Trichoderma virens and Pseudomonas chlororaphis Differentially Regulate Maize Resistance to Anthracnose Leaf Blight and Insect Herbivores When Grown in Sterile versus Non-Sterile Soils

Soil-borne Trichoderma spp. have been extensively studied for their biocontrol activities against pathogens and growth promotion ability in plants. However, the beneficial effect of Trichoderma on inducing resistance against insect herbivores has been underexplored. Among diverse Trichoderma species, consistent with previous reports, we showed that root colonization by T. virens triggered induced systemic resistance (ISR) to the leaf-infecting hemibiotrophic fungal pathogens Colletotrichum graminicola. Whether T. virens induces ISR to insect pests has not been tested before. In this study, we investigated whether T. virens affects jasmonic acid (JA) biosynthesis and defense against fall armyworm (FAW) and western corn rootworm (WCR). Unexpectedly, the results showed that T. virens colonization of maize seedlings grown in autoclaved soil suppressed wound-induced production of JA, resulting in reduced resistance to FAW. Similarly, the bacterial endophyte Pseudomonas chlororaphis 30-84 was found to suppress systemic resistance to FAW due to reduced JA. Further comparative analyses of the systemic effects of these endophytes when applied in sterile or non-sterile field soil showed that both T. virens and P. chlororaphis 30-84 triggered ISR against C. graminicola in both soil conditions, but only suppressed JA production and resistance to FAW in sterile soil, while no significant impact was observed when applied in non-sterile soil. In contrast to the effect on FAW defense, T. virens colonization of maize roots suppressed WCR larvae survival and weight gain. This is the first report suggesting the potential role of T. virens as a biocontrol agent against WCR.

Antifungal mechanism of cell-free supernatant produced by Trichoderma virens and its efficacy for the control of pear Valsa canker

Introduction

Pear Valsa canker, caused by Valsa pyri (V. pyri), poses a major threat to pear production. We aimed to assess the effectiveness of the cell-free supernatant (CFS) produced by Trichoderma virens (T. virens) to control the development of pear Valsa canker and reveal the inhibitory mechanism against the pathogenic fungi.

Results

Using morphological characteristics and phylogenetic analysis, the pathogen G1H was identified as V. pyri, and the biocontrol fungus WJ561 was identified as Trichoderma virens. CFS derived from WJ561 exhibited strong inhibition of mycelial growth and was capable of reducing the pathogenicity of V. pyri on pear leaves and twigs. Scanning electron microscopy (SEM) observations revealed deformations and shrinkages in the fungal hyphae treated with CFS. The CFS also destroyed the hyphal membranes leading to the leakage of cellular contents and an increase in the malondialdehyde (MDA) content. Additionally, CFS significantly inhibited the activities of catalase (CAT) and superoxide dismutase (SOD), and downregulated the expression of antioxidant defense-related genes in V. pyri, causing the accumulation of reactive oxygen species (ROS). Artesunate, identified as the main component in CFS by liquid chromatograph-mass spectrometry (LC-MS), exhibited antifungal activity against V. pyri.

Conclusion

Our findings demonstrate the promising potential of T. virens and its CFS in controlling pear Valsa canker. The primary inhibitory mechanism of CFS involves multiple processes, including membrane damage and negatively affecting enzymatic detoxification pathways, consequently leading to hyphal oxidative damage of V. pyri. This study lays a theoretical foundation for the utilization of T. virens to control V. pyri in practical production.

First Report of Polygonatum cyrtonema Hua Root Rot Caused by Trichoderma virens in China

