Search Results (43)

Maize production is increasingly challenged by climate change, which affects plant physiology, fungal colonization, and mycotoxin contamination. Aspergillus flavus, a saprophytic fungus, thrives in warm, dry conditions, leading to aflatoxin B1 (AFB1) accumulation, and posing significant food safety risks. Macro- and micro-climatic factors, including temperature, humidity, and precipitation, influence kernel development, leaf wetness duration, and mycotoxin biosynthesis. Nitrogen availability and irrigation play crucial roles in modulating plant responses to these stressors, affecting chlorophyll content, yield parameters, and fungal interactions. To investigate these interactions, a Completely Randomized Design (CRD) was employed from 2020 to 2022 to assess physiological changes in SY Orpheus maize hybrid under varying climatic conditions. Rising temperatures and declining relative humidity (RH) significantly reduced kernel number per ear length from 25.60 ± 0.34 in 2020 to 17.89 ± 0.39 in 2022 (p < 0.05), impacting yield. The AFB1 levels peaked in 2021 (156.88 ± 59.02 µg/kg), coinciding with lower humidity and increased fungal stress. Water availability improved kernel numbers and reduced AFB1 accumulation (p < 0.05) but did not significantly affect the total fungal load (p > 0.05). Nitrogen supplementation enhanced plant vigor, suppressed AFB1 biosynthesis, and influenced spectral indices. Potential confounding factors such as soil variability and microbial interactions may require further investigations. Full article

The initiation and specification of germline cells are crucial for plant reproduction and the continuity of species. In Arabidopsis thaliana, auxin plays a vital role in guiding the transition of somatic cells into germline fate, orchestrating the specification of both male archesporial cells and female megaspore mother cells. This process is regulated through interaction with the transcription factor Sporocyteless/Nozzle, which forms a feedback mechanism that modulates germ cell specialization. Auxin biosynthesis, polar transport, and signal transduction pathways collectively ensure the accurate determination of germ cell fate. Furthermore, the coordination of auxin signaling with epigenetic regulation and miRNA-mediated control fine-tunes the differentiation between germline and somatic cells. This review discusses the mechanisms underlying auxin-guided germ cell specification. It proposes future research directions, including studies on PIN-FORMED-mediated polar transport, the role of the YUCCA family in auxin biosynthesis, and the involvement of the Transport Inhibitors Response 1/Auxn Signaling F-Box-Auxin Response Factor (TIR1/AFB-ARF) signaling pathway in germ cell fate determination. These insights will enhance our understanding of plant reproductive biology and provide new strategies for crop breeding. Full article

This investigation evaluates the comparative efficacy of Cinnamomum burmannii leaf essential oil (YXYO) and its main active ingredients as a novel preservative to protect stored food commodities from fungal infestations, aflatoxin B₁ (AFB₁) contamination caused by Aspergillus flavus. Morphological observations utilizing SEM and TEM revealed significant alterations in treated samples, alongside a decrease in ergosterol content and a dose-dependent disruption of the antioxidant system and energy system. Transcriptomic analysis suggested that differentially expressed genes were predominantly associated with spore growth, the cell wall, the cell membrane, oxidative stress, energy metabolism, and aflatoxin biosynthesis. Solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS) identified ten active ingredients in YXYO, including borneol, α-terpineol, terpinen-4-ol, etc. Moreover, an effective inhibition of A. flavus infection in peanuts was observed with the application of 30 μL/disc of YXYO and a blend of its active compounds. Full article

