Detoxification of the Fusarium mycotoxin deoxynivalenol by a UDP-glucosyltransferase from Arabidopsis thaliana

Priority actions for Fusarium head blight resistance in durum wheat: Insights from the wheat initiative

Fusarium head blight (FHB), mainly caused by Fusarium graminearum and Fusarium culmorum, is a major wheat disease. Significant efforts have been made to improve resistance to FHB in bread wheat (Triticum aestivum), but more work is needed for durum wheat (Triticum turgidum spp. durum). Bread wheat has ample genetic variation for resistance breeding, which can be readily exploited, while durum wheat is characterized by higher disease susceptibility and fewer valuable resistance sources. The Wheat Initiative - Expert Working Group on Durum Wheat Genomics and Breeding has promoted a scientific discussion to define the key actions that should be prioritized for achieving resistance in durum wheat comparable to that found in bread wheat. Here, a detailed state of the art and novel tools to improve FHB resistance in durum are presented, together with a perspective on the next steps forward. A meta-analysis grouping all quantitative trait loci (QTL) associated with FHB resistance in both bread and durum wheat has been conducted to identify hotspot regions that do not overlap with Rht alleles, which are known to negatively correlate with FHB resistance. A detailed list of QTL related to FHB resistance and deoxynivalenol contamination and durum lines carrying different sources of FHB resistance are provided as a strategic resource. QTL, closely linked markers and durum wheat lines carrying the useful alleles, can be selected to design an effective breeding program. Finally, we highlight the priority actions that should be implemented to achieve satisfactory resistance to FHB in durum wheat.

Insights into functional divergence, catalytic versatility and specificity of small molecule glycosyltransferases

Glycosylation is one of the most fundamental biochemical processes in cells. It plays crucial roles in diversifying plant natural products for structures, bioavailability and bioactivity, and thus, renders the glycosylated compounds valuable as food additives, nutraceuticals and pharmaceuticals. Moreover, glycosylated compounds impact plant growth, development and stress response. Therefore, understanding the biochemical function of the glycosyltransferases (GTs) is crucial to the elucidation of natural product biosynthetic pathways, improving plant traits and development of processes for industrially-important compounds. UDP-dependent glycosyltransferases (UGTs) that belong to the glycosyltransferase family-1 (GT1) and catalyze the transfer of glycosyl moieties from UDP-sugars to various small molecules, are the key players in natural product glycosylation. Recent studies also found the involvement of non-canonical cellulose synthase-like (CesAs) and glycosyl hydrolase (GH) family enzymes in the glycosylation of plant specialized metabolites. Decades of research on GTs provided critical insights into catalytic mechanism, substrate/product specificity and catalytic promiscuity, but biochemical function and physiological roles of GTs in majority of the natural product biosynthetic pathways remain to be understood. It is also important to redefine high-throughput strategies of GT mining to uncover novel biochemical function, considering that GTs are the large superfamily members in plants and other organisms. This review underscores the roles of GTs in small molecule glycosylation, plant development and stress responses, highlighting the catalytic versatility and substrate/product specificity of GTs in shaping plant metabolic diversity, and discusses the emerging strategies for mining of uncharacterized GTs to unravel biochemical and physiological functions and to elucidate natural product biosynthetic pathways.

Identification and characterization of Morganella morganii strain YC12-C3 and Enterococcus faecalis strain YC12-C10 and elucidation of its deoxynivalenol-degrading potential

Deoxynivalenol ( DON) is one of the most harmful mycotoxins in food or feed or Traditional Chinese Medicine. An efficient and applicable method for the detoxification of DON is urgently developed. 1152 strains were isolated from the intestinal contents of crucian. Morganella morganii YC12-C3 and Enterococcus faecalis YC12-C10 were screened with the highest degradation rate of DON via HPLC methods. The optimal degradation condition of YC12-C3 and YC12-C10 is co-cultured 24 h and 36 h at 28 ℃ in LB medium with pH 7 and 1.0% inoculation dosage, respectively. LC-MS/MS and 1H NMR results show that YC12-C10 and YC12-C3 can transform DON to 3-deoxy-6-demethanol-DON, a new metabolite biotransformed from DON, by deoxidization at C3 hydroxy and de-methanal reaction at methanol moiety of C6. In addition, the DON-degradation in agricultural material assay showed that YC12-C10 and YC12-C3 can degrade 150 μg·kg-1 DON in Coix lacryma-jobi, with a degradation rate of 68.89% and 59.94%, respectively. This result shows that YC12-C10 and YC12-C3 have a sound efficiency in removing DON ability in Coix lacryma-jobi, providing a new strain resource and application technique for biological detoxification of DON in food or feed or TCM industry.

Characterization of deoxynivalenol dehydrogenase from Pelagibacterium sp. SCN 63-126 and its application

Deoxynivalenol (DON), a type-B trichothecene mycotoxin, is primarily produced by Fusarium species and widely pollutes wheat and other grains. Enzymatic treatment of DON has been widely studied in recent years. Here, we present the biochemical identification of the DON dehydrogenase from Pelagibacterium sp. SCN 63-126 (Pe DDH). After removing the signal peptide, Pe DDH is effectively expressed in its soluble form. Biochemical identification indicates that the optimal temperature and pH of Pe DDH against DON is 35 ℃ and pH 8.5. Furthermore, Pe DDH is activated significantly in the presence of Ca2+, Mg2+, and Cu2+, and alternatively activated by pyrroloquinoline quinone (PQQ), phenazine methosulfate (PMS), and 2, 6-dichlorophenolindophenol (DCPIP). When PQQ, PMS, and DCPIP are combined, Pe DDH (60 µg/mL) effectively degrads DON (150 µM) in just 5 min, suggesting a synergistic effect of three cofactors on DON degradation. All these results suggest a great potential of Pe DDH in the control of DON contamination.

Occurrence of modified mycotoxins in Latin America: an up-to-date review

The Latin America region has a considerable extent of varied climate conditions: from tropical, subtropical, and warm temperate to temperate. Among the surface territory, different agricultural products are produced, making them an important food source for human consumption. Fungal species commonly colonize those important agricultural products and often contaminate them with mycotoxins that have a major impact on health, welfare, and productivity. Nowadays, special attention is paid to modified mycotoxins, which are those that cannot be detected by conventional analytical methods. However, little data about their natural occurrence in food and feed is available, especially in Latin American countries, where, among all the countries in this region, only a few of them are working on this subject. Thus, the present review summarizes the published information available in order to determine the possible human exposure risk to these toxins.

Selective biotic stressors' action on seed germination: A review

In the realm of plant biology and agriculture, seed germination serves as a fundamental process with far-reaching implications for crop production and environmental health. This comprehensive review seeks to unravel the intricate web of interactions between some biotic stressors and seed germination, addressing the pertinent issue of how these stressors influence seed germination. Different chemicals produced by interacting plants (different parts), fungi, bacteria, or insects can either promote or inhibit seed germination. Releasing chemicals that modulate signaling pathways and cellular processes significantly disrupt essential cellular functions. This disruption leads to diverse germination outcomes, introducing additional layers of complexity to this regulatory landscape. The chemicals perturb enzyme activity and membrane integrity, imposing unique challenges on the germination process. Understanding the mechanisms- how allelochemicals, mycotoxins, or bacterial toxins affect seed germination or the modes of action holds promise for more sustainable agricultural practices, enhanced pest control, and improved environmental outcomes. In sum, this review contributes to a fundamental exposition of the pivotal role of biotic stressors in shaping the germination of seeds.

