Production of zearalenone, T-2 toxin, and deoxynivalenol by Fusarium spp. isolated from plant materials grown in North Carolina

Zearalenone and ß-Zearalenol But Not Their Glucosides Inhibit Heat Shock Protein 90 ATPase Activity

The mycotoxin zearalenone (ZEN) is produced by many plant pathogenic Fusarium species. It is well known for its estrogenic activity in humans and animals, but whether ZEN has a role in plant–pathogen interaction and which process it is targeting in planta was so far unclear. We found that treatment of Arabidopsis thaliana seedlings with ZEN induced transcription of the AtHSP90.1 gene. This heat shock protein (HSP) plays an important role in plant–pathogen interaction, assisting in stability and functionality of various disease resistance gene products. Inhibition of HSP90 ATPase activity impairs functionality. Because HSP90 inhibitors are known to induce HSP90 gene expression and due to the structural similarity with the known HSP90 inhibitor radicicol (RAD), we tested whether ZEN and its phase I metabolites α- and ß-zearalenol are also HSP90 ATPase inhibitors. Indeed, AtHSP90.1 and wheat TaHSP90-2 were inhibited by ZEN and ß-zearalenol, while α-zearalenol was almost inactive. Plants can efficiently glycosylate ZEN and α/ß-zearalenol. We therefore tested whether glucosylation has an effect on the inhibitory activity of these metabolites. Expression of the A. thaliana glucosyltransferase UGT73C6 conferred RAD resistance to a sensitive yeast strain. Glucosylation of RAD, ZEN, and α/ß-zearalenol abolished the in vitro inhibitory activity with recombinant HSP90 purified from Escherichia coli. In conclusion, the mycotoxin ZEN has a very prominent target in plants, HSP90, but it can be inactivated by glycosylation. This may explain why there is little evidence for a virulence function of ZEN in host plants.

Dispositions and tissue residue of zearalenone and its metabolites α-zearalenol and β-zearalenol in broilers

Zearalenone (ZEA) is a secondary fungal metabolite produced mainly by a Fusarium graminearum. To clarify the toxicokinetics, and residues of ZEA and its major metabolites α-zearalenol (α-ZOL) and β-zearalenol (β-ZOL) in chickens, ZEA was then administered intravenously (iv) or orally (po) to broiler chickens at a dosage of 1.2 mg/kg body weight. The concentrations of ZEA, α-ZOL and β-ZOL in the plasma and various tissues were quantified using LC-MS/MS. The plasma concentrations of ZEA were measurable up to 2 h after iv and po administration, and the concentrations of α-ZOL and β-ZOL were detected up to 4 h after both types of administration. A two-compartment model was developed to describe the toxicokinetic of ZEA in broilers. The values of t1/2β and Vd were 1.36 ± 0.29 h and 6.40 ± 0.89 l/kg, respectively. The absolute oral bioavailability was 29.66 ± 5.6%. ZEA, α-ZOL and β-ZOL were measurable in the vital organs after po administration. These results suggest that ZEA is absorbed from the gastrointestinal tract and it has ability to penetrate into the various tissues of broiler chickens.

The fate of the fusarium mycotoxin zearalenone in maize cell suspension cultures

The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid - chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase - treatment Up to 50% of the mycotoxin added was bound to a non extractable or "bound" residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions.

The phytotoxicity ofFusarium metabolites: An update since 1989

The present article summarises the published phytotoxic effects of severalFusarium metabolites (mycotoxins, phytotoxins, antibiotics and pigments) since 1989. The phytotoxicity of many of the commonly isolated metabolites cannot be disputed, but their role in pathogenesis ofFusarium-induced plant diseases is uncertain. Plant species/varieties differ in their susceptibililty resistance to these toxinsin vitro, as well as toFusarium pathogens under field conditions. Such variations in plant response may reflect resistance mechanisms that operate at several levels, including an initial ability to prevent fungal invasion; prevention of fungal spread and toxin tolerance or degradation. Little is known about the mode of action of most of these metabolites on either animal or plant cells. Several novelFusarium metabolites have been isolated in the past few years. Many are toxic to animals and cell lines, but assessment of their phytotoxicity has largely been neglected. Since many plant pathogenic Fusaria produce a plethora of metabolites, the additive or synergistic actions of toxins in combination must be considered in plant pathology.

