The Metabolic Fate of Deoxynivalenol and Its Acetylated Derivatives in a Wheat Suspension Culture: Identification and Detection of DON-15-O-Glucoside, 15-Acetyl-DON-3-O-Glucoside and 15-Acetyl-DON-3-Sulfate

Distribution and safety evaluation of deoxynivalenol and its derivatives throughout the wheat product processing chain

The distribution of deoxynivalenol (DON) and its derivatives 3-acetyldeoxynivalenol (3-Ac-DON) and 15-acetyldeoxynivalenol (15-Ac-DON) throughout the wheat processing chain were systemically evaluated by one-to-one corresponding studies of the whole processing chain. DON and its derivatives were determined by liquid chromatography-mass spectrometry (LC-MS/MS) in wheat grains and corresponding wheat bran, wheat flour, and semi-finished and finished wheat flour-based products. This investigation showed that wheat grain processing to wheat flour significantly decreased the levels of DON by approximately 52.7%-68.2%. Wheat flour processing of wheat flour-based products decreased the DON concentration by approximately 7.0%-70.6%. Among the processing methods, biscuit making showed the largest reduction (70.6%). The co-occurrence frequency of DON with low levels of 3-Ac-DON and 15-Ac-DON was significantly greater in wheat grains and wheat bran than in wheat flour. For wheat flour-based products, only the distribution pattern of 3-Ac-DON was observable in processed wheat flour products prepared using grains heavily contaminated with DON. In China, to the best of our knowledge, the processing factors (PFs) of DON in wheat flour and wheat flour-based products were systematically evaluated for the first time. The average PF of DON was 0.35 for wheat flour and the average PFs were 0.37-0.84 for wheat flour-based products, with biscuits having the smallest PF (0.37), indicating DON significantly decreasing in biscuit making. Furthermore, dietary exposure assessment of DON indicated an acceptable overall health risk in Chinese consumers, with the highest exposure being observed in infants and young children. This study provides important references for classified management of DON limits in wheat and its various products in China.

Reduction of Fusarium head blight and trichothecene contamination in transgenic wheat expressing Fusarium graminearum trichothecene 3-O-acetyltransferase

Fusarium graminearum, the causal agent of Fusarium head blight (FHB), produces various mycotoxins that contaminate wheat grains and cause profound health problems in humans and animals. Deoxynivalenol (DON) is the most common trichothecene found in contaminated grains. Our previous study showed that Arabidopsis-expressing F. graminearum trichothecene 3-O-acetyltransferase (FgTRI101) converted DON to 3-acetyldeoxynivalenol (3-ADON) and excreted it outside of Arabidopsis cells. To determine if wheat can convert and excrete 3-ADON and reduce FHB and DON contamination, FgTRI101 was cloned and introduced into wheat cv Bobwhite. Four independent transgenic lines containing FgTRI101 were identified. Gene expression studies showed that FgTRI101 was highly expressed in wheat leaf and spike tissues in the transgenic line FgTri101-1606. The seedlings of two FgTri101 transgenic wheat lines (FgTri101-1606 and 1651) grew significantly longer roots than the controls on media containing 5 µg/mL DON; however, the 3-ADON conversion and excretion was detected inconsistently in the seedlings of FgTri101-1606. Further analyses did not detect 3-ADON or other possible DON-related products in FgTri101-1606 seedlings after adding deuterium-labeled DON into the growth media. FgTri101-transgenic wheat plants showed significantly enhanced FHB resistance and lower DON content after they were infected with F. graminearum, but 3-ADON was not detected. Our study suggests that it is promising to utilize FgTRI101, a gene that the fungus uses for self-protection, for managing FHB and mycotoxin in wheat production.