Polygonatum cyrtonema Hua is a traditional Chinese medicine, which has anti-oxidant, anti-inflammatory, immunomodulatory, and other pharmacological effects (Lu et al. 2023). In June 2022, A disease of root rot was observed on P. cyrtonema plants in Tonggu County (28°63'89″N, 114°48'07″E), Jiangxi Province, China. The disease incidence was approximately 30% in a surveyed area of 3 hectares, which contained approximately 20,000 plants. Initially, the above-ground parts of the plants did not show any obvious symptoms. However, the underground roots exhibited red-brown spots that gradually expanded and sunken areas appeared, and the diseased plants presented leaf chlorosis and red-brown discoloration of the tubers, eventually leading to plant death. To identify the pathogen, symptomatic root tissues (0.5×0.5×0.5cm) from the lesion margin surface were sterilized with 75% ethanol for 30s, 3% NaClO for 3 min followed by rinsing three times with sterile water. The sterile root pieces were placed on potato dextrose agar (PDA) and incubated at 25℃. Thirteen pure fungal isolates with the same morphological characteristics were obtained by monosporic isolation from 20 pieces of roots, and the representative isolates, HJGF1-1, HJGF1-2 were used for morphological studies and phylogenetic analyses. Initially, the two colonies on PDA appeared white with cotton-shaped aerial hyphae, which later turned light green to green and formed concentric rings. At the end of the conidiophores, 3 to 6 pear-shaped branches are irregularly gathered, and the angles between the branches are acute. The conidia were mostly solitary ellipsoid or obovate with the size of (3.7-5.9) × (3.6-4.5) μm (n=100). These morphological characteristics are consistent with the description of a Trichoderma spp. (Kamala et al. 2015). For molecular identification, the internal transcribed spacer (ITS), translation elongation factor 1-alpha (TEF-1α) and RNA polymerase II second largest subunit (RPB2) sequences were PCR amplified using primer pairs of ITS1/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone et al. 1999), and RPB2-5F2/RPB2-7cR (O'Donnell et al. 2022), respectively. BLAST analysis showed that the ITS, TEF-1α and RPB2 sequences of isolates HJGF1-1 (GenBank accession nos. OR229621, OR290791, OR334600) and HJGF1-2 (GenBank accession nos. OR229622, OR290792, OR334600) showed 99%-100% identity with multiple GenBank sequences of Trichoderma virens. A phylogenetic tree based on concatenated sequences of ITS, TEF-1α and RPB2 using maximum-likelihood analyses revealed that the two isolates HJGF1-1 and HJGF1-2 were in the same clade with T. virens strains. The two isolates were identified as T. virens based on the morphological characteristics and molecular phylogeny. To test pathogenicity, ten healthy P. cyrtonema plants (one tuber each, 5 tubers per isolate, n=10) in the field were pin-pricked with a sterile needle and pour-inoculated with 5 mL spore suspension per tuber (1× 107 conidia/ mL) with a temperature of about 28℃. Another five tubers were were pin-pricked with a sterile needle, inoculated with sterile water and served as controls. The resulting symptoms were similar to those on the original infected plants in the field, and control tubers remained symptomless fourteen days after inoculation. T. virens was reisolated from the diseased tubers, nevertheless no pathogenic fungus was isolated from the control tubers. T. virens has been reported causing disease on tulip bulb (Lou et al. 2003) but has not previously been reported causing disease on P. cyrtonema. Although several species of Trichoderma are known to be beneficial microorganisms, the beneficial fungus may have had an evolutionary period of interaction with plants in which it behaved as a plant pathogen (Poveda et al. 2022). To our knowledge, this is the first report of T. virens infecting P. cyrtonema in China. This result may expanded the etiological study of T. virens and the control strategy of P. cyrtonema root rot.

Electrochemical and biosensing properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens

We investigated the bioelectrochemical properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens (TvGDH) and its electrochemical behaviour when immobilized on a graphite electrode. TvGDH was recently shown to have an unusual substrate spectrum and to prefer maltose over glucose as substrate, and hence could be of interest as recognition element in a maltose sensor. In this study, we determined the redox potential of TvGDH, which is -0.268 ± 0.007 V vs. SHE, and advantageously low to be used with many redox mediators or redox polymers. The enzyme was entrapped in, and wired by an osmium redox polymer (poly(1-vinylimidazole-co-allylamine)-{[Os(2,2'-bipyridine)₂Cl]Cl}) with formal redox potential of +0.275 V vs. Ag|AgCl via poly(ethylene glycol) diglycidyl ether crosslinking onto a graphite electrode. When the TvGDH-based biosensor was tested with maltose it showed a sensitivity of 1.7 μA mM^-1cm^-2, a linear range of 0.5-15 mM, and a detection limit of 0.45 mM. Furthermore, it gave the lowest apparent Michaelis-Menten constant (K_{M app}) of 19.2 ± 1.5 mM towards maltose when compared to other sugars. The biosensor is also able to detect other saccharides including glucose, maltotriose and galactose, these however also interfere with maltose sensing.

Virenscarotins A-M, thirteen undescribed carotane sesquiterpenes from the fungus Trichoderma virens

A document investigation on the fungus Trichoderma virens led to the isolation of thirteen undescribed carotane sesquiterpenes and homologous. All structures were elucidated on the basis of NMR and HRESIMS data, and their absolute configurations were assigned by ECD calculation. Especially, virenscarotins A and B were first ramifications forged by aldol condensation of 4-hydroxy-3-isopentenyl-benzaldehyde with two hydroxyl groups in ring A of traditional carotane sesquiterpenes. Ring rearrangement/expansion and oxidative cleavage of normal carotane sesquiterpenes lead to the six-membered ring A of compound virenscarotin C and the ring A cleavage of compound virenscarotin D. All compounds were evaluated for cytotoxic, anti-inflammatory, and seed germination inhibitory activities.

Purification, identification and characterization of Nag2 N-acetylglucosaminidase from Trichoderma virens strain mango

BACKGROUND

N-acetylglucosaminidase (NAGase) could liberate N-acetylglucosamine (GlcNAc) from GlcNAc-containing oligosaccharides. Trichoderma spp. is an important source of chitinase, particularly NAGase for industrial use. nag1 and nag2 genes encoding NAGase, are found in the genome in Trichoderma spp. The deduced Nag1 and Nag2 shares ~ 55% homology in Trichoderma virens. Most studies were focus on Nag1 and nag1 previously.