Aflatoxin B1 (AFB1) and Ochratoxin A (OTA) are considered the most important mycotoxins in terms of food safety. The aim of this study was to evaluate the hepatotoxicity of AFB1 and OTA exposure in Wistar rats and to assess the beneficial effect of fermented whey (FW) and pumpkin (P) as functional ingredients through a proteomic approach. For the experimental procedures, rats were fed AFB1 and OTA individually or in combination, with the addition of FW or a FW-P mixture during 28 days. For proteomics analysis, peptides were separated using a LC-MS/MS-QTOF system and differentially expressed proteins (DEPs) were statistically filtered (p < 0.05) distinguishing males from females. Gene ontology visualization allowed the identification of proteins involved in important biological processes such as the response to xenobiotic stimuli and liver development. Likewise, KEGG pathway analysis reported the metabolic routes as the most affected, followed by carbon metabolism and biosynthesis of amino acids. Overall, the results highlighted a strong downregulation of DEPs in the presence of AFB1 and OTA individually but not with the mixture of both, suggesting a synergistic effect. However, FW and P have helped in the mitigation of processes triggered by mycotoxins. Full article

The risk of Aspergillus flavus contamination is expanding with global warming. Targeting the pathogenicity of A. flavus at its source and diminishing its colonization within the host may be a potential control strategy. Oxidative stress transcription factor AtfA plays a pivotal role in A. flavus pathogenicity by combating reactive oxygen species (ROS) generated by host immune cells. This study employed chromatin immunoprecipitation sequencing to elucidate the binding sites and epigenetic mechanisms of AtfA under oxidative stress. Among the total 1022 identified potential AtfA-binding peaks, a 10-bp region predominated by 5′-DRTGTTGCAA-3′, which is highly similar to the AP-1 binding motif was predicted. The significantly regulated genes exhibited a variety of biological functions, including regulation of filamentous growth, response to extracellular stimulus, and regulation of gene expression. Moreover, AtfA indirectly influenced these processes via the MAPK signaling pathway, carbon metabolism, and fatty acid metabolism in response to oxidative stress. The absence of atfA contributed to the decrease in the growth and development, sporulation, AFB₁ biosynthesis, and invasion ability of A. flavus under oxidative stress. These findings suggest that AtfA is critical to overcome oxidative stress induced by the host immune cells during the infection, providing a novel target for early prevention of A. flavus contamination. Full article

Conidia are important for the dispersal of Aspergillus flavus, which usually generates aflatoxin B1 (AFB1) and poses a threat to the safety of agricultural food. The development of conidia is usually susceptible to changes in environmental conditions, such as nutritional status and light. However, how the light signal is involved in the conidiation in A. flavus is still unknown. In this study, LreA was identified to respond to blue light and mediate the promotion of conidiation in A. flavus, which is related to the central development pathway. At the same time, blue light inhibited the biosynthesis of AFB1, which was mediated by LreA and attributed to the transcriptional regulation of aflR and aflS expression. Our findings disclosed the function and mechanism of the blue light sensor LreA in regulating conidiation and AFB1 biosynthesis, which is beneficial for the prevention and control of A. flavus and mycotoxins. Full article

The European Rapid Alert System for Food and Feed (RASFF) has shown 1133 notifications for spices and herbs in the last 10 years (2013–2023). The analysis of these notifications indicated that 58.7% (665 alerts) of the alerts corresponded to chemical hazards. Mycotoxins corresponding to aflatoxin B1 (24 alerts) and ochratoxin A (39 alerts) were found in 19.4% of the samples. Due to the presence of these biological hazards in foodstuffs, comprehensive knowledge of their molecular mechanisms of action is required as part of the risk assessment strategy. Aflatoxin B1 (AFB1) is a known potent carcinogen that has been linked to liver cancer in humans and animals. Its toxic effects consist of forming DNA adducts, causing mutations, and interfering with cellular processes. On the other hand, ochratoxin A (OTA) is known to be nephrotoxic, hepatotoxic, carcinogenic, and immunosuppressive in both humans and animals. OTA targets the kidneys and liver, exerting its toxic effects similarly to AFB1, i.e., through DNA damage, oxidative stress, and interference with cellular processes. This communication reviews the molecular mechanism of action underlying the toxicity of AFB1 and OTA found in herbs and spices in Europe, focusing on their biosynthesis, toxicodynamics, interaction with cellular components, and the resulting biochemical pathways leading to adverse health effects. Moreover, it discusses potential strategies for mitigating their presence in spices, emphasizing the importance of hazard characterization for effective risk management and regulation. Full article