Recalling the reported toxicity assessment of deoxynivalenol, mitigating strategies and its toxicity mechanisms: Comprehensive review

Mycotoxins frequently contaminate a variety of food items, posing significant concerns for both food safety and public health. The adverse consequences linked to poisoning from these substances encompass symptoms such as vomiting, loss of appetite, diarrhea, the potential for cancer development, impairments to the immune system, disruptions in neuroendocrine function, genetic damage, and, in severe cases, fatality. The deoxynivalenol (DON) raises significant concerns for both food safety and human health, particularly due to its potential harm to vital organs in the body. It is one of the most prevalent fungal contaminants found in edible items used by humans and animals globally. The presence of harmful mycotoxins, including DON, in food has caused widespread worry. Altered versions of DON have arisen as possible risks to the environment and well-being, as they exhibit a greater propensity to revert back to the original mycotoxins. This can result in the buildup of mycotoxins in both animals and humans, underscoring the pressing requirement for additional investigation into the adverse consequences of these modified mycotoxins. Furthermore, due to the lack of sufficient safety data, accurately evaluating the risk posed by modified mycotoxins remains challenging. Our review study delves into conjugated forms of DON, exploring its structure, toxicity, control strategies, and a novel animal model for assessing its toxicity. Various toxicities, such as acute, sub-acute, chronic, and cellular, are proposed as potential mechanisms contributing to the toxicity of conjugated forms of DON. Additionally, the study offers an overview of DON's toxicity mechanisms and discusses its widespread presence worldwide. A thorough exploration of the health risk evaluation associated with conjugated form of DON is also provided in this discussion.

Suspect and nontarget screening of mycotoxins and their modified forms in wheat products based on ultrahigh-performance liquid chromatography-high resolution mass spectrometry

Various forms of mycotoxins commonly exist in food and pose a significant risk to human health. Here a comprehensive suspect and nontarget screening strategy for both parent and modified mycotoxins was developed using ultrahigh-performance liquid chromatography-high resolution mass spectrometry (UHPLCHRMS). We constructed an in-house MS/MS database containing 82 mycotoxins in 8 categories. Then fragmentation characteristics of different classes of mycotoxins were rapidly extracted by a Python program "Fragmentation pattern screener (FPScreener)" and nontarget screening rules were determined by analyzing the frequencies and average intensities of fragmentation characteristics. Using the suspect and nontarget screening strategy, we successfully identified six parent mycotoxins and eight modified mycotoxins with different confidence levels in contaminated wheat and flour samples. This strategy enables screening of unknown parents and modified mycotoxins in food matrices with corresponding fragmentation characteristics.

Mechanisms of deoxynivalenol (DON) degradation during different treatments: a review

Deoxynivalenol (DON) is one of the main trichothecenes, that causes health-related issues in humans and animals and imposes considerable financial loss to the food industry each year. Numerous treatments have been reported in the literature on the degradation of DON in food products. These treatments include thermal, chemical, biological/enzymatic, irradiation, light, ultrasound, ozone, and atmospheric cold plasma treatments. Each of these methods has different degradation efficacy and degrades DON by a distinct mechanism, which leads to various degradation byproducts with different toxicity. This manuscript focuses to review the degradation of DON by the aforementioned treatments, the chemical structure and toxicity of the byproducts, and the degradation pathway of DON. Based on the type of treatment, DON can be degraded to norDONs A-F, DON lactones, and ozonolysis products or transformed into de-epoxy deoxynivalenol, DON-3-glucoside, 3-acetyl-DON, 7-acetyl-DON, 15-acetyl-DON, 3-keto-DON, or 3-epi-DON. DON is a major problem for the grain industry and the studies focusing on DON degradation mechanisms could be helpful to select the best method and overcome the DON contamination in grains.

