Zearalenone (ZEA) is an estrogenic polyketide-derived mycotoxin that is produced by several Fusarium spp. This mycotoxin is often found in F. graminearum-infected cereals and causes a number of illnesses in animals, including humans. The genetic information of the ZEA biosynthetic pathway has been characterized in F. graminearum using forward and reverse genetic approaches. Four genes responsible for ZEA biosynthesis, including two polyketide synthase (PKS) genes, are located in the ZEA biosynthetic gene cluster. In addition to two PKSs, ZEB1 and ZEB2 encode an isoamyl alcohol oxidase and a transcription activator carrying a basic leucine zipper (bZIP) DNA-binding domain, respectively. ZEB2 produces two isoforms (ZEB2L and ZEB2S) via an alternative promoter. ZEB2L and ZEB2S interact with each other and participate in the autoregulation of ZEB2 expression as an activator and an inhibitor, respectively, during ZEA biosynthesis. The catalytic and regulatory subunits of the cyclic AMP (cAMP)-dependent protein kinase A (PKA) pathway in F. graminearum, CPK1 and PKR, negatively regulate ZEA biosynthesis. In particular, it was found that the PKA pathway regulates ZEB2L transcriptionally and post-transcriptionally during ZEA production. These results increase our understanding of regulatory mechanisms underlying ZEA biosynthesis in F. graminearum.
Fungivorous insects are serious hazard as potential contaminants in food. This study investigated fungi and their mycotoxins isolated from fungivorous insects (minute brown scavenger beetles [Latridiidae]) captured in a building located in Chiba, Narashino. We trapped 18 insects (heads) and isolated 780 colonies of fungi from them, which we classified into 3 genera: Penicillium (90.1%), Aspergillus (7.7%), Cladosporium (1.0%) and others (1.2%). The population of these fungi reflected that of fungi isolated from the environment inhabited by the insects. In the genus Aspergillus, sterigmatocystin and cyclopiazonic acid were detected by a simultaneous detection system of liquid chromatography-quadrupole time-of-flight mass spectrometry when the isolates were cultured in medium. These findings strongly suggest that Latridiidae are not only a physical but also a microbial hazard as a vector for the spread of mycotoxin-producing fungi in factories for food products and the storage of cereals.
Dichlorvos-ammonia (DV-AM) method is a sensitive detection method for aflatoxigenic fungi by distinguishing white (negative) colony and red (positive) colony. In this study, DV-AM method was applied for the isolation of aflatoxigenic fungi from soil samples from sugarcane field in Okinawa, Japan. At first screening, we isolated six positive colonies from one sample of the collected 25 independent samples. Chemical analyses demonstrated that these positive isolates could produce both B-type and G-type aflatoxins. Morphological and phylogenic analyses of two isolates (OKI-12, OKI-16) indicated that they were Aspergillus pseudonomius located in Aspergillus nomius clade. These results demonstrated that the DV-AM method is practically useful for the isolation of minor species of aflatoxigenic Aspergilli.
We investigated the production of fungal metabolites as a biological response to Kampo medicines by incubating the filamentous fungus Emericella nidulans IFM 60678 with Kampo medicines and analyzing the culture extracts by HPLC. E. nidulans IFM 60678 was found to produce sterigmatocystin (ST) upon incubation with Shakuyaku-kanzo-to. Further investigation revealed that the production of ST is stimulated by Peony root (Paeonia lactiflora), a component of Shakuyaku-kanzo-to. Peony root extract induced ST production in 21 of 27 (78%) non-ST-producing E. nidulans strains but did not induce the production of ST or aflatoxins in 22 non-ST-producing Aspergillus flavus strains. This result suggested that Peony root extract may induce ST production by E. nidulans specifically. Several other crude drugs, and especially Alisma tuber (Alisma orientale), Bupleurum root (Bupleurum falcatum), Japanese Angelica root (Angelica acutiloba), and Pinellia tuber (Pinellia ternata), potently induced ST production. Our unique and simple method might help identify new natural products and new regulatory strategies applicable to mycotoxin production.
Trichodermol, a non-Fusarium trichothecene, was fed to Tri5 gene-disrupted fusaria, which lack the gene encoding the enzyme for the first step of trichothecene biosynthesis. A tandem mass spectrum of the obtained product suggested that trichodermol was conjugated with hexose at position C-4 by ΔTri5 mutants of Fusarium sporotrichioides and F. graminearum.
1) The distribution of fungal mycelium and mycotoxins such as sterigmatocystin, aflatoxin, citrinin in individual brown rice kernels were studied. The mycotoxin was found near the invading mycelium of the mycotoxin-producing fungi, which was principally present around germ. The mycotoxin originally presented in moldy brown rice decreased during milling but was not completely removed from highly damaged kernels. 2) The distribution of aflatoxin-producing fungi in soil of sugarcane fields and on harvested sugarcane stem of the seven of the Southernmost islands were investigated. Atypical types of A. paraisiticus and A. flavus tentatively identified in morphology were detected. Molecular study cleraly showed atypical A. parasiticus was classified as a intermediate of new genotype between A. parasiticus and A. flavus and atypical A. flavus was as atypical type of A. nomius. Recent report demonstrated new type of A. parasiticus distributed in the sugarcane field of South Texas, USA. Sugarcane cultivation has attributed the biodiversty of aflatoxin-producing fungi in the fields.
In Japan, the Food Safety Commission (FSC) is an organization conducting the risk assessment on food safety in a scientific, independent and fair manner. FSC has 12 Expert Committees that operate to either implement risk assessments on individual hazards such as food additives, pesticides and so on. Expert Committee for mycotoxins and natural toxins is one of those committees, which is in charge on risk assessments of mycotoxins in foods. Until now, this committee has published the risk assessment reports on total aflatoxins, deoxynivalenol and nivalenol, ochratoxin A, aflatoxin M1 in milk and aflatoxin B1 in feeds, ochratoxin A, and fumonisins.
In this paper, discussions on the risk assessments of deoxynivalenol, nivalenol, aflatoxin M1 in milk, aflatoxin B1 in feeds, ochratoxin A and fumonisins are reviewed.
Food poisoning by marin biotoxins scarcely occurs, but with severe cases occasionally. This manuscript describes the outline of food poisoning by marin biotoxins focused on shellfish poisoning toxins, and its prevention and regulation. Also, it discusses on issues of analytical methods for shellfish poisoning toxins, present and future.
Aminoacyl-tRNA synthetases (aaRSs) play a vital role in protein translation, establishing the genetic code by catalyzing an attachment of amino acids to their cognate tRNAs. Now, novel non-canonical functions of aaRSs have begun to emerge, uncovering numerous roles of aaRSs in higher eukaryotes, such as cancer signaling, immune response, and nutrition signaling. A recent study summarized in this report demonstrated a relationship between plant aaRS and a mycotoxin DON.
The first APEC Conference on Mycotoxin Prevention and Control in Food and Feed Commodities in Asia-Pacific Region was held in Beijing, China, during October 26-27, 2017. The overview of the conference is reported.