The biological control of Aspergillus flavus and A. parasiticus by non-aflatoxigenic strains has been introduced in cotton- and peanut-cultivating fields and proven successful at reducing aflatoxin (AFB) contamination of crops and agricultural soils. In this study, a non-aflatoxigenic strain, A. flavus ATCC 9643 (ATCC 9643), was evaluated for its ability to competitively inhibit the growth of an aflatoxigenic strain, A. flavus ATCC 22546 (ATCC 22546), and mitigate AFB production in ATCC 22546 during competitive growth. To comparatively analyze the suppressive effect of ATCC 9643 on ATCC 22546, a non-aflatoxigenic strain (A. flavus ATCC 96045, known as AF36) was used as a positive control in some experiments. The two non-aflatoxigenic strains did not produce AFB₁ or AFB₂ owing to the absence of several AFB biosynthesis-related genes, especially aflK and aflL, which encode versicolorin B synthase and desaturase, respectively. To create a competitive growth environment, ATCC 9643 and ATCC 22546 were co-inoculated into a solid agar medium, and they grew at similar rates when added at a 1:1 ratio. Increasing the inoculum rate of ATCC 9643 (1:1, 1:3, 1:5) dramatically inhibited ATCC 22546 growth, and AFB production was effectively decreased by about 84%, 95%, and 97% by treatment with ATCC 9643. On rice, ATCC 22546 attenuated ATCC 9643 growth only when the rice was submerged in distilled water, whereas agar addition enhanced it. Taken together, ATCC 9643 is a promising candidate biological agent for suppressing aflatoxigenic A. flavus strain growth and alleviating AFB contamination. Further studies on AFB reduction in crop fields, including cotton-cultivation and maize-cultivation fields, are warranted. Full article

Aspergillus flavus and its carcinogenic secondary metabolites, aflatoxins, not only cause serious losses in the agricultural economy, but also endanger human health. Rhein, a compound extracted from the Chinese herbal medicine Rheum palmatum L. (Dahuang), exhibits good anti-inflammatory, anti-tumor, and anti-oxidative effects. However, its effect and underlying mechanisms against Aspergillus flavus have not yet been fully illustrated. In this study, we characterized the inhibition effect of rhein on A. flavus mycelial growth, sporulation, and aflatoxin B₁ (AFB₁) biosynthesis and the potential mechanism using RNA-seq analysis. The results indicate that A. flavus mycelial growth and AFB₁ biosynthesis were significantly inhibited by 50 μM rhein, with a 43.83% reduction in colony diameter and 87.2% reduction in AFB₁ production. The RNA-seq findings demonstrated that the differentially expressed genes primarily participated in processes such as spore formation and development, the maintenance of cell wall and membrane integrity, management of oxidative stress, the regulation of the citric acid cycle, and the biosynthesis of aflatoxin. Biochemical verification experiments further confirmed that 50 μM rhein effectively disrupted cell wall and membrane integrity and caused mitochondrial dysfunction through disrupting energy metabolism pathways, leading to decreased ATP synthesis and ROS accumulation, resulting in impaired aflatoxin biosynthesis. In addition, a pathogenicity test showed that 50 μM rhein inhibited A. flavus spore growth in peanut and maize seeds by 34.1% and 90.4%, while AFB₁ biosynthesis was inhibited by 60.52% and 99.43%, respectively. In conclusion, this research expands the knowledge regarding the antifungal activity of rhein and provides a new strategy to mitigate A. flavus contamination. Full article

