroxidase and polyphenol oxidase in tomato plants, compared to FOW. These reactions differed depending on whether JE was applied foliarly or via the soil. Finally, the use of Jania sp. could be utilized commercially as an ecologically acceptable method to protect tomato plants against FOW.

Biochemical characterization and antifungal activity of a recombinant ß-1,3-glucanase FlGluA from Flavobacterium sp. NAU1659.

ß-1,3-glucanases can degrade ß-1,3-glucoside bonds in ß-glucan which is the main cell-wall component of most of fungi, and have the crucial application potential in plant protection and food processing. Herein, a ß-1,3-glucanase FlGluA from Flavobacterium sp. NAU1659 composed of 333 amino acids with a predicted molecular mass of 36.6 kDa was expressed in Escherichia coli BL21, purified and characterized. The deduced amino acid sequence of FlGluA showed the high identity with the ß-1,3-glucanase belonging to glycoside hydrolase (GH) family 16. Enzymological characterization indicated FlGluA had the highest activity on zymosan A, with a specific activity of 3.87 U/mg, followed by curdlan (1.16 U/mg) and pachymaran (0.88 U/mg). It exhibited optimal catalytic activity at the pH 5.0 and 40 °C, and was stable when placed at 4 °C for 12 h in the range of pH 3.0-8.0 or at a temperature below 50 °C for 3 h. Its catalytic activity was enhanced by approximately 36 % in the presence of 1 mM Cr3+. The detection of thin-layer chromatography and mass spectrometry showed FlGluA hydrolyzed zymosan A mainly to glucose and disaccharide, and trace amounts of tetrasaccharide and pentasaccharide, however, it had no action on laminaribiose, indicating its endo-ß-1,3-glucanase activity. The mycelium growth of F. oxysporum treated by FlGluA was inhibited, with approximately 37 % of inhibition rate, revealing the potential antifungal activity of the enzyme. These results revealed the hydrolytic properties and biocontrol activity of FlGluA, laying a crucial foundation for its potential application in agriculture and industry.

Prenylated Flavonoids Isolated from the Root of Sophora flavescens as Potent Antifungal Agents against Botrytis cinerea.

Sophora flavescens, a traditional Chinese herb, produces a wide range of secondary metabolites with a broad spectrum of biological activities. In this study, we isolated six isopentenyl flavonoids (1-6) from the roots of S. flavescens and evaluated their activities against phytopathogenic fungi. In vitro activities showed that kurarinone and sophoraflavanone G displayed broad spectrum and superior activities, among which sophoraflavanone G displayed excellent activity against tested fungi, with EC50 values ranging from 4.76 to 13.94 µg/mL. Notably, kurarinone was easily purified and showed potential activity against Rhizoctonia solani, Botrytis cinerea, and Fusarium graminearum with EC50 values of 16.12, 16.55, and 16.99 µg/mL, respectively. Consequently, we initially investigated the mechanism of kurarinone against B. cinerea. It was found that kurarinone disrupted cell wall components, impaired cell membrane integrity, increased cell membrane permeability, and affected cellular energy metabolism, thereby exerting its effect against B. cinerea. Therefore, kurarinone is expected to be a potential candidate for the development of plant fungicides.

Purification, Structural Characterization, and Anticandidal Activity of a Chitin-Binding Peptide with High Similarity to Hevein and Endochitinase Isolated from Pepper Seeds.

With the emergence of multidrug-resistant microorganisms, microbial agents have become a serious global threat, affecting human health and various plants. Therefore, new therapeutic alternatives, such as chitin-binding proteins, are necessary. Chitin is an essential component of the fungal cell wall, and chitin-binding proteins exhibit antifungal activity. In the present study, chitin-binding peptides isolated from Capsicum chinense seeds were characterized and evaluated for their in vitro antimicrobial effect against the growth of Candida and Fusarium fungi. Proteins were extracted from the seeds and subsequently the chitin-binding proteins were separated by chitin affinity chromatography. After chromatography, two fractions, Cc-F1 (not retained on the column) and Cc-F2 (retained on the column), were obtained. Electrophoresis revealed major protein bands between 6.5 and 26.6 kDa for Cc-F1 and only a ~ 6.5 kDa protein band for Cc-F2, which was subsequently subjected to mass spectrometry. The protein showed similarity with hevein-like and endochitinase and was then named Cc-Hev. Data are available via ProteomeXchange with identifier PXD054607. Next, we predicted the three-dimensional structure of the peptides and performed a peptide docking with (NAG)3. Subsequently, growth inhibition assays were performed to evaluate the ability of the peptides to inhibit microorganism growth. Cc-Hev inhibited the growth of C. albicans (up to 75% inhibition) and C. tropicalis (100% inhibition) and induced a 65% decrease in cell viability for C. albicans and 100% for C. tropicalis. Based on these results, new techniques to combat fungal diseases could be developed through biotechnological applications; therefore, further studies are needed.