Fast Deoxynivalenol Determination in Cereals Using a White Light Reflectance Spectroscopy Immunosensor

Deoxynivalenol (DON) is a mycotoxin produced by certain Fusarium species and found in a high percentage of wheat and maize grains cultured worldwide. Although not so toxic as other mycotoxins, it exhibits both chronic and acute toxicity, and therefore methods for its fast and accurate on-site determination are highly desirable. In the current work, we employ an optical immunosensor based on White Light Reflectance Spectroscopy (WLRS) for the fast and sensitive immunochemical label-free determination of DON in wheat and maize samples. The assay is completed in 12 min and has a quantification limit of 2.5 ng/mL in buffer corresponding to 125 μg/kg in whole grain which is lower than the maximum allowable concentrations set by the regulatory authorities for grains intended for human consumption. Several extraction protocols have been compared, and the highest recovery (>90%) was achieved employing distilled water. In addition, identical calibration curves were received in buffer and wheat/maize extraction matrix providing the ability to analyze the grain samples using calibrators in buffer. Recoveries of DON from spiked wheat and maize grain samples ranged from 92.0(±4.0) to 105(±4.0)%. The analytical performance of the WLRS immunosensor, combined with the short analysis time and instrument portability, supports its potential for on-site determinations.

Transcriptomic and Exometabolomic Profiling Reveals Antagonistic and Defensive Modes of Clonostachys rosea Action Against Fusarium graminearum

The mycoparasite Clonostachys rosea ACM941 is under development as a biocontrol organism against Fusarium graminearum, the causative agent of Fusarium head blight in cereals. To identify molecular factors associated with this interaction, the transcriptomic and exometabolomic profiles of C. rosea and F. graminearum GZ3639 were compared during coculture. Prior to physical contact, the antagonistic activity of C. rosea correlated with a response heavily dominated by upregulation of polyketide synthase gene clusters, consistent with the detected accumulation of corresponding secondary metabolite products. Similarly, prior to contact, trichothecene gene clusters were upregulated in F. graminearum, while those responsible for fusarielin and fusarin biosynthesis were downregulated, correlating with an accumulation of trichothecene products in the interaction zone over time. A concomitant increase in 15-acetyl deoxynivalenol-3-glucoside in the interaction zone was also detected, with C. rosea established as the source of this detoxified mycotoxin. After hyphal contact, C. rosea was found to predominantly transcribe genes encoding cell wall-degradation enzymes, major facilitator superfamily sugar transporters, anion:cation symporters, as well as alternative carbon source utilization pathways, together indicative of a transition to necrotropism at this stage. F. graminearum notably activated the transcription of phosphate starvation pathway signature genes at this time. Overall, a number of signature molecular mechanisms likely contributing to antagonistic activity by C. rosea against F. graminearum, as well as its mycotoxin tolerance, are identified in this report, yielding several new testable hypotheses toward understanding the basis of C. rosea as a biocontrol agent for continued agronomic development and application.

Stable Isotope-Assisted Metabolomics for Deciphering Xenobiotic Metabolism in Mammalian Cell Culture

Xenobiotics are ubiquitous in the environment and modified in the human body by phase I and II metabolism. Liquid chromatography coupled to high resolution mass spectrometry is a powerful tool to investigate these biotransformation products. We present a workflow based on stable isotope-assisted metabolomics and the bioinformatics tool MetExtract II for deciphering xenobiotic metabolites produced by human cells. Its potential was demonstrated by the investigation of the metabolism of deoxynivalenol (DON), an abundant food contaminant, in a liver carcinoma cell line (HepG2) and a model for colon carcinoma (HT29). Detected known metabolites included DON-3-sulfate, DON-10-sulfonate 2, and DON-10-glutathione as well as DON-cysteine. Conjugation with amino acids and an antibiotic was confirmed for the first time. The approach allows the untargeted elucidation of human xenobiotic products in tissue culture. It may be applied to other fields of research including drug metabolism, personalized medicine, exposome research, and systems biology to better understand the relevance of in vitro experiments.