Expression of 3alpha- and 3beta-hydroxy steroid dehydrogenase mRNA in COCs and granulosa cells determines Zearalenone biotransformation

Zearalenone (ZEA) is a mycoestrogen found in diverse food and feed materials, particularly in corn and small grains. Following ingestion, the parent zearalenone is converted predominantly into alpha-zearalenol (alpha-ZOL) and beta-zearalenol (beta-ZOL) by hepatic hydroxy steroid dehydrogenases (HSD). The present study demonstrated by standard RT-PCR the expression of 3alpha- and 3beta-HSD also in porcine cumulus oocyte complexes (COCs) and granulosa cells isolated form cumulus oocyte complexes. Analysis of the rate of bioconversion of zearalenone (ZEA) by the cultured granulose cells showed the extra-hepatic production of both hydroxy metabolites of ZEA with alpha-ZOL being the dominating metabolites as previously observed in incubations with liver microsomes. The endogenous steroids 5alpha-dihydrotestosterone (5alpha-DHT), and progesterone (PGTN), both known substrates for 3alpha-HSD inhibited the conversion of ZEA into alpha-ZOL. In the presence of pregnelonone (PGN), a major substrate for 3beta-HSD only a slight inhibitory effect on the apparent beta-ZOL formation could be observed. In conclusion, these data indicate that both 3alpha- and 3beta-HSDs are expressed in porcine COCs and GCs, whereas the biotransformation experiments confirm the involvement of these enzymes in the extra-hepatic biotransformation of ZEA.

Reexamination ofFusarium graminearum NRRL-13820and NRRL-13852 reported as type A trichothecene producers

NRRL-13820 and NRRL-13852 are reported to be two atypicalFusarium graminearum strains type A trichothecene producers [T-2 toxin (T-2) and diacetoxy-scirpenol (DAS)]. These two strains were reexamined by morphological, genetical (DNA / DNA relatedness) and toxicological techniques and compared with 28 wildF graminearum isolates obtained from corn in Italy and the USA. The isolate NRRL-13820 was morphologically confirmed as a typical isolate ofF graminearum, while the isolate NRRL-13852 showed some peculiar characteristics. Nuclear DNA comparison between NRRL-13820 and NRRL-13852 displayed 49% similarity and showed 94 % and 44 % relatedness, respectively, when compared withF graminearum NRRL-13833, which is a well assessed type B trichothecene producer [deoxynivalenol (DON) and 15-acetyldeoxynivalenol]. NRRL-13820, NRRL-13852, and NRRL-13833, as well as the 28 wild isolates, were not able to synthesize T-2, HT-2 nor DAS. Finally, NRRL-13820 and NRRL-13833, but not NRRL-13852, were able to produce DON (120 and 40/μg/g, respectively). The data support the concept that the production of examined type A trichothecenes is very rare inF graminearum.

Toxicity and trichothecene production by Fusarium acuminatum subsp. acuminatum and Fusarium acuminatum subsp. armeniacum

The toxicity of cultures of Fusarium acuminatum subsp. acuminatum and Fusarium acuminatum subsp. armeniacum grown on Weet-Bix medium was assessed using a chick bioassay. Thirty-nine of 45 cultures of F. a. armeniacum tested produced at least 50% mortality in the chick bioassay. In contrast, of the 26 cultures of F. a. acuminatum tested, only nine produced at least 50% mortality. Selected extracts of both subspecies were analyzed by gas chromatography after clean-up and hydrolysis for the four main trichothecene families, namely; nivalenol (NIV), deoxynivalenol (DON), scirpentriol (Sctol), and T-2 tetraol (T-2tol). Levels of up to 500 micrograms/g and 7 micrograms/g of T-2tol were detected in F. a. armeniacum and F. a. acuminatum extracts respectively. Four cultures each of F. a. armeniacum and F. a. acuminatum were also grown on two solid media (Weet-Bix and Vermiculite) and two liquid media (MYRO and GYEP). Culture extracts were again tested for toxicity and analyzed for trichothecene production. Cultures of F. a. armeniacum grown on the solid media and on MYRO produced the highest toxicity. Levels of up to 168, 129, 150, and 8 micrograms/g of T-2tol were detected in cultures of F. a. armeniacum on Weet-Bix, Vermiculite, MYRO, and GYEP respectively. In contrast, only trace amounts of T-2tol were detected in extracts of F. a. acuminatum on all media. Sctol levels of less than 0.5 microgram/g were also detected in some cultures of both subspecies on solid media, but only F. a. armeniacum produced trace levels of Sctol on liquid media.(ABSTRACT TRUNCATED AT 250 WORDS)