Actinobacteria Isolated from Soils of Arid Saharan Regions Display Simultaneous Antifungal and Plant Growth Promoting Activities.

Application of actinobacteria has grown exponentially in recent years in sustainable agricultural. Most actinobacterial inoculants are tailored to function as either biocontrol agents or biofertilizers. Hence, there is the need to obtain and include multifunctional actinobacterial strains in inocula formulations. In this research, 90 actinobacterial isolates were isolated from rhizospheric and non-rhizospheric soils of Algerian Saharan arid regions and were screened for their activity against the phytopathogenic fungi Alternaria alternata, Aspergillus flavus, Botrytis cinerea, Fusarium oxysporum, and Fusarium solani. Five isolates that inhibited at least three of these fungi were characterized according to morphological, environmental and biochemical parameters, and were preliminarily identified as Streptomyces enissocaesilis A1, Streptomyces olivoverticillatus A5, Streptomyces erumpens A6, Streptomyces cavourensis A8, and Streptomyces microflavus A20. These strains were then screened for plant growth promoting activities. All strains produced siderophores, hydrocyanic acid, ammonia and the auxin indole-3-acetic acid (IAA) and were capable of solubilizing phosphate. The highest producer of siderophores (69.19 percent siderophore units), ammonia (70.56 µg mL-1) and IAA (148.76 µg mL-1) was strain A8, A20, and A5, respectively. These findings showed that the five actinobacteria are multipurpose strains with simultaneous antifungal and plant growth promoting activities and have the potential to be used for sustainable agricultural practices, particularly in arid regions.

Baseline tebuconazole sensitivity and potential resistant risk in Fusarium Graminearum.

BACKGROUND: The Fusarium head blight caused by Fusarium graminearum results in reduced crop yields and the potential for vomitoxin contamination, which poses a risk to both human and livestock health. The primary method of control relies on the application of chemical fungicides. RESULTS: The current study found that the tebuconazole sensitivity of 165 F. graminearum isolates collected from the Huang-Huai-Hai region of China between 2019 and 2023 ranged from 0.005 to 2.029 µg/mL, with an average EC50 value of 0.33 ± 0.03 µg/mL. The frequency distribution conformed to a unimodal curve around the mean, and therefore provides a useful reference for monitoring the emergence of tebuconazole resistance in field populations of F. graminearum. No cross-resistance was detected between tebuconazole and other unrelated fungicides such as flutriafol, propiconazole and fluazinam, but there was a clear negative cross-resistance with triazole fungicides including fludioxonil, epoxiconazole, hexaconazole, and metconazole. Analysis of five tebuconazole-resistant mutants produced under laboratory conditions indicated that although the mycelial growth of the mutants were significantly (p < 0.05) reduced, spore production and germination rates could be significantly (p < 0.05) increased. However, pathogenicity tests confirmed a severe fitness cost associated with tebuconazole resistance, as all of the mutants completely loss the ability to infect host tissue. Furthermore, in general the resistant mutants were found to have increased sensitivity to abiotic stress, such as ionic and osmotic stress, though not to Congo red and oxidative stress, to which they were more tolerant. Meanwhile, molecular analysis identified several point mutations in the CYP51 genes of the mutants, which resulted in two substitutions (I281T, and T314A) in the predicted sequence of the FgCYP51A subunit, as well as seven (S195F, Q332V, V333L, L334G, M399T, E507G, and E267G) in the FgCYP51C subunit. In addition, it was also noted that the expression of the CYP51 genes in one of the mutants, which lacked point mutations, was significantly up-regulated in response to tebuconazole treatment. CONCLUSIONS: These results provide useful data that allow for more rational use of tebuconazole in the control of F. graminearum, as well as for more effective monitoring of fungicide resistance in the field.

New gel from a water-soluble Carboxymethyl chitosan-Cinnamaldehyde Schiff base derivative as an effective preservative against soft rot in ginger.

Ginger, valued for its culinary and medicinal properties, suffers substantial production loss-up to 90 %-due to fungal soft rot. To combat this, we have developed an environmentally sustainable antifungal polysaccharide gel derived from a water-soluble Schiff base of O-carboxymethyl chitosan (CMC) and cinnamaldehyde (CIN). Terpene incorporation was confirmed via various characterization techniques, including Fourier transform infrared (FT-IR), pH-dependent release, solubility, thermogravimetric analysis, and UV-vis spectra. Results showed successful grafting of CIN onto the polysaccharide, at a CIN:CMC ratio of 120 mg/g. In vitro evaluation demonstrated significant antifungal activity against F. oxysporum, with a MIC value of 159.25 µg/mL. Application of the CMC=CIN gel to ginger rhizomes inhibited spore germination in all evaluated wounds, enhancing gloss and appearance. These findings validate the efficacy of this novel, environmentally friendly gel in preventing ginger loss caused by fungal infections.

