## 4 Discussion  
The impressive number of TSs we found in the genomes analyzed demonstrate that terpenoid biosynthesis has a great impact on the diversity and complexity of SMs in _Trichoderma_. Indeed, the TS-gene inventory of these species (15-23 genes per genome) clearly outnumbers those found in other fungi considered as rich producers of SMs, such as _Aspergillus_ spp. (2-10 genes per genome) [30; 94]. This reflects the importance of TSs and terpenoids in the ecology of _Trichoderma_. However, most of the _Trichoderma_ TSs have not yet been characterized [30], and available information about the diversity of TSs in _Trichoderma_ is scarce. Thus, we focused on characterizing the TS-gene arsenal of this genus, providing a complete overview of the nature and diversity of the _Trichoderma_ terpenoid biosynthetic inventory. Although TS family size is very homogeneous within _Trichoderma_, we were able to identify clade-specific TSs, which reflect particular portions of the terpenoid inventory shared by phylogenetically close species. Thus, despite their similar terpenoid biosynthetic potential, the species of _Trichoderma_ have adapted their terpene production according to different environmental demands. Species of Viride clade constitute an example, as they are missing in some groups of TSs that are present in the other clades, although they have evolved specific TSs, which are absent in other species of the genus. According to our results, _Trichoderma_ spp. have a huge potential for sesquiterpene biosynthesis. We identified eight groups of sesquiTSs, which constitute almost a third of the total number of TSs found in this work. Species of Viride are particularly rich in sesquiTS belonging to the TRI5-superfamily, and they also contain HAD-like TSs, which are absent in species of other clades. These HAD-like proteins harbor a DxDTT motif, which is a variant of the DxDD found in Class II diTS [95; 96]. [PERSON] et al. [97] reported that some sesquiTS can contain HAD-like domains and DxDTT motifs, leading to FPP cyclization through a protonation step, instead of by an ionization step. We hypothesized that HAD-like TSs might be particular bifunctional sesquiTS, synthesizing specific metabolites of Viride clade. Previous studies reported that some _Trichoderma_ spp. have the potential to synthesize longiborneol [19], an intermediate of the culmorin biosynthetic pathway [19; 56]. According to our results, longiborneol biosynthesis is very widespread in _Trichoderma_, but is absent in species of the Viride clade. Since culmorin production has not been reported in _Trichoderma_, longiborneol could be synthesized as a sole compound or as an intermediate of unknown biosynthetic pathways in these species. Most of these proteins show a conserved D(D/E)HFD motif, which is partially conserved (NDHFD) in proteins of _T. arundinaceum_ and _T. breicompactum_. Site-directed mutagenesis and crystallography studies on TSs have revealed that the first aspartate residue (D) of the metal-binding motif interacts directly with Mg\({}^{2+}\)[98], and its replacement can lead to anomalous cyclization products or a product mixture [99]. According to this,longiborneol synthases of Brevicompactum species could be actually involved in terpenoid blend formation or in the biosynthesis of newly terpenoids. We found that most _Trichoderma_ spp. can potentially produce presilphiperfolan-8\(\beta\)-ol. This compound is thought to play a central role in the biosynthesis of a wide range of polycyclic sesquiterpenes in fungi [73]. Thus, these TSs may contribute to generating a variety of structurally complex terpenoids in _Trichoderma_. Proteins sharing similarity with fungal pentalenene synthases were also identified, which are involved in the biosynthesis of the parent hydrocarbon of the pentalenolactone family of fungal antibiotics [100]. Nevertheless, the variability found on the structure of the active center of these proteins suggests that some of them probably synthesize sesquiterpenoids others than pentalenene.