Detoxifying bacterial genes for deoxynivalenol epimerization confer durable resistance to Fusarium head blight in wheat

Fusarium head blight (FHB) and the presence of mycotoxin deoxynivalenol (DON) pose serious threats to wheat production and food safety worldwide. DON, as a virulence factor, is crucial for the spread of FHB pathogens on plants. However, germplasm resources that are naturally resistant to DON and DON-producing FHB pathogens are inadequate in plants. Here, detoxifying bacteria genes responsible for DON epimerization were used to enhance the resistance of wheat to mycotoxin DON and FHB pathogens. We characterized the complete pathway and molecular basis leading to the thorough detoxification of DON via epimerization through two sequential reactions in the detoxifying bacterium Devosia sp. D6-9. Epimerization efficiently eliminates the phytotoxicity of DON and neutralizes the effects of DON as a virulence factor. Notably, co-expressing of the genes encoding quinoprotein dehydrogenase (QDDH) for DON oxidation in the first reaction step, and aldo-keto reductase AKR13B2 for 3-keto-DON reduction in the second reaction step significantly reduced the accumulation of DON as virulence factor in wheat after the infection of pathogenic Fusarium, and accordingly conferred increased disease resistance to FHB by restricting the spread of pathogenic Fusarium in the transgenic plants. Stable and improved resistance was observed in greenhouse and field conditions over multiple generations. This successful approach presents a promising avenue for enhancing FHB resistance in crops and reducing mycotoxin contents in grains through detoxification of the virulence factor DON by exogenous resistance genes from microbes.

Expression of endogenous UDP-glucosyltransferase in endophyte Phomopsis liquidambaris reduces deoxynivalenol contamination in wheat

Fusarium head blight is a devastating disease that causes severe yield loses and mycotoxin contamination in wheat grain. Additionally, balancing the trade-off between wheat production and disease resistance has proved challenging. This study aimed to expand the genetic tools of the endophyte Phomopsis liquidambaris against Fusarium graminearum. Specifically, we engineered a UDP-glucosyltransferase-expressing P. liquidambaris strain (PL-UGT) using ADE1 as a selection marker and obtained a deletion mutant using an inducible promoter that drives Cas9 expression. Our PL-UGT strain converted deoxynivalenol (DON) into DON-3-G in vitro at a rate of 71.4 % after 36 h. DON inactivation can be used to confer tolerance in planta. Wheat seedlings inoculated with endophytic strain PL-UGT showed improved growth compared with those inoculated with wildtype P. liquidambaris. Strain PL-UGT inhibited the growth of Fusarium graminearum and reduced infection rate to 15.7 %. Consistent with this finding, DON levels in wheat grains decreased from 14.25 to 0.56 μg/g when the flowers were pre-inoculated with PL-UGT and then infected with F. graminearum. The expression of UGT in P. liquidambaris was nontoxic and did not inhibit plant growth. Endophytes do not enter the seeds nor induce plant disease, thereby representing a novel approach to fungal disease control.

O-Glycosyltransferase Gene BnaC09.OGT Involved in Regulation of Unsaturated Fatty Acid Biosynthesis for Enhancing Osmotic Stress Tolerance in Brassica napus L

Osmotic stress is a major threaten to the growth and yield stability of Brassica napus. Post-translational modification with O-linked β-N-acetylglucosamine (O-GlcNAc) is ubiquitous in plants, and participates in a variety of signal transduction and metabolic regulation. However, studies on the role of O-GlcNAc transferase (OGT) in osmotic stress tolerance of plants are limited. In previous study, a O-glycosyltransferase, named BnaC09.OGT, was identified from the B. napus variety 'Zhongshuang 11' by yeast one hybrid with promoter of BnaA01.GPAT9. It was found that BnaC09.OGT localized in both nucleus and cytoplasm. The spatiotemporal expression pattern of BnaC09.OGT exhibited tissue specificity in developmental seed, especially in 15 days after pollination. In view of osmotic stress inducing, the BnaC09.OGT overexpression and knockout transgenic lines were constructed for biological function study. Phenotypic analysis of BnaC09.OGT overexpression seedlings demonstrated that BnaC09.OGT could enhance osmotic stress tolerance than WT and knockout lines in euphylla stage under 15% PEG6000 treatment after 7 days. In addition, compared with WT and knockout lines, overexpression of BnaC09.OGT had significantly higher activities of antioxidant enzymes (SOD and POD), higher content of soluble saccharide, and while significantly less content of malondialdehyde, proline and anthocyanidin under 15% PEG6000 treatment after 7 days. On the other hand, the unsaturated fatty acid content of BnaC09.OGT overexpression was significantly higher than that of WT and knockout lines, so it is speculated that the BnaC09.OGT could increase unsaturated fatty acid biosynthesis for osmotic stress tolerance by promoting the expression of BnaA01.GPAT9 in glycerolipid biosynthesis. In summary, the above results revealed that the function of BnaC09.OGT provides new insight for the analysis of the pathway of O-glycosylation in regulating osmotic stress tolerance in B. napus.

Oerskovia flava sp. nov., a deoxynivalenol (DON)-degrading actinomycete isolated from the rhizosphere soil of long-term continuous cropping cucumber

The deoxynivalenol (DON)-degrading bacterium JB1-3-2 T was isolated from a rhizosphere soil sample of cucumber collected from a greenhouse located in Zhenjiang, Eastern China. The JB1-3-2 T strain is a Gram-stain-positive, nonmotile and round actinomycete. Growth was observed at temperatures between 15 and 40 ℃ (optimum, 35 ℃), in the presence of 15% (w/v) NaCl (optimum, 3%), and at pH 3 and 11 (optimum, 7). The major cellular fatty acids identified were anteiso-C15:0, iso-C16:0 and anteiso-C17:0. Genome sequencing revealed a genome size of 4.11 Mb and a DNA G + C content of 72.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the JB1-3-2 T strain was most closely related to type strains of the Oerskovia species, with the highest sequence similarity to Oerskovia turbata NRRL B-8019 T (98.2%), and shared 98.1% sequence identity with other valid type strains of this genus. Digital DNA‒DNA hybridization (dDDH) and average nucleotide identity (ANI) showed 21.8-22.2% and 77.2-77.3% relatedness, respectively, between JB1-3-2 T and type strains of the genus Oerskovia. Based on genotypic, phylogenetic, chemotaxonomic, physiological and biochemical characterization, Oerskovia flava, a novel species in the genus Oerskovia, was proposed, and the type strain was JB1-3-2 T (= CGMCC 1.18555 T = JCM 35248 T). Additionally, this novel strain has a DON degradation ability that other species in the genus Oerskovia do not possess, and glutathione-S-transferase was speculated to be the key enzyme for strain JB1-3-2 T to degrade DON.

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.

Phyllosphere bacterial community dynamics in response to bacterial wildfire disease: succession and interaction patterns

Plants interact with complex microbial communities in which microorganisms play different roles in plant development and health. While certain microorganisms may cause disease, others promote nutrient uptake and resistance to stresses through a variety of mechanisms. Developing plant protection measures requires a deeper comprehension of the factors that influence multitrophic interactions and the organization of phyllospheric communities. High-throughput sequencing was used in this work to investigate the effects of climate variables and bacterial wildfire disease on the bacterial community's composition and assembly in the phyllosphere of tobacco (Nicotiana tabacum L.). The samples from June (M1), July (M2), August (M3), and September (M4) formed statistically separate clusters. The assembly of the whole bacterial population was mostly influenced by stochastic processes. PICRUSt2 predictions revealed genes enriched in the M3, a period when the plant wildfire disease index reached climax, were associated with the development of the wildfire disease (secretion of virulence factor), the enhanced metabolic capacity and environmental adaption. The M3 and M4 microbial communities have more intricate molecular ecological networks (MENs), bursting with interconnections within a densely networked bacterial population. The relative abundances of plant-beneficial and antagonistic microbes Clostridiales, Bacillales, Lactobacillales, and Sphingobacteriales, showed significant decrease in severally diseased sample (M3) compared to the pre-diseased samples (M1/M2). Following the results of MENs, we further test if the correlating bacterial pairs within the MEN have the possibility to share functional genes and we have unraveled 139 entries of such horizontal gene transfer (HGT) events, highlighting the significance of HGT in shaping the adaptive traits of plant-associated bacteria across the MENs, particularly in relation to host colonization and pathogenicity.

