“…This evidence includes the correlation between the production of monoterpene secretion products and the presence of amoe-boid leucoplasts in the corresponding secretory cells (Cheniclet and Carde, 1985), the biosynthesis of unmodified monoterpenes by isolated leucoplasts (Pauly et al, 1986;Soler et al, 1992), and the documented origin of monoterpenes by the nonmevalonate pathway (Eisenreich et al, 1997;Sagner et al, 1998) that is known to be localized in plastids (Eisenreich et al, 1998;Lichtenthaler, 1999). In addition, both geranyl diphosphate synthase, which catalyzes the condensation of the primary metabolites isopentenyl diphosphate and dimethylallyl diphosphate to the acyclic precursor of monoterpenes, and (Ϫ)-limonene synthase, which catalyzes the first dedicated step of monoterpene biosynthesis in peppermint, are encoded as preproteins bearing N-terminal plastidial targeting sequences (Colby et al, 1993;Burke et al, 1999).…”