Immunolocalization of the Major Latex Proteins in Developing Laticifers of Opium Poppy ( Papaver somniferum)

Abstract

The most abundant protein species in poppy latex is a group of low molecular weight peptides which have been termed the major latex proteins or MLPs. In the present investigation the subcellular distribution of MLPs in developing poppy laticifers is examined using ultrastructural immunolocalization. In mature laticifers the MLPs are localized in a subpopulation of the latex vesicles. In some laticifers the protein appears to be compartmentalized within individual vesicles. Associated with the mature laticifers are cells which also contain MLPs in a large central, apparently protein-filled, vacuole. These cells are interpreted to be developing laticifers. Based on these observations a new model for laticifer vesiculation is presented in which fragmentation of a large central vacuole of immature laticifer elements gives rise to the highly vesiculated cytoplasm observed in the mature latex vessel.