## 1 Introduction  
_Trichoderma_ species are well known as biocontrol agents of plant diseases in a broad variety of crops [1], and their ability to produce a huge diversity of antimicrobial compounds and cell wall degrading enzymes has been extensively studied and reviewed [2; 3; 4; 5]. Among the secondary metabolites produced by _Trichoderma_, the terpenes include hundreds of different compounds with a huge diversity of physiological activities. Terpenes arise from the repetitive fusion of branched five-carbon units based on an isopentane skeleton, and most of the chemical intermediates in their biosynthetic pathway are known. In fungi, the first enzyme involved in the terpene pathway is 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), which metabolizes HMG-CoA to mevalonic acid (MVA). Subsequently, the isomerization of mevalonate produces isopentenyl diphosphate (IPP), which condenses with dimethylallyl diphosphate to produce geranyl diphosphate (GPP), the key precursor of monoterpene biosynthesis. This molecule is condensed again with IPP, affording farnesyl diphosphate (FPP), a common intermediate in the production of: (i) geranylgeranyl diphosphate (GGPP) and its diterpene derivatives; (ii) trichodiene and the subsequent sesquiterpene compounds, including trichothecene fungal toxins; and (iii) squalene, as a precursor of the triterpene pathway to produce prenylated proteins, sterols (ergosterol), ubiquitones, dolichols and other secondary metabolites [6; 7] as well as plant carotenoids, gibberellins, tocopherols and chlorophylls [8]. The biosynthesis of trichothecenes has mainly been documented in _Fusarium_ species, and their biosynthesis has been extensively reviewed [9; 10]. Recently, most of the steps involved in the trichothecene biosynthesis in _Trichoderma_ species have been described and the genes characterized [11]. _Trichoderma_ _brevicompactum_ has been classified within the clade _Brevicompactum_[12], which includes species with a common pathway from FPP to trichodermol. From trichodermol the pathway diverges to produce harzianum A in _T. arundinaceum_, _T. turrialbense_ and _T. protrudens_ or trichodermin, in _T. brevicompactum_. The _tri5_ gene, involved in the biosynthesis of trichodiene from FPP, has recently been cloned and characterized [11; 13]. Additionally, another 7 genes involved in trichodermin biosynthesis have been identified in the _T. brevicompactum_ genome. These genes are grouped in a _core cluster_[11]. Interestingly, the _tri5_ gene is located outside this cluster, being an exception of the trichothecene biosynthetic clusters described until now in _Fusarium_[14] and _Myvothecium_[15] where _tri5_ gene is located inside the clusters. Transformants of _T. brevicompactum_ IBT 40841, with a higher level of _tri5_ gene expression, had higher levels of trichodermin production and greater antibiotic activity against several yeast strains. A significant increase in the level of production of the antioxidants tyrosol and hydroxytyrosol was also detected in the _tri5_-overexpressing transformantsants [13]. Tyrosol is a phenolic antioxidant metabolite that is present in olive oil and wine [16], yeast [17], and _T. viride_[18] and _T. brevicompactum_ cultures [13]. It is synthesized from a transamination reaction of L-tyrosine and 2-oxoglutarate, giving rise to L-glutamic acid and _p_-hydroxyphenyl-pyruvate. The later product is then decarboxylated, and the resulting aldehyde is reduced to tyrosol [19; 20; 21]. It has been shown that the tyrosol acts as aquorum-sensing molecule, which accelerates the morphological transition from yeasts to hyphae and facilitates biofilm production [17]. Hydroxyytrosol is a derivative of tyrosol with antioxidant properties due to its ortho-dihydroxyphenolic group [19]. The relationship between the tyrosol/hydroxytrosol and trichodermin is not clear and needs additional studies.