Trichothecene production by Trichoderma brevicompactum

Effects of trichothecene production by Trichoderma arundinaceum isolates from bean-field soils on the defense response, growth and development of bean plants (Phaseolus vulgaris)

The trichothecene toxin-producing fungus Trichoderma arundinaceum has potential as a biological control agent. However, most biocontrol studies have focused only on one strain, IBT 40837. In the current study, three Trichoderma isolates recovered from bean-field soils produced the trichothecene harzianum A (HA) and trichodermol, the latter being an intermediate in the HA biosynthesis. Based on phylogenetic analysis, the three isolates were assigned to the species T. arundinaceum. Their genome sequences had a high degree of similarity to the reference IBT 40837 strain, in terms of total genome size, number of predicted genes, and diversity of putative secondary metabolite biosynthetic gene clusters. HA production by these bean-field isolates conferred significant in vitro antifungal activity against Rhizoctonia solani and Sclerotinia sclerotiorum, which are some of the most important bean pathogens. Furthermore, the bean-field isolates stimulated germination of bean seeds and subsequent growth of above ground parts of the bean plant. Transcriptomic analysis of bean plants inoculated with these T. arundinaceum bean-field soil isolates indicated that HA production significantly affected expression of plant defense-related genes; this effect was particularly significant in the expression of chitinase-encoding genes. Together, these results indicate that Trichoderma species producing non-phytotoxic trichothecenes can induce defenses in plants without negatively affecting germination and development.

Identification of polyketide synthase genes required for aspinolide biosynthesis in Trichoderma arundinaceum

The fungus Trichoderma arundinaceum exhibits biological control activity against crop diseases caused by other fungi. Two mechanisms that likely contribute to this activity are upregulation of plant defenses and production of two types of antifungal secondary metabolites: the sesquiterpenoid harzianum A (HA) and the polyketide-derived aspinolides. The goal of the current study was to identify aspinolide biosynthetic genes as part of an effort to understand how these metabolites contribute to the biological control activity of T. arundinaceum. Comparative genomics identified two polyketide synthase genes (asp1 and asp2) that occur in T. arundinaceum and Aspergillus ochraceus, which also produces aspinolides. Gene deletion and biochemical analyses in T. arundinaceum indicated that both genes are required for aspinolide production: asp2 for formation of a 10-member lactone ring and asp1 for formation of a butenoyl subsituent at position 8 of the lactone ring. Gene expression and comparative genomics analyses indicated that asp1 and asp2 are located within a gene cluster that occurs in both T. arundinaceum and A. ochraceus. A survey of genome sequences representing 35 phylogenetically diverse Trichoderma species revealed that intact homologs of the cluster occurred in only two other species, which also produced aspinolides. An asp2 mutant inhibited fungal growth more than the wild type, but an asp1 mutant did not, and the greater inhibition by the asp2 mutant coincided with increased HA production. These findings indicate that asp1 and asp2 are aspinolide biosynthetic genes and that loss of either aspinolide or HA production in T. arundinaceum can be accompanied by increased production of the other metabolite(s). KEY POINTS: • Two polyketide synthase genes are required for aspinolide biosynthesis. • Blocking aspinolide production increases production of the terpenoid harzianum A. • Aspinolides and harzianum A act redundantly in antibiosis of T. arundinaceum.

In Vitro Assessment of Organic and Residual Fractions of Nematicidal Culture Filtrates from Thirteen Tropical Trichoderma Strains and Metabolic Profiles of Most-Active

The nematicidal properties of Trichoderma species have potential for developing safer biocontrol agents. In the present study, 13 native Trichoderma strains from T. citrinoviride, T. ghanense (2 strains), T. harzianum (4), T. koningiopsis, T. simmonsii, and T. virens (4) with nematicidal activity were selected and cultured in potato dextrose broth to obtain a culture filtrate (CF) for each. Each CF was partitioned with ethyl acetate to obtain organic (EA) and residual filtrate (RF) fractions, which were then tested on second-stage juveniles (J2s) of the nematodes Meloidogyne javanica and M. incognita in a microdilution assay. The most lethal strains were T. harzianum Th43-14, T. koningiopsis Th41-11, T. ghanense Th02-04, and T. virens Th32-09, which caused 51–100% mortality (%M) of J2s of both nematodes, mainly due to their RF fractions. Liquid chromatography–diode array detector-electrospray-high resolution mass spectrometry analysis of the most-active fractions revealed sesquiterpene and polyketide-like metabolites produced by the four active strains. These native Trichoderma strains have a high potential to develop safer natural products for the biocontrol of Meloidogyne species.

Distribution, Function, and Evolution of a Gene Essential for Trichothecene Toxin Biosynthesis in Trichoderma

Trichothecenes are terpenoid toxins produced by species in 10 fungal genera, including species of Trichoderma. The trichothecene biosynthetic gene (tri) cluster typically includes the tri5 gene, which encodes a terpene synthase that catalyzes formation of trichodiene, the parent compound of all trichothecenes. The two Trichoderma species, Trichoderma arundinaceum and T. brevicompactum, that have been examined are unique in that tri5 is located outside the tri cluster in a genomic region that does not include other known tri genes. In the current study, analysis of 35 species representing a wide range of the phylogenetic diversity of Trichoderma revealed that 22 species had tri5, but only 13 species had both tri5 and the tri cluster. tri5 was not located in the cluster in any species. Using complementation analysis of a T. arundinaceum tri5 deletion mutant, we demonstrated that some tri5 homologs from species that lack a tri cluster are functional, but others are not. Phylogenetic analyses suggest that Trichoderma tri5 was under positive selection following its divergence from homologs in other fungi but before Trichoderma species began diverging from one another. We propose two models to explain these diverse observations. One model proposes that the location of tri5 outside the tri cluster resulted from loss of tri5 from the cluster in an ancestral species followed by reacquisition via horizontal transfer. The other model proposes that in species that have a functional tri5 but lack the tri cluster, trichodiene production provides a competitive advantage.

