Mutations and Metabolic Factors Affecting Interaction of Toxigenic and Atoxigenic Aspergillus flavus

TL;DR

This study explores how genetic and metabolic factors influence the interaction between toxin-producing and non-toxin-producing Aspergillus flavus strains, offering insights for better biological control of aflatoxin contamination.

Contribution

The study identifies key genetic mutations and metabolic differences that affect aflatoxin production and strain interactions in Aspergillus flavus.

Findings

Aflatoxin gene clusters and AFB1 production were analyzed, revealing intron losses and high-impact mutations in aflL and aflLa genes in atoxigenic strains.

Key mutation hotspots in norA/aflE, verA/aflN, and omtA/aflP genes can lead to false-negative PCR results, complicating strain identification.

Toxigenic and atoxigenic strains showed morphological changes during co-culture, likely mediated by diffusible molecules, and differed in linoleic acid reduction products.

Abstract

Aflatoxin B1 (AFB1) produced by Aspergillus flavus poses severe food safety risks. Competitive exclusion using atoxigenic A. flavus strains offers a promising biological control approach to managing agricultural contamination by reducing populations of toxigenic strains and aflatoxin levels. However, reliable identification of atoxigenic strains remains challenging, and the mechanisms underlying competitive interactions between toxigenic and atoxigenic strains require clarification for effective implementation. Therefore, this study systematically analysed A. flavus strains for aflatoxin gene clusters and AFB1 production to address these critical gaps. Our analysis revealed that atoxigenic strains had intron losses and high-impact mutations in several genes, particularly aflL and aflLa, which affect aflatoxin biosynthesis. Key genes norA/aflE, verA/aflN, and omtA/aflP emerged as mutation hotspots, sometimes causing false-negative PCR results that complicate strain identification. Also, AFB1 production was inversely related to spore concentration on MEA medium, with fewer spores resulting in higher toxin levels. Interaction tests demonstrated that toxigenic and atoxigenic strains exhibited morphological changes only when co-cultured without physical separation, suggesting that this was mediated by diffusible molecules. Furthermore, differences in the levels of linoleic acid reduction products distinguished toxigenic from atoxigenic strains. These findings thus illuminate the complex genetic and metabolic factors influencing aflatoxin production and fungal interactions.

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