Detection of peptaibols and partial cloning of a putative peptaibol synthetase gene fromT. harzianum CECT 2413

Eleven-Residue Peptaibols Isolated from Trichoderma Longibrachiatum Rifai DMG-3-1-1 and Their Structure-Activity Relationship

Total 23 eleven-residue peptaibols, including five reported ones (1-5) in our previous work, were isolated from the fungus Trichoderma longibrachiatum Rifai DMG-3-1-1, which was obtained from the mushroom Clitocybe nebularis (Batsch) P. Kumm. The structures of the 13 new peptaibols (6-10 and 12-19) were determined by their NMR and MALDI-MS/MS data, their absolute structures were further determined by Marfey's analyses and their ECD data. Careful comparison of the structures of 1-23 showed that only seven residues varied including the 2nd (Gln 2 /Asn 2 ), 3rd (Ile 3 /Val 3 ), 4th (Ile 4 /Val 4 ), 6th (Pro 6 /Hyp 6 ), 8 th (Pro 6 /Hyp 6 ), 10th (Pro 10 /Hyp 10 ) and 11th (Leuol 11 /Ileol 11 /Valol 11 ) residues. Comparison of the IC 50 s against the three tested cell lines of 1-23 indicated that 2nd, 3rd and 4th amino acid residues affected their cytotoxicities powerfully. Compounds 2, 5, 9, 11, 21 and 22 showed moderate antibacterial activities against Staphylococcus aureus MRSA T144, which also showed stronger cytotoxicities against BV2 and MCF-7 cells.

Front line defenders of the ecological niche! Screening the structural diversity of peptaibiotics from saprotrophic and fungicolous Trichoderma/Hypocrea species

Approximately 950 individual sequences of non-ribosomally biosynthesised peptides are produced by the genus Trichoderma/Hypocrea that belong to a perpetually growing class of mostly linear antibiotic oligopeptides, which are rich in the non-proteinogenic α-aminoisobutyric acid (Aib). Thus, they are comprehensively named peptaibiotics. Notably, peptaibiotics represent ca. 80 % of the total inventory of secondary metabolites currently known from Trichoderma/Hypocrea. Their unique membrane-modifying bioactivity results from amphipathicity and helicity, thus making them ideal candidates in assisting both colonisation and defence of the natural habitats by their fungal producers. Despite this, reports on the in vivo-detection of peptaibiotics have scarcely been published in the past. In order to evaluate the significance of peptaibiotic production for a broader range of potential producers, we screened nine specimens belonging to seven hitherto uninvestigated fungicolous or saprotrophic Trichoderma/Hypocrea species by liquid chromatography coupled to electrospray high resolution mass spectrometry. Sequences of peptaibiotics found were independently confirmed by analysing the peptaibiome of pure agar cultures obtained by single-ascospore isolation from the specimens. Of the nine species examined, five were screened positive for peptaibiotics. A total of 78 peptaibiotics were sequenced, 56 (=72 %) of which are new. Notably, dihydroxyphenylalaninol and O-prenylated tyrosinol, two C-terminal residues, which have not been reported for peptaibiotics before, were found as well as new and recurrent sequences carrying the recently described tyrosinol residue at their C-terminus. The majority of peptaibiotics sequenced are 18- or 19-residue peptaibols. Structural homologies with 'classical representatives' of subfamily 1 (SF1)-peptaibiotics argue for the formation of transmembrane ion channels, which are prone to facilitate the producer capture and defence of its substratum.

Overexpression of the Trichoderma brevicompactum tri5 gene: effect on the expression of the trichodermin biosynthetic genes and on tomato seedlings

Trichoderma brevicompactum IBT 40841 produces trichodermin, a trichothecene-type toxin that shares most of the steps of its biosynthesis with harzianum A, another trichothecene produced by several Trichoderma species. The first specific step in the trichothecene biosynthesis is carried out by a terpene cylcase, trichodiene synthase, that catalyzes the conversion of farnesyl pyrophosphate to trichodiene and that is encoded by the tri5 gene. Overexpression of tri5 resulted in increased levels of trichodermin production, but also in an increase in tyrosol and hydroxytyrosol production, two antioxidant compounds that may play a regulatory role in trichothecene biosynthesis, and also in a higher expression of three trichothecene genes, tri4, tri6 and tri10, and of the erg1 gene, which participates in the synthesis of triterpenes. The effect of tri5 overexpression on tomato seedling disease response was also studied.