Verification of TRI3 Acetylation of Trichodermol to Trichodermin in the Plant Endophyte Trichoderma taxi

Trichodermin, a trichothecene first isolated in Trichoderma species, is a sesquiterpenoid antibiotic that exhibits significant inhibitory activity to the growth of many pathogenic fungi such as Candida albicans, Rhizoctonia solani, and Botrytis cinerea by inhibiting the peptidyl transferase involved in eukaryotic protein synthesis. Trichodermin has also been shown to selectively induce cell apoptosis in several cancer cell lines and thus can act as a potential lead compound for developing anticancer therapeutics. The biosynthetic pathway of trichodermin in Trichoderma has been identified, and most of the involved genes have been functionally characterized. An exception is TRI3, which encodes a putative acetyltransferase. Here, we report the identification of a gene cluster that contains seven genes expectedly involved in trichodermin biosynthesis (TRI3, TRI4, TRI6, TRI10, TRI11, TRI12, and TRI14) in the trichodermin-producing endophytic fungus Trichoderma taxi. As in Trichoderma brevicompactum, TRI5 is not included in the cluster. Functional analysis provides evidence that TRI3 acetylates trichodermol, the immediate precursor, to trichodermin. Disruption of TRI3 gene eliminated the inhibition to R. solani by T. taxi culture filtrates and significantly reduced the production of trichodermin but not of trichodermol. Both the inhibitory activity and the trichodermin production were restored when native TRI3 gene was reintroduced into the disruption mutant. Furthermore, a His-tag-purified TRI3 protein, expressed in Escherichia coli, was able to convert trichodermol to trichodermin in the presence of acetyl-CoA. The disruption of TRI3 also resulted in lowered expression of both the upstream biosynthesis TRI genes and the regulator genes. Our data demonstrate that T. taxi TRI3 encodes an acetyltransferase that catalyzes the esterification of the C-4 oxygen atom on trichodermol and thus plays an essential role in trichodermin biosynthesis in this fungus.

Bioprospecting Trichoderma: A Systematic Roadmap to Screen Genomes and Natural Products for Biocontrol Applications

Natural products derived from microbes are crucial innovations that would help in reaching sustainability development goals worldwide while achieving bioeconomic growth. Trichoderma species are well-studied model fungal organisms used for their biocontrol properties with great potential to alleviate the use of agrochemicals in agriculture. However, identifying and characterizing effective natural products in novel species or strains as biological control products remains a meticulous process with many known challenges to be navigated. Integration of recent advancements in various "omics" technologies, next generation biodesign, machine learning, and artificial intelligence approaches could greatly advance bioprospecting goals. Herein, we propose a roadmap for assessing the potential impact of already known or newly discovered Trichoderma species for biocontrol applications. By screening publicly available Trichoderma genome sequences, we first highlight the prevalence of putative biosynthetic gene clusters and antimicrobial peptides among genomes as an initial step toward predicting which organisms could increase the diversity of natural products. Next, we discuss high-throughput methods for screening organisms to discover and characterize natural products and how these findings impact both fundamental and applied research fields.

Characterisation of two unique sesquiterpenoids from Trichoderma hypoxylon

Two new sesquiterpenoids, 1-2, together with three known compounds, were isolated from Trichoderma hypoxylon. Among the known compounds, compound 4 was isolated as naturally occurring compound for the first time. The structures of these new compounds were characterized by HR-ESI-MS and spectroscopic methods including 1D and 2D NMR. The absolute configurations of 1-2 were assigned by electronic circular dichroism (ECD) calculations.

Polyketides produced by the entomopathogenic fungus Metarhizium anisopliae induce Candida albicans growth

Metarhizium anisopliae is an important entomopathogenic species and model for arthropod-fungus interaction studies. This fungus harbors a diverse arsenal of unexplored secondary metabolite biosynthetic gene clusters, which are suggested to perform diverse roles during host interaction and soil subsistence as a saprophytic species. Here we explored an unusual carnitine acyltransferase domain-containing highly reducing polyketide synthase found in the genome of M. anisopliae. Employing heterologous expression in Aspergillus nidulans, two new polyketides were obtained, named BAA and BAB, as well as one known polyketide [(2Z,4E,6E)-octa-2,4,6-trienedioic acid]. Intra-hemocoel injection of the most abundant compound (BAA) in the model-arthropod Galleria mellonella larvae did not induce mortality or noticeable alterations, suggesting that this compound may not harbor insecticidal activity. Also, the potential role of such molecules in polymicrobial interactions was evaluated. Determination of minimum inhibitory concentration assays using distinct fungal species revealed that BAA and BAB did not alter Cryptococcus neoformans growth, while BAA exhibited weak antifungal activity against Saccharomyces cerevisiae. Unexpectedly, these compounds increased Candida albicans growth compared to control conditions. Furthermore, BAA can mitigate the fungicidal effects of fluconazole over C. albicans. Although the exact role of these compounds on the M. anisopliae life cycle is elusive, the described results add up to the complexity of secondary metabolites produced by Metarhizium spp. Moreover, up to our knowledge, these are the first polyketides isolated from filamentous fungi that can boost the growth of another fungal species.

Antifungal and Antimicroalgal Trichothecene Sesquiterpenes from the Marine Algicolous Fungus Trichoderma brevicompactum A-DL-9-2

Eight new trichothecene derivatives, trichodermarins G-N (1-8), and two new cuparene derivatives, trichocuparins A (9) and B (10), as well as six known trichothecenes (11-16) were isolated from the fungal strain Trichoderma brevicompactum A-DL-9-2 obtained from the inner tissue of the marine red alga Chondria tenuissima. The structures and relative configurations of 1-10 were assigned by NMR and MS data, and the absolute configurations of 1, 2, and 9 were established by X-ray diffraction. Compound 8 features an aminosugar unit bond to the trichothecene framework for the first time, while 9 and 10 represent the first occurrence of cuparene sesquiterpenes in Trichoderma. All the isolates were assayed for growth inhibition of five phytopathogenic fungi (Botrytis cinerea, Cochliobolus miyabeanus, Fusarium oxysporum f. sp. cucumerium, Fusarium oxysporum f. sp. niveum, and Phomopsis asparagi) and four marine phytoplankton species (Amphidinium carterae, Heterocapsa circularisquama, Heterosigma akashiwo, and Prorocentrum donghaiense). Several of them exhibited significant inhibitory activities against the fungi and phytoplankton tested of which trichodermin (12) showed the highest antifungal and antimicroalgal activities with MIC and IC₅₀ values being 4.0 and 0.82 μg/mL, respectively.

Trichothecene macrolides from the endophytic fungus Paramyrothecium roridum and their cytotoxic activity

The chemical investigation of the secondary metabolites of Paramyrothecium roridum (homotypic synonym: Myrothecium roridum), an endophytic fungus isolated from the medicinal plant Morinda officinalis, led to the isolation of twelve cytotoxic trichothecene macrolides, including two new ones, named myrothecines H and I. The structures of the new macrolides were elucidated by extensive spectroscopic measurements analyses. In addition, the cytotoxic activities of these compounds were evaluated against SF-268, NCI-H460, and HepG-2 tumor cell lines, and all isolated compounds (1-12) exhibited significant cytotoxic activity with the IC₅₀ ranging from 0.0002-16.2 μM. Moreover, the inhibitory activity of myrothecines H and I was evidenced by inducing phosphorylation of JNK (c-Jun N-terminal protein kinase) protein and the PARP (poly ADP-ribose polymerase) cleavage, and eventually induce apoptosis of HepG-2 cells. The results indicated that myrothecines H and I could be applied as chemotherapeutic agents.

