SntB triggers the antioxidant pathways to regulate development and aflatoxin biosynthesis in Aspergillus flavus

• Published in: bioRxiv
• Main Authors: Wu, Dandan, Yang, Chi, Yao, Yanfang, Ma, Dongmei, Lin, Hong, Ling, Hao, Xin, Wenwen, Ye, Kangfu, Sun, Minghui, Yule Hu, Yang, Yanling, Zhuang, Zhenhong
• Format: Paper
• Language: English
• Published: Cold Spring Harbor Cold Spring Harbor Laboratory Press 20.12.2023
• Subjects: Aflatoxins; Aspergillus flavus; Bisulfite; Cellular stress response; Chromatin; Contamination; Epigenetics; Gene deletion; Homologous recombination; Immunoprecipitation; Menadione; Molecular modelling; Morphogenesis; Mycotoxins; Oxidants; Oxidative stress; Phenotypes; Ribonucleic acid; RNA; Sclerotia; Virulence
• DOI: 10.1101/2023.12.19.572357

The epigenetic reader SntB was identified as an important transcriptional regulator of growth, development, and secondary metabolite synthesis in Aspergillus flavus. However, the underlying molecular mechanism is still unclear. In this study, sntB gene deletion (ΔsntB), complementary (Com-sntB), and HA tag fused to snt2 (snt2-HA) strains were constructed by using the homologous recombination method, respectively. Our results revealed that deletion ofsntB inhibited the processes of mycelia growth, conidial production, sclerotia formation, aflatoxin synthesis, and ability to colonize host compared to wild type (WT), and the defective phenotype of knockout strain ΔsntB can be restored by its complementary strain Com-sntB. Chromatin immunoprecipitation sequencing (ChIP-seq) of sntB-HA and WT and RNA sequencing (RNA-seq) of ΔsntBand WT strains revealed that SntB played key roles in oxidative stress response of A. flavus. The function of catC (encode a catalase) gene was further analyzed based on the integration results of ChIP-seq and RNA-seq. In ΔsntB strain, the relative expression level of catC was significantly higher than in WT strain, while a secretory lipase encoding gene (G4B84_008359) was down-regulated. Under the stress of oxidant menadione sodium bisulfite (MSB), the deletion ofsntB obvious down-regulated the expression level of catC. After deletion of catCgene, the mycelia growth, conidial production, and sclerotia formation were inhibited, while aflatoxin synthesis was increased compared to the WT strain. Results also showed that the inhibition rate of MSB to ΔcatC strain was significantly lower than that of WT group and AFB1 yield of the ΔcatC strain was significantly decreased than that of WT strain under the stress of MSB. Our study revealed the potential machinery that SntB regulated fungal morphogenesis, mycotoxin anabolism, and fungal virulence through the axle of from SntB to fungal virulence and mycotoxin bio-synthesis, i.e. H3K36me3 modification-SntB-Peroxisomes-Lipid hydrolysis-fungal virulence and mycotoxin bio-synthesis. The results of the study shad lights into the SntB mediated epigenetic regulation pathway of fungal mycotoxin anabolism and virulence, which provided potential strategy for control the contamination of A. flavusand its aflatoxins.Competing Interest StatementThe authors have declared no competing interest.