Toxicity and action mechanisms of silver nanoparticles against the mycotoxin-producing fungus Fusarium graminearum

Introduction: Fusarium graminearum is a most destructive fungal pathogen that causes Fusarium head blight (FHB) disease in cereal crops, resulting in severe yield loss and mycotoxin contamination in food and feed. Silver nanoparticles (AgNPs) are extensively applied in multiple fields due to their strong anti-microbial activity and are considered alternatives to fungicides. However, the antifungal mechanisms and the effects of AgNPs on mycotoxin production have not been well characterized.Objectives: This study aimed to investigate the antifungal activity and mechanisms of AgNPs against both fungicide-resistant and fungicide-sensitive F. graminearum strains, determine their effects on mycotoxin deoxynivalenol (DON) production, and evaluate the potential of AgNPs for FHB management in the field.Methods: Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluores-cence microscopy were used to examine the fungal morphological changes caused by AgNPs. In addition, RNA-Seq, qRT-PCR, and western blotting were conducted to detect gene transcription and DON levels. Results: AgNPs with a diameter of 2 nm exhibited effective antifungal activity against both fungicide-sen-sitive and fungicide-resistant strains of F. graminearum. Further studies showed that AgNP application could impair the development, cell structure, cellular energy utilization, and metabolism pathways of this fungus. RNA-Seq analysis and sensitivity determination revealed that AgNP treatment significantly induced the expression of azole-related ATP-binding cassette (ABC) transporters without compromising the control efficacy of azoles in F. graminearum. AgNP treatment stimulated the generation of reactive oxygen species (ROS), subsequently induced transcription of DON biosynthesis genes, toxisome forma-tion, and mycotoxin production.Conclusion: This study revealed the underlying mechanisms of AgNPs against F. graminearum, determined their effects on DON production, and evaluated the potential of AgNPs for controlling fungicide-resistant F. graminearum strains. Together, our findings suggest that combinations of AgNPs with DON-reducing fungicides could be used for the management of FHB in the future.(c) 2022 The Authors. Published by Elsevier B.V. on behalf of Cairo University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Fusarium graminearum is a destructive fungal pathogen causing Fusarium head blight (FHB) disease in cereal crops, leading to yield loss and mycotoxin contamination. Silver nanoparticles (AgNPs) show effective antifungal activity against fungicide-resistant and fungicide-sensitive F. graminearum strains, while inducing ROS generation, DON biosynthesis gene expression, and mycotoxin production. AgNPs have the potential to manage FHB in combination with DON-reducing fungicides.