Herbicidal efficacy of harzianums produced by the biofertilizer fungus, Trichoderma brevicompactum

Herbicides are important tools for weed control in modern agriculture. In the search for potential herbicidal natural products from fungal species, harzianum A and B were identified from the biofertilizer fungus, Trichoderma brevicompactum. In the phytotoxicity assays on the dicot species Brassica chinensis, harzianum A and B reduced both shoot and root lengths at low concentrations and inhibited the seed germination at 2 μg mL⁻¹. In addition, harzianum A and B also exhibited phytotoxicity against monocots, Oryza sativa L. cv. Nipponbare and Echinochloa crusgalli L. Beauv.. Compared with a common herbicide, 2,4-dichlorophenoxyacetic acid, harzianum A and B performed similar activity in a pot assay, and were more effective in post-emergence than pre-emergence conditions. Harzianum A and B have potential as efficient herbicide for controlling important dicotyledon and monocotyledon weeds at low concentrations. They can be sprayed in liquid form in both pre- and post-emergence conditions. Our results confirmed the importance of these molecules for the development of new herbicides.

Synthesis of Trichodermin Derivatives and Their Antimicrobial and Cytotoxic Activities

Trichothecene mycotoxins are recognized as highly bioactive compounds that can be used in the design of new useful bioactive molecules. In Trichoderma brevicompactum, the first specific step in trichothecene biosynthesis is carried out by a terpene cyclase, trichodiene synthase, that catalyzes the conversion of farnesyl diphosphate to trichodiene and is encoded by the tri5 gene. Overexpression of tri5 resulted in increased levels of trichodermin, a trichothecene-type toxin, which is a valuable tool in preparing new molecules with a trichothecene skeleton. In this work, we developed the hemisynthesis of trichodermin and trichodermol derivatives in order to evaluate their antimicrobial and cytotoxic activities and to study the chemo-modulation of their bioactivity. Some derivatives with a short chain at the C-4 position displayed selective antimicrobial activity against Candida albicans and they showed MIC values similar to those displayed by trichodermin. It is important to highlight the cytotoxic selectivity observed for compounds 9, 13, and 15, which presented average IC₅₀ values of 2 μg/mL and were cytotoxic against tumorigenic cell line MCF-7 (breast carcinoma) and not against Fa2N4 (non-tumoral immortalized human hepatocytes).

Structural Diversity and Bioactivities of Peptaibol Compounds From the Longibrachiatum Clade of the Filamentous Fungal Genus Trichoderma

This study examined the structural diversity and bioactivity of peptaibol compounds produced by species from the phylogenetically separated Longibrachiatum Clade of the filamentous fungal genus Trichoderma, which contains several biotechnologically, agriculturally and clinically important species. HPLC-ESI-MS investigations of crude extracts from 17 species of the Longibrachiatum Clade (T. aethiopicum, T. andinense, T. capillare, T. citrinoviride, T. effusum, T. flagellatum, T. ghanense, T. konilangbra, T. longibrachiatum, T. novae-zelandiae, T. pinnatum, T. parareesei, T. pseudokoningii, T. reesei, T. saturnisporum, T. sinensis, and T. orientale) revealed several new and recurrent 20-residue peptaibols related to trichobrachins, paracelsins, suzukacillins, saturnisporins, trichoaureocins, trichocellins, longibrachins, hyporientalins, trichokonins, trilongins, metanicins, trichosporins, gliodeliquescins, alamethicins and hypophellins, as well as eight 19-residue sequences from a new subfamily of peptaibols named brevicelsins. Non-ribosomal peptide synthetase genes were mined from the available genome sequences of the Longibrachiatum Clade. Their annotation and product prediction were performed in silico and revealed full agreement in 11 out of 20 positions regarding the amino acids predicted based on the signature sequences and the detected amino acids incorporated. Molecular dynamics simulations were performed for structural characterization of four selected peptaibol sequences: paracelsins B, H and their 19-residue counterparts brevicelsins I and IV. Loss of position R6 in brevicelsins resulted in smaller helical structures with higher atomic fluctuation for every residue than the structures formed by paracelsins. We observed the formation of highly bent, almost hairpin-like, helical structures throughout the trajectory, along with linear conformation. Bioactivity tests were performed on the purified peptaibol extract of T. reesei on clinically and phytopathologically important filamentous fungi, mammalian cells, and Arabidopsis thaliana seedlings. Porcine kidney cells and boar spermatozoa proved to be sensitive to the purified peptaibol extract. Peptaibol concentrations ≥0.3 mg ml-1 deterred the growth of A. thaliana. However, negative effects to plants were not detected at concentrations below 0.1 mg ml-1, which could still inhibit plant pathogenic filamentous fungi, suggesting that those peptaibols reported here may have applications for plant protection.

Lipidomics characterization of the alterations of Trichoderma brevicompactum membrane glycerophospholipids during the fermentation phase

The biological membrane lipid composition has been demonstrated to greatly influence the secretion of secondary metabolites. This study was conducted to investigate the periodical alterations of whole cellular lipids and their associations with secondary products in Trichoderma brevicompactum. An electrospray ionization–mass spectrometry-based lipidomics strategy was used to acquire the metabolic profiles of membrane lipids during fermentation. Univariate analyses showed that most fungi glycerophospholipids were significantly altered at the early phase compared with the late phase. In addition, correlation analyses showed high correlations between phosphatidylcholine alterations and fermentation duration. In addition, the fermentation-associated alterations of phosphatidylcholines were found to be in accordance with the degrees of unsaturation of acyl-chains. Harzianum A reached a maximum on the 12th day, while trichodermin and 6-pentyl-2H-pyran-2-one showed the highest abundances on the 9th day, both of which were inclined to correlate with the alterations of phosphatidylcholines and phosphatidylethanolamines, respectively. These findings demonstrated that the alterations of the membrane lipid species in Trichoderma spp. were associated with the fermentation phases and might influence the secretion of specific secondary products, which may be useful in studying the optimization of secondary products in Trichoderma spp.