RESULTS

The native NAGase (TvmNAG2) was purified to homogeneity with molecular mass of ~ 68 kDa on SDS-PAGE analysis, and identified as Nag2 by MALDI/MS analysis from an isolate T. virens strain mango. RT-PCR analyses revealed that only nag2 gene was expressed in liquid culture of T. virens, while both of nag1 and nag2 were expressed in T. virens cultured on the plates. TvmNAG2 was thermally stable up to 60 °C for 2 h, and the optimal pH and temperature were 5.0 and 60-65 °C, respectively, using p-nitrophenyl-N-acetyl-β-D-glucosaminide (pNP-NAG) as substrate. The hydrolytic product of colloidal chitin by TvmNAG2 was suggested to be GlcNAc based on TLC analyses. Moreover, TvmNAG2 possesses antifungal activity, inhibiting the mycelium growth of Sclerotium rolfsii. And it was resistant to the proteolysis by papain and trypsin.

CONCLUSIONS

The native Nag2, TvmNAG2 was purified and identified from T. virens strain mango, as well as enzymatic properties. To our knowledge, it is the first report with the properties of native Trichoderma Nag2.

Mixtures of Biological Control Agents and Organic Additives Improve Physiological Behavior in Cape Gooseberry Plants under Vascular Wilt Disease

This study aimed to assess the soil application of mixtures of biological control agents (BCAs) (Trichoderma virens and Bacillus velezensis) and organic additives (chitosan and burnt rice husk) on the physiological and biochemical behavior of cape gooseberry plants exposed to Fusarium oxysporum f. sp. physali (Foph) inoculum. The treatments with inoculated and non-inoculated plants were: (i) T. virens + B. velezensis (Mix), (ii) T. virens + B. velezensis + burnt rice husk (MixRh), (iii) T. virens + B. velezensis + chitosan (MixChi), and (iv) controls (plants without any mixtures). Plants inoculated and treated with Mix or MixChi reduced the area under the disease progress curve (AUDPC) (57.1) and disease severity index (DSI) (2.97) compared to inoculated plants without any treatment (69.3 for AUDPC and 3.2 for DSI). Additionally, these groups of plants (Mix or MixChi) obtained greater leaf water potential (~-0.5 Mpa) and a lower MDA production (~12.5 µmol g^-2 FW) than plants with Foph and without mixtures (-0.61 Mpa and 18.2 µmol g^-2 FW, respectively). The results suggest that MixChi treatments may be a promising alternative for vascular wilt management in cape gooseberry crops affected by this disease.

Transcriptome Dynamics Underlying Chlamydospore Formation in Trichoderma virens GV29-8

Trichoderma spp. are widely used biocontrol agents which are antagonistic to a variety of plant pathogens. Chlamydospores are a type of propagules produced by many fungi that have thick walls and are highly resistant to adverse environmental conditions. Chlamydospore preparations of Trichoderma spp. can withstand various storage conditions, have a longer shelf life than conidial preparations and have better application potential. However, large-scale production of chlamydospores has proven difficult. To understand the molecular mechanisms governing chlamydospore formation (CF) in Trichoderma fungi, we performed a comprehensive analysis of transcriptome dynamics during CF across 8 different developmental time points, which were divided into 4 stages according to PCA analysis: the mycelium growth stage (S1), early and middle stage of CF (S2), flourishing stage of CF (S3), and late stage of CF and mycelia initial autolysis (S4). 2864, 3206, and 3630 DEGs were screened from S2 vs S1, S3 vs S2, and S4 vs S3, respectively. We then identified the pathways and genes that play important roles in each stage of CF by GO, KEGG, STC and WGCNA analysis. The results showed that DEGs in the S2 vs S1 were mainly enriched in organonitrogen compound metabolism, those in S3 vs S2 were mainly involved in secondary metabolite, cell cycle, and N-glycan biosynthesis, and DEGs in S4 vs S3 were mainly involved in lipid, glycogen, and chitin metabolic processes. We speculated that mycelial assimilation and absorption of exogenous nitrogen in the early growth stage (S1), resulted in subsequent nitrogen deficiency (S2). At the same time, secondary metabolites and active oxygen free radicals released during mycelial growth produced an adverse growth environment. The resulting nitrogen-deficient and toxin enriched medium may stimulate cell differentiation by initiating cell cycle regulation to induce morphological transformation of mycelia into chlamydospores. High expression of genes relating to glycogen, lipid, mannan, and chitin synthetic metabolic pathways during the flourishing (S3) and late stages (S4) of CF may be conducive to energy storage and cell wall construction in chlamydospores. For further verifying the functions of the amino sugar and nucleotide sugar metabolism (tre00520) pathway in the CF of T. virens GV29-8 strain, the chitin synthase gene (TRIVIDRAFT_90152), one key gene of the pathway, was deleted and resulted in the dysplasia of mycelia and an incapability to form normal chlamydospores, which illustrated the pathway affecting the CF of T. virens GV29-8 strain. Our results provide a new perspective for understanding the genetics of biochemical pathways involved in CF of Trichoderma spp.

