Sesquiterpene synthase involved in the biosynthesis of volatile compounds (PubMed:21818683). Mediates the conversion of (2E,6E)-farnesyl diphosphate ((EE)-FPP) into (+)-thujopsene, beta-bisabolene, alpha-cederene, beta-acoradiene, (E)-gamma-bisabolene, (Z)-alpha-bisabolene, (Z)-beta-farnesene and (E)-beta-farnesene, and of (2Z,6Z)-farnesyl diphosphate ((ZZ)-FPP) into (E)-gamma-bisabolene, (E)-alpha-bisabolene, (E)-beta-farnesene, (Z)-beta-farnesene, beta-bisabolene, beta-acoradiene and alpha-acoradiene (PubMed:21818683). Can act with a low efficiency as a monoterpene synthase with geranyl diphosphate (GPP) as substrate, thus producing beta-myrcene, limonene and terpinolene (PubMed:21818683). (2E,6E)-farnesyl diphosphate = (E)-gamma-bisabolene + diphosphate (2Z,6Z)-farnesyl diphosphate = (E)-gamma-bisabolene + diphosphate (2Z,6Z)-farnesyl diphosphate = (E)-alpha-bisabolene + diphosphate (2Z,6Z)-farnesyl diphosphate = (Z)-beta-farnesene + diphosphate (2E,6E)-farnesyl diphosphate = (E)-beta-farnesene + diphosphate (2E,6E)-farnesyl diphosphate = (+)-thujopsene + diphosphate (2Z,6Z)-farnesyl diphosphate = (E)-beta-farnesene + diphosphate (2E,6E)-farnesyl diphosphate = (Z)-beta-farnesene + diphosphate (2Z,6Z)-farnesyl diphosphate = beta-acoradiene + diphosphate (2Z,6Z)-farnesyl diphosphate = alpha-acoradiene + diphosphate (2Z,6Z)-farnesyl diphosphate = beta-bisabolene + diphosphate (2E,6E)-farnesyl diphosphate = (-)-alpha-cedrene + diphosphate (2E,6E)-farnesyl diphosphate = beta-bisabolene + diphosphate (2E,6E)-farnesyl diphosphate = beta-acoradiene + diphosphate (2Z,6Z)-farnesyl diphosphate = (-)-alpha-cedrene + diphosphate (2E)-geranyl diphosphate = diphosphate + terpinolene (2E)-geranyl diphosphate = diphosphate + limonene (2E)-geranyl diphosphate = beta-myrcene + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family. Tpsa subfamily.