Trichodiene synthase; part of the core gene cluster that mediates the biosynthesis of trichothecenes, a very large family of chemically related bicyclic sesquiterpene compounds acting as mycotoxins, including T2-toxin (PubMed:11352533, PubMed:2817906). The biosynthesis of trichothecenes begins with the cyclization of farnesyl diphosphate to trichodiene and is catalyzed by the trichodiene synthase TRI5 (PubMed:3800398, PubMed:7873527, PubMed:8823172). Trichodiene undergoes a series of oxygenations catalyzed by the cytochrome P450 monooxygenase TRI4 (PubMed:7651333). TRI4 controls the addition of four oxygens at C-2, C-3, C-11, and the C-12, C-13-epoxide to form the intermediate isotrichotriol (PubMed:16917519). Isotrichotriol then undergoes a non-enzymatic isomerization and cyclization to form isotrichodermol (PubMed:2317042). During this process, the oxygen at the C-2 position becomes the pyran ring oxygen and the hydroxyl group at C-11 is lost (PubMed:2317042). More complex type A trichothecenes are built by modifying isotrichodermol through a series of paired hydroxylation and acetylation or acylation steps (PubMed:11352533). Isotrichodermol is converted to isotrichodermin by the acetyltransferase TRI101 (PubMed:10583973). TRI101 encodes a C-3 transacetylase that acts as a self-protection or resistance factor during biosynthesis and that the presence of a free C-3 hydroxyl group is a key component of Fusarium trichothecene phytotoxicity (PubMed:10583973). A second hydroxyl group is added to C-15 by the trichothecene C-15 hydroxylase TRI11, producing 15-decalonectrin, which is then acetylated by TRI3, producing calonectrin (PubMed:9435078, PubMed:8593041). A third hydroxyl group is added at C-4 by the cytochrome P450 monooxygenase TRI13, converting calonectrin to 3,15-diacetoxyspirpenol, which is subsequently acetylated by the acetyltransferase TRI7 (PubMed:12135578, PubMed:11352533). A fourth hydroxyl group is added to C-8 by the cytochrome P450 monooxygenase TRI1, followed by the addition of an isovaleryl moiety by TRI16 (PubMed:12620849, PubMed:14532047). Finally, the acetyl group is removed from the C-3 position by the trichothecene C-3 esterase TRI8 to produce T-2 toxin (PubMed:12039755). (2E,6E)-farnesyl diphosphate = diphosphate + trichodiene Some of the cofactor binding sites show unusual localization within the protein. Benzyl triethylammonium cation (BTAC) acts as a competitive inhibitor of trichodiene synthase reaction in the presence of pyrophosphate (PPi) (PubMed:17678871). Optimum pH is 6.75-7.75. Sesquiterpene biosynthesis; trichothecene biosynthesis. Expression is positively regulated by the trichothecene cluster-specific transcription activator TRI10 (PubMed:12732543). Expression is induced between 18h and 21h growth on GYEP medium (PubMed:16347944). The initial detection of trichothecenes occurs several hours after the initial detection of TRI5 (PubMed:16347944). The initiation of trichothecene biosynthesis occurs with a high concentration of glucose remaining in the culture medium (PubMed:16347944). Trichothecenes are sesquiterpenoid toxins that act by inhibiting protein biosynthesis. Belongs to the trichodiene synthase family.