Dear Editor,The tropical plant Madagascar periwinkle Catharanthus roseus (L.) G.Don is a rich source of plant-derived medicinal terpenoid indole alkaloids (TIAs),including the anti-hypertensive ajmalicine,the sedative compound serpentine,and the anticancer drugs vinblastine and vincristine.However,the latter two compounds are produced in C roseus plants only in very low amounts.Elicitors such as hormones (e.g.jasmonates or salicylic acid) activate plant natural defense responses,including increased secondary metabolite production (EI-Sayed and Verpoorte,2007;Lackman et al.,2011).There are two different metabolic pathways for the biosynthesis of terpenoids leading to the formation of the Cs central precursor isopentenyl diphosphate (IPP),namely the classical cytosolic mevalonate pathway and the mevalonate-independent plastidic 2-C-methyI-D-erythritol 4-phosphate (MEP) pathway.