IMMUNOCYTOCHEMICAL LOCALIZATION OF VINDOLINE IN MESOPHYLL PROTOPLASTS OF CATHARANTHUS-ROSEUS

Leaves of Catharanthus roseus synthesize the monoterpenoid indole alkaloid, vindoline, while its site of accumulation has not been identified. In order to study the intracellular localization of vindoline, antivindoline antisera were raised in rabbits and used with in situ immunofluorescence and immunogold labelling techniques. While labelling of isolated protoplast preparations showed an intense green fluorescence in the protoplast vacuoles, indicative of the location of vindoline labelled with fluorescein, the high fluorescence intensity did not allow for the recognition of other subcellular compartments. However, the use of cryotechniques coupled with immunogold labelling revealed that the label of vindoline was present in small vesicles and the cytoplasmic area bordering the plasmalemma. A substantial amount of label was also observed in the central vacuole and, to a much lesser extent, in the chloroplasts.