Analysis of the UDP-Glucosyltransferase (UGT) Gene Family and Its Functional Involvement in Drought and Salt Stress Tolerance in Phoebe bournei

Uridine diphosphate glycosyltransferases (UDP-GTs, UGTs), which are regulated by UGT genes, play a crucial role in glycosylation. In vivo, the activity of UGT genes can affect the availability of metabolites and the rate at which they can be eliminated from the body. UGT genes can exert their regulatory effects through mechanisms such as post-transcriptional modification, substrate subtype specificity, and drug interactions. Phoebe bournei is an economically significant tree species that is endemic to southern China. Despite extensive studies on the UGT gene family in various species, a comprehensive investigation of the UGT family in P. bournei has not been reported. Therefore, we conducted a systematic analysis to identify 156 UGT genes within the entire P. bournei genome, all of which contained the PSPG box. The PbUGT family consists of 14 subfamilies, consistent with Arabidopsis thaliana. We observed varying expression levels of PbUGT genes across different tissues in P. bournei, with the following average expression hierarchy: leaf > stem xylem > stem bark > root xylem > root bark. Covariance analysis revealed stronger covariance between P. bournei and closely related species. In addition, we stressed the seedlings with 10% NaCl and 10% PEG-6000. The PbUGT genes exhibited differential expression under drought and salt stresses, with specific expression patterns observed under each stress condition. Our findings shed light on the transcriptional response of PbUGT factors to drought and salt stresses, thereby establishing a foundation for future investigations into the role of PbUGT transcription factors.

Similarities in Structure and Function of UDP-Glycosyltransferase Homologs from Human and Plants

The uridine diphosphate glycosyltransferase (UGT) superfamily plays a key role in the metabolism of xenobiotics and metabolic wastes, which is essential for detoxifying those species. Over the last several decades, a huge effort has been put into studying human and mammalian UGT homologs, but family members in other organisms have been explored much less. Potentially, other UGT homologs can have desirable substrate specificity and biological activities that can be harnessed for detoxification in various medical settings. In this review article, we take a plant UGT homology, UGT71G1, and compare its structural and biochemical properties with the human homologs. These comparisons suggest that even though mammalian and plant UGTs are functional in different environments, they may support similar biochemical activities based on their protein structure and function. The known biological functions of these homologs are discussed so as to provide insights into the use of UGT homologs from other organisms for addressing human diseases related to UGTs.

Discovering New Substrates of a UDP-Glycosyltransferase with a High-Throughput Method

UDP-glycosyltransferases (UGTs) form a large enzyme family that is found in a wide range of organisms. These enzymes are known for accepting a wide variety of substrates, and they derivatize xenobiotics and metabolites for detoxification. However, most UGT homologs have not been well characterized, and their potential for biomedical and environmental applications is underexplored. In this work, we have used a fluorescent assay for screening substrates of a plant UGT homolog by monitoring the formation of UDP. We optimized the assay such that it could be used for high-throughput screening of substrates of the Medicago truncatula UGT enzyme, UGT71G1, and our results show that 34 of the 159 screened compound samples are potential substrates. With an LC-MS/MS method, we confirmed that three of these candidates indeed were glycosylated by UGT71G1, which includes bisphenol A (BPA) and 7-Ethyl-10-hydroxycamptothecin (SN-38); derivatization of these toxic compounds can lead to new environmental and medical applications. This work suggests that UGT homologs may recognize a substrate profile that is much broader than previously anticipated. Additionally, it demonstrates that this screening method provides a new means to study UDP-glycosyltransferases, facilitating the use of these enzymes to tackle a wide range of problems.

Enzymatic Degradation of Deoxynivalenol with the Engineered Detoxification Enzyme Fhb7

In the era of global climate change, the increasingly severe Fusarium head blight (FHB) and deoxynivalenol (DON) contamination have caused economic losses and brought food and feed safety concerns. Recently, an FHB resistance gene Fhb7 coding a glutathione-S transferase (GST) to degrade DON by opening the critical toxic epoxide moiety was identified and opened a new window for wheat breeding and DON detoxification. However, the poor stability of Fhb7 and the elusiveness of the catalytic mechanism hinder its practical application. Herein, we report the first structure of Fhb7 at 2.41 Å and reveal a unique catalytic mechanism of epoxide opening transformation in GST family proteins. Furthermore, variants V29P and M10 showed that 5.5-fold and 266.7-fold longer half-life time than wild-type, respectively, were identified. These variants offer broad substrate scope, and the engineered biosafe Bacillus subtilis overexpressing the variants shows excellent DON degradation performance, exhibiting potential at bacterium engineering to achieve DON detoxification in the feed and biomedicine industry. This work provides a profound mechanistic insight into the enzymatic activities of Fhb7 and paves the way for further utilizing Fhb7-related enzymes in crop breeding and DON detoxification by synthetic biology.

Development of a fumonisin-sensitive Saccharomyces cerevisiae indicator strain and utilization for activity testing of candidate detoxification genes

IMPORTANCE

Fumonisins can cause diseases in animals and humans consuming Fusarium-contaminated food or feed. The search for microbes capable of fumonisin degradation, or for enzymes that can detoxify fumonisins, currently relies primarily on chemical detection methods. Our constructed fumonisin B1-sensitive yeast strain can be used to phenotypically detect detoxification activity and should be useful in screening for novel fumonisin resistance genes and to elucidate fumonisin metabolism and resistance mechanisms in fungi and plants, and thereby, in the long term, help to mitigate the threat of fumonisins in feed and food.

Update on the state of research to manage Fusarium head blight

Fusarium head blight (FHB) is one of the most devastating diseases of cereal crops, causing severe reduction in yield and quality of grain worldwide. In the United States, the major causal agent of FHB is the mycotoxigenic fungus, Fusarium graminearum. The contamination of grain with mycotoxins, including deoxynivalenol and zearalenone, is a particularly serious concern due to its impact on the health of humans and livestock. For the past few decades, multidisciplinary studies have been conducted on management strategies designed to reduce the losses caused by FHB. However, effective management is still challenging due to the emergence of fungicide-tolerant strains of F. graminearum and the lack of highly resistant wheat and barley cultivars. This review presents multidisciplinary approaches that incorporate advances in genomics, genetic-engineering, new fungicide chemistries, applied biocontrol, and consideration of the disease cycle for management of FHB.

Mechanisms by which microbial enzymes degrade four mycotoxins and application in animal production: A review

Mycotoxins are toxic compounds that pose a serious threat to animal health and food safety. Therefore, there is an urgent need for safe and efficient methods of detoxifying mycotoxins. As biotechnology has continued to develop, methods involving biological enzymes have shown great promise. Biological enzymatic methods, which can fundamentally destroy the structures of mycotoxins and produce degradation products whose toxicity is greatly reduced, are generally more specific, efficient, and environmentally friendly. Mycotoxin-degrading enzymes can thus facilitate the safe and effective detoxification of mycotoxins which gives them a huge advantage over other methods. This article summarizes the newly discovered degrading enzymes that can degrade four common mycotoxins (aflatoxins, zearalenone, deoxynivalenol, and ochratoxin A) in the past five years, and reveals the degradation mechanism of degrading enzymes on four mycotoxins, as well as their positive effects on animal production. This review will provide a theoretical basis for the safe treatment of mycotoxins by using biological enzyme technology.