Isolation and Characterization of Antibacterial Carotane Sesquiterpenes from Artemisia argyi Associated Endophytic Trichoderma virens QA-8

Carotane sesquiterpenes are commonly found in plants but are infrequently reported in the fungal kingdom. Chemical investigation of Trichoderma virens QA-8, an endophytic fungus associated with the inner root tissue of the grown medicinal herb Artemisia argyi H. Lév. and Vaniot, resulted in the isolation and characterization of five new carotane sesquiterpenes trichocarotins I-M (1-5), which have diverse substitution patterns, and seven known related analogues (6-12). The structures of these compounds were established on the basis of a detailed interpretation of their NMR and mass spectroscopic data, and the structures including the relative and absolute configurations of compounds 1-3, 5, 9, and 10 were confirmed by X-ray crystallographic analysis. In the antibacterial assays, all isolates exhibited potent activity against Escherichia coli EMBLC-1, with MIC values ranging from 0.5 to 32 µg/mL, while 7β-hydroxy CAF-603 (7) strongly inhibited Micrococcus luteus QDIO-3 (MIC = 0.5 µg/mL). Structure-activity relationships of these compounds were discussed. The results from this study demonstrate that the endophytic fungus T. virens QA-8 from the planted medicinal herb A. argyi is a rich source of antibacterial carotane sesquiterpenes, and some of them might be interesting for further study to be developed as novel antibacterial agents.

The Role of Cell Wall Degrading Enzymes in Antagonistic Traits of Trichoderma virens Against Rhizoctonia solani

Background:

High antagonistic ability of different Trichoderma species against a diverse range of plant pathogenic fungi has led them to be used as a biological fungicide in agriculture. They can also promote plant growth, fertility, resistance to stress, and absorption of nutrients. They are also opportunistic and symbiotic pathogens, which can lead to the activation of plant defense mechanisms.

Objectives:

The aim of this present study was to investigate possible enhancement of lytic enzymes production and biocontrol activity of T. virens against Rhizoctonia solani through gamma radiation and to find the relationship between changes in lytic enzyme production and antagonistic activity of T. virens.

Material and Methods:

Dual culture conditions were used to evaluate the antagonistic effect of T. virens and its gamma mutants against R. solani. Then, their chitinase and cellulase activities were measured. For more detailed investigation of enzymes, densitometry pattern of the proteins was extracted from the T. virens wild-type and its mutants were obtained via SDS-polyacrylamide gel electrophoresis.

Results:

The mutant T.vi M₈, T. virens wild-type and mutant T.vi M₂₀ strains showed the maximum antagonistic effects against the pathogen, respectively. Data showed that the mutant T. vi M₈ reduced the growth of R. solani by 58 %. The mutants revealed significantly different (p<0.05) protein contents, chitinase and cellulase production (mg.mL^-1) and activity (U.mL-1) compared to the wild-type strain. The highest extracellular protein production in the supernatant of chitinase and cellulase TFM was observed for the T.vi M₁₁ and T.vi M₁₇ strains, respectively. The T.vi M₁₂ and wild-type strains secreted chitinase and cellulase significantly more than other strains did. Densitometry of SDS-PAGE gel bands indicated that both the amount and diversity of chitinase related proteins in the selected mutant (T. vi M₈) were far higher than those of the wild-type. The diversity of molecular weight of proteins extracted from the T. virens M₈ (20 proteins or bands) was very high compared to the wild-type (10 proteins) and mutant T.vi M₁₅ (2 proteins).

Conclusions:

Overall, there was a strong link between the diversity of various chitinase proteins and the antagonistic properties of the mutant M8.

Mycosynthesis of Silver Nanoparticles Using Screened Trichoderma Isolates and Their Antifungal Activity against Sclerotinia sclerotiorum

To control the disease caused by Sclerotinia sclerotiorum, a total of 15 isolates of the Trichoderma species was screened for the biosynthesis of silver nanoparticles (AgNPs). Among them, the highest yield occurred in the synthesis of AgNPs using a cell-free aqueous filtrate of T.virens HZA14 producing gliotoxin. The synthetic AgNPs were charactered by SEM, EDS, TEM, XRD, and FTIR. Electron microscopy studies revealed that the size of AgNPs ranged from 5–50 nm and had spherical and oval shapes with smooth surfaces. Prepared AgNPs interacted with protein, carbohydrate and heterocyclic compound molecules, and especially, interaction patterns of AgNPs with the gliotoxin molecule were proposed. The antifungal activity assays demonstrated that percentage inhibition of the prepared AgNPs was 100, 93.8 and 100% against hyphal growth, sclerotial formation, and myceliogenic germination of sclerotia at a concentration of 200 μg/mL, respectively. The direct interaction between nanoparticles and fungal cells, including AgNPs’ contact, accumulation, lamellar fragment production and micropore or fissure formation on fungal cell walls, was revealed by SEM and EDS. These will extend our understanding of the mechanisms of AgNPs’ action for preventing diversified fungal disease.

Cadinane and carotane derivatives from the marine algicolous fungus Trichoderma virens RR-dl-6-8

Eight cadinane derivatives, trichocadinins H - N (1-7) and methylhydroheptelidate (8), and two carotane derivatives, 14-O-methyltrichocarotin G (9) and 14-O-methyl CAF-603 (10), including eight new ones (1-6, 9, and 10), were isolated from the culture of Trichoderma virens RR-dl-6-8 obtained from the organohalogen-enriched marine red alga Rhodomela confervoides. Their structures and relative configurations were established by analysis of NMR and mass spectroscopic data, and the absolute configurations were assigned on the basis of ECD curves, highlighted by the ECD diversity of carboxylic acid derivatives. Among the isolates, 1 with a halogen atom and 8, a new naturally occurring compound, are 2,3-seco-cadinane sesquiterpenes, and the epimeric 2 and 3 feature a 2-nor-cadinane skeleton. A commercially-sourced compound with the same planar structure as that of 7 has been reported in a patent, but its configuration was not given. Compounds 1-10 exhibited growth inhibition of some marine phytoplankton species.