Synthesis, characterization and antifungal activity of imidazole chitosan derivatives.

Five novel imidazole-functionalized chitosan derivatives 3a-3e were synthesized via addition reactions of chitosan with imidazole derivatives. The partial incorporation of imidazole moiety in chitosan were confirmed by FTIR, UV, 1H NMR, XRD, SEM and GPC. Meanwhile, the antifungal activity against three common plant pathogenic fungi: Phytophthora nicotianae (P. nicotianae), Fusarium graminearum (F. graminearum) and Rhizoctonia solani (R. solani), was assayed in vitro at 0.5 and 1.0 mg/mL by hyphal measurement, and the introduction of imidazole group can influence the antifungal activity. At 0.5 mg/mL, 3e inhibited P. nicotianae growth by 42 % and had an inhibitory index against R. solani of 50 %. Derivative 3e was more effective than unmodified chitosan whose antifungal index was 17 % against P. nicotianae and 22 % against R. solani. To our surprise, at 1.0 mg/mL, the inhibition rate of 3e against R. solani can reach 99 %, while the inhibition rate of chitosan is only 38 %. These results indicated that some imidazole chitosan derivatives with enhanced antifungal activities could serve as potential biomaterial for antifungal application.

The effect of natural herbicide from Fusarium equiseti crude extract on the aquatic weed water hyacinth (Eichornia crassipes (Mart.) Solms).

In this study, Fusarium equiseti was isolated from the weed plant Tridax procumbens in an agricultural field and a crude extract produced with 75% ethanol for use as active ingredient material in natural herbicides. The herbicidal effect of F. equiseti extract was tested on water hyacinth (Eichornia crassipes), an invasive aquatic weed, by leaf disk assay at concentrations of 0.05%, 0.1%, and 0.2% w/v crude extract. Dose-dependent visual toxicity symptoms were evident after three days, namely chlorosis, yellow leaves surrounded by dark brown edges. Photosynthetic pigments (chlorophyll a, b, and carotenoids) and membrane integrity (as electrolyte leakage and malondialdehyde content) were evaluated following the leaf disk test. 3 days after treatment, photosynthetic pigment contents showed dose-dependent decreases, while both measures of membrane integrity showed dose-dependent increases with increasing extract concentration. In addition, a cytogenetic assay was conducted on Allium cepa L. root, in which mitotic index reduction and depigmentation were evident as early as 24 h after herbicide application. Finally, anatomical analysis of treated E. crassipes leaves revealed degradation or damage of the ground tissue. All told, our results support the F. equiseti crude-based natural herbicide cloud as a sustainable alternative in agriculture.

FolIws1-driven nuclear translocation of deacetylated FolTFIIS ensures conidiation of Fusarium oxysporum.

Plant diseases caused by fungal pathogens pose a great threat to crop production. Conidiation of fungi is critical for disease epidemics and serves as a promising drug target. Here, we show that deacetylation of the FolTFIIS transcription elongation factor is indispensable for Fusarium oxysporum f. sp. lycopersici (Fol) conidiation. Upon microconidiation, Fol decreases K76 acetylation of FolTFIIS by altering the level of controlling enzymes, allowing for its nuclear translocation by FolIws1. Increased nuclear FolTFIIS enhances the transcription of sporulation-related genes and, consequently, enables microconidia production. Deacetylation of FolTFIIS is also critical for the production of macroconidia and chlamydospores, and its homolog has similar functions in Botrytis cinerea. We identify two FolIws1-targeting chemicals that block the conidiation of Fol and have effective activity against a wide range of pathogenic fungi without harm to the hosts. These findings reveal a conserved mechanism of conidiation regulation and provide candidate agrochemicals for disease management.

Green Synthesis and Antifungal Activities of Novel N-Aryl Carbamate Derivatives.

