Involved in sesquiterpene (C15) biosynthesis. The major products are beta-caryophyllene and alpha-humulene. Does not convert geranyl diphosphate (GPP) to any monoterpenes. Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed exclusively in flowers. Expressed in the flower stigmata and also detected in the mesocarp cell layers of the silique wall. Induced in response to the caterpillar P.xylostella feeding. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Does not emit (E)-beta-caryophyllene, alpha-copaene and alpha-humulene. Belongs to the terpene synthase family. Tpsa subfamily.