Modified Fusarium Mycotoxins in Cereals and Their Products-Metabolism, Occurrence, and Toxicity: An Updated Review

Mycotoxins are secondary fungal metabolites, toxic to humans, animals and plants. Under the influence of various factors, mycotoxins may undergo modifications of their chemical structure. One of the methods of mycotoxin modification is a transformation occurring in plant cells or under the influence of fungal enzymes. This paper reviews the current knowledge on the natural occurrence of the most important trichothecenes and zearalenone in cereals/cereal products, their metabolism, and the potential toxicity of the metabolites. Only very limited data are available for the majority of the identified mycotoxins. Most studies concern biologically modified trichothecenes, mainly deoxynivalenol-3-glucoside, which is less toxic than its parent compound (deoxynivalenol). It is resistant to the digestion processes within the gastrointestinal tract and is not absorbed by the intestinal epithelium; however, it may be hydrolysed to free deoxynivalenol or deepoxy-deoxynivalenol by the intestinal microflora. Only one zearalenone derivative, zearalenone-14-glucoside, has been extensively studied. It appears to be more reactive than deoxynivalenol-3-glucoside. It may be readily hydrolysed to free zearalenone, and the carbonyl group in its molecule may be easily reduced to α/β-zearalenol and/or other unspecified metabolites. Other derivatives of deoxynivalenol and zearalenone are poorly characterised. Moreover, other derivatives such as glycosides of T-2 and HT-2 toxins have only recently been investigated; thus, the data related to their toxicological profile and occurrence are sporadic. The topics described in this study are crucial to ensure food and feed safety, which will be assisted by the provision of widespread access to such studies and obtained results.

UDP-Glucosyltransferases from Rice, Brachypodium, and Barley: Substrate Specificities and Synthesis of Type A and B Trichothecene-3-O-β-d-glucosides

Trichothecene toxins are confirmed or suspected virulence factors of various plant-pathogenic Fusarium species. Plants can detoxify these to a variable extent by glucosylation, a reaction catalyzed by UDP-glucosyltransferases (UGTs). Due to the unavailability of analytical standards for many trichothecene-glucoconjugates, information on such compounds is limited. Here, the previously identified deoxynivalenol-conjugating UGTs HvUGT13248 (barley), OsUGT79 (rice) and Bradi5g03300 (Brachypodium), were expressed in E. coli, affinity purified, and characterized towards their abilities to glucosylate the most relevant type A and B trichothecenes. HvUGT13248, which prefers nivalenol over deoxynivalenol, is also able to conjugate C-4 acetylated trichothecenes (e.g., T-2 toxin) to some degree while OsUGT79 and Bradi5g03300 are completely inactive with C-4 acetylated derivatives. The type A trichothecenes HT-2 toxin and T-2 triol are the kinetically preferred substrates in the case of HvUGT13248 and Bradi5g03300. We glucosylated several trichothecenes with OsUGT79 (HT-2 toxin, T-2 triol) and HvUGT13248 (T-2 toxin, neosolaniol, 4,15-diacetoxyscirpenol, fusarenon X) in the preparative scale. NMR analysis of the purified glucosides showed that exclusively β-D-glucosides were formed regio-selectively at position C-3-OH of the trichothecenes. These synthesized standards can be used to investigate the occurrence and toxicological properties of these modified mycotoxins.

Chemical synthesis of culmorin metabolites and their biologic role in culmorin and acetyl-culmorin treated wheat cells

The Fusarium metabolite culmorin (1) is receiving increased attention as an "emerging mycotoxin". It co-occurs with trichothecene mycotoxins and potentially influences their toxicity. Its ecological role and fate in plants is unknown. We synthesized sulfated and glucosylated culmorin conjugates as potential metabolites, which are expected to be formed in planta, and used them as reference compounds. An efficient procedure for the synthesis of culmorin sulfates was developed. Diastereo- and regioselective glucosylation of culmorin (1) was achieved by exploiting or preventing unexpected acyl transfer when using different glucosyl donors. The treatment of a wheat suspension culture with culmorin (1) revealed an in planta conversion of culmorin into culmorin-8-glucoside (6) and culmorin acetate, but no sulfates or culmorin-11-glucoside (7) was found. The treatment of wheat cells with the fungal metabolite 11-acetylculmorin (2) revealed its rapid deacetylation, but also showed the formation of 11-acetylculmorin-8-glucoside (8). These results show that plants are capable of extensively metabolizing culmorin.