UDP-glucosyltransferase HvUGT13248 confers type II resistance to Fusarium graminearum in barley

Fusarium head blight (FHB) of barley (Hordeum vulgare) causes yield losses and accumulation of trichothecene mycotoxins (e.g. deoxynivalenol [DON]) in grains. Glucosylation of DON to the nontoxic DON-3-O-glucoside (D3G) is catalyzed by UDP-glucosyltransferases (UGTs), such as barley UGT13248. We explored the natural diversity of UGT13248 in 496 barley accessions and showed that all carried potential functional alleles of UGT13248, as no genotypes showed strongly increased seedling sensitivity to DON. From a TILLING population, we identified 2 mutant alleles (T368I and H369Y) that, based on protein modeling, likely affect the UDP-glucose binding of UGT13248. In DON feeding experiments, DON-to-D3G conversion was strongly reduced in spikes of these mutants compared to controls, and plants overexpressing UGT13248 showed increased resistance to DON and increased DON-to-D3G conversion. Moreover, field-grown plants carrying the T368I or H369Y mutations inoculated with Fusarium graminearum showed increased FHB disease severity and reduced D3G production. Barley is generally considered to have type II resistance that limits the spread of F. graminearum from the infected spikelet to adjacent spikelets. Point inoculation experiments with F. graminearum showed increased infection spread in T368I and H369Y across the spike compared to wild type, while overexpression plants showed decreased spread of FHB symptoms. Confocal microscopy revealed that F. graminearum spread to distant rachis nodes in T368I and H369Y mutants but was arrested at the rachis node of the inoculated spikelet in wild-type plants. Taken together, our data reveal that UGT13248 confers type II resistance to FHB in barley via conjugation of DON to D3G.

Meta-QTL analysis in wheat: progress, challenges and opportunities

Wheat, an important cereal crop globally, faces major challenges due to increasing global population and changing climates. The production and productivity are challenged by several biotic and abiotic stresses. There is also a pressing demand to enhance grain yield and quality/nutrition to ensure global food and nutritional security. To address these multifaceted concerns, researchers have conducted numerous meta-QTL (MQTL) studies in wheat, resulting in the identification of candidate genes that govern these complex quantitative traits. MQTL analysis has successfully unraveled the complex genetic architecture of polygenic quantitative traits in wheat. Candidate genes associated with stress adaptation have been pinpointed for abiotic and biotic traits, facilitating targeted breeding efforts to enhance stress tolerance. Furthermore, high-confidence candidate genes (CGs) and flanking markers to MQTLs will help in marker-assisted breeding programs aimed at enhancing stress tolerance, yield, quality and nutrition. Functional analysis of these CGs can enhance our understanding of intricate trait-related genetics. The discovery of orthologous MQTLs shared between wheat and other crops sheds light on common evolutionary pathways governing these traits. Breeders can leverage the most promising MQTLs and CGs associated with multiple traits to develop superior next-generation wheat cultivars with improved trait performance. This review provides a comprehensive overview of MQTL analysis in wheat, highlighting progress, challenges, validation methods and future opportunities in wheat genetics and breeding, contributing to global food security and sustainable agriculture.

Bamboo polysaccharides elicit hypocrellin A biosynthesis of a bambusicolous fungus Shiraia sp. S9

Hypocrellin A (HA), a fungal perylenequinone from bambusicolous Shiraia species, is a newly developed photosensitizer for photodynamic therapy in cancer and other infectious diseases. The lower yield of HA is an important bottleneck for its biomedical application. This study is the first report of the enhancement of HA production in mycelium culture of Shiraia sp. S9 by the polysaccharides from its host bamboo which serve as a strong elicitor. A purified bamboo polysaccharide (BPSE) with an average molecular weight of 34.2 kDa was found to be the most effective elicitor to enhance fungal HA production and characterized as a polysaccharide fraction mainly composed of arabinose and galactose (53.7: 36.9). When BPSE was added to the culture at 10 mg/L on day 3, the highest HA production of 422.8 mg/L was achieved on day 8, which was about 4.0-fold of the control. BPSE changed the gene expressions mainly responsible for central carbon metabolism and the cellular oxidative stress. The induced generation of H2O2 and nitric oxide was found to be involved in both the permeabilization of cell membrane and HA biosynthesis, leading to enhancements in both intra- and extracellular HA production. Our results indicated the roles of plant polysaccharides in host-fungal interactions and provided a new elicitation technique to improve fungal perylenequinone production in mycelium cultures.

The Fusarium graminearum Transporters Abc1 and Abc6 Are Important for Xenobiotic Resistance, Trichothecene Accumulation, and Virulence to Wheat

The plant pathogenic fungus Fusarium graminearum is the causal agent of Fusarium head blight (FHB) disease on small-grain cereals. F. graminearum produces trichothecene mycotoxins such as deoxynivalenol (DON) that are required for full virulence. DON must be exported outside the cell to cause FHB disease, a process that may require the involvement of membrane-bound transporters. In this study, we show that the deletion of membrane-bound transporters results in reduced DON accumulation as well as reduced FHB symptoms on wheat. Deletion of the ATP-binding cassette (ABC) transporter gene Abc1 results in the greatest reduction in DON accumulation and virulence. Deletion of another ABC transporter gene, Abc6, also reduces FHB symptoms to a lesser degree. Combining deletions fails to reduce DON accumulation or virulence in an additive fashion, even when a ∆abc1 deletion is included. Heterologous expression of F. graminearum transporters in a DON-sensitive strain of yeast confirms Abc1 as a major DON resistance mechanism; furthermore, it suggests that Abc1 is directly participating in DON transport rather than facilitating DON transport though other means. Yeast expression further indicates that multiple transporters, including Abc1, play an important role in resistance to the wheat phytoalexin 2-benzoxazolinone (BOA) and other xenobiotics. Thus, Abc1 may contribute to virulence on wheat both by facilitating export of DON and by providing resistance to the wheat phytoalexin BOA. This research provides useful information that may aid in designing novel management techniques of FHB or other destructive plant diseases.

The function of UDP-glycosyltransferases in plants and their possible use in crop protection

Glycosyltransferases catalyse the transfer of a glycosyl moiety from a donor to an acceptor. Members of this enzyme class are ubiquitous throughout all kingdoms of life and are involved in the biosynthesis of countless types of glycosides. Family 1 glycosyltransferases, also referred to as uridine diphosphate-dependent glycosyltransferases (UGTs), glycosylate small molecules such as secondary metabolites and xenobiotics. In plants, UGTs are recognised for their multiple functionalities ranging from roles in growth regulation and development, in protection against pathogens and abiotic stresses and in adaptation to changing environments. In this study, we review UGT-mediated glycosylation of phytohormones, endogenous secondary metabolites, and xenobiotics and contextualise the role this chemical modification plays in the response to biotic and abiotic stresses and plant fitness. Here, the potential advantages and drawbacks of altering the expression patterns of specific UGTs along with the heterologous expression of UGTs across plant species to improve stress tolerance in plants are discussed. We conclude that UGT-based genetic modification of plants could potentially enhance agricultural efficiency and take part in controlling the biological activity of xenobiotics in bioremediation strategies. However, more knowledge of the intricate interplay between UGTs in plants is needed to unlock the full potential of UGTs in crop resistance.