Autophagy, a conserved cellular recycling process, plays a crucial role in maintaining homeostasis under stress conditions. It also regulates the development and virulence of numerous filamentous fungi. In this study, we investigated the specific function of ATG8, a reliable autophagic marker, in the opportunistic pathogen Aspergillus flavus. To investigate the role of atg8 in A. flavus, the deletion and complemented mutants of atg8 were generated according to the homologous recombination principle. Deletion of atg8 showed a significant decrease in conidiation, spore germination, and sclerotia formation compared to the WT and atg8^C strains. Additionally, aflatoxin production was found severely impaired in the ∆atg8 mutant. The stress assays demonstrated that ATG8 was important for A. flavus response to oxidative stress. The fluorescence microscopy showed increased levels of reactive oxygen species in the ∆atg8 mutant cells, and the transcriptional result also indicated that genes related to the antioxidant system were significantly reduced in the ∆atg8 mutant. We further found that ATG8 participated in regulating the pathogenicity of A. flavus on crop seeds. These results revealed the biological role of ATG8 in A. flavus, which might provide a potential target for the control of A. flavus and AFB1 biosynthesis. Full article

Aspergillus flavus is an important fungus that produces aflatoxins, among which aflatoxin B₁ (AFB₁) is the most toxic and contaminates food and poses a high risk to human health. AFB₁ interacts with another mycotoxin sterigmatocystin (STC), which is also a precursor of AFB₁. Herein, we determined the effect of STC on AFB₁ by evaluating A. flavus transcriptomic and proteomic profiles in the presence or absence of STC by RNA-seq and isobaric tagging, respectively. Overall, 3377 differentially expressed genes were identified by RNA-seq. These genes were mainly associated with the cellular component organisation and biosynthesis, the synthesis of valine, leucine, and isoleucine, and the synthesis of aflatoxin. Clustered genes responsible for AFB₁ biosynthesis exhibited varying degrees of downregulation, and norB expression was completely suppressed in the experimental group. During proteomic analysis, 331 genes were differentially expressed in response to STC. These differentially expressed proteins were associated with cell parts and catalytic and antioxidant activities. Differentially expressed proteins predominantly participated in metabolic pathways associated with aflatoxin biosynthesis, glycolysis/gluconeogenesis, glutathione metabolism, and carbon metabolism. Notably, the upregulated and downregulated enzymes in carbohydrate and glutathione metabolisms may serve as potential gateways for inhibiting aflatoxin biosynthesis. Moreover, twelve proteins including seven downregulated ones involved in aflatoxin biosynthesis were identified; among them, AflG was the most downregulated, suggesting that it may be the key enzyme responsible for inhibiting aflatoxin synthesis. These findings provide novel insights into A. flavus control and the mechanisms regulating mycotoxin production. Full article

Aflatoxin B1 (AFB1) is the most potent naturally occurring carcinogen for humans and animals produced by the common fungus Aspergillus flavus (A. flavus). Aflatoxin (AF) contamination in commodities is a global concern related to the safety of food and feed, and it also impacts the agricultural economy. In this study, we investigated the AFB1-inhibiting activity of a new benzaldehyde derivative, 2-[(2-methylpyridin-3-yl)oxy]benzaldehyde (MPOBA), on A. flavus. It was found that MPOBA inhibited the production of AFB1 by A. flavus, with an IC₅₀ value of 0.55 mM. Moreover, the inhibition of conidiation was also observed at the same concentration. The addition of MPOBA resulted in decreased transcript levels of the aflR gene, which encodes a key regulatory protein for the biosynthesis of AF, and also decreased transcript levels of the global regulator genes veA and laeA. These results suggested that MPOBA has an effect on the regulatory mechanism of the development and differentiation of conidia, leading to the inhibition of AFB1 production. In addition, the cytotoxicity study showed that MPOBA had a very low cytotoxic effect on the Madin-Darby canine kidney (MDCK) cell line. Therefore, MPOBA may be a potential compound for developing practically effective agents to control AF contamination. Full article

