Hybrid PKS-NRPS synthetase; part of the gene cluster that mediates the biosynthesis of trichosetin, a trans-fused decalin-containing tetramic acid with antimicrobial activity. The PKS module of PKS-NRPS1 together with the enoylreductase (ER) catalyze the formation of the polyketide unit which is then conjugated to L-serine by the condensation domain of the PKS-NRPS1 NRPS module. Activity of the Dieckmann cyclase domain (RED) results in release of the Dieckmann product intermediate. Diels-Alderase (DA) is involved in endo-selective Diels-Alder cycloaddition to form the decalin ring, leading to the production of N-desmethylequisetin also called trichosetin. The cluster does not contain the equisetin N-methyltransferase and consequently, trichosetin is isolated as final product