Genome-wide association analysis of type II resistance to Fusarium head blight in common wheat

Background

Fusarium head blight (FHB) is a disease affecting wheat spikes caused by some Fusarium species and leads to cases of severe yield reduction and seed contamination. Identifying resistance genes/QTLs from wheat germplasm may help to improve FHB resistance in wheat production.

Methods

Our study evaluated 205 elite winter wheat cultivars for FHB resistance. A high-density 90K SNP array was used for genotyping the panel. A genome-wide association study (GWAS) from cultivars from three different environments was performed using a mixed linear model (MLM).

Results

Sixty-six significant marker-trait associations (MTAs) were identified (P < 0.001) on fifteen chromosomes that explained the phenotypic variation ranging from 5.4 to 11.2%. Some important new MTAs in genomic regions involving FHB resistance were found on chromosomes 2A, 3B, 5B, 6A, and 7B. Six MTAs at 92 cM on chromosome 7B were found in cultivars from two different environments. Moreover, there were 11 MTAs consistently associated with diseased spikelet rate and diseased rachis rate as pleiotropic effect loci and D_contig74317_533 on chromosome 5D was novel for FHB resistance. Eight new candidate genes of FHB resistance were predicated in wheat in this study. Three candidate genes, TraesCS5D02G006700, TraesCS6A02G013600, and TraesCS7B02G370700 on chromosome 5DS, 6AS, and 7BL, respectively, were perhaps important in defending against FHB by regulating intramolecular transferase activity, GTP binding, or chitinase activity in wheat, but further validation in needed. In addition, a total of five favorable alleles associated with wheat FHB resistance were discovered. These results provide important genes/loci for enhancing FHB resistance in wheat breeding by marker-assisted selection.

Global distribution, toxicity to humans and animals, biodegradation, and nutritional mitigation of deoxynivalenol: A review

Deoxynivalenol (DON) is one of the main types of B trichothecenes, and it causes health-related issues in humans and animals and imposes considerable challenges to food and feed safety globally each year. This review investigates the global hazards of DON, describes the occurrence of DON in food and feed in different countries, and systematically uncovers the mechanisms of the various toxic effects of DON. For DON pollution, many treatments have been reported on the degradation of DON, and each of the treatments has different degradation efficacies and degrades DON by a distinct mechanism. These treatments include physical, chemical, and biological methods and mitigation strategies. Biodegradation methods include microorganisms, enzymes, and biological antifungal agents, which are of great research significance in food processing because of their high efficiency, low environmental hazards, and drug resistance. And we also reviewed the mechanisms of biodegradation methods of DON, the adsorption and antagonism effects of microorganisms, and the different chemical transformation mechanisms of enzymes. Moreover, nutritional mitigation including common nutrients (amino acids, fatty acids, vitamins, and microelements) and plant extracts was discussed in this review, and the mitigation mechanism of DON toxicity was elaborated from the biochemical point of view. These findings help explore various approaches to achieve the best efficiency and applicability, overcome DON pollution worldwide, ensure the sustainability and safety of food processing, and explore potential therapeutic options with the ability to reduce the deleterious effects of DON in humans and animals.

Transcriptional Profiling Reveals the Wheat Defences against Fusarium Head Blight Disease Regulated by a NAC Transcription Factor

The wheat NAC transcription factor TaNACL-D1 enhances resistance to the economically devastating Fusarium head blight (FHB) disease. The objective of this study was to decipher the alterations in gene expression, pathways and biological processes that led to enhanced resistance as a result of the constitutive expression of TaNACL-D1 in wheat. Transcriptomic analysis was used to determine the genes and processes enhanced in wheat due to TaNACL-D1 overexpression, both in the presence and absence of the causal agent of FHB, Fusarium graminearum (0- and 1-day post-treatment). The overexpression of TaNACL-D1 resulted in more pronounced transcriptional reprogramming as a response to fungal infection, leading to the enhanced expression of genes involved in detoxification, immune responses, secondary metabolism, hormone biosynthesis, and signalling. The regulation and response to JA and ABA were differentially regulated between the OE and the WT. Furthermore, the results suggest that the OE may more efficiently: (i) regulate the oxidative burst; (ii) modulate cell death; and (iii) induce both the phenylpropanoid pathway and lignin synthesis. Thus, this study provides insights into the mode of action and downstream target pathways for this novel NAC transcription factor, further validating its potential as a gene to enhance FHB resistance in wheat.

Multiple Clonostachys rosea UDP-Glycosyltransferases Contribute to the Production of 15-Acetyl-Deoxynivalenol-3-O-Glycoside When Confronted with Fusarium graminearum

Mycotoxins, derived from toxigenic fungi such as Fusarium, Aspergillus, and Penicillium species have impacted the human food chain for thousands of years. Deoxynivalenol (DON), is a tetracyclic sesquiterpenoid type B trichothecene mycotoxin predominantly produced by F. culmorum and F. graminearum during the infection of corn, wheat, oats, barley, and rice. Glycosylation of DON is a protective detoxification mechanism employed by plants. More recently, DON glycosylating activity has also been detected in fungal microparasitic (biocontrol) fungal organisms. Here we follow up on the reported conversion of 15-acetyl-DON (15-ADON) into 15-ADON-3-O-glycoside (15-ADON-3G) in Clonostachys rosea. Based on the hypothesis that the reaction is likely being carried out by a uridine diphosphate glycosyl transferase (UDP-GTase), we applied a protein structural comparison strategy, leveraging the availability of the crystal structure of rice Os70 to identify a subset of potential C. rosea UDP-GTases that might have activity against 15-ADON. Using CRISPR/Cas9 technology, we knocked out several of the selected UDP-GTases in the C. rosea strain ACM941. Evaluation of the impact of knockouts on the production of 15-ADON-3G in confrontation assays with F. graminearum revealed multiple UDP-GTase enzymes, each contributing partial activities. The relationship between these positive hits and other UDP-GTases in fungal and plant species is discussed.

Pasta cooking influence on in vitro bioaccessibility of type B trichothecenes, acrylamide and hydroxymethylfurfural

The study evaluated the effect of cooking time on the levels of type B trichothecenes (TCT_B), acrylamide (AA) and hydroxymethylfurfural (HMF) in semolina pasta and their bioaccessibilities in order to propose strategies to reduce the daily exposure of these natural and processing contaminants. Three brands of commercial pasta were submitted to different cooking times (7, 10 and 13 min). Subsequently, the in vitro bioaccessibility trials, permeation across the intestinal membrane and estimation of daily exposure were carried out. The lowest cooking time (7 min) resulted in high reductions of TCT_B (88%) and AA + HMF (76.7%) contents found on the raw pasta. The concentrations of deoxynivalenol (DON) and AA were higher after the digestion (bioaccessibilities >100%) than after the pasta cooking. About 25.6% of DON and 100% of AA found in the small intestine digestible fraction were able to permeate the intestinal membrane. The risk of exposure was below the recommended safe limits since the estimated daily exposure values were 0.22 µg/kg per body weight/day for DON and 0.26 µg/kg per body weight/day for AA. Therefore, cooking pasta for 7 min at a pasta:water ratio of 1:10 (w/v) mitigates the contaminants and promotes the greater formation of resistant starch.