Effect of primary processing on the distribution of free and modified Fusarium mycotoxins in naturally contaminated oats

Oat (Avena sativa L.) ranks seventh in the world cereal production and is considered to be an important source for many valuable components of nutritional and biological importance, i.e. proteins, fats, carbohydrates, fibre, minerals and vitamins. Because of these properties the amount of oat used for human consumption has increased progressively during the last years. Unfortunately, the quality of this grain crop is often compromised by mycotoxin contamination, which is relatively ubiquitous despite efforts to control the problem. Therefore, it is important to investigate the distribution pattern of mycotoxins and their conjugated derivatives in contaminated oat grains. For this purpose we have developed a state-of-the-art multi-mycotoxin high-resolution mass spectrometry method and analysed oat samples for their content of the most important mycotoxins commonly occurring in Norwegian cereal grain. Quantitative mapping of selected Fusarium free and modified mycotoxins was performed in fractions collected during processing trials consisting of dehulling and sequential pearling. Both the derivative free mycotoxins and their metabolites were mainly present in the hulls compared to the oat kernel, thus dehulling resulted in a significant reduction of the total mycotoxin load, followed by some further reduction by pearling. Furthermore, free and modified mycotoxins were unevenly distributed in relation to each other throughout the grain fractions, showing a shift towards glucosidated forms, such as deoxynivalenol-3-glucoside and HT-2-3-glucoside in the oat kernel, which highlights potential food safety concerns associated with in planta modified mycotoxins.

Fate of deoxynivalenol and deoxynivalenol-3-glucoside during cereal-based thermal food processing: a review study

Deoxynivalenol (DON), the most commonly occurring trichothecene in nature, may affect animal and human health through causing diarrhea, vomiting, gastrointestinal inflammation, and immunomodulation. DON-3-glucoside (DON-3G) as a major plant metabolite of the mycotoxin is another "emerging" food safety issue in recent years. Humans may experience potential health risks by consuming DON-contaminated food products. Thus, it is crucial for human and animal health to study also the degradation of DON and DON-3G during thermal food processing. Baking, boiling, steaming, frying, and extrusion cooking are commonly used during thermal food processing and have promising effects on the reduction of mycotoxins in food. For DON, however, the observed effects of these methods, as reported in numerous studies, are ambiguous and do not present a clear picture with regard to reduction or transformation. This review summarized the influence of thermal processing on the stability of DON and the formation of degradation/conversion products. Besides this, also a release of DON and DON-3G from food matrix as well as the release of DON from DON-3G during processing is discussed. In addition, some conflicting findings as reported from the studies on thermal processing as well as cause-effect relationships of the different thermal procedures are explored. Finally, the potential toxic profiles of DON degradation products are discussed as well when data are available.

Detoxification of Deoxynivalenol via Glycosylation Represents Novel Insights on Antagonistic Activities of Trichoderma when Confronted with Fusarium graminearum

Deoxynivalenol (DON) is a mycotoxin mainly produced by the Fusarium graminearum complex, which are important phytopathogens that can infect crops and lead to a serious disease called Fusarium head blight (FHB). As the most common B type trichothecene mycotoxin, DON has toxic effects on animals and humans, which poses a risk to food security. Thus, efforts have been devoted to control DON contamination in different ways. Management of DON production by Trichoderma strains as a biological control-based strategy has drawn great attention recently. In our study, eight selected Trichoderma strains were evaluated for their antagonistic activities on F. graminearum by dual culture on potato dextrose agar (PDA) medium. As potential antagonists, Trichoderma strains showed prominent inhibitory effects on mycelial growth and mycotoxin production of F. graminearum. In addition, the modified mycotoxin deoxynivalenol-3-glucoside (D3G), which was once regarded as a detoxification product of DON in plant defense, was detected when Trichoderma were confronted with F. graminearum. The occurrence of D3G in F. graminearum and Trichoderma interaction was reported for the first time, and these findings provide evidence that Trichoderma strains possess a self-protection mechanism as plants to detoxify DON into D3G when competing with F. graminearum.

