Limonene synthase (LS) catalyses the stereo-specific cyclization of geranyl diphosphate (GPP) to form a monocyclic monoterpene, limonene. In an attempt to engineer monoterpene biosynthesis, three expression constructs of LS cDNA of Perilla frutescens, which were designed to be localized in either the plastid, the cytosol or the endoplasmic reticulum (ER), were introduced into tobacco in order t...