Expression of a heptelidic acid-insensitive recombinant GAPDH from Trichoderma virens, and its biochemical and biophysical characterization

Trichoderma virens genome harbors two isoforms of GAPDH, one (gGPD) involved in glycolysis and the other one (vGPD) in secondary metabolism. vGPD is expressed as part of the "vir" cluster responsible for the biosynthesis of volatile sesquiterpenes. The secondary metabolism-associated GAPDH is tolerant to the anti-cancer metabolite heptelidic acid (HA), produced by T. virens. Characterizing the HA-tolerant form of GAPDH, thus has implications in cancer therapy. In order to get insight into the mechanism of HA-tolerance of vGPD, we have purified recombinant form of this protein. The protein displays biochemical and biophysical characteristics analogous to the gGPD isoform. It exists as a tetramer with Tm of about 56.5 °C, and displays phosphorylation enzyme activity with Km and Kcat of 0.38 mM and 2.55 sec^-1, respectively. The protein weakly binds to the sequence upstream of the vir4 gene that codes for the core enzyme (a terpene cyclase) of the "vir" cluster. The EMSA analysis indicates that vGPD may not act as a transcription factor driving the "vir" cluster, at least not by directly binding to the promoter region. We also succeeded in obtaining small crystals of this protein. We have constructed structural models of vGPD and gGPD of T. virens. In silico constrained docking analysis reveals weaker binding of heptelidic acid in vGPD, compared to gGPD protein.

Deletion of the Trichoderma virens NRPS, Tex7, induces accumulation of the anti-cancer compound heptelidic acid

The anticancer antibiotic heptelidic acid is a sesquiterpene lactone produced by the beneficial plant fungus Trichoderma virens. This species has been separated into two strains, referred to as P and Q, based on its biosynthesis of secondary metabolites; notably, only P-strains were reported to produce heptelidic acid. While characterizing a Q-strain of T. virens containing a directed mutation in the non-ribosomal peptide synthetase encoding gene Tex7, the appearance of an unknown compound in anomalously large quantities was visualized by TLC. Using a combination of HPLC, LC-MS/MS, and NMR spectroscopy, this compound was identified as heptelidic acid. This discovery alters the strain classification structure of T. virens. Additionally, the Tex7 mutants inhibited growth of maize seedlings, while retaining the ability to induce systemic resistance against the foliar fungal pathogen, Cochliobolus heterostrophus.

Whole Genome Sequencing Reveals Major Deletions in the Genome of M7, a Gamma Ray-Induced Mutant of Trichoderma virens That Is Repressed in Conidiation, Secondary Metabolism, and Mycoparasitism

Trichoderma virens is a commercial biofungicide used in agriculture. We have earlier isolated a mutant of T. virens using gamma ray-induced mutagenesis. This mutant, designated as M7, is defective in morphogenesis, secondary metabolism, and mycoparasitism. The mutant does not produce conidia, and the colony is hydrophilic. M7 cannot utilize cellulose and chitin as a sole carbon source and is unable to parasitize the plant pathogens Rhizoctonia solani and Pythium aphanidermatum in confrontation assay. Several volatile (germacrenes, beta-caryophyllene, alloaromadendrene, gamma-muurolene) and non-volatile (viridin, viridiol, gliovirin, heptelidic acid) metabolites are not detected in M7. In transcriptome analysis, many genes related to secondary metabolism, carbohydrate metabolism, hydrophobicity, and transportation, among others, were found to be downregulated in the mutant. Using whole genome sequencing, we identified five deletions in the mutant genome, totaling about 250 kb (encompassing 71 predicted ORFs), which was confirmed by PCR. This study provides novel insight into genetics of morphogenesis, secondary metabolism, and mycoparasitism and eventually could lead to the identification of novel regulators of beneficial traits in plant beneficial fungi Trichoderma spp. We also suggest that this mutant can be developed as a microbial cell factory for the production of secondary metabolites and proteins.

Expression, purification, crystallization and X-ray diffraction studies of a novel root-induced secreted protein from Trichoderma virens

