A methanolic extract of Zanthoxylum bungeanum modulates secondary metabolism regulator genes in Aspergillus flavus and shuts down aflatoxin production
Scientific reports(2022)
Abstract
Aflatoxin B1 (AFB1) is a food-borne toxin produced by Aspergillus flavus and a few similar fungi. Natural anti-aflatoxigenic compounds are used as alternatives to chemical fungicides to prevent AFB1 accumulation. We found that a methanolic extract of the food additive Zanthoxylum bungeanum shuts down AFB1 production in A. flavus . A methanol sub-fraction (M20) showed the highest total phenolic/flavonoid content and the most potent antioxidant activity. Mass spectrometry analyses identified four flavonoids in M20: quercetin, epicatechin, kaempferol-3-O-rhamnoside, and hyperoside. The anti-aflatoxigenic potency of M20 (IC 50 : 2–4 µg/mL) was significantly higher than its anti-proliferation potency (IC 50 : 1800–1900 µg/mL). RNA-seq data indicated that M20 triggers significant transcriptional changes in 18 of 56 secondary metabolite pathways in A. flavus , including repression of the AFB1 biosynthesis pathway. Expression of aflR , the specific activator of the AFB1 pathway, was not changed by M20 treatment, suggesting that repression of the pathway is mediated by global regulators. Consistent with this, the Velvet complex, a prominent regulator of secondary metabolism and fungal development, was downregulated. Decreased expression of the conidial development regulators brlA and Medusa, genes that orchestrate redox responses, and GPCR/oxylipin-based signal transduction further suggests a broad cellular response to M20. Z. bungeanum extracts may facilitate the development of safe AFB1 control strategies.
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Key words
Antifungal agents,Fungi,Transcriptomics,Science,Humanities and Social Sciences,multidisciplinary
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