Trichothecenes from a Soil-Derived Trichoderma brevicompactum

Six new (1-6), together with seven known (7-13), trichothecenes were isolated from the soil-derived Trichoderma brevicompactum PSU-RSPG27. Their structures were established using spectroscopic data. The structure of 1 was confirmed by X-ray data. Trichodermin (7) exhibited the most potent activity against Plasmodium falciparum (K1 strain) with an IC₅₀ value of 0.1 μM, while other trichothecenes (1, 8, 9, and 12) were much less active, with IC₅₀ values in the range of 7.1-9.6 μM. Compound 7 displayed activity against noncancerous Vero cells with an IC₅₀ value of 0.4 μM. The remaining compounds showed moderate to weak activity, with IC₅₀ values in the range of 6.9-15.3 μM. Compounds 7 and 12 were active against human oral carcinoma (KB) cells with IC₅₀ values of 2.4 and 3.7 μM, respectively. Additionally, compounds 7 and 12 displayed antifungal activity against Candida albicans with the respective MIC values of 1 and 2 μg/mL and were active against Cryptococcus neoformans with equal MIC values of 4 μg/mL.

Co-Culture Systems for the Production of Secondary Metabolites: Current and Future Prospects

Microorganisms are the great sources of Natural Products (NPs); these are imperative to their survival apart from conferring competitiveness amongst each other within their environmental niches. Primary and secondary metabolites are the two major classes of NPs that help in cell development, where antimicrobial activity is closely linked with secondary metabolites. To capitalize on the effects of secondary metabolites, co-culture methods have been often used to develop an artificial microbial community that promotes the action of these metabolites. Different analytical techniques will subsequently be employed based on the metabolite specificity and sensitivity to further enhance the metabolite induction. Liquid Chromatography-Mass Spectrometry (LC-MS) and Gas Chromatography (GC)-MS are commonly used for metabolite separation while Nuclear Magnetic Resonance (NMR) and Mass Spectrometry (MS) have been used as tools to elucidate the structure of compounds. This review intends to discuss current systems in use for co-culture in addition to its advantages, with discourse into the investigation of specific techniques in use for the detailed study of secondary metabolites. Further advancements and focus on co-culture technologies are required to fully realize the massive potential in synthetic biological systems.

Plant defense against fungal pathogens by antagonistic fungi with Trichoderma in focus

Fungal diseases cause considerable damage to the economically important crops worldwide thus posing continuous threat to global food security. Management of these diseases is normally done via utilization of chemicals that have severe negative impact upon human health and surrounding ecosystems. Finding eco-friendly alternatives has led the researchers to focus towards biological control of fungal diseases through biocontrol agents such as antagonistic fungi (AF) and other microorganisms. AF include various genera of fungi that cure the fungal diseases on plants effectively. Furthermore, they play a regulatory role in various plant physiological pathways and interactions. AF are highly host specific having negligible effects on non-target organisms and have fast mass production capability. However, understanding the mechanisms of the effects of AF on plant diseases is a prerequisite for their effective utilization as biocontrol agent. Trichoderma is one of the most important fungal genera known for its antagonistic activity against disease causing fungal pathogens. Therefore, in this review, we have focused upon Trichoderma-mediated fungal diseases management via illustrating its taxonomy, important strains, biodiversity and mode of action. Furthermore, we have assessed the criteria to be followed for selection of AF and the factors influencing their efficiency. Finally, we evaluated the advantages and limitations of Trichoderma as AF. We conclude that effective AF utilization against fungal pathogens can serve as a safe strategy for our Planet.

Requirement of Two Acyltransferases for 4- O-Acylation during Biosynthesis of Harzianum A, an Antifungal Trichothecene Produced by Trichoderma arundinaceum

Trichothecenes are sesquiterpenoid toxins produced by multiple fungi, including plant pathogens, entomopathogens, and saprotrophs. Most of these fungi have the acyltransferase-encoding gene tri18. Even though its function has not been determined, tri18 is predicted to be involved in trichothecene biosynthesis because of its pattern of expression and its location near other trichothecene biosynthetic genes. Here, molecular genetic, precursor feeding, and analytical chemistry experiments indicate that in the saprotroph Trichoderma arundinaceum the tri18-encoded acyltransferase (TRI18) and a previously characterized acyltransferase (TRI3) are required for conversion of the trichothecene biosynthetic intermediate trichodermol to harzianum A, an antifungal trichothecene analog with an octa-2,4,6-trienedioyl acyl group. On the basis of the results, we propose that TRI3 catalyzes trichothecene 4- O-acetylation, and subsequently, TRI18 catalyzes replacement of the resulting acetyl group with octa-2,4,6-trienedioyl to form harzianum A. Thus, the findings provide evidence for a previously unrecognized two-step acylation process during trichothecene biosynthesis in T. arundinaceum and possibly other fungi.

Safety of the fungal workhorses of industrial biotechnology: update on the mycotoxin and secondary metabolite potential of Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei

This review presents an update on the current knowledge of the secondary metabolite potential of the major fungal species used in industrial biotechnology, i.e., Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei. These species have a long history of safe use for enzyme production. Like most microorganisms that exist in a challenging environment in nature, these fungi can produce a large variety and number of secondary metabolites. Many of these compounds present several properties that make them attractive for different industrial and medical applications. A description of all known secondary metabolites produced by these species is presented here. Mycotoxins are a very limited group of secondary metabolites that can be produced by fungi and that pose health hazards in humans and other vertebrates when ingested in small amounts. Some mycotoxins are species-specific. Here, we present scientific basis for (1) the definition of mycotoxins including an update on their toxicity and (2) the clarity on misclassification of species and their mycotoxin potential reported in literature, e.g., A. oryzae has been wrongly reported as an aflatoxin producer, due to misclassification of Aspergillus flavus strains. It is therefore of paramount importance to accurately describe the mycotoxins that can potentially be produced by a fungal species that is to be used as a production organism and to ensure that production strains are not capable of producing mycotoxins during enzyme production. This review is intended as a reference paper for authorities, companies, and researchers dealing with secondary metabolite assessment, risk evaluation for food or feed enzyme production, or considerations on the use of these species as production hosts.

Antiproliferative and Antimicrobial Activities of Secondary Metabolites and Phylogenetic Study of Endophytic Trichoderma Species From Vinca Plants

