Does not possess diterpene synthase activity. Predominantly expressed in roots but also in leaves and stems. Belongs to the terpene synthase family. Tpsa subfamily. TPS20 in Arabidopsis ecotype Columbia lacks dolabellane-type diterpene synthase activity because of a 17 amino acid deletion and several mutations in its sequence. TPS20 protein in ecotype Cvi is functional and possesses dolabellane-type diterpene synthase activity. Truncated N-terminus. Intron retention.