Higher Fusarium Toxin Accumulation in Grain of Winter Triticale Lines Inoculated with Fusarium culmorum as Compared with Wheat

Resistance to Fusarium head blight in 32 winter triticale and 34 winter wheat accessions was evaluated. Triticale and wheat were sown in field experiments in two locations. At the time of flowering, heads were inoculated with three Fusarium culmorum isolates. Fusarium head blight index was scored and after the harvest percentage of Fusarium damaged kernels was assessed. Grain was analysed for type B trichothecenes (deoxynivalenol and derivatives, nivalenol) and zearalenone (ZEN) content. The average Fusarium head blight indexes were 28.0% for wheat and 19.2% for triticale accessions. The percentage of Fusarium damaged kernels was also higher for wheat and came to 55.6%, while for triticale this figure was 40.2%. The average content of deoxynivalenol (DON) for wheat amounted to 11.65 mg/kg and was lower than the result for triticale which was 14.12 mg/kg. The average contents of nivalenol were similar in both cereals: 4.13 mg/kg and 5.19 mg/kg for wheat and triticale respectively. Considerable amounts of DON derivatives in the cereals were also detected. The ZEN content in the grain was 0.60 mg/kg for wheat and 0.66 mg/kg for triticale. Relationships between Fusarium head blight index, Fusarium damaged kernels and mycotoxin contents were statistically significant for wheat and mostly insignificant for triticale. Triticale proved to have less infected heads and kernels than wheat. However, the content of type B trichothecenes was higher in triticale grain than in wheat grain.

Identification of a novel human deoxynivalenol metabolite enhancing proliferation of intestinal and urinary bladder cells

The mycotoxin deoxynivalenol (DON) is an abundant contaminant of cereal based food and a severe issue for global food safety. We report the discovery of DON-3-sulfate as a novel human metabolite and potential new biomarker of DON exposure. The conjugate was detectable in 70% of urine samples obtained from pregnant women in Croatia. For the measurement of urinary metabolites, a highly sensitive and selective LC-MS/MS method was developed and validated. The method was also used to investigate samples from a duplicate diet survey for studying the toxicokinetics of DON-3-sulfate. To get a preliminary insight into the biological relevance of the newly discovered DON-sulfates, in vitroexperiments were performed. In contrast to DON, sulfate conjugates lacked potency to suppress protein translation. However, surprisingly we found that DON-sulfates enhanced proliferation of human HT-29 colon carcinoma cells, primary human colon epithelial cells (HCEC-1CT) and, to some extent, also T24 bladder cancer cells. A proliferative stimulus, especially in tumorigenic cells raises concern on the potential impact of DON-sulfates on consumer health. Thus, a further characterization of their toxicological relevance should be of high priority.

Hydrolytic Fate of 3/15-Acetyldeoxynivalenol in Humans: Specific Deacetylation by the Small Intestine and Liver Revealed Using in Vitro and ex Vivo Approaches