Endophytic fungi have been recognized as a potential source of bioactive secondary metabolites. The endophytic Trichoderma species were isolated from Vinca plants (Vinca major, Vinca herbacea, and Vinca minor), found in Iran and screened for antimicrobial and anti-proliferative activity. Based on morphological and phylogenetic analyses, four fungal species were identified: T. asperellum, T. brevicompactum, T. koningiopsis, and T. longibrachiatum. In addition, endophytic fungi bioactivity of methanol and ethyl acetate extracts (7.8–250 μgml⁻¹) were assessed against a panel of pathogenic fungi and bacteria and IC₈₀ was calculated. Data showed that both methanol and ethyl acetate extracts from all endophytic isolates had significant cytotoxic effects against the model target fungus Pyricularia oryzae. Further research indicated that they had significant antimicrobial bioactivity against the human pathogenic bacteria Staphylococcus aureus and Escherichia coli, and plant pathogenic bacteria Ralstonia solanacearum and Clavibacter michiganensis as well. According to the bioactivity results, crude ethyl acetate extract of T. koningiopsis VM115 isolate was determined for TLC and GC-MS analysis. An antifungal compound was isolated from ethyl acetate extract of T. koningiopsis VM115 based on bioassay guided fractionation. The ¹H-NMR and ¹³C-NMR spectroscopic data showed that the compound was trichodermin, which exhibited strong fungicidal effects against P. oryzae, Aspergillus fumigatus, and Botrytis cinera with MICs of 31.25 μg ml⁻¹ through in vitro antifungal tests. GC-MS analysis identified six classes of volatile compound produced by T. koningiopsis VM115 (alcohols, esters, pyrones (lactones), acids, furanes and lipids). 6-n-pentyl-6H-pyran-2-one (6PP) was identified as one of the most abundant metabolites in this research. These results indicate that the fungal endophytes from Vinca plants had antibacterial and cytotoxic activities; evidence that endophytes are a good source of biological activity and compounds. This work is the first report of Trichodermin production by T. koningiopsis species.

A highly efficient genetic system for the identification of a harzianum B biosynthetic gene cluster in Trichoderma hypoxylon

Trichoderma hypoxylon is a fungicolous species which produces rich secondary metabolites. However, no genetic transformation method is available for further studies. Here, we developed a marker-less transformation system based on the complementation of an uridine/uracil biosynthetic gene by protoplast transformation. An uridine/uracil auxotrophic mutant of Δthpyr4 was obtained by using a positive screening protocol with 5'-fluoroorotic acid as a selective reagent. To improve the homologous integration rates, the orthologues of ku70 and lig4 which play critical roles in non-homologous end-joining recombination were disrupted. The resulting thlig4 mutant showed remarkable transformation rates of 89 %, while no change was found in the thku70 deletion mutant compared with the WT strain. This suggests that thlig4 play a key role in the non-homologous recombination in this strain. Using this system, the biosynthetic gene cluster of trichothecene (tri) harzianum B was identified by deletion of the thtri5 in T. hypoxylon. Comparative genome analysis revealed that the trichothecene biosynthetic gene cluster in T. hypoxylon shared similar organizations with T. arundinaceum and T. brevicompactum, even though their encoded products are different in structures. Taken together, the highly efficient genetic system provides a convenient tool for studying the biosynthetic diversity and mining the novel natural product from the fungi.

Tri11, tri3, and tri4 genes are required for trichodermin biosynthesis of Trichoderma brevicompactum

Trichoderma brevicompactum and T. arundinaceum both can synthesize trichodermin with strong antifungal activity and high biotechnological value. The two Trichoderma species have a tri cluster, which includes seven genes (tri14, tri12, tri11, tri10, tri3, tri4, and tri6) that encode transport and regulatory enzymes required for the biosynthesis of trichodermin. Here, we isolated T. brevicompactum 0248 transformants with disrupted tri11, tri4, or tri3 gene. We also described the effect of tri11, tri3, or tri4 deletion on the expression of other genes in the tri cluster. Targeted Δtri3 knockout mutant exhibited a sharp decline in the production of trichodermin, and trichodermol, which is a substrate for trichodermin production, accumulated. Thus, the results demonstrated that tri3 was responsible for the biosynthesis of trichodermin, and the tri3 gene-encoded enzyme catalyzed the acetylation reaction of the hydroxy group at C-4 of the trichodermin skeleton. In addition, tri4 and tri11 deletion mutants were generated to evaluate the roles of tri4 and tri11 in trichodermin biosynthesis, respectively. Deletion mutant strain Δtri4 or Δtri11 did not produce trichodermin in T. brevicompactum, indicating that tri4 and tri11 are essential for trichodermin biosynthesis. This is the first to report the function of tri3, tri4 and tri11 in T. brevicompactum, although the role of tri4 and tri11 has already been described for T. arundinaceum by Cardoza et al. (Appl Environ Microbiol 77:4867-4877, 2011).

Identification of a novel fungus, Trichoderma asperellum GDFS1009, and comprehensive evaluation of its biocontrol efficacy

Due to its efficient broad-spectrum antimicrobial activity, Trichoderma has been established as an internationally recognized biocontrol fungus. In this study, we found and identified a novel strain of Trichoderma asperellum, named GDFS1009. The mycelium of T. asperellum GDFS1009 exhibits a high growth rate, high sporulation capacity, and strong inhibitory effects against pathogens that cause cucumber fusarium wilt and corn stalk rot. T. asperellum GDFS1009 secretes chitinase, glucanase, and protease, which can degrade the cell walls of fungi and contribute to mycoparasitism. The secreted xylanases are good candidates for inducing plant resistance and enhancing plant immunity against pathogens. RNA sequencing (RNA-seq) and gas chromatography-mass spectrometry (GC-MS) showed that T. asperellum GDFS1009 produces primary metabolites that are precursors of antimicrobial compounds; it also produces a variety of antimicrobial secondary metabolites, including polyketides and alkanes. In addition, this study speculated the presence of six antimicrobial peptides via ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS/MS). Future studies should focus on these antimicrobial metabolites for facilitating widespread application in the field of agricultural bio-control.

De Novo Transcriptome Analysis of Plant Pathogenic Fungus Myrothecium roridum and Identification of Genes Associated with Trichothecene Mycotoxin Biosynthesis

Myrothecium roridum is a plant pathogenic fungus that infects different crops and decreases the yield of economical crops, including soybean, cotton, corn, pepper, and tomato. Until now, the pathogenic mechanism of M. roridum has remained unclear. Different types of trichothecene mycotoxins were isolated from M. roridum, and trichothecene was considered as a plant pathogenic factor of M. roridum. In this study, the transcriptome of M. roridum in different incubation durations was sequenced using an Illumina Hiseq 2000. A total of 35,485 transcripts and 25,996 unigenes for M. roridum were obtained from 8.0 Gb clean reads. The protein-protein network of the M. roridum transcriptome indicated that the mitogen-activated protein kinases signal pathway also played an important role in the pathogenicity of M. roridum. The genes related to trichothecene biosynthesis were annotated. The expression levels of these genes were also predicted and validated through quantitative real-time polymerase chain reaction. Tri5 gene encoding trichodiene synthase was cloned and expressed, and the purified trichodiene synthase was able to catalyze farnesyl pyrophosphate into different kinds of sesquiterpenoids.Tri4 and Tri11 genes were expressed in Escherichia coli, and their corresponding enzymatic properties were characterized. The phylogenetic tree of trichodiene synthase showed a great discrepancy between the trichodiene synthase from M. roridum and other species. Our study on the genes related to trichothecene biosynthesis establishes a foundation for the M. roridum hazard prevention, thus improving the yields of economical crops.

