Metabolism of zearalenone by genetically modified organisms expressing the detoxification gene from Clonostachys rosea.
(17/185)
Zearalenone (ZEN) is converted to a nontoxic product by a lactonohydololase encoded by zhd101. An enhanced green fluorescent protein (EGFP) gene was fused to zhd101 (i.e., egfp::zhd101) and expressed in Escherichia coli. Both recombinant ZHD101 and EGFP::ZHD101 were purified to homogeneity and characterized. Maximal activity of ZHD101 toward ZEN was measured at approximately 37 to 45 degrees C and pH 10.5 (k(cat) at 30 degrees C, 0.51 s(-1)). The enzyme was irreversibly inactivated at pH values below 4.5 or by treatment with serine protease inhibitors. ZHD101 was also active against five ZEN cognates, although the efficiencies were generally low; e.g., the k(cat) was highest with zearalanone (1.5 s(-1)) and lowest with beta-zearalenol (0.075 s(-1)). EGFP::ZHD101 had properties similar to those of the individual proteins with regard to the EGFP fluorescence and lactonohydrolase activity. Fortuitously, EGFP::ZHD101 exhibited a good correlation between the fluorescence intensity and reaction velocity under various pH conditions. We therefore used egfp::zhd101 to visually monitor the lactonohydrolase activity in genetically modified organisms and evaluated the usefulness of zhd101 for in vivo detoxification of ZEN. While recombinant E. coli and transgenic rice calluses exhibited strong EGFP fluorescence and completely degraded ZEN in liquid media, recombinant Saccharomyces cerevisiae gave poor fluorescence and did not eliminate all the toxicity of the mycotoxin in the medium; i.e., the rest of ZEN was transformed into an unfavorable substrate, beta-zearalenol, by an as-yet-unidentified reductase and remained in the medium. Even so, as much as 75% of ZEN was detoxified by the yeast transformant, which is better than the detoxification system in which food-grade Lactobacillus strains are used (H. El-Nezami, N. Polychronaki, S. Salminen, and H. Mykkuane, Appl. Environ. Microbiol. 68:3545-3549, 2002). An appropriate combination of a candidate host microbe and the codon-optimized synthetic gene may contribute significantly to establishing a mycotoxin detoxification system for food and feed. (+info)
Effect of zearalenone on days 7 to 10 post-mating on blastocyst development and endometrial morphology in sows.
(18/185)
First litter sows in naturally occurring post-weaning estrus were hand mated to proven boars and were fed a diet supplemented with zearalenone, an estrogenic mycotoxin (1 mg zearalenone/kg body weight), or a control diet on days 7 through 10 after mating. Embryos (blastocysts) and endometrial biopsies were collected from control and treated sows on days 9, 11, and 13 after mating. All blastocysts harvested on day 9 were spherical; treatment of sows with zearalenone had no effect on blastocyst development. Blastocysts collected from treated sows on day 11 were in stages of elongation comparable to those of blastocysts from control sows but had mild degenerative changes in the embryonic disks, characterized by slightly retarded development and an increase in the number of necrotic cells. Blastocysts collected from treated sows on day 13 were in an advanced stage of degeneration, characterized by circumferential constrictive division, fragmentation, and degeneration and disorganization of the embryonic disk. Feeding zearalenone to pregnant sows had no effect on the normal decrease in height of the endometrial luminal epithelium on days 9 through 13 after mating and no effect on morphologic appearance of secretory vesicles in the endometrial glandular epithelium. The dosage scheme of zearalenone used in this study did not cause any morphologic changes in the endometrium that could be associated with hyperestrogenism. (+info)
Microbial products trigger amino acid exudation from plant roots.
(19/185)
Plants naturally cycle amino acids across root cell plasma membranes, and any net efflux is termed exudation. The dominant ecological view is that microorganisms and roots passively compete for amino acids in the soil solution, yet the innate capacity of roots to recover amino acids present in ecologically relevant concentrations is unknown. We find that, in the absence of culturable microorganisms, the influx rates of 16 amino acids (each supplied at 2.5 microm) exceed efflux rates by 5% to 545% in roots of alfalfa (Medicago sativa), Medicago truncatula, maize (Zea mays), and wheat (Triticum aestivum). Several microbial products, which are produced by common soil microorganisms such as Pseudomonas bacteria and Fusarium fungi, significantly enhanced the net efflux (i.e. exudation) of amino acids from roots of these four plant species. In alfalfa, treating roots with 200 microm phenazine, 2,4-diacetylphloroglucinol, or zearalenone increased total net efflux of 16 amino acids 200% to 2,600% in 3 h. Data from (15)N tests suggest that 2,4-diacetylphloroglucinol blocks amino acid uptake, whereas zearalenone enhances efflux. Thus, amino acid exudation under normal conditions is a phenomenon that probably reflects both active manipulation and passive uptake by microorganisms, as well as diffusion and adsorption to soil, all of which help overcome the innate capacity of plant roots to reabsorb amino acids. The importance of identifying potential enhancers of root exudation lies in understanding that such compounds may represent regulatory linkages between the larger soil food web and the internal carbon metabolism of the plant. (+info)
Media for identification of Gibberella zeae and production of F-2-(Zearalenone).