Carbamate is a key structural motif in the development of fungicidal compounds, which is still promising and robust in the discovery of green pesticides. Herein, we report the synthesis and evaluation of the fungicidal activity of 35 carbamate derivatives, among which 19 compounds were synthesized in our previous report. These derivatives were synthesized from aromatic amides in a single step, which was a green oxidation process for Hofmann rearrangement using oxone, KCl and NaOH. Their chemical structures were characterized by 1H NMR, 13C NMR and high-resolution mass spectrometry. Their antifungal activity was tested against seven plant fungal pathogens. Many of the compounds exhibited good antifungal activity in vitro (inhibitory rate > 60% at 50 µg/mL). Compound 1ag exhibited excellent broad-spectrum antifungal activities with inhibition rates close to or higher than 70% at 50 µg/mL. Notably, compound 1af demonstrated the most potent inhibition against F. graminearum, with an EC50 value of 12.50 µg/mL, while compound 1z was the most promising candidate fungicide against F. oxysporum (EC50 = 16.65 µg/mL). The structure-activity relationships are also discussed in this paper. These results suggest that the N-aryl carbamate derivatives secured by our green protocol warrant further investigation as potential lead compounds for novel antifungal agents.

Synthesis and Biological Activities of C1-Substituted Acylhydrazone ß-Carboline Analogues as Antifungal Candidates.

In our ongoing work to create potential antifungal agents, we synthesized and tested a group of C1-substituted acylhydrazone ß-carboline analogues 9a-o and 10a-o for their effectiveness against Valsa mali, Fusarium solani, Fusarium oxysporum, and Fusarium graminearum. Their compositions were analyzed using different spectral techniques, such as 1H/13C NMR and HRMS, with the structure of 9l being additionally confirmed through X-ray diffraction. The antifungal evaluation showed that, among all the target ß-carboline analogues, compounds 9n and 9o exhibited more promising and broad-spectrum antifungal activity than the commercial pesticide hymexazol. Several intriguing findings regarding structure-activity relationships (SARs) were examined. In addition, the cytotoxicity test showed that these acylhydrazone ß-carboline analogues with C1 substitutions exhibit a preference for fungi, with minimal harm to healthy cells (LO2). The reported findings provide insights into the development of ß-carboline analogues as new potential antifungal agents.

Discovery of a Hybrid Molecule with Phytotoxic Activity by Genome Mining, Heterologous Expression, and OSMAC Strategy.

Genome mining in association with the OSMAC (one strain, many compounds) approach provides a feasible strategy to extend the chemical diversity and novelty of natural products. In this study, we identified the biosynthetic gene cluster (BGC) of restricticin, a promising antifungal agent featuring a reactive primary amine, from the fungus Aspergillus sclerotiorum LZDX-33-4 by genome mining. Combining heterologous expression and the OSMAC strategy resulted in the production of a new hybrid product (1), along with N-acetyl-restricticin (2) and restricticinol (3). The structure of 1 was determined by spectroscopic data, including optical rotation and electronic circular dichroism (ECD) calculations, for configurational assignment. Compound 1 represents a fusion of restricticin and phytotoxic cichorin. The biosynthetic pathway of 1 was proposed, in which the condensation of a primary amine of restricticin with a precursor of cichorine was postulated. Compound 1 at 5 mM concentration inhibited the growth of the shoots and roots of Lolium perenne, Festuca arundinacea, and Lactuca sativa with inhibitory rates of 71.3 and 88.7% for L. perenne, 79.4 and 73.0% for F. arundinacea, and 58.2 and 52.9% for L. sativa. In addition, compound 1 at 25 µg/mL showed moderate antifungal activity against Fusarium fujikuroi and Trichoderma harzianum with inhibition rates of 22.6 and 31.6%, respectively. These results suggest that heterologous expression in conjunction with the OSMAC approach provides a promising strategy to extend the metabolite novelty due to the incorporation of endogenous metabolites from the host strain with exogenous compounds, leading to the production of more complex compounds and the acquisition of new physiological functions.

Phytotoxic Isocassadiene-Type Diterpenoids from Tomato Fusarium Crown and Root Rot Pathogen Fusarium oxysporum f. sp. radicis-lycopersici.

Fusarium crown and root rot (FCRR) has emerged as a highly destructive soil-borne disease, posing a significant threat to the safe cultivation of tomatoes in recent years. The pathogen of tomato FCRR is Fusarium oxysporum f. sp. radicis-lycopersici (Forl). To explore potential phytotoxins from Forl, eight undescribed diterpenoids namely fusariumic acids A-H (1-8) were isolated. Their structures were elucidated by using spectroscopic data analyses, quantum chemical calculations, and X-ray crystallography. Fusariumic acids A (1) and C-H (3-8) were typical isocassadiene-type diterpenoids, while fusariumic acid B (2) contained a cage-like structure with an unusual 7,8-seco-isocassadiene skeleton. A biosynthetic pathway of 2 was proposed. Fusariumic acids A (1) and C-H (3-8) were further assessed for their phytotoxic effects on tomato seedlings at 200 µg/mL. Among them, fusariumic acid F (6) exhibited the strongest inhibition against the hypocotyl and root elongation of tomato seedlings, with inhibitory rates of 61.3 and 45.3%, respectively.