Transient expression of strictosidine synthase in tobacco leaves by vacuum infiltration.

Strictosidine synthase (STR) is the key enzyme involved in early steps of biosynthesis of monoterpenoid indole alkaloids. STR catalyzes the condensation of tryptamine with secologanin into strictosidine. The gene encoding STR targeted to different subcellular compartments was transiently expressed in the tobacco leaves. In vitro STR enzymatic activity was measured by the depletion of tryptamine indicated by fluorescence. The results showed that the recombinant STR was effectively expressed as soluble protein in three subcellular compartments-chloroplast, vacuole and endoplasmic reticulum in the leaves of tobacco by Western blot analysis and STR enzymatic assay.