Laccase activity in Trichoderma virens

Fungal laccases are involved in multiple functions, such as lignin degradation, pigments (melanin) synthesis and degradation, detoxification and pathogenesis. Furthermore, they are useful biocatalysts for several biotechnological applications. The laccase gene function was previously analysed in T. virens, an effective biocontrol agent: six genes were identified and one of them was deleted and shown to be involved in the mycoparasitic activity against B. cinerea sclerotia. Laccase activity in some Trichoderma spp. is also associated with the production of green pigment in conidial spores. Further investigations on the laccase gene family in T. virens were performed in order to explore mechanisms putatively involved in ligninolysis, conidiogenesis and industrial dyes decolorization. Laccase functions in lignocellulosic process and sporulation mechanisms were studied by growing T. virens on two different substrates: wheat straw liquid medium, containing lignocellulose as the only carbon source, or solid Hölker medium, formulated to induce spore formation. In addition liquid cultures containing twelve commercial textile dyes were set up and T. virens efficiently decolorized three of them. Biochemical and expression analyses performed on these different experimental systems suggested different roles of the relative enzymes in regulating multiple mechanisms. In conclusion information is gained about some properties of the T. virens laccase gene family. Six genes are shown to be differentially involved in physiological processes in T. virens some of which are important for its fitness or antagonistic attitude and other are exploitable in biotechnological applications related to ligninolysis or to textile dyes decolorization.