In addition to deoxynivalenol (DON), acetylated derivatives, i.e., 3-acetyl and 15-acetyldexynivalenol (or 3/15ADON), are present in cereals leading to exposure to these mycotoxins. Animal and human studies suggest that 3/15ADON are converted into DON after their ingestion through hydrolysis of the acetyl moiety, the site(s) of such deacetylation being still uncharacterized. We used in vitro and ex vivo approaches to study the deacetylation of 3/15ADON by enzymes and cells/tissues present on their way from the food matrix to the blood in humans. We found that luminal deacetylation by digestive enzymes and bacteria is limited. Using human cells, tissues and S9 fractions, we were able to demonstrate that small intestine and liver possess strong deacetylation capacity compared to colon and kidneys. Interestingly, in most cases, deacetylation was more efficient for 3ADON than 15ADON. Although we initially thought that carboxylesterases (CES) could be responsible for the deacetylation of 3/15ADON, the use of pure human CES1/2 and of CES inhibitor demonstrated that CES are not involved. Taken together, our original model system allowed us to identify the small intestine and the liver as the main site of deacetylation of ingested 3/15ADON in humans.

Relationship between Fusarium spp. diversity and mycotoxin contents of mature grains in southern Belgium

Over a 4-year period (2010-13), a survey aiming at determining the occurrence of Fusarium spp. and their relations to mycotoxins in mature grains took place in southern Belgium. The most prevalent species were F. graminearum, F. avenaceum, F. poae and F. culmorum, with large variations between years and locations. An even proportion of mating type found for F. avenaceum, F. culmorum, F. cerealis and F. tricinctum is usually a sign of ongoing sexual recombination. In contrast, an unbalanced proportion of mating type was found for F. poae and no MAT1-2 allele was present in the F. langsethiae population. Genetic chemotyping indicates a majority of deoxynivalenol (DON)-producing strains in F. culmorum (78%, all 3-ADON producers) and F. graminearum (95%, mostly 15-ADON producers), while all F. cerealis strains belong to the nivalenol (NIV) chemotype. Between 2011 and 2013, DON, NIV, enniatins (ENNs) and moniliformin (MON) were found in each field in various concentrations. By comparison, beauvericin (BEA) was scarcely detected and T-2 toxin, zearalenone and α- and β-zearalenols were never detected. Principal component analysis revealed correlations of DON with F. graminearum, ENNs and MON with F. avenaceum and NIV with F. culmorum, F. cerealis and F. poae. BEA was associated with the presence of F. tricinctum and, to a lesser extent, with the presence of F. poae. The use of genetic chemotype data revealed that DON concentrations were mostly influenced by DON-producing strains of F. graminearum and F. culmorum, whereas the concentrations of NIV were influenced by the number of NIV-producing strains of both species added to the number of F. cerealis and F. poae strains. This study emphasises the need to pay attention to less-studied Fusarium spp. for future Fusarium head blight management strategies, as they commonly co-occur in the field and are associated with a broad spectrum of mycotoxins.

Identification and Characterization of Carboxylesterases from Brachypodium distachyon Deacetylating Trichothecene Mycotoxins

Increasing frequencies of 3-acetyl-deoxynivalenol (3-ADON)-producing strains of Fusarium graminearum (3-ADON chemotype) have been reported in North America and Asia. 3-ADON is nearly nontoxic at the level of the ribosomal target and has to be deacetylated to cause inhibition of protein biosynthesis. Plant cells can efficiently remove the acetyl groups of 3-ADON, but the underlying genes are yet unknown. We therefore performed a study of the family of candidate carboxylesterases (CXE) genes of the monocot model plant Brachypodium distachyon. We report the identification and characterization of the first plant enzymes responsible for deacetylation of trichothecene toxins. The product of the BdCXE29 gene efficiently deacetylates T-2 toxin to HT-2 toxin, NX-2 to NX-3, both 3-ADON and 15-acetyl-deoxynivalenol (15-ADON) into deoxynivalenol and, to a lesser degree, also fusarenon X into nivalenol. The BdCXE52 esterase showed lower activity than BdCXE29 when expressed in yeast and accepts 3-ADON, NX-2, 15-ADON and, to a limited extent, fusarenon X as substrates. Expression of these Brachypodium genes in yeast increases the toxicity of 3-ADON, suggesting that highly similar genes existing in crop plants may act as susceptibility factors in Fusarium head blight disease.