The TOR kinase pathway is relevant for nitrogen signaling and antagonism of the mycoparasite Trichoderma atroviride

Trichoderma atroviride (Ascomycota, Sordariomycetes) is a well-known mycoparasite applied for protecting plants against fungal pathogens. Its mycoparasitic activity involves processes shared with plant and human pathogenic fungi such as the production of cell wall degrading enzymes and secondary metabolites and is tightly regulated by environmental cues. In eukaryotes, the conserved Target of Rapamycin (TOR) kinase serves as a central regulator of cellular growth in response to nutrient availability. Here we describe how alteration of the activity of TOR1, the single and essential TOR kinase of T. atroviride, by treatment with chemical TOR inhibitors or by genetic manipulation of selected TOR pathway components affected various cellular functions. Loss of TSC1 and TSC2, that are negative regulators of TOR complex 1 (TORC1) in mammalian cells, resulted in altered nitrogen source-dependent growth of T. atroviride, reduced mycoparasitic overgrowth and, in the case of Δtsc1, a diminished production of numerous secondary metabolites. Deletion of the gene encoding the GTPase RHE2, whose mammalian orthologue activates mTORC1, led to rapamycin hypersensitivity and altered secondary metabolism, but had an only minor effect on vegetative growth and mycoparasitic overgrowth. The latter also applied to mutants missing the npr1-1 gene that encodes a fungus-specific kinase known as TOR target in yeast. Genome-wide transcriptome analysis confirmed TOR1 as a regulatory hub that governs T. atroviride metabolism and processes associated to ribosome biogenesis, gene expression and translation. In addition, mycoparasitism-relevant genes encoding terpenoid and polyketide synthases, peptidases, glycoside hydrolases, small secreted cysteine-rich proteins, and G protein coupled receptors emerged as TOR1 targets. Our results provide the first in-depth insights into TOR signaling in a fungal mycoparasite and emphasize its importance in the regulation of processes that critically contribute to the antagonistic activity of T. atroviride.

Friendly microbes help rice to grow and suppress its pathogens: Trichoderma and Bacillus Vs Xanthomonas in rice

Use of biological control for the management of diseases has gained huge awareness and importance in the present situation of climate change and food residues. Biocontrol agents play interesting role in developing plant health and provide protection against biotic and abiotic stresses. In this study, we isolated Trichoderma and Bacillus sp. isolated from soil samples collected from rice fields in Kharif 2019. Profiling based on the pH of the soil, the fungal bioagents were more present in slightly acidic to neutral pH (5.8-7.2) whereas bacterial bioagents in slightly neutral to basic (7.4-8.3). The isolates were screened for their ability to produce phytohormones, cell-wall degrading enzyme and biofilm. Based on biochemical screening two Trichoderma isolates (T6 and T7) and two Bacillus isolates (B1and B5) were subjected to glasshouse studies. Per cent diseased leaf area and lesion length of plants treated with B1 were found to be effective against pathogen. However, the plant growth promotion was more enhanced by T6. Scanning electron microscopy and molecular characterisation along with their phylogenetic analysis proved the identity of isolate B1 as Bacillus subtilis and T6 as Trichoderma atroviride.

Cultivar Contributes to the Beneficial Effects of Bacillus subtilis PTA-271 and Trichoderma atroviride SC1 to Protect Grapevine Against Neofusicoccum parvum

Grapevine trunk diseases (GTDs) are a big threat for global viticulture. Without effective chemicals, biocontrol strategies are developed as alternatives to better cope with environmental concerns. A combination of biological control agents (BCAs) could even improve sustainable disease management through complementary ways of protection. In this study, we evaluated the combination of Bacillus subtilis (Bs) PTA-271 and Trichoderma atroviride (Ta) SC1 for the protection of Chardonnay and Tempranillo rootlings against Neofusicoccum parvum Bt67, an aggressive pathogen associated to Botryosphaeria dieback (BD). Indirect benefits offered by each BCA and their combination were then characterized in planta, as well as their direct benefits in vitro. Results provide evidence that (1) the cultivar contributes to the beneficial effects of Bs PTA-271 and Ta SC1 against N. parvum, and that (2) the in vitro BCA mutual antagonism switches to the strongest fungistatic effect toward Np-Bt67 in a three-way confrontation test. We also report for the first time the beneficial potential of a combination of BCA against Np-Bt67 especially in Tempranillo. Our findings highlight a common feature for both cultivars: salicylic acid (SA)-dependent defenses were strongly decreased in plants protected by the BCA, in contrast with symptomatic ones. We thus suggest that (1) the high basal expression of SA-dependent defenses in Tempranillo explains its highest susceptibility to N. parvum, and that (2) the cultivar-specific responses to the beneficial Bs PTA-271 and Ta SC1 remain to be further investigated.

Are Trichoderma atroviride and Trichoderma harzianum Effective to Control Fusarium Associated With Tomato Wilt?