Deoxynivalenol accumulation and detoxification in cereals and its potential role in wheat-Fusarium graminearum interactions

Deoxynivalenol (DON) is a prominent mycotoxin showing significant accumulation in cereal plants during infection by the phytopathogen Fusarium graminearum. It is a virulence factor that is important in the spread of F. graminearum within cereal heads, and it causes serious yield losses and significant contamination of cereal grains. In recent decades, genetic and genomic studies have facilitated the characterization of the molecular pathways of DON biosynthesis in F. graminearum and the environmental factors that influence DON accumulation. In addition, diverse scab resistance traits related to the repression of DON accumulation in plants have been identified, and experimental studies of wheat-pathogen interactions have contributed to understanding detoxification mechanisms in host plants. The present review illustrates and summarizes the molecular networks of DON mycotoxin production in F. graminearum and the methods of DON detoxification in plants based on the current literature, which provides molecular targets for crop improvement programs. This review also comprehensively discusses recent advances and challenges related to genetic engineering-mediated cultivar improvements to strengthen scab resistance. Furthermore, ongoing advancements in genetic engineering will enable the application of these molecular targets to develop more scab-resistant wheat cultivars with DON detoxification traits.

Improvement of catalytic activity of sorbose dehydrogenase for deoxynivalenol degradation by rational design

Deoxynivalenol (DON) is the most frequently contaminated mycotoxin in food and feed worldwide, causing significant economic losses and health risks. Physical and chemical detoxification methods are widely used, but they cannot efficiently and specifically remove DON. In the study, the combination of bioinformatics screening and experimental verification confirmed that sorbose dehydrogenase (SDH) can effectively convert DON to 3-keto-DON and a substance that removes four hydrogen atoms for DON. Through rational design, the Vmax of the mutants F103L and F103A were increased by 5 and 23 times, respectively. Furthermore, we identified catalytic sites W218 and D281. SDH and its mutants have broad application conditions, including temperature ranges of 10-45 °C and pH levels of 4-9. Additionally, the half-lives of F103A at 90 °C (processing temperature) and 30 °C (storage temperature) were 60.1 min and 100.5 d, respectively. These results suggest that F103A has significant potential in the detoxification application of DON.

Hazard characterisation for significant mycotoxins in food

This review updates the current status of activities related to hazard characterisation for mycotoxins, with special reference to regulatory work accomplished within the European Union. Because the relevant information on these topics is widely scattered in the scientific literature, this review intends to provide a condensed overview on the most pertinent aspects. Human health risk assessment is a procedure to estimate the nature and potential for harmful effects of mycotoxins on human health due to exposure to them via contaminated food. This assessment involves hazard identification, hazard characterisation, exposure assessment, and risk characterisation. Mycotoxins covered in this review are aflatoxins, ochratoxin A, cyclopiazonic acid, citrinin, trichothecenes (deoxynivalenol, nivalenol, T-2, and HT-2 toxins), fumonisins, zearalenone, patulin, and ergot alkaloids. For mycotoxins with clear genotoxic/carcinogenic properties, the focus is on the margin of exposure approach. One of its goals is to document predictive characterisation of the human hazard, based on studies in animals using conditions of low exposure. For the other, non-genotoxic toxins, individual 'no adverse effect levels' have been established, but structural analogues or modified forms may still complicate assessment. During the process of hazard characterisation, each identified effect is assessed for human relevance. The estimation of a 'safe dose' is the hazard characterisation endpoint. The final aim of all of these activities is to establish a system, which is able to minimise and control the risk for the consumer from mycotoxins in food. Ongoing research on mycotoxins constantly comes up with new findings, which may have to be implemented into this system.

Deoxynivalenol in food and feed: Recent advances in decontamination strategies

Deoxynivalenol (DON) is a mycotoxin that contaminates animal feed and crops around the world. DON not only causes significant economic losses, but can also lead diarrhea, vomiting, and gastroenteritis in humans and farm animals. Thus, there is an urgent need to find efficient approaches for DON decontamination in feed and food. However, physical and chemical treatment of DON may affect the nutrients, safety, and palatability of food. By contrast, biological detoxification methods based on microbial strains or enzymes have the advantages of high specificity, efficiency, and no secondary pollution. In this review, we comprehensively summarize the recently developed strategies for DON detoxification and classify their mechanisms. In addition, we identify remaining challenges in DON biodegradation and suggest research directions to address them. In the future, an in-depth understanding of the specific mechanisms through which DON is detoxified will provide an efficient, safe, and economical means for the removal of toxins from food and feed.

Environmental Conditions After Fusarium Head Blight Visual Symptom Development Affect Contamination of Wheat Grain with Deoxynivalenol and Deoxynivalenol-3-Glucoside

Fusarium head blight (FHB) of wheat, caused by the fungus Fusarium graminearum, is associated with grain contamination with mycotoxins such as deoxynivalenol (DON). Although FHB is often positively correlated with DON, this relationship can break down under certain conditions. One possible explanation for this could be the conversion of DON to DON-3-glucoside (D3G), which is typically missed by common DON testing methods. The objective of this study was to quantify the effects of temperature, relative humidity (RH), and preharvest rainfall on DON, D3G, and the D3D/DON relationship. D3G levels were higher in grain from spikes exposed to 100% RH than to 70, 80, or 90% RH at 20 and 25°C across all tested levels of mean FHB index (percentage of diseased spikelets per spike). Mean D3G contamination was higher at 20°C than at 25 or 30°C. There were significantly positive linear relationships between DON and D3G. Rainfall treatments resulted in significantly higher mean D3G than the rain-free check and induced preharvest sprouting, as indicated by low falling numbers (FNs). There were significant positive relationships between the rate of increase in D3G per unit increase in DON (a measure of conversion) and sprouting. As FN decreased, the rate of D3G conversion increased, and this rate of conversion per unit decrease in FN was greater at relatively low than at high mean DON levels. These results provide strong evidence that moisture after FHB visual symptom development was associated with DON-to-D3G conversion and constitute valuable new information for understanding this complex disease-mycotoxin system.

Identification of a UDP-glucosyltransferase conferring deoxynivalenol resistance in Aegilops tauschii and wheat

Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.

Microbial detoxification of mycotoxins in food

Mycotoxins are toxic secondary metabolites produced by certain genera of fungi including but not limited to Fusarium, Aspergillus, and Penicillium. Their persistence in agricultural commodities poses a significant food safety issue owing to their carcinogenic, teratogenic, and immunosuppressive effects. Due to their inherent stability, mycotoxin levels in contaminated food often exceed the prescribed regulatory thresholds posing a risk to both humans and livestock. Although physical and chemical methods have been applied to remove mycotoxins, these approaches may reduce the nutrient quality and organoleptic properties of food. Microbial transformation of mycotoxins is a promising alternative for mycotoxin detoxification as it is more specific and environmentally friendly compared to physical/chemical methods. Here we review the biological detoxification of the major mycotoxins with a focus on microbial enzymes.

Modified Mycotoxins, a Still Unresolved Issue

Mycotoxins are toxic secondary metabolites produced by filamentous microfungi on almost every agricultural commodity worldwide. After the infection of crop plants, mycotoxins are modified by plant enzymes or other fungi and often conjugated to more polar substances, like sugars. The formed—often less toxic—metabolites are stored in the vacuole in soluble form or bound to macromolecules. As these substances are usually not detected during routine analysis and no maximum limits are in force, they are called modified mycotoxins. While, in most cases, modified mycotoxins have lower intrinsic toxicity, they might be reactivated during mammalian metabolism. In particular, the polar group might be cleaved off (e.g., by intestinal bacteria), releasing the native mycotoxin. This review aims to provide an overview of the critical issues related to modified mycotoxins. The main conclusion is that analytical aspects, toxicological evaluation, and exposure assessment merit more investigation.