Mycotoxin production by Fusarium species isolated from New Zealand maize fields

Forty Fusarium isolates obtained from maize fields were screened for moniliformin production on maize kernels. Twelve isolates, including seven of F. subglutinans, were found to produce moniliformin at levels ranging from 0.4 to 64 ppm. Twenty six isolates were also screened for production of deoxynivalenol, diacetoxyscirpenol, T-2 toxin and zearalenone. Of these, 22, including all 11 isolates of F. graminearum, produced zearalenone at levels ranging from 0.1 to 96.0 ppm, while 13 produced T-2 toxin at low levels, (less than 1.1 ppm). Deoxynivalenol and diacetoxyscirpenol were each produced by six isolates, also at low levels (less than 1.0 ppm). Three isolates of F. graminearum and one of F. sambucinum produced four toxins simultaneously.

Naturally occurring Fusarium toxins in New Zealand maize

Twenty samples of maize collected from healthy growing crops and at harvest time and during storage were screened for four Fusarium toxins (deoxynivalenol, diacetoxyscirpenol, T-2 toxin and zearalenone) by gas chromatography-mass spectrometry and thin-layer chromatography. Seventeen samples (85%) contained one or more of these toxins. Zearalenone was present in 15 samples at levels ranging between 0.1 and 16 ppm. Deoxynivalenol, diacetoxyscirpenol and T-2 toxin were found in 11, 6 and 13 samples respectively, all at levels below 1 ppm. This work documents the first reported natural occurrence of Fusarium toxins in New Zealand maize, and it is concluded that all four of the mycotoxins studied are prevalent in apparently healthy standing crops as well as in stored maize.

Risk assessment of the mycotoxin zearalenone

Trans-zearalenone, a resorcylic acid lactone, also known as F-2 toxin, is a nonsteroidal estrogenic mycotoxin produced by numerous species of Fusarium. As a result zearalenone is found in a number of cereal crops and their derived food products. A closely related substance "zeranol" (zearalanol) is at present being used in the United States and Canada as an anabolic agent in beef cattle. Zearalenone has been implicated in numerous incidences of mycotoxicosis in farm animals, especially pigs. In this report the health risks to Canadians due to the presence of zearalenone in food products have been evaluated. The first part of the report deals with the physicochemical aspects, mycology, laboratory production, and natural occurrence in plant products and animal products of zearalenone. The stability of zearalenone in foods and feeds, the effects of food processing, and the removal from foods and feeds by physicochemical means are also discussed. From these data the daily exposure of Canadians to zearalenone from food consumption has been estimated to be in the range of 0.05-0.10 microgram/kg b.w./day (mean and 90th percentile of eaters, respectfully) for young children, the highest consumption group on a body weight basis. The second part of the report deals with the metabolic disposition of zearalenone as well as the available toxicity data base of zearalenone in laboratory animals, farm animals, and humans. Studies in various species (rodents, rabbits, pigs, monkeys) including man have shown that zearalenone has estrogenic and anabolic activity. Its major effects are on reproduction, including reproductive organs and their function, leading to hyperestrogenism. Zearalenone has been implicated in numerous incidences of hyperestrogenism in farm animals, especially pigs. For reproductive effects a no adverse effect level (NOAEL) of 0.06 mg/kg b.w./day was estimated for the pubertal pig, the most sensitive species tested. Important differences in the biotransformation of zearalenone were noted, with greater amounts of alpha-zearalenol, the more estrogenic metabolite, formed in man and the pig compared to rodents. In addition, the biological half-life of these substances was longer in man than in other species tested. The binding of zearalenone to estrogen receptors was approximately 20-fold lower than that seen with 17 beta-estradiol in several assays.(ABSTRACT TRUNCATED AT 400 WORDS)