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

Abstract

The epigenetic reader SntB was identified as an important transcriptional regulator of growth, development, and secondary metabolite synthesis inAspergillus flavus. However, the underlying molecular mechanism is still unclear. In this study,sntBgene deletion (ΔsntB), complementary (Com-sntB), and HA tag fused tosnt2(snt2-HA) strains were constructed by using the homologous recombination method, respectively. Our results revealed that deletion ofsntBinhibited 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 ΔsntBcan be restored by its complementary strain Com-sntB. Chromatin immunoprecipitation sequencing (ChIP-seq) ofsntB-HA and WT and RNA sequencing (RNA-seq) of ΔsntBand WT strains revealed that SntB played key roles in oxidative stress response ofA. flavus. The function ofcatC(encode a catalase) gene was further analyzed based on the integration results of ChIP-seq and RNA-seq. In ΔsntBstrain, the relative expression level ofcatCwas 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 ofsntBobvious down-regulated the expression level ofcatC. After deletion ofcatCgene, 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 ΔcatCstrain was significantly lower than that of WT group and AFB1 yield of the ΔcatCstrain 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 light into the SntB mediated epigenetic regulation pathway of fungal mycotoxin anabolism and virulence, which provided potential strategy for control the contamination ofA. flavusand its aflatoxins.