Detoxification of monoterpenes by a family of plant glycosyltransferases

Plant monoterpenes are challenging compounds, since they often act as solvents, and thus have both phytotoxic and antimicrobial properties. In this study an approach is developed to identify and characterize enzymes that can detoxify monoterpenoids, and thus would protect both plants and microbial production systems from these compounds. Plants respond to the presence of monoterpenes by expressing glycosyltransferases (UGTs), which conjugate the monoterpenoids into glycosides. By identifying these enzymes in a transcriptomics approach using Mentha × piperita, a family of UGTs was identified which is active on cyclic monoterpenoids such as menthol, and on acyclic monoterpenoids such as geranic acid. Other members of this family, from tomato, were also shown to be active on these monoterpenoids. In vitro and in vivo activity of different UGTs were tested with different substrates. We found that some glycosyltransferases significantly affect the toxicity of selected monoterpenoids in Escherichia coli, suggesting that glycosyltransferases can protect cells from monoterpenoid toxicity.

Tissue-specific transcriptome responses to Fusarium head blight and Fusarium root rot

Fusarium head blight (FHB) and Fusarium root rot (FRR) are important diseases of small-grain cereals caused by Fusarium species. While host response to FHB has been subject to extensive study, very little is known about response to FRR and the transcriptome responses of FHB and FRR have not been thoroughly compared. Brachypodium distachyon (Bd) is an effective model for investigating host responses to both FHB and FRR. In this study the transcriptome response of Bd to F. graminearum (Fg) infection of heads and roots was investigated. An RNA-seq analysis was performed on both Bd FHB and FRR during the early infection. Additionally, an RNA-seq analysis was performed on in vitro samples of Fg for comparison with Fg gene expression in planta. Differential gene expression and gene-list enrichment analyses were used to compare FHB and FRR transcriptome responses in both Bd and Fg. Differential expression of selected genes was confirmed using RT-qPCR. Most genes associated with receptor signalling, cell-wall modification, oxidative stress metabolism, and cytokinin and auxin biosynthesis and signalling genes were generally upregulated in FHB or were downregulated in FRR. In contrast, Bd genes involved in jasmonic acid and ethylene biosynthesis and signalling, and antimicrobial production were similarly differentially expressed in both tissues in response to infection. A transcriptome analysis of predicted Fg effectors with the same infected material revealed elevated expression of core tissue-independent genes including cell-wall degradation enzymes and the gene cluster for DON production but also several tissue-dependent genes including those for aurofusarin production and cutin degradation. This evidence suggests that Fg modulates its transcriptome to different tissues of the same host.

Genome-wide identification, evolution and function analysis of UGTs superfamily in cotton

Glycosyltransferases mainly catalyse the glycosylation reaction in living organisms and widely exists in plants. UGTs have been identified from G. raimondii, G. arboreum and G. hirsutum. However, Genome-wide systematic analysis of UGTs superfamily have not been studied in G. barbadense. 752 UGTs were identified from four cotton species and grouped into 18 clades, of which R was newly discovered clades. Most UGTs were clustered at both ends of the chromosome and showed a heterogeneous distribution. UGT proteins were widely distributed in cells, with the highest distribution in chloroplasts. UGTs of the same clade shared similar intron/exon structural features. During evolution, the gene family has undergone strong selection for purification. UGTs were significantly enriched in “transcriptional activity (GO:0016758)” and “metabolic processes (GO:0008152)”. Genes from the same clade differed in function under various abiotic stresses. The analysis of cis-acting element and qRT–PCR may indicate that GHUGTs play important roles in plant growth, development and abiotic stress. We further found that GHUGT74-2 plays an important role under submergence. The study broadens the understanding of UGTs in terms of gene characteristics, evolutionary processes, and gene function in cotton and provides a new way to systematically and globally understand the structure–function relationship of multigene families in the evolutionary process.

Transcriptional response of a target plant to benzoxazinoid and diterpene allelochemicals highlights commonalities in detoxification

BACKGROUND

Plants growing in proximity to other plants are exposed to a variety of metabolites that these neighbors release into the environment. Some species produce allelochemicals to inhibit growth of neighboring plants, which in turn have evolved ways to detoxify these compounds.

RESULTS

In order to understand how the allelochemical-receiving target plants respond to chemically diverse compounds, we performed whole-genome transcriptome analysis of Arabidopsis thaliana exposed to either the benzoxazinoid derivative 2-amino- 3H-phenoxazin-3-one (APO) or momilactone B. These two allelochemicals belong to two very different compound classes, benzoxazinoids and diterpenes, respectively, produced by different Poaceae crop species.

CONCLUSIONS

Despite their distinct chemical nature, we observed similar molecular responses of A. thaliana to these allelochemicals. In particular, many of the same or closely related genes belonging to the three-phase detoxification pathway were upregulated in both treatments. Further, we observed an overlap between genes upregulated by allelochemicals and those involved in herbicide detoxification. Our findings highlight the overlap in the transcriptional response of a target plant to natural and synthetic phytotoxic compounds and illustrate how herbicide resistance could arise via pathways involved in plant-plant interaction.

Fusarium culmorum Produces NX-2 Toxin Simultaneously with Deoxynivalenol and 3-Acetyl-Deoxynivalenol or Nivalenol

Fusarium culmorum is a major pathogen of grain crops. Infected plants accumulate deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), or nivalenol (NIV), which are mycotoxins of the trichothecene B group. These toxins are also produced by F. graminearum species complex. New trichothecenes structurally similar to trichothecenes B but lacking the carbonyl group on C-8, designated NX toxins, were recently discovered in atypical isolates of F. graminearum from North America. Only these isolates and a few strains of a yet to be characterized Fusarium species from South Africa are known to produce NX-2 and other NX toxins. Here, we report that among 20 F. culmorum strains isolated from maize, wheat, and oat in Europe and Asia over a period of 70 years, 18 strains produced NX-2 simultaneously with 3-ADON and DON or NIV. Rice cultures of strains producing 3-ADON accumulated NX-2 in amounts corresponding to 2−8% of 3-ADON (1.2−36 mg/kg). A strain producing NIV accumulated NX-2 and NIV at comparable amounts (13.6 and 10.3 mg/kg, respectively). In F. graminearum, producers of NX-2 possess a special variant of cytochrome P450 monooxygenase encoded by TRI1 that is unable to oxidize C-8. In F. culmorum, producers and nonproducers of NX-2 possess identical TRI1; the reason for the production of NX-2 is unknown. Our results indicate that the production of NX-2 simultaneously with trichothecenes B is a common feature of F. culmorum.

Identification and Functional Characterisation of Two Oat UDP-Glucosyltransferases Involved in Deoxynivalenol Detoxification

Oat is susceptible to several Fusarium species that cause contamination with different trichothecene mycotoxins. The molecular mechanisms behind Fusarium resistance in oat have yet to be elucidated. In the present work, we identified and characterised two oat UDP-glucosyltransferases orthologous to barley HvUGT13248. Overexpression of the latter in wheat had been shown previously to increase resistance to deoxynivalenol (DON) and nivalenol (NIV) and to decrease disease the severity of both Fusarium head blight and Fusarium crown rot. Both oat genes are highly inducible by the application of DON and during infection with Fusarium graminearum. Heterologous expression of these genes in a toxin-sensitive strain of Saccharomyces cerevisiae conferred high levels of resistance to DON, NIV and HT-2 toxins, but not C4-acetylated trichothecenes (T-2, diacetoxyscirpenol). Recombinant enzymes AsUGT1 and AsUGT2 expressed in Escherichia coli rapidly lost activity upon purification, but the treatment of whole cells with the toxin clearly demonstrated the ability to convert DON into DON-3-O-glucoside. The two UGTs could therefore play an important role in counteracting the Fusarium virulence factor DON in oat.