The pathogenic fungi, such as Fusarium in the rhizosphere of tomato (Solanum lycopersicum) negatively affects the yield and quality of the plant. A number of biological control agents have been used for protecting tomato plants against wilt diseases including various fungal species. The objective of this study was to evaluate the antagonism effects of Trichoderma atroviride and T. harzianum against the pathogen Fusarium sp. associated with tomato wilt. In this study, the antagonism of these Trichoderma spp. against the Fusarium sp. was tested in vitro by the dual culture technique, and the percentage inhibition of radial growth (PIRG) and the antagonism reaction (scale 1-5) were evaluated. The results showed that T. atroviride and T. harzianum led to 70.8% PIRG and scale 1 antagonism reaction, and 40.6% PIRG and scale 3 antagonism reaction against Fusarium sp. associated with tomato wilt after 7 days of incubation, respectively. These results indicate that application of T. atroviride and T. harzianum may be promising approach for biological control of Fusarium wilt of tomato and may play an important role in sustainable agriculture.

Peptaibol-Containing Extracts of Trichoderma atroviride and the Fight Against Resistant Microorganisms and Cancer Cells

Fighting resistance to antibiotics and chemotherapeutics has brought bioactive peptides to the fore. Peptaibols are short α-aminoisobutyric acid-containing peptides produced by Trichoderma species. Here, we studied the production of peptaibols by Trichoderma atroviride O1 and evaluated their antibacterial and anticancer activity against drug-sensitive and multidrug-resistant bacterium and cancer cell lines. This was substantiated by an analysis of the activity of the peptaibol synthetase-encoding gene. Atroviridins, 20-residue peptaibols were detected using MALDI-TOF mass spectrometry. Gram-positive bacteria were susceptible to peptaibol-containing extracts of T. atroviride O1. A synergic effect of extract constituents was possible, and the biolo-gical activity of extracts was pronounced in/after the peak of peptaibol synthetase activity. The growth of methicillin-resistant Staphylococcus aureus was reduced to just under 10% compared to the control. The effect of peptaibol-containing extracts was strongly modulated by the lipoteichoic acid and only slightly by the horse blood serum present in the cultivation medium. Peptaibol-containing extracts affected the proliferation of human breast cancer and human ovarian cancer cell lines in a 2D model, including the multidrug-resistant sublines. The peptaibols influenced the size and compactness of the cell lines in a 3D model. Our findings indicate the molecular basis of peptaibol production in T. atroviride O1 and the potential of its peptaibol-containing extracts as antimicrobial/anticancer agents.

Avaliação da compatibilidade in vitro de microrganismos (Bacillus subtilis, Pseudomonas fluorescens e Trichoderma atroviride) com fungicidas comerciais, para a produção sustentável de amendoim

A aplicação de fungicidas na semente de amendoim é uma necessidade na semeadura, porém a aplicação combinada com produtos biológicos pode reduzir os efeitos do uso de agroquímicos, favorecendo a qualidade do grão como alimento. O objetivo deste trabalho foi avaliar a compatibilidade in vitro de microrganismos (Bacillus subtilis, Pseudomonas fluorescens e Trichoderma atroviride) com fungicidas comerciais para a produção sustentável de amendoim. Os testes de compatibilidade foram realizados no Laboratório do Centro de Transferência de Qualidade Agroalimentar (FCA UNC). Foram avaliados três combinações de fungicidas comerciais disponíveis no setor de amendoim (F1, F2, F3), em diferentes doses (0, 30, 50, 100 e 1000 mg.l-1). Em placas de petri com meio APG com cada fungicida, foram inseridos B. subtilis, P. fluorescens e T. atroviride, que foram mantidos em câmaras com condições controladas. Sete dias após a semeadura, o crescimento bacteriano foi avaliado de acordo com a escala de compatibilidade e para Trichoderma foi calculada a porcentagem de inibição do crescimento radial (PICR). O delineamento foi completamente aleatório; para cada biológico, foram avaliadas três repetições para cada fungicida e dose. Todo o teste foi repetido três vezes. Os dados foram submetidos à análise de variância e os valores médios do PICR foram comparados por Tukey (p<0,05). Os resultados mostraram um efeito diferencial dos fungicidas sobre os biológicos. F1 (Tiabendazol + Fludioxonil + Metalaxil-M + Azoxistrobina) pode ser combinado com P. fluorescens em todas as doses e B. subtilis em doses não superiores a 50 mg.l-1. F2 (Ipconazol + Metalaxil) e F3 (Ipconazol + Metalaxil M + Carboxina) podem ser aplicados com P. fluorescens mesmo em altas concentrações. Apenas F3 pode ser combinado com T. atroviride até 100 mg.l-1. A combinação correta de fungicidas e produtos biológicos contribuirá efetivamente para a sustentabilidade do sistema de produção de amendoim.