Overexpression of the trichodiene synthase gene tri5 increases trichodermin production and antimicrobial activity in Trichoderma brevicompactum

Trichoderma brevicompactum produces trichodermin, a simple trichothecene-type toxin that shares the first steps of the sesquiterpene biosynthetic pathway with other phytotoxic trichothecenes from Fusarium spp. Trichodiene synthase catalyses the conversion of farnesyl pyrophosphate to trichodiene and it is encoded by the tri5 gene that was cloned and analysed functionally by homologous overexpression in T. brevicompactum. tri5 expression was up-regulated in media with glucose, H(2)O(2) or glycerol. tri5 repression was observed in cultures supplemented with the antioxidants ferulic acid and tyrosol. Acetone extracts of tri5-overexpressing transformants displayed higher antifungal activity than those from the wild-type. Chromatographic and spectroscopic analyses revealed that tri5 overexpression led to an increased production of trichodermin and tyrosol. Agar diffusion assays with these two purified metabolites from the tri5-overexpressing transformant T. brevicompactum Tb41tri5 showed that only trichodermin had antifungal activity against Saccharomyces cerevisiae, Kluyveromyces marxianus, Candida albicans, Candida glabrata, Candida tropicalis and Aspergillus fumigatus, in most cases such activity being higher than that observed for amphotericin B and hygromycin. Our results point to the significant role of tri5 in the production of trichodermin and in the antifungal activity of T. brevicompactum.

Two classes of new peptaibols are synthesized by a single non-ribosomal peptide synthetase of Trichoderma virens

Peptaibols are a group of small peptides having a high α-aminoisobutyric acid (Aib) content and produced by filamentous fungi, especially by the members of the genus Trichoderma (anamorph Hypocrea). These antibiotics are economically important for their anti-microbial and anti-cancer properties as well as ability to induce systemic resistance in plants against microbial invasion. In this study we present sequences of two classes (11-residue and 14-residue) of peptaibols produced by the biocontrol fungus Trichoderma virens. Of the 35 11-residue peptaibols sequenced, 18 are hitherto not described, and all the 53 14-residue sequences described by us here are new. We have also identified a peptaibol synthetase (non-ribosomal peptide synthetase, NRPS) with 14 complete modules in the genome of this fungus and disruption of this single gene (designated as tex2) resulted in the loss of both the classes of peptaibols. We, thus present here an unprecedented case where a single NRPS encodes for two classes of peptaibols. The new peptaibols identified here could have applications as therapeutic agents for the management of human and plant health.

Fungal genus Hypocrea/Trichoderma: from barcodes to biodiversity

Hypocrea/Trichoderma is a genus of soil-borne or wood-decaying fungi containing members important to mankind as producers of industrial enzymes and biocontrol agents against plant pathogens, but also as opportunistic pathogens of immunocompromised humans and animals, while others can cause damage to cultivated mushroom. With the recent advent of a reliable, BarCode-aided identification system for all known taxa of Trichoderma and Hypocrea, it became now possible to study some of the biological fundamentals of the diversity in this fungal genus in more detail. In this article, we will therefore review recent progress in (1) the understanding of the geographic distribution of individual taxa; (2) mechanisms of speciation leading to development of mushroom diseases and facultative human mycoses; and (3) the possible correlation of specific traits of secondary metabolism and molecular phylogeny.

Dothideomycete plant interactions illuminated by genome sequencing and EST analysis of the wheat pathogen Stagonospora nodorum

Stagonospora nodorum is a major necrotrophic fungal pathogen of wheat (Triticum aestivum) and a member of the Dothideomycetes, a large fungal taxon that includes many important plant pathogens affecting all major crop plant families. Here, we report the acquisition and initial analysis of a draft genome sequence for this fungus. The assembly comprises 37,164,227 bp of nuclear DNA contained in 107 scaffolds. The circular mitochondrial genome comprises 49,761 bp encoding 46 genes, including four that are intron encoded. The nuclear genome assembly contains 26 classes of repetitive DNA, comprising 4.5% of the genome. Some of the repeats show evidence of repeat-induced point mutations consistent with a frequent sexual cycle. ESTs and gene prediction models support a minimum of 10,762 nuclear genes. Extensive orthology was found between the polyketide synthase family in S. nodorum and Cochliobolus heterostrophus, suggesting an ancient origin and conserved functions for these genes. A striking feature of the gene catalog was the large number of genes predicted to encode secreted proteins; the majority has no meaningful similarity to any other known genes. It is likely that genes for host-specific toxins, in addition to ToxA, will be found among this group. ESTs obtained from axenic mycelium grown on oleate (chosen to mimic early infection) and late-stage lesions sporulating on wheat leaves were obtained. Statistical analysis shows that transcripts encoding proteins involved in protein synthesis and in the production of extracellular proteases, cellulases, and xylanases predominate in the infection library. This suggests that the fungus is dependant on the degradation of wheat macromolecular constituents to provide the carbon skeletons and energy for the synthesis of proteins and other components destined for the developing pycnidiospores.