Cytotoxic trichothecene-type sesquiterpenes from the sponge-derived fungus Stachybotrys chartarum with tyrosine kinase inhibition

Bioassay-guided fractionation of a sponge associated fungus Stachybotrys chartarum resulted in the isolation of 15 trichothecene-based sesquiterpenes with inhibitory effects against tumor cell lines.

Trichoderma Biodiversity of Agricultural Fields in East China Reveals a Gradient Distribution of Species

We surveyed the Trichoderma (Hypocreales, Ascomycota) biodiversity in agricultural fields in four major agricultural provinces of East China. Trichoderma strains were identified based on molecular approaches and morphological characteristics. In three sampled seasons (spring, summer and autumn), 2078 strains were isolated and identified to 17 known species: T. harzianum (429 isolates), T. asperellum (425), T. hamatum (397), T. virens (340), T. koningiopsis (248), T. brevicompactum (73), T. atroviride (73), T. fertile (26), T. longibrachiatum (22), T. pleuroticola (16), T. erinaceum (16), T. oblongisporum (2), T. polysporum (2), T. spirale (2), T. capillare (2), T. velutinum (2), and T. saturnisporum (1). T. harzianum, T. asperellum, T. hamatum, and T. virens were identified as the dominant species with dominance (Y) values of 0.057, 0.052, 0.048, and 0.039, respectively. The species amount, isolate numbers and the dominant species of Trichoderma varied between provinces. Zhejiang Province has shown the highest diversity, which was reflected in the highest species amount (14) and the highest Shannon–Wiener diversity index of Trichoderma haplotypes (1.46). We observed that relative frequencies of T. hamatum and T. koningiopsis under rice soil were higher than those under wheat and maize soil, indicating the preference of Trichoderma to different crops. Remarkable seasonal variation was shown, with summer exhibiting the highest biodiversity of the studied seasons. These results show that Trichoderma biodiversity in agricultural fields varies by region, crop, and season. Zhejiang Province (the southernmost province in the investigated area) had more T. hamatum than Shandong Province (the northernmost province), not only in isolate amounts but also in haplotype amounts. Furthermore, at haplotype level, only T. hamatum showed a gradient distribution from south to north in correspondence analysis among the four dominant species. The above results would contribute to the application of Trichoderma biocontrol strains.

The Terpenoid Biosynthesis Toolkit of Trichoderma

The widely used biotechnologically important fungi belonging to the genus Trichoderma are rich sources of secondary metabolites. Even though the genomes of several Trichoderma spp. have been published, and data are available on the genes involved in biosynthesis of non-ribosomal peptide synthetases and polyketide synthases, no genome-wide data are available for the terpenoid biosynthesis machinery in these organisms. In the present study, we have identified the genes involved in terpene biosynthesis in the genomes of three Trichoderma spp., viz., T. virens, T. atroviride and T. reesei. While the genes involved in the condensation steps are highly conserved across the three species, these fungi differed in the number and organization of terpene cyclases. T. virens genome harbours eleven terpene cyclases, while T. atroviride harbours seven, and T. reeseisix in their genomes; seven, three and two being part of putative secondary metabolism related gene clusters.

Familiar Stranger: Ecological Genomics of the Model Saprotroph and Industrial Enzyme Producer Trichoderma reesei Breaks the Stereotypes

The filamentous fungus Trichoderma reesei (Hypocreales, Ascomycota) has properties of an efficient cell factory for protein production that is exploited by the enzyme industry, particularly with respect to cellulase and hemicellulase formation. Under conditions of industrial fermentations it yields more than 100g secreted protein L(-1). Consequently, T. reesei has been intensively studied in the 20th century. Most of these investigations focused on the biochemical characteristics of its cellulases and hemicellulases, on the improvement of their properties by protein engineering, and on enhanced enzyme production by recombinant strategies. However, as the fungus is rare in nature, its ecology remained unknown. The breakthrough in the understanding of the fundamental biology of T. reesei only happened during 2000s-2010s. In this review, we compile the current knowledge on T. reesei ecology, physiology, and genomics to present a holistic view on the natural behavior of the organism. This is not only critical for science-driven further improvement of the biotechnological applications of this fungus, but also renders T. reesei as an attractive model of filamentous fungi with superior saprotrophic abilities.

Trichodiene Production in a Trichoderma harzianum erg1-Silenced Strain Provides Evidence of the Importance of the Sterol Biosynthetic Pathway in Inducing Plant Defense-Related Gene Expression

Trichoderma species are often used as biocontrol agents against plant-pathogenic fungi. A complex molecular interaction occurs among the biocontrol agent, the antagonistic fungus, and the plant. Terpenes and sterols produced by the biocontrol fungus have been found to affect gene expression in both the antagonistic fungus and the plant. The terpene trichodiene (TD) elicits the expression of genes related to tomato defense and to Botrytis virulence. We show here that TD itself is able to induce the expression of Botrytis genes involved in the synthesis of botrydial (BOT) and also induces terpene gene expression in Trichoderma spp. The terpene ergosterol, in addition to its role as a structural component of the fungal cell membranes, acts as an elicitor of defense response in plants. In the present work, using a transformant of T. harzianum, which is silenced in the erg1 gene and accumulates high levels of squalene, we show that this ergosterol precursor also acts as an important elicitor molecule of tomato defense-related genes and induces Botrytis genes involved in BOT biosynthesis, in both cases, in a concentration-dependent manner. Our data emphasize the importance of a balance of squalene and ergosterol in fungal interactions as well as in the biocontrol activity of Trichoderma spp.

Effects of Trichothecene Production on the Plant Defense Response and Fungal Physiology: Overexpression of the Trichoderma arundinaceum tri4 Gene in T. harzianum

Trichothecenes are fungal sesquiterpenoid compounds, the majority of which have phytotoxic activity. They contaminate food and feed stocks, resulting in potential harm to animals and human beings. Trichoderma brevicompactum and T. arundinaceum produce trichodermin and harzianum A (HA), respectively, two trichothecenes that show different bioactive properties. Both compounds have remarkable antibiotic and cytotoxic activities, but in addition, trichodermin is highly phytotoxic, while HA lacks this activity when analyzed in vivo. Analysis of Fusarium trichothecene intermediates led to the conclusion that most of them, with the exception of the hydrocarbon precursor trichodiene (TD), have a detectable phytotoxic activity which is not directly related to the structural complexity of the intermediate. In the present work, the HA intermediate 12,13-epoxytrichothec-9-ene (EPT) was produced by expression of the T. arundinaceum tri4 gene in a transgenic T. harzianum strain that already produces TD after transformation with the T. arundinaceum tri5 gene. Purified EPT did not show antifungal or phytotoxic activity, while purified HA showed both antifungal and phytotoxic activities. However, the use of the transgenic T. harzianum tri4 strain induced a downregulation of defense-related genes in tomato plants and also downregulated plant genes involved in fungal root colonization. The production of EPT by the transgenic tri4 strain raised levels of erg1 expression and reduced squalene accumulation while not affecting levels of ergosterol. Together, these results indicate the complex interactions among trichothecene intermediates, fungal antagonists, and host plants.

