Bifunctional ent-kaurene synthase; part of the gene cluster that mediates the biosynthesis of gibberellins (GAs), diterpenoids that may provide a selective advantage during infection of the preferred host plant, rice (PubMed:23825955, PubMed:9917370, PubMed:10347043, PubMed:12750377, PubMed:15925394). Gibberellins (GAs) are diterpenoids and are synthesized via the mevalonate pathway (PubMed:12750377). Biosynthesis of the major metabolite GA3 (gibberellic acid) from geranylgeranyl diphosphate (GGPP) requires 13 steps (PubMed:12750377). The GGPP produced by the geranylgeranyl diphosphate synthase GGS2 is converted to ent-kaurene via ent-copalyldiphosphate in a two-step cyclization reaction performed by the bifunctional ent-copalyl diphosphate synthase/ent-kaurene synthase enzyme (CPS/KS) (PubMed:9745028, PubMed:10803977, PubMed:12750377). Ent-Kaurene is metabolized to GAs by a series of oxidation reactions catalyzed by cytochrome P450 monooxygenases (PubMed:9917370, PubMed:12750377). Cytochrome P450 monooxygenase P450-4 is an ent-kaurene oxidase that catalyzes the three oxidation steps between ent-kaurene and ent-kaurenoic acid (PubMed:11472927). The highly multifunctional cytochrome P450 monooxygenase P450-1 then catalyzes four steps involving oxidation at two carbon atoms, in the main pathway from ent-kaurenoic acid to GA14 via GA12-aldehyde as well as producing kaurenolides and fujenoic acids as by-products (PubMed:11320210). The cytochrome P450 monooxygenase P450-2 then converts GA14 to GA4 by removal of C-20 (PubMed:11943776). GA4 is further converted to GA7 by the GA4 desaturase DES via 1,2-desaturation before cytochrome P450 monooxygenase P450-3, a 13-hydroxylase, hydroxylates GA7 to GA3, the final product of the GA-biosynthetic pathway (PubMed:12750377). ent-copalyl diphosphate = diphosphate + ent-kaur-16-ene (2E,6E,10E)-geranylgeranyl diphosphate = ent-copalyl diphosphate Binds 3 Mg(2+) ions per subunit. Plant hormone biosynthesis; gibberellin biosynthesis. Expression is induced under gibberellin-producing conditions (PubMed:9917370). The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Impairs the production of gibberellins (PubMed:9917370). Belongs to the terpene synthase family.