Formation of atroviridin by Hypocrea atroviridis is conidiation associated and positively regulated by blue light and the G protein GNA3

Species of the mycoparasitic fungal genus Hypocrea/Trichoderma are prominent producers of peptaibols, a class of small linear peptides of fungal origin. Some of these peptaibols have been shown to act synergistically with cell-wall-degrading enzymes in the inhibition of the growth of other fungi in vitro and in vivo. Here we present the structure of the Hypocrea atroviridis peptaibol synthetase gene (pbs1), deduced from the genome sequence of H. atroviridis. It consists of 19 typical peptide synthetase modules with the required additional modifying domains at the N and C termini. Phylogenetic and similarity analyses of the individual amino acid-activating modules is consistent with its ability to synthesize atroviridins. Matrix-assisted laser desorption ionization-time of flight mass spectrometry of surface-grown cultures of H. atroviridis showed that no peptaibols were formed during vegetative growth, but a microheterogenous mixture of atroviridins accumulated when the colonies started to sporulate. This correlation between sporulation and atroviridin formation was shown to be independent of the pathway inducing sporulation (i.e., light, mechanical injury and carbon starvation, respectively). Atroviridin formation was dependent on the function of the two blue light regulators, BLR1 and BLR2, under some but not all conditions of sporulation and was repressed in a pkr1 (regulatory subunit of protein kinase A) antisense strain with constitutively active protein kinase A. Conversely, however, loss of function of the Galpha-protein GNA3, which is a negative regulator of sporulation and leads to a hypersporulating phenotype, fully impairs atroviridin formation. Our data show that formation of atroviridin by H. atroviridis occurs in a sporulation-associated manner but is uncoupled from it at the stage of GNA3.

Intact-cell MALDI-TOF mass spectrometry analysis of peptaibol formation by the genus Trichoderma/Hypocrea: can molecular phylogeny of species predict peptaibol structures?

Peptaibols are characteristic linear alpha-aminoisobutyrate-containing peptides produced by certain Ascomycetes, especially of the genus Hypocrea/Trichoderma [Hypocrea and Trichoderma are the names for the teleo- and anamorph forms of the same taxon; where known to occur in nature, the teleomorph is used to name the species. To aid the inexperienced reader, both names (the less well known one in parentheses) are given at the first mention of each species.] Here we have investigated whether phylogenetic relationships within Trichoderma permit a prediction of the peptaibol production profiles. To this end, representative strains from a third (28) of the known species of Trichoderma, identified by the sequences of diagnostic genes and covering most clades of the established multilocus phylogeny of Trichoderma/Hypocrea, were investigated by intact-cell MALDI-TOF mass spectrometry. Peptaibols were detected in all strains, and some strains were found to produce up to five peptide families of different sizes. Comparison of the data with phylogenies derived from rRNA spacer regions (ITS1 and 2) and RNA polymerase subunit B (rpb2) gene sequences did not show a strict correlation with the types and sequences of the peptaibols produced, but the production of some groups of peptaibols appears to be found only in some clades or sections of the genus, which could be used for more targeted screening of novel compounds of this type. In an analysis of peptaibol structures, we have defined conserved key positions and have further identified and compared sequences of the corresponding adenylate domains within non-ribosomal peptide synthetases producing trichovirins, paracelsins and atroviridins. These phylogenies are not concordant with those of their producers Hypocrea virens, Hypocrea jecorina and Hypocrea atroviridis as obtained from ITS1 and 2, and rpb2, respectively, and therefore hint at a complex history of peptaibol diversity.

Facts and Challenges in the Understanding of the Biosynthesis of Peptaibols byTrichoderma

Species of the mitosporic filamentous fungal genus Trichoderma are prominent producers of both short (7-11 residues) and long (18-20 residues) peptaibols and peptaibiotics, which are thought to be involved in their interaction with other living systems. Numerous reviews are available regarding biodiversity, structure, and mode of action of these peptide derivatives, but little emphasis has been paid to the physiology and genetics of their formation. In this review article, we used the recent knowledge on biosynthesis and production of these components to speculate on some of the unknown points. We also highlight areas where further research is most urgently needed.

Peptaibols of trichoderma

The fungal genus Trichoderma has various applications in industry and in medicine, and several species have economic importance as sources of enzymes, antibiotics, plant growth promoters, decomposers of xenobiotics, and as commercial biofungicides. Peptaibiotics and peptaibols are a class of linear peptides synthesized by such fungi, and more than 300 have been described to date. Of this class, those compounds exhibiting antimicrobial activity are referred to as antibiotic peptides. In this review, the biosynthesis, fermentation, structure elucidation (by MS and NMR techniques in particular) and biological activity of antibiotic peptides from Trichoderma species are described.