Phylogeny and taxonomical investigation of Trichoderma spp. from Indian region of Indo-Burma Biodiversity hot spot region with special reference to Manipur

Towards assessing the genetic diversity and occurrence of Trichoderma species from the Indian region of Indo-Burma Biodiversity hotspot, a total of 193 Trichoderma strains were isolated from cultivated soils of nine different districts of Manipur comprising 4 different agroclimatic zones. The isolates were grouped based on the morphological characteristics. ITS-RFLP of the rDNA region using three restriction digestion enzymes: Mob1, Taq1, and Hinf1, showed interspecific variations among 65 isolates of Trichoderma. Based on ITS sequence data, a total of 22 different types of representative Trichoderma species were reported and phylogenetic analysis showed 4 well-separated main clades in which T. harzianum was found to be the most prevalent spp. among all the Trichoderma spp. Combined molecular and phenotypic data leads to the development of a taxonomy of all the 22 different Trichoderma spp., which was reported for the first time from this unique region. All these species were found to produce different extrolites and enzymes responsible for the biocontrol activities against the harmful fungal phytopathogens that hamper in food production. This potential indigenous Trichoderma spp. can be targeted for the development of suitable bioformulation against soil and seedborne pathogens in sustainable agricultural practice.

Synthesis, antifungal activity, and QSAR study of novel trichodermin derivatives

In an attempt to discover more potential antifungal agents, in this study, 21 novel trichodermin derivatives containing conjugated oxime ester (5a-5u) were designed and synthesized and were screened for in vitro antifungal activity. The bioassay tests showed that some of them exhibited good inhibitory activity against the tested pathogenic fungi. Compound 5a exhibited better activity against Pyricularia oryzae and Sclerotonia sclerotiorum than trichodermin, and compound 5j showed particular activity against P.oryzae and Botrytis cinerea. The quantitative structure-activity relationship (QSAR) indicated that log P and hardness were two critical parameters for the biological activities. The result suggested that these would be potential lead compounds for the development of fungicides with further structure modification.

Synthesis and biological evaluation of novel trichodermin derivatives as antifungal agents

To discover more potential antifungal agents, 17 novel trichodermin derivatives were designed and synthesized by modification of 3 and 4a. The structures of all the synthesized compounds were confirmed by (1)H NMR, ESI-MS and HRMS. Their antifungal activities against Ustilaginoidea oryzae and Pyricularia oryzae were evaluated. Most of the target compounds showed potent inhibitory activity, in which 4g showed superior inhibitory effects than 4a and commercial fungicide prochloraz. Furthermore, 4h demonstrated comparable inhibitory activity to 4a. Moreover, 4i and 4l exhibited excellent inhibitory activity for Pyricularia oryzae. Additionally, compound 9 was found to be more active against all tested fungal strains than 3, with EC50 values of 0.47 and 3.71 mg L(-1), respectively.

Transcriptome sequencing and gene expression analysis of Trichoderma brevicompactum under different culture conditions

Background

Trichoderma brevicompactum is the Trichoderma species producing simple trichothecenes-trichodermin, a potential antifungal antibiotic and a protein synthesis inhibitor. However, the biosynthetic pathway of trichodermin in Trichoderma is not completely clarified. Therefore, transcriptome and gene expression profiling data for this species are needed as an important resource to better understand the mechanism of the trichodermin biosynthesis and provide a blueprint for further study of T. brevicompactum.

Results

In this study, de novo assembly of the T. brevicompactum transcriptome using the short-read sequencing technology (Illumina) was performed. In addition, two digital gene expression (DGE) libraries of T. brevicompactum under the trichodermin-producing and trichodermin-nonproducing culture conditions, respectively, were constructed to identify the differences in gene expression. A total of 23,351 unique transcripts with a mean length of 856 bp were obtained by a new Trinity de novo assembler. The variations of the gene expression under different culture conditions were also identified. The expression profiling data revealed that 3,282 unique transcripts had a significantly differential expression under the trichodermin-producing condition, as compared to the trichodermin-nonproducing condition. This study provides a large amount of transcript sequence data that will contribute to the study of the trichodermin biosynthesis in T. brevicompactum. Furthermore, quantitative real-time PCR (qRT-PCR) was found to be useful to confirm the differential expression of the unique transcripts.

Conclusion

Our study provides considerable gene expression information of T. brevicompactum at the transcriptional level,which will help accelerate the research on the trichodermin biosynthesis. Additionally, we have demonstrated the feasibility of using the Illumina sequencing based DGE system for gene expression profiling, and have shed new light on functional studies of the genes involved in T. brevicompactum biosynthesis.

Unraveling the efficient applications of secondary metabolites of various Trichoderma spp

Recent shift in trends of agricultural practices from application of synthetic fertilizers and pesticides to organic farming has brought into focus the use of microorganisms that carryout analogous function. Trichoderma spp. is one of the most popular genera of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. Exploitation of the diverse nature of secondary metabolites produced by different species of Trichoderma augments their extensive utility in agriculture and related industries. As a result, Trichoderma has achieved significant success as a powerful biocontrol agent at global level. The endorsement of Trichoderma spp. by scientific community is based on the understanding of its mechanisms of action against a large set of fungal, bacterial and in certain cases viral infections. However, it is still an agnostic view that there could be any single major mode of operation, although it is argued that all mechanisms operate simultaneously in a synchronized fashion. The central idea behind this review article is to emphasize the potentiality of applications of target specific secondary metabolites of Trichoderma for controlling phytopathogens as a substitute of commercially available whole organism formulations. With the aim to this point, we have compiled an inclusive list of secondary metabolites produced by different species of Trichoderma and their applications in diverse areas with the major emphasis on agriculture. Outlining the importance and diverse activities of secondary metabolites of Trichoderma besides its relevance to agriculture would generate greater understanding of their other important and beneficial applications apart from target specific biopesticides.

Mycotoxins: occurrence, toxicology, and exposure assessment

Mycotoxins are abiotic hazards produced by certain fungi that can grow on a variety of crops. Consequently, their prevalence in plant raw materials may be relatively high. The concentration of mycotoxins in finished products is usually lower than in raw materials. In this review, occurrence and toxicology of the main mycotoxins are summarised. Furthermore, methodological approaches for exposure assessment are described. Existing exposure assessments, both through contamination and consumption data and biomarkers of exposure, for the main mycotoxins are also discussed.

