AUTHOR=Zhao Yarong , Huang Chulan , Zeng Rui , Chen Peirong , Xu Kaihang , Huang Xiaomei , Wang Xu 

TITLE=AflaILVB/G/I and AflaILVD are involved in mycelial production, aflatoxin biosynthesis, and fungal virulence in Aspergillus flavus

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2024.1372779

DOI=10.3389/fcimb.2024.1372779

ISSN=2235-2988

ABSTRACT=<p>Aflatoxins (AFs) are produced by fungi such as <italic>Aspergillus flavus</italic> and <italic>A. parasiticus</italic> and are one of the most toxic mycotoxins found in agricultural products and food. Aflatoxin contamination, which requires the control of <italic>A. flavus</italic>, remains problematic because of the lack of effective strategies and the exploration of new compounds that can inhibit <italic>A. flavus</italic> growth and mycotoxin production is urgently required to alleviate potential deleterious effects. Acetohydroxy acid synthase (AHAS) and dihydroxy acid dehydratase are important enzymes in the biosynthetic pathways of branched-chain amino acids (BCAAs), including isoleucine, leucine, and valine. Enzymes involved in BCAA biosynthesis are present in bacteria, plants, and fungi, but not in mammals, and are therefore, attractive targets for antimicrobial and herbicide development. In this study, we characterized <italic>AflaILVB/G/I</italic> and <italic>AflaILVD</italic>, which encode the catalytic and regulatory subunits of AHAS and dihydroxy acid dehydratase, from the pathogenic fungus <italic>Aspergillus flavus</italic>. The <italic>AflaILVB/G/I</italic> and <italic>AflaILVD</italic> deletion mutant grew slower and produced smaller colonies than the wild-type strain when grown on glucose minimal medium, potato dextrose agar, and yeast extract medium for three days at 28°C, and disruption of <italic>AflaILVB/G/I</italic> caused a significant reduction in conidia production when grown on all kinds of media. Cellular stress assays determined that all strains were sensitive to H<sub>2</sub>O<sub>2</sub>. Importantly, the pathogenicity and aflatoxin production were affected when <italic>AflaILVB/G/I</italic> and <italic>AflaILVD</italic> were knocked out, particularly <italic>AflaILVB/G/I</italic>. A series of genes that encoded enzymes involved in aflatoxin synthesis were downregulated, meaning that the knockout of <italic>AflaILVB/G/I</italic> influenced aflatoxin synthesis in <italic>A. flavus</italic> strain WT. Collectively, our results demonstrate the potential value of antifungals targeting <italic>AflaILVB/G/I</italic> in <italic>A. flavus</italic>.</p>