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Efficacy of short-synthetic antifungal peptides on pathogenic Aspergillus flavus
S Manju Devi1, Navya Raj2, R B Sashidhar1
1Department of Biochemistry, University College of Science, Osmania University, Hyderabad 500007, Telangana State, India.
Abstract:
The efficacies of three short synthetic antifungal peptides were tested for their inhibitory action on pathogenic fungi, Aspergillus flavus. The sequences of the short synthetic peptides are PPD1- FRLHF, 66-10-FRLKFH, 77-3- FRLKFHF, respectively. These test peptides inhibited fungal growth and showed a membranolytic activity. The fungal biomass and ergosterol levels were significantly low in peptides treated samples. Further, the fungal cell wall component chitin was also found to be lower in peptides treated samples. Scanning electron microscopic images also showed highly wrinkled fungal mycelia. Significant membrane permeabilisation as well as potassium ion leakage was also observed in fungal samples treated with peptides. To assess the membrane damage, the uptake of Sytox green dye was employed. At tested concentration, peptides induced fungal membrane damage as evidenced by the green fluorescence. Further, at tested concentration, these peptides induced an oxidative stress in A.flavus as evidenced by an increase in the ROS production, malondialdehyde levels, increase in the antioxidant enzymes - superoxide dismutase, catalase with concomitant decrease in the reduced glutathione content. Additionally, a growth dependent reduction in aflatoxin levels were also observed in peptides treated samples. Docking studies on the interaction of the peptides with a trans-membrane protein calcium ATPase of A. flavus showed that all the peptides were able to bind to the protein with high z rank score. The activity of the calcium ATPase was significantly decreased in peptides treated fungal samples, thereby validating the docking results. Among all the tested peptides, 77-3 peptide exhibited the maximal membrane damage property.
Insights
Three synthetic antifungal peptides effectively inhibited Aspergillus flavus growth by damaging fungal membranes and increasing oxidative stress. Peptide 77-3 showed the strongest membrane damage, reducing fungal biomass and aflatoxin production.
Area of Science:
- Mycology
- Biochemistry
- Antimicrobial Peptides
Background:
- Pathogenic fungi like Aspergillus flavus pose significant threats to agriculture and human health.
- Developing novel antifungal agents is crucial to combat drug-resistant fungal infections.
- Synthetic peptides offer a promising avenue for targeted antifungal therapies.
Purpose of the Study:
- To evaluate the antifungal efficacy of three novel synthetic peptides against Aspergillus flavus.
- To investigate the mechanism of action, including membrane damage and oxidative stress induction.
- To assess the impact of peptides on fungal biomass, ergosterol, chitin, and aflatoxin production.
Main Methods:
- Treatment of Aspergillus flavus with synthetic peptides (PPD1-FRLHF, 66-10-FRLKFH, 77-3-FRLKFHF).
- Assessment of fungal growth, biomass, ergosterol, chitin, and potassium ion leakage.
- Microscopic analysis (SEM) and Sytox green dye uptake for membrane integrity.
- Measurement of reactive oxygen species (ROS), malondialdehyde (MDA), antioxidant enzymes, and reduced glutathione (GSH).
- Molecular docking studies with A. flavus calcium ATPase.
Main Results:
- All tested peptides inhibited fungal growth and exhibited membranolytic activity.
- Significant reduction in fungal biomass, ergosterol, and chitin levels observed.
- Peptides induced membrane permeabilization, potassium ion leakage, and Sytox green uptake.
- Increased oxidative stress markers (ROS, MDA) and altered antioxidant status (SOD, CAT, GSH).
- Peptide 77-3 demonstrated maximal membrane damage; docking confirmed interaction with calcium ATPase, reducing its activity.
Conclusions:
- Short synthetic antifungal peptides are effective inhibitors of Aspergillus flavus.
- Membrane damage and induced oxidative stress are key mechanisms of peptide action.
- These peptides represent potential candidates for developing new antifungal strategies against A. flavus.
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