Small secreted cysteine-rich proteins (SSCPs) from fungi play an important role in fungi-host interactions. The plant-beneficial fungi Trichoderma spp. are in use worldwide as biocontrol agents and protect the host plant from soil-borne as well as foliar pathogens. Recently, a novel SSCP, Tsp1, has been identified in the secreted protein pool of T. virens and is overinduced upon its interaction with the roots of the maize plant. The protein was observed to be well conserved in the Ascomycota division of fungi, and its homologs are present in many plant-pathogenic fungi such as Fusarium oxysporum and Magnaporthe oryzae. However, none of these homologs have yet been characterized. Recombinant Tsp1 protein has been expressed and purified using an Escherichia coli expression system. The protein, with four conserved cysteines, forms a dimer in solution as observed by size-exclusion chromatography. The dimerization, however, does not involve disulfide bonds. Circular-dichroism data suggested that the protein has a β-strand-rich secondary structure that matched well with the secondary structure predicted using bioinformatics methods. The protein was crystallized using sodium malonate as a precipitant. The crystals diffracted X-rays to 1.7 Å resolution and belonged to the orthorhombic space group P212121 (Rmeas = 5.4%), with unit-cell parameters a = 46.3, b = 67.0, c = 173.2 Å. The Matthews coefficient (VM) of the crystal is 2.32 Å3 Da-1, which corresponds to nearly 47% solvent content with four subunits of Tsp1 protein in the asymmetric unit. This is the first report of the structural study of any homolog of the novel Tsp1 protein. These structural studies will help in understanding the classification and function of the protein.

Trichothioneic acid, a new antioxidant compound produced by the fungal strain Trichoderma virens FKI-7573

A new nitrogen-containing compound, trichothioneic acid, was discovered from the metabolites of fungal strain FKI-7573 using a mass spectrometry screening method guided by odd number of molecular weights, which indicates compounds that contain an odd number of nitrogen atoms. Strain FKI-7573 was isolated from soil collected in Obihiro, Hokkaido, Japan, and identified as Trichoderma virens by a sequence analysis of the internal transcribed spacer region, including 5.8S ribosomal RNA. The structure of trichothioneic acid was determined by mass spectrometry, nuclear magnetic resonance spectroscopy, electronic circular dichroism spectra, and chemical degradation analyses. These analyses revealed that trichothioneic acid consists of heptelidic acid and l-ergothioneine, and contains three nitrogen atoms. Trichothioneic acid exhibited hydroxyl radical-scavenging and singlet oxygen-quenching activities.

Sesquiterpenes with Phytopathogenic Fungi Inhibitory Activities from Fungus Trichoderma virens from Litchi chinensis Sonn

A new monosesquiterpene diacetylgliocladic acid (1), a new dimeric sesquiterpene divirensol H (9), and two exceptionally novel trimeric sesquiterpene trivirensols A and B (11 and 12), together with another eight known congeners, were purified from an endophytic fungus Trichoderma virens FY06, derived from Litchi chinensis Sonn. whose fruit is a delicious and popular food. All of them were identified by comprehensive spectroscopic analysis, combined with biosynthetic considerations. Trivirensols A and B are unprecedented trimers of which three subunits are connected by two ester bonds of the sesquiterpene class. Relative to the positive control triadimefon, all the tested metabolites showed strong inhibitory activities against at least one phytopathogenic fungus among Penicillium italicum, Fusarium oxysporum, Fusarium graminearum, Colletotrichum musae, and Colletotrictum gloeosporioides. Notably, as metabolites of the endophytic fungus from L. chinensis, they all presented strong antifungal activities against C. gloeosporioides which causes anthracnose in L. chinensis.

Differential expression analysis of Trichoderma virens RNA reveals a dynamic transcriptome during colonization of Zea mays roots

Background

Trichoderma spp. are majorly composed of plant-beneficial symbionts widely used in agriculture as bio-control agents. Studying the mechanisms behind Trichoderma-derived plant benefits has yielded tangible bio-industrial products. To better take advantage of this fungal-plant symbiosis it is necessary to obtain detailed knowledge of which genes Trichoderma utilizes during interaction with its plant host. In this study, we explored the transcriptional activity undergone by T. virens during two phases of symbiosis with maize; recognition of roots and after ingress into the root cortex.

Results

We present a model of T. virens – maize interaction wherein T. virens experiences global repression of transcription upon recognition of maize roots and then induces expression of a broad spectrum of genes during colonization of maize roots. The genes expressed indicate that, during colonization of maize roots, T. virens modulates biosynthesis of phytohormone-like compounds, secretes a plant-environment specific array of cell wall degrading enzymes and secondary metabolites, remodels both actin-based and cell membrane structures, and shifts metabolic activity. We also highlight transcription factors and signal transduction genes important in future research seeking to unravel the molecular mechanisms of T. virens activity in maize roots.

Conclusions

T. virens displays distinctly different transcriptional profiles between recognizing the presence of maize roots and active colonization of these roots. A though understanding of these processes will allow development of T. virens as a bio-control agent. Further, the publication of these datasets will target future research endeavors specifically to genes of interest when considering T. virens – maize symbiosis.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5651-z) contains supplementary material, which is available to authorized users.

Inhibition of Phytophthora species, agents of cocoa black pod disease, by secondary metabolites of Trichoderma species

Cocoa production is affected by the black pod disease caused by several Phytophthora species that bring, about each year, an estimated loss of 44% of world production. Chemical control remains expensive and poses an enormous risk of poisoning for the users and the environment. Biocontrol by using antagonistic microorganisms has become an alternative to the integrated control strategy against this disease. Trichoderma viride T7, T. harzanium T40, and T. asperellum T54, which showed in vivo and in vitro antagonistic activity against P. palmivora, were cultured and mycelia extracted. Inhibition activity of crude extracts was determined, and then organic compounds were isolated and characterized. The in vitro effect of each compound on the conidia germination and mycelia growth of four P. palmivora, two P. megakaria, and one P. capsici was evaluated. T. viride that displayed best activities produced two active metabolites, viridin and gliovirin, against P. palmivora and P. megakaria strains. However, no activity against P. capsici was observed. Besides being active separately, these two compounds have a synergistic effect for both inhibitions, mycelia growth and conidia germination. These results provide the basis for the development of a low-impact pesticide based on a mixture of viridin and gliovirine.

