Recognizing that rice produced numerous labdane-related diterpenoid natural products, and the opportunity presented by the publication of the rice genome sequence, we began by carrying out a functional genomics based investigation of the rice diterpene synthases. Given the relative paucity of characterized diterpene synthases at that time, this effort more than doubled the number of molecularly identified functionally distinct such enzymes. Strikingly, we further uncovered a functionally distinct pair of alleles for one of the rice class I diterpene synthases, which led to isolation of a single residue ‘switch’ for product outcome.