Trichodermin induces cell apoptosis through mitochondrial dysfunction and endoplasmic reticulum stress in human chondrosarcoma cells

Chondrosarcoma is the second most common primary bone tumor, and it responds poorly to both chemotherapy and radiation treatment. Nalanthamala psidii was described originally as Myxosporium in 1926. This is the first study to investigate the anti-tumor activity of trichodermin (trichothec-9-en-4-ol, 12,13-epoxy-, acetate), an endophytic fungal metabolite from N. psidii against human chondrosarcoma cells. We demonstrated that trichodermin induced cell apoptosis in human chondrosarcoma cell lines (JJ012 and SW1353 cells) instead of primary chondrocytes. In addition, trichodermin triggered endoplasmic reticulum (ER) stress protein levels of IRE1, p-PERK, GRP78, and GRP94, which were characterized by changes in cytosolic calcium levels. Furthermore, trichodermin induced the upregulation of Bax and Bid, the downregulation of Bcl-2, and the dysfunction of mitochondria, which released cytochrome c and activated caspase-3 in human chondrosarcoma. In addition, animal experiments illustrated reduced tumor volume, which led to an increased number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells and an increased level of cleaved PARP protein following trichodermin treatment. Together, this study demonstrates that trichodermin is a novel anti-tumor agent against human chondrosarcoma cells both in vitro and in vivo via mitochondrial dysfunction and ER stress.

Characterization of microbial communities and fungal metabolites on field grown strawberries from organic and conventional production

The background levels of culturable indigenous microbial communities (microbiotas) on strawberries were examined in a field survey with four conventional and four organic growers with different production practise and geographic distribution. The microbiota on apparently healthy strawberries was complex including potential plant pathogens, opportunistic human pathogens, plant disease biocontrol agents and mycotoxin producers. The latter group was dominated by Penicillium spp. and Aspergillus niger was also isolated. As expected, bacteria were the most abundant and diverse group of the strawberry microbiota followed by yeasts and filamentous fungi. No obvious correlation between grower practice and the strawberry microbiota was observed. Differences between microbiotas on strawberries from conventional systems with up to 10 fungicide spray treatments and organic production systems were insignificant. Mycotoxins were not detected in mature strawberries from any of the eight different growers neither in additional samples of low quality berries. However, isolates of Penicillium expansum and A. niger produced high amounts of mycotoxins when incubated on strawberries at 25°C. Penicillium polonicum produced cyclopenol, cyclopenin, and viridicatin on the artificially infected berries, while Alternaria arborescens produced tenuazonic acid, Alternaria tenuissima produced altertoxin I and altenuene, and Trichoderma spp. produced several peptaibols. In conclusion, native strawberry microbiotas are highly diverse both in terms of taxonomic groups and functional traits that are important in relation to plant and human health.

Mass spectrometry-based chemotaxonomic classification of Penicillium species (P. echinulatum, P. expansum, P. solitum, and P. oxalicum) and its correlation with antioxidant activity

In this study, 4 Penicillium species (17 strains) were classified on the basis of metabolite profile (chemotaxonomy) by using liquid chromatography-electrospray ionization ion trap-mass spectrometry (LC-ESI-MS), gas chromatography-ion trap-mass spectrometry (GC-IT-MS) and multivariate statistical analysis. The LC-ESI-MS-based dendrogram was similar to the internal transcribed spacer (ITS)-based dendrogram, in that Penicillium oxalicum was separated from the other 3 species. Moreover, vermiculidiol, meleagrin, oxaline, glandicolin A and B, and secalonic acid D were identified as metabolites that enable discrimination of Penicillium species by partial least squares discriminant analysis (PLS-DA). Evaluation of the species-specific metabolites produced by P. expansum, P. echinulatum, and P. solitum revealed that the 3 species differed from each other. On the other hand, GC-IT-MS-based dendrogram revealed that P. expansum was clearly classified separately from the other 3 species, and this result correlated with the antioxidant activity of the 4 species: P. expansum had a higher radical scavenging activity than the other 3 species. The metabolites produced in higher amounts in P. expansum were gluconic acid (12, 29, 33); andrastin A (16), B (15), and C (17); chaetoglobosin C (14), a class of sugar (31, 32); and salicylic acid (28). The results of this study demonstrated that metabolite-based chemotaxonomy could be used not only as a classification method but also as a tool for evaluation of species-specific activities.

8-{[(E)-3-(2-Chloro-phen-yl)acrylo-yloxy]imino}-12,13-ep-oxy-trichethec-9-en-4-yl (E)-3-(2-chloro-phen-yl)acrylate

In the title compound, C₃₃H₃₁Cl₂NO₆, the five-membered ring displays an envelope conformation, whereas the two six-membered rings both exhibit a chair conformation. As for the seven-membered ring, the dihedral angle between the mean planes formed by the four C atoms of the envelope unit and the three C and one O atoms of the six-membered chair is 69.08 (4)°, and these two mean planes are nearly perpendicular to the ep­oxy ring, making dihedral angles of 87.53 (4) and 88.67 (4)°, respectively.

Dereplication of microbial natural products by LC-DAD-TOFMS

Dereplication, the rapid identification of known compounds present in a mixture, is crucial to the fast discovery of novel natural products. Determining the elemental composition of compounds in mixtures and tentatively identifying natural products using MS/MS and UV/vis spectra is becoming easier with advances in analytical equipment and better compound databases. Here we demonstrate the use of LC-UV/vis-MS-based dereplication using data from UV/vis diode array detection and ESI+/ESI- time-of-flight MS for assignment of 719 microbial natural product and mycotoxin reference standards. ESI+ was the most versatile ionization method, detecting 93% of the compounds, although with 12% ionizing poorly. Using ESI+ alone, 56.1% of the compounds could be unambiguously assigned based on characteristic patterns of multiple adduct ions. Using ESI-, 36.4% of the compounds could have their molecular mass assigned unambiguously using multiple adduct ions, while a further 41% of the compounds were detected only as [M - H]-. The most reliable interpretations of conflicting ESI+ and ESI- data on a chromatographic peak were from the ionization polarity with the most intense ionization. Poor ionization was most common with small molecules (<200 Da). In ESI-, these were often polar and basic, while in ESI+ they were small aromatic acids or anthraquinones. No single ion-source settings could be applied over a m/z 60-2000 range. However, continuous switching among three settings (e.g., for 0.5 s each) during the chromatographic run allowed MS of both small labile molecules and large peptides, and pseudo MS/MS data on labile molecules since the settings for large molecules often induce fragmentation into small molecules.