The Aspergilli and Their Mycotoxins: Metabolic Interactions With Plants and the Soil Biota

Abstract

Species of the highly diverse fungal genus Aspergillus are well-known agricultural pests, and, most importantly, producers of various mycotoxins threatening food safety worldwide. Mycotoxins are studied predominantly from the perspectives of human and livestock health. Meanwhile, their roles are far less known in nature. However, to understand the factors behind mycotoxin production, the roles of the toxins of Aspergilli must be understood from a complex ecological perspective, taking mold-plant, mold-microbe, and mold-animal interactions into account. The Aspergilli may switch between saprophytic and pathogenic lifestyles, and the production of secondary metabolites, such as mycotoxins, may vary according to these fungal ways of life. Recent studies highlighted the complex ecological network of soil microbiotas determining the niches that Aspergilli can fill in. Interactions with the soil microbiota and soil macro-organisms determine the role of secondary metabolite production to a great extent. While, upon infection of plants, metabolic communication including fungal secondary metabolites like aflatoxins, gliotoxin, patulin, cyclopiazonic acid, and ochratoxin, influences the fate of both the invader and the host. In this review, the role of mycotoxin producing Aspergillus species and their interactions in the ecosystem are discussed. We intend to highlight the complexity of the roles of the main toxic secondary metabolites as well as their fate in natural environments and agriculture, a field that still has important knowledge gaps.

A Review on Mycotoxins and Microfungi in Spices in the Light of the Last Five Years

“…Moreover, their contamination is further supported by local subtropical and tropical climate characterized by high temperatures, heavy rainfalls, and relative humidity providing suitable conditions for fungal growth and thus mycotoxin production [ 1 , 2 , 16 , 17 ]. Fungal growth is also affected by the landform, soil types, and its properties, as well as interactions between the microfungus and micro- and macro-organisms in the soil [ 18 , 19 ]. Mycotoxins in the soil can be absorbed by plant roots and transported via the xylem to plant tissues [ 20 ].…”

Biological Control and Mitigation of Aflatoxin Contamination in Commodities

“…The effects of bacteria and yeasts have also been studied extensively to reduce already manifested AF contamination [ 4 , 5 , 7 ]. Biological detoxification by microorganisms relies on the binding and transformation of AFs into less toxic metabolites by microbial biomass [ 4 , 5 , 21 ]. These post-harvest methods are needed as, despite the encouraging results, pre-harvest biocontrol methods have their drawbacks.…”

“…Regarding the background of the AFs production, the regulation of the AF gene clusters is still studied intensively [ 3 ]. The ecology of the AF-producer fungi is remarkably complex, and most likely, interactions of the producer fungal species with host plants and the soil micro- and macrobiota should be considered in detail to reach a deeper understanding of the reasons for AF production [ 4 ].…”

Chemical repertoire and biosynthetic machinery of the Aspergillus flavus secondary metabolome: A review

“…These examples gave the first ecological clues about the impact of aflatoxin–insect interactions in the existence of both aflatoxigenic and nonaflatoxigenic chemotypes among A. flavus populations. Apart from antiinsectan activity, other ecological implications for aflatoxins in the modulation of oxidative stress (Reverberi et al., 2008) as well as in plant pathogenesis (e.g., phytotoxic effects) and soil microbiota have been proposed (reviewed in Pfliegler, Pócsi, Győri, & Pusztahelyi, 2019).…”