Transcriptome Profiling of a Common Mistletoe Species Parasitizing Four Typical Host Species in Urban Southwest China

Comparing gene expressions among parasitic plants infecting different host species can have significant implications for understanding host–parasite interactions. Taxillus nigrans is a common hemiparasitic species in Southwest China that parasitizes a variety of host species. However, a lack of nucleotide sequence data to date has hindered transcriptome-level research on T. nigrans. In this study, the transcriptomes of T. nigrans individuals parasitizing four typical host species (Broussonetia papyrifera (Bpap), a broad-leaved tree species; Cryptomeria fortunei (Cfor), a coniferous tree species; Cinnamomum septentrionale (Csep), an evergreen tree species; and Ginkgo biloba (Gbil), a deciduous-coniferous tree species) were sequenced, and the expression profiles and metabolic pathways were compared among hosts. A total of greater than 400 million reads were generated in nine cDNA libraries. These were de novo assembled into 293823 transcripts with an N50 value of 1790 bp. A large number of differentially expressed genes (DEGs) were identified when comparing T. nigrans individuals on different host species: Bpap vs. Cfor (1253 DEGs), Bpap vs. Csep (864), Bpap vs. Gbil (517), Cfor vs. Csep (259), Cfor vs. Gbil (95), and Csep vs. Gbil (40). Four hundred and fifteen unigenes were common to all six pairwise comparisons; these were primarily associated with Cytochrome P450 and environmental adaptation, as determined in a KEGG enrichment analysis. Unique unigenes were also identified, specific to Bpap vs. Cfor (808 unigenes), Bpap vs. Csep (329 unigenes), Bpap vs. Gbil (87 unigenes), Cfor vs. Csep (108 unigenes), Cfor vs. Gbil (32 unigenes), and Csep vs. Gbil comparisons (23 unigenes); partial unigenes were associated with the metabolism of terpenoids and polyketides regarding plant hormone signal transduction. Weighted gene co-expression network analysis (WGCNA) revealed four modules that were associated with the hosts. These results provide a foundation for further exploration of the detailed molecular mechanisms involved in plant parasitism.

The control of Fusarium growth and decontamination of produced mycotoxins by lactic acid bacteria

Global crop and food contamination with mycotoxins are one of the primary worldwide concerns, while there are several restrictions regarding approaching conventional physical and chemical mycotoxins decontamination methods due to nutrition loss, sensory attribute reduction in foods, chemical residual, inconvenient operation, high cost of equipment, and high energy consumption of some methods. In this regard, the overarching challenges of mycotoxin contamination in food and food crops require the development of biological decontamination strategies. Using certain lactic acid bacteria (LAB) as generally recognized safe (GRAS) compounds is one of the most effective alternatives due to their potential to release antifungal metabolites against various fungal factors species. This review highlights the potential applications of LAB as biodetoxificant agents and summarizes their decontamination activities against Fusarium growth and Fusarium mycotoxins released into food/feed. Firstly, the occurrence of Fusarium and the instrumental and bioanalytical methods for the analysis of mycotoxins were in-depth discussed. Upgraded knowledge on the biosynthesis pathway of mycotoxins produced by Fusarium offers new insightful ideas clarifying the function of these secondary metabolites. Moreover, the characterization of LAB metabolites and their impact on the decontamination of the mycotoxin from Fusarium, besides the main mechanisms of mycotoxin decontamination, are covered. While the thematic growth inhibition of Fusarium and decontamination of their mycotoxin by LAB is very complex, approaching certain lactic acid bacteria (LAB) is worth deeper investigations.

Structure-Function Analysis of a Quinone-Dependent Dehydrogenase Capable of Deoxynivalenol Detoxification

The pyrroloquinoline quinone (PQQ)-dependent dehydrogenase DepA detoxifies deoxynivalenol (DON) by converting the C3-OH into a keto group. Herein, two crystal structures of DepA and its complex with PQQ were determined, together with biochemical evidence confirming the interactions of DepA with PQQ and DON and revealing a unique tyrosine residue important for substrate selection. Furthermore, four loops over the active site essential for DepA activity were identified, of which three loops were stabilized by PQQ, and the fourth loop invisible in both structures was considered important for binding DON, together constituting a lid for the active site. Preliminary engineering of the loop showed its potential for enzyme improvement. This study provides structural insights into how a PQQ-dependent dehydrogenase is equipped with the function of DON conversion and for the first time shows the necessity of a lid structure for PQQ-dependent dehydrogenase activity, laying foundation for structure-based design to enhance catalysis efficiency.

Chromosome-level genome of Entada phaseoloides provides insights into genome evolution and triterpenoid saponins biosynthesis

As a medicinal herbal plant, Entada phaseoloides has high levels of secondary metabolites, particularly triterpenoid saponins, which are important resources for scientific research and medical applications. However, the lack of a reference genome for this genus has limited research on its evolution and utilization of its medicinal potential. In this study, we report a chromosome-scale genome assembly for E. phaseoloides using Illumina, Nanopore long reads, and high-throughput chromosome conformation capture technology. The assembled reference genome is 456.18 Mb (scaffold N50=30.9 Mb; contig N50=6.34 Mb) with 95.71 % of the sequences anchored onto 14 pseudochromosomes. E. phaseoloides was estimated to diverge from the Leguminosae lineage at approximately 72.0 million years ago. With the integration of transcriptomic and metabolomic data, gene expression patterns and metabolite profiling of E. phaseoloides were determined in different tissues. The pattern of gene expression and metabolic profile of the kernel were distinct from those of other tissues. Furthermore, the evolution of certain gene families involved in the biosynthesis of triterpenoid saponins and terpenes was analyzed and offer new insights into the formation of these two metabolites. Four CYP genes, one UGT gene and related transcription factors were identified as candidate genes contributing to regulation of triterpenoid saponins biosynthesis. As the first high-quality assembled reference genome in the genus Entada, it will not only provide new information for the evolutionary study of this genus and conservation biology of E. phaseoloides but also lay a foundation for the formation and utilization of secondary metabolites in medicinal plants.

Identification of Candidate Genes Associated With Tolerance to Apple Replant Disease by Genome-Wide Transcriptome Analysis

Apple replant disease (ARD) is a worldwide economic risk in apple cultivation for fruit tree nurseries and fruit growers. Several studies on the reaction of apple plants to ARD are documented but less is known about the genetic mechanisms behind this symptomatology. RNA-seq analysis is a powerful tool for revealing candidate genes that are involved in the molecular responses to biotic stresses in plants. The aim of our work was to find differentially expressed genes in response to ARD in Malus. For this, we compared transcriptome data of the rootstock ‘M9’ (susceptible) and the wild apple genotype M. ×robusta 5 (Mr5, tolerant) after cultivation in ARD soil and disinfected ARD soil, respectively. When comparing apple plantlets grown in ARD soil to those grown in disinfected ARD soil, 1,206 differentially expressed genes (DEGs) were identified based on a log2 fold change, (LFC) ≥ 1 for up– and ≤ −1 for downregulation (p < 0.05). Subsequent validation revealed a highly significant positive correlation (r = 0.91; p < 0.0001) between RNA-seq and RT-qPCR results indicating a high reliability of the RNA-seq data. PageMan analysis showed that transcripts of genes involved in gibberellic acid (GA) biosynthesis were significantly enriched in the DEG dataset. Most of these GA biosynthesis genes were associated with functions in cell wall stabilization. Further genes were related to detoxification processes. Genes of both groups were expressed significantly higher in Mr5, suggesting that the lower susceptibility to ARD in Mr5 is not due to a single mechanism. These findings contribute to a better insight into ARD response in susceptible and tolerant apple genotypes. However, future research is needed to identify the defense mechanisms, which are most effective for the plant to overcome ARD.