Essential APSES Transcription Factors for Mycotoxin Synthesis, Fungal Development, and Pathogenicity in Aspergillus flavus

Abstract

Aflatoxins are a potent carcinogenic mycotoxin and has become a research model of fungal secondary metabolism (SM). Via systematically investigating the APSES transcription factors (TFs), two APSES proteins were identified: AfRafA and AfStuA. These play central roles in the synthesis of mycotoxins including aflatoxin and cyclopiazonic acid, and fungal development and are consequently central to the pathogenicity of the aflatoxigenic A. flavus. Loss of AfRafA not only dramatically suppressed aflatoxin cluster expression, subsequently reducing toxin synthesis both in vitro and in vivo, but also impaired conidia and sclerotia development. More importantly, aflatoxin biosynthesis as well as conidia and sclerotia development were fully blocked in ΔAfStuA. In addition, our results supported that AfStuA regulated the aflatoxin synthesis in an AflR-dependent manner. Intriguingly, it was revealed that AfRafA and AfStuA exert an antagonistic role in the regulation of biosynthesis of cyclopiazonic acid. In summary, two global transcriptional regulators for fungal development, mycotoxin production, and seed pathogenicity of the A. flavus system have been established. The two novel regulators of mycotoxins are promising targets for future plant breeding and for the development of fungicides.

AoStuA, an APSES transcription factor, regulates the conidiation, trap formation, stress resistance and pathogenicity of the nematode‐trapping fungus Arthrobotrys oligospora

“…Moreover, conidial formation was observed with an established side‐shot approach (Yao et al ., ). To calculate the conidial germination rates, 50‐μL aliquots of 10 5 conidia mL −1 suspensions of the WT strain and mutants were used to inoculate WA medium.…”

“…The conidial concentration in the suspension was determined by microscopic counting in a haemocytometer and converted to the number of conidia per cm 2 of plate culture as an estimate of conidial yield . Moreover, conidial formation was observed with an established side-shot approach (Yao et al, 2017). To calculate the conidial germination rates, 50-μL aliquots of 10 5 conidia mL −1 suspensions of the WT strain and mutants were used to inoculate WA medium.…”

Antioxidant‐related catalase CTA1 regulates development, aflatoxin biosynthesis, and virulence in pathogenic fungus Aspergillus flavus

“…The A. flavus infection in the peanut and maize seeds was carried out by a previously described protocol (Yao et al, 2017). All samples of seed cotyledon were washed four times with 0.05% sodium hypochlorite, 75% ethanol and sterile water respectively.…”

Lysine acetylation contributes to development, aflatoxin biosynthesis and pathogenicity in Aspergillus flavus

“…For further analysis, the extracts were filtered (0.22 um) and determined by Waters HPLC with a MYCOTOX C18 column at 42 C as previously described, and AFB 1 was used as standard. Pathogenicity assays of A. flavus strains on peanut and maize seeds were performed following previously description with a minor modification (Yao et al, 2017). Both peanut and maize seeds, which were washed with 75% ethanol and sterilized water, were inoculated with 10 6 spores of all strains and cultured in the dark at 29 C for 5 days with daily addition of sterilized water to the plates.…”