Light Regulates Secreted Metabolite Production and Antagonistic Activity in Trichoderma

Secondary metabolism is one of the main mechanisms <i>Trichoderma</i> uses to explore and colonize new niches, and 6-pentyl-α-pyrone (6-PP) is an important secondary metabolite in this process. This work focused on standardizing a method to investigate the production of 6-PP. Ethanol and ethyl acetate were both effective solvents for quantifying 6-PP in solution and had limited solubility in potato-dextrose-broth media. The 6-PP extraction using ethyl acetate provided a rapid and efficient process to recover this metabolite. The 6-PP was readily produced during the development of <i>Trichoderma atroviride</i> growing in the dark, but light suppressed its production. The 6-PP was purified, and its spectrum by nuclear magnetic resonance and mass spectroscopy was identical to that of commercial 6-PP. Light also induced or suppressed other unidentified metabolites in several other species of <i>Trichoderma</i>. The antagonistic activity of <i>T. atroviride</i> was influenced by light, as suppression of plant pathogens was greater in the dark. The secreted metabolite production on potato-dextrose-agar was differentially regulated by light, indicating that <i>Trichoderma</i> produced several metabolites with antagonistic activity against plant pathogens. Light has an important influence on the secondary metabolism and antagonistic activity of <i>Trichoderma</i>, and this trait is of key relevance for selecting antagonistic <i>Trichoderma</i> strains for plant protection.