Involved in tanshinone biosynthesis in hairy roots (PubMed:19905026, PubMed:26077765, PubMed:21082262). Catalyzes the conversion of geranylgeranyl diphosphate (GGPP) to copalyl diphosphate (CPP) (PubMed:19905026, PubMed:26077765, PubMed:21082262). (2E,6E,10E)-geranylgeranyl diphosphate = (+)-copalyl diphosphate Secondary metabolite biosynthesis; terpenoid biosynthesis. Induced by jasmonate (MeJA) in roots. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity, presumably through binding to Mg(2+). Plant silencing CPS1 are impaired in tanshinone biosynthesis in hairy roots (PubMed:26077765). CPS1-silenced plants exhibit an obvious white-color root phenotype compared with wild-type roots, which have the characteristic reddish color associated with tanshinones (PubMed:26077765). Belongs to the terpene synthase family.