Different mechanisms of Trichoderma virens-mediated resistance in tomato against Fusarium wilt involve the jasmonic and salicylic acid pathways

In the present study, we investigated the role of Trichoderma virens (TriV_JSB100) spores or cell-free culture filtrate in the regulation of growth and activation of the defence responses of tomato (Solanum lycopersicum) plants against Fusarium oxysporum f. sp. lycopersici by the development of a biocontrol-plant-pathogen interaction system. Two-week-old tomato seedlings primed with TriV_JSB100 spores cultured on barley grains (BGS) or with cell-free culture filtrate (CF) were inoculated with Fusarium pathogen under glasshouse conditions; this resulted in significantly lower disease incidence in tomato Oogata-Fukuju plants treated with BGS than in those treated with CF. To dissect the pathways associated with this response, jasmonic acid (JA) and salicylic acid (SA) signalling in BGS- and CF-induced resistance was evaluated using JA- and SA-impaired tomato lines. We observed that JA-deficient mutant def1 plants were susceptible to Fusarium pathogen when they were treated with BGS. However, wild-type (WT) BGS-treated tomato plants showed a higher JA level and significantly lower disease incidence. SA-deficient mutant NahG plants treated with CF were also found to be susceptible to Fusarium pathogen and displayed low SA levels, whereas WT CF-treated tomato plants exhibited moderately lower disease levels and substantially higher SA levels. Expression of the JA-responsive defensin gene PDF1 was induced in WT tomato plants treated with BGS, whereas the SA-inducible pathogenesis-related protein 1 acidic (PR1a) gene was up-regulated in WT tomato plants treated with CF. These results suggest that TriV_JSB100 BGS and CF differentially induce JA and SA signalling cascades for the elicitation of Fusarium oxysporum resistance in tomato.

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Endo-1,4-β-d-glucanase (EG), as a key constituent of cellulase taking the responsibility of cutting β-1,4 glycosidic bonds, plays the essential role in the process of degrading cellulose by cellulase. Cloning and expressing the EG gene is important to the cellulase research and application. In this work, a novel EG gene was cloned from Trichoderma virens ZY-01, which was a cellulase secreting microbe isolated by our laboratory. The DNA sequence showed that the length of the cloned EG is 1069 bp, which had 95.2% similarity to the EG IV from T. viride AS 3.3711. Further, the expression vector pET-32a-EG was constructed and was successfully heterologously expressed in Escherichia coli. The expression product was purified with Ni²⁺ affinity chromatography and its enzymatic properties were investigated. The SDS-PAGE showed the target protein is 39 kDa, which is consistent with the translated result from the DNA sequence. The kinetic parameter for the expression product was K_m = 13.71 mg/mL and V_max=0.51 μmol/min·mL. The optimal reaction pH and temperature was pH = 7.0 and T = 40 °C, which is similar to the native EG produced by Trichoderma virens ZY-01. It provides the foundation for the endo-1,4-β-d-glucanase further evolution and application.

A Novel Cellulase Produced by a Newly Isolated Trichoderma virens

Screening and obtaining a novel high activity cellulase and its producing microbe strain is the most important and essential way to improve the utilization of crop straw. In this paper, we devoted our efforts to isolating a novel microbe strain which could produce high activity cellulase. A novel strain Trichoderma virens ZY-01 was isolated from a cropland where straw is rich and decomposed, by using the soil dilution plate method with cellulose and Congo red. The strain has been licensed with a patent numbered ZL 201210295819.6. The cellulase activity in the cultivation broth could reach up to 7.4 IU/mL at a non-optimized fermentation condition with the newly isolated T. virens ZY-01. The cellulase was separated and purified from the T. virens culture broth through (NH₄)₂SO₄ fractional precipitation, anion-exchange chromatography and gel filtration chromatography. With the separation process, the CMC specific activity increased from 0.88 IU/mg to 31.5 IU/mg with 35.8 purification fold and 47.04% yield. Furthermore, the enzymatic properties of the cellulase were investigated. The optimum temperature and pH is 50 °C and pH 5.0 and it has good thermal stability. Zn²⁺, Ca²⁺ and Mn²⁺ could remarkably promote the enzyme activity. Conversely, Cu²⁺ and Co²⁺ could inhibit the enzymatic activity. This work provides a new highly efficient T. virens strain for cellulase production and shows good prospects in practical application.