(20/185)
Media are described for the isolaton of Fusarium graminearum in the perithecial state, Gibberella zeae, and for the production of F-2 (zearalenone) by Fusarium species. On soil extract-corn meal agar isolated medium, G. Zeae produced perithecia in 9 to 14 days under a 12-h photoperiod. Species of Fusarium were screened for F-2 production on a liquid medium. From strains that produced F-2, the yields, from stationary cultures of G. zeae and F. culmorum after 12 days of incubation, ranged from 22 to 86 mg/liter. Three strains produced no F-2. Glumatic acid, starch, yeast extract,and the proper ratio of medium volume-to-flask volume were necessary for F-2 synthesis. (+info)
Effects of prepubertal exposure to xenoestrogen on development of estrogen target organs in female CD-1 mice.
(21/185)
BACKGROUND: There have been no previous reports comparing the effects of prepubertal xenoestrogen exposure on development of the reproductive tract and mammary glands in female mice. The effects of genistein (GEN), resveratrol (RES), zearalenone (ZEA), zeranol (ZER), bisphenol A (BPA) and diethylstilbestrol (DES) were examined. MATERIALS AND METHODS: Beginning at 15 days of age, female CD-1 mice were administered 4 daily subcutaneous injections of 10 mg/kg/day of GEN, RES, ZEA, ZER or BPA, or 10 microg/kg/day of DES dissolved in dimethylsulfoxide (DMSO), or DMSO vehicle. Vaginal opening was checked; estrous cyclicity was monitored from 5, 9 or 21 weeks of age for 21 consecutive days; 6 animals per group were autopsied at 4, 8 and 24 weeks of age. RESULTS: Prepubertal exposure to GEN, ZEA, ZER and DES (but not RES or BPA) accelerated puberty onset (vaginal opening). Vaginal smears indicated that all xenoestrogen-treated mice were cycling, but ZEA-, ZER- and DES-treated mice spent more time in estrus. At 4 weeks of age, absence of corpora lutea (anovulatory ovary) was observed in the untreated controls (33%, 2/6) and the GEN (50%, 3/6), RES (50%, 3/6), ZEA (100%, 6/6), ZER (100%, 6/6), BPA (83%, 5/6) and DES groups (100%, 6/6). At 8 weeks of age, absence of corpora lutea was observed in the ZEA (33%, 2/6) group. Corpora lutea were present in all mice sacrificed at 24 weeks of age. Groups that received prepubertal xenoestrogen injections exhibited no morphological abnormalities of the uterus and vagina, and exhibited mammary gland growth similar to that of the untreated controls at all time-points. CONCLUSION: GEN, ZEA, ZER and DES (but not RES or BPA) caused early vaginal opening; mice exposed to ZEA, ZER or DES spent more time in the estrus phase; ZEA-treated mice had a longer period of anovulatory ovary than other xenoestrogen-treated mice; however, none of the xenoestrogens tested altered the uterine or vaginal morphology or mammary gland growth. (+info)
Zearalenone, deoxynivalenol, and T-2 toxin associated with stalk rot in corn.
(22/185)
The mycotoxins zearalenone (2.8 micrograms/g), deoxynivalenol (1.5 microgram/g), and T-2 toxin (110 ng/g) have been found in the pith of corn stalks standing in the field. Such contaminated stalks may contribute to mycotoxicoses of farm animals. (+info)
Bioactivation of zearalenone by porcine hepatic biotransformation.
(23/185)
Zearalenone (ZEA) is a resorcylic acid lactone derivative produced by various Fusarium species that are widely found in food and feeds. The structure of zearalenone is flexible enough to allow a conformation able to bind to mammalian oestrogen receptors, where it acts as an agonist. Using oestrogen-dependent Human Breast Cancer (MCF-7) cells, the oestrogenic activity of zearalenone and its derivatives were compared using 17 beta-oestradiol as a positive control. The results obtained demonstrate that the oestrogenic potency of ZEA derivatives could be ranked in the following order: alpha-zearalenol > alpha-zearalanol > zearalenone > beta-zearalenol. Since pigs have been reported to be among the most sensitive animal species, biotransformation studies with pig liver subcellular fractions were conducted. These studies indicated that alpha-zearalenol is the main hepatic metabolite of zearalenone in pigs, and it is assumed that 3 alpha- and 3 beta-hydroxysteroid dehydrogeneases are involved in the hepatic biotransformation, since the formation of alpha-zearalenol and beta-zearalenol could be inhibited by prototypic substrates for either enzyme. The bioactivation of ZEA into the more active alpha-zearalenol seems to provide a possible explanation for the observed high sensitivity of pigs towards feeding-stuffs contaminated with the mycotoxin. (+info)
Incidence of zearalenol (Fusarium mycotoxin) in animal feed.
(24/185)
Zearalenol, the reduction product of zearalenone produced by Fusarium roseum growing in cereals, was found for the first time naturally occurring in oats and corn. This metabolite is three to four times more active estrogenically than zearalenone. (+info)