As a filamentous pathogenic fungus with high-yield of aflatoxin B₁, Aspergillus flavus is commonly found in various agricultural products. It is crucial to develop effective strategies aimed at the prevention of the contamination of A. flavus and aflatoxin. Hexokinase AfHxk1 is a critical enzyme in fungal glucose metabolism. However, the role of AfHxk1 in A. flavus development, aflatoxin biosynthesis, and virulence has not yet been explored. In this study, afHxk1 gene deletion mutant (ΔafHxk1), complementary strain (Com-afHxk1), and the domain deletion strains (afHxk1^ΔD1 and afHxk1^ΔD2) were constructed by homologous recombination. Phenotype study and RT-qPCR revealed that AfHxk1 upregulates mycelium growth and spore and sclerotia formation, but downregulates AFB₁ biosynthesis through related classical signaling pathways. Invading models and environmental stress analysis revealed that through involvement in carbon source utilization, conidia germination, and the sensitivity response of A. flavus to a series of environmental stresses, AfHxk1 deeply participates in the regulation of pathogenicity of A. flavus to crop kernels and Galleria mellonella larvae. The construction of domain deletion strains, afHxk1^ΔD1 and afHxk1^ΔD2, further revealed that AfHxk1 regulates the morphogenesis, mycotoxin biosynthesis, and the fungal pathogenicity mainly through its domain, Hexokinase_2. The results of this study revealed the biological role of AfHxk1 in Aspergillus spp., and might provide a novel potential target for the early control of the contamination of A. flavus. Full article

Fungal infection and mycotoxin contamination are major hazards to the safe storage and distribution of foods and feeds consumed by humans and livestock. This study investigated the antifungal and antiaflatoxigenic activities of massoia essential oil (MEO) and its major constituent, C10 massoia lactone (C10), against aflatoxin B (AFB)-producing Aspergillus flavus ATCC 22546. Their antifungal activities were evaluated using a disc diffusion assay, agar dilution method, and a mycelial growth inhibition assay with the AFB analysis using liquid chromatography triple quadrupole mass spectrometry. MEO and C10 exhibited similar antifungal and antiaflatoxigenic activities against A. flavus. C10 was a primary constituent in MEO and represented up to 45.1% of total peak areas analyzed by gas chromatography–mass spectrometry, indicating that C10 is a major compound contributing to the antifungal and antiaflatoxigenic activities of MEO. Interestingly, these two materials increased AFB production in A. flavus by upregulating the expression of most genes related to AFB biosynthesis by 3- to 60-fold. Overall, MEO and C10 could be suitable candidates as natural preservatives to control fungal infection and mycotoxin contamination in foods and feeds as Generally Recognized As Safe (GRAS) in the Flavor and Extract Manufacturers Association of the United States (FEMA), and MEO is a more suitable substance than C10 because of its wider range of uses and higher allowed concentration than C10. Full article

Phenyllactic acid (PLA), a promising food preservative, is safe and effective against a broad spectrum of food-borne pathogens. However, its mechanisms against toxigenic fungi are still poorly understood. In this study, we applied physicochemical, morphological, metabolomics, and transcriptomics analyses to investigate the activity and mechanism of PLA inhibition of a typical food-contaminating mold, Aspergillus flavus. The results showed that PLA effectively inhibited the growth of A. flavus spores and reduced aflatoxin B₁ (AFB₁) production by downregulating key genes associated with AFB₁ biosynthesis. Propidium iodide staining and transmission electron microscopy analysis demonstrated a dose-dependent disruption of the integrity and morphology of the A. flavus spore cell membrane by PLA. Multi-omics analyses showed that subinhibitory concentrations of PLA induced significant changes in A. flavus spores at the transcriptional and metabolic levels, as 980 genes and 30 metabolites were differentially expressed. Moreover, KEGG pathway enrichment analysis indicated PLA-induced cell membrane damage, energy-metabolism disruption, and central-dogma abnormality in A. flavus spores. The results provided new insights into the anti-A. flavus and -AFB₁ mechanisms of PLA. Full article