Expression of an endochitinase gene from Trichoderma virens confers enhanced tolerance to Alternaria blight in transgenic Brassica juncea (L.) czern and coss lines

An endochitinase gene 'ech42' from the biocontrol fungus 'Trichoderma virens' was introduced to Brassica juncea (L). Czern and Coss via Agrobaterium tumefaciens mediated genetic transformation method. Integration and expression of the 'ech42' gene in transgenic lines were confirmed by PCR, RT-PCR and Southern hybridization. Transgenic lines (T1) showed expected 3:1 Mendelian segregation ratio when segregation analysis for inheritance of transgene 'hpt' was carried out. Fluorimetric analysis of transgenic lines (T0 and T1) showed 7 fold higher endochitinase activity than the non-transformed plant. Fluorimetric zymogram showed presence of endochitinase (42 kDa) in crude protein extract of transgenic lines. In detached leaf bioassay with fungi Alternaria brassicae and Alternaria brassicicola, transgenic lines (T0 and T1) showed delayed onset of lesions as well as 30-73 % reduction in infected leaf area compared to non-transformed plant.

Arabidopsis thaliana polyamine content is modified by the interaction with different Trichoderma species

Plants are associated with a wide range of microorganisms throughout their life cycle, and some interactions result on plant benefits. Trichoderma species are plant beneficial fungi that enhance plant growth and development, contribute to plant nutrition and induce defense responses. Nevertheless, the molecules involved in these beneficial effects still need to be identify. Polyamines are ubiquitous molecules implicated in plant growth and development, and in the establishment of plant microbe interactions. In this study, we assessed the polyamine profile in Arabidopsis plants during the interaction with Trichoderma virens and Trichoderma atroviride, using a system that allows direct plant-fungal contact or avoids their physical interaction (split system). The plantlets that grew in the split system exhibited higher biomass than the ones in direct contact with Trichoderma species. After 3 days of interaction, a significant decrease in Arabidopsis polyamine levels was observed in both systems (direct contact and split). After 5 days of interaction polyamine levels were increased. The highest levels were observed with T. atroviride (split system), and with T. virens (direct contact). The expression levels of Arabidopsis ADC1 and ADC2 genes during the interaction with the fungi were also assessed. We observed a time dependent regulation of ADC1 and ADC2 genes, which correlates with polyamine levels. Our data show an evident change in polyamine profile during Arabidopsis - Trichoderma interaction, accompanied by evident alterations in plant root architecture. Polyamines could be involved in the changes undergone by plant during the interaction with this beneficial fungus.

Characteristics of a β-1,4-D endoglucanase from Trichoderma virens wholly applied in a palm-fruit husk-based diet for poultry layers

The characteristics of an endoglucanase produced by a Trichoderma virens strain T9 newly isolated from a palm-fruit husk dump site, its physiological characteristics and enzyme production were studied. Whole cells of the depolymerizing-enzyme producing T. virens were applied to palm-fruit husk and bird performance characteristics when employed as poultry diet additive were considered. Endoglucanase activity in submerged fermentation was 1.6 nkat. Optimum activity was recorded at pH 6.0 and 55°C. The enzyme retained 50% residual glucanase activity at 70°C for 10 minutes. 1.0% Tween-80 and SDS yielded endoglucanase activity 2.15 times higher than the control. Activity was boosted by 20mM Ca²⁺ (115.0%); 10mM K⁺ (106.5%); and was totally inhibited by 1mM Hg²⁺. The addition of T. virens-fermented palm-fruit husk with other layer feed components on the bird characteristics showed that change in bird weight between the control and test birds were not significantly different (p>0.05) but differed in terms of daily feed ingested (p<0.05). The feed to weight-gain ratio was best with the unmodified palm-fruit husk based diet (8.59). There was no significant difference in the egg weights from modified palm-fruit husk based diet and control (p>0.05). The shell thickness (0.64mm) and yolk content (23.61%) were highest in the microbially-modified husk diet.

The alternative to maize based diets proffered by the application of T. virens-modified palm-fruit husk in poultry nutrition in terms of bird weight and feed to weight-gain ratio affords the poultry farmer an economic advantage and allows for a greater utilization of the maize in human diets.

Expression of a fungal endochitinase gene in transgenic tomato and tobacco results in enhanced tolerance to fungal pathogens

Development of transgenic Nicotiana tabacum and Lycopersicon esculentum expressing an endochitinase (ech42) gene from biocontrol fungus Trichoderma virens using Agrobacterium-mediated genetic transformation is reported in this paper. Integration of transgene in the genome of transgenic plants was demonstrated using polymerase chain reaction and Southern-blot hybridization, while expression was ascertained by reverse transcription polymerase chain reaction. Histochemical analysis confirmed the expression of GUS enzyme in transformed shoots. Levels of endochitinase enzyme in transgenic plants were found to be up to 10 fold higher compared to control plants. Endochitinase enzyme of 42 kDa was also visualized on SDS-PAGE gel using fluorimetric zymogram in transgenic plants. Endochitinase activity was found to be higher in leaf and stem than the root tissue in transgenic tomato plants. Transgenic lines of both plants showed enhanced resistance to fungal pathogens and a strong negative correlation was found between expression level of endochitinase enzyme and size of disease lesions. Inheritance of transgene, expression and resistance to fungal pathogens of T1 transgenic tobacco lines was also analysed. The results of the present studies show that ech42 is a promising candidate gene for developing fungal disease resistance in tomato plants.