Transcriptomic profiling of Aspergillus flavus in response to 5-azacytidine

Area of Science:

• * Mycology and Fungal Genetics
• * Epigenetics and Secondary Metabolism
• * Molecular Biology and Genomics

Background:

• * Aspergillus flavus is a significant pathogen producing toxic aflatoxins (AF).
• * 5-Azacytidine (5-AC), a DNA methyltransferase inhibitor, is used to study epigenetic regulation and fungal secondary metabolism.
• * Previous research indicated 5-AC affects A. flavus development and inhibits AF production, despite the fungus lacking DNA methylation.

Purpose of the Study:

• * To elucidate the molecular mechanisms by which 5-AC influences gene expression in Aspergillus flavus.
• * To investigate the impact of 5-AC on fungal development and secondary metabolite production, specifically aflatoxins.
• * To identify key regulatory genes and pathways affected by 5-AC treatment.

Main Methods:

• * RNA-sequencing (RNA-Seq) was employed to analyze the transcriptome of A. flavus after 5-AC treatment.
• * Quantitative analysis of gene expression changes, including identification of differentially expressed genes (DEGs).
• * Gene Ontology (GO) functional enrichment analysis to understand the biological roles of DEGs.

Main Results:

• * 240 genes were significantly differentially expressed (Q-value < 0.05) upon 5-AC treatment.
• * Key developmental regulator genes, veA (decreased expression) and brlA (increased expression), were identified.
• * Aflatoxin biosynthetic gene cluster expression remained low and largely unchanged, with aflR and aflS showing no differential expression.

Conclusions:

• * 5-AC affects A. flavus development by modulating veA and brlA expression, impacting sclerotia formation.
• * AF production is inhibited by 5-AC through suppressed veA expression and dysregulated carboxypeptidase activity affecting aflatoxisomes.
• * Suppressed veA expression disrupts the VelB-LaeA complex, leading to co-regulated changes in fungal development and secondary metabolism.