ONE VACUOLE OR 2 VACUOLES - DO PROTEIN STORAGE VACUOLES ARISE DE-NOVODURING PEA COTYLEDON DEVELOPMENT

Using improved fixation procedures for both conventional and immune-el ectron microscopy, we have reinvestigated the problem of protein stora ge vacuole (PSV) biogenesis in developing pea (Pisum sativum L.) cotyl edons. Our results show that PSV develop de novo and the vegetative va cuoles degenerate. The PSV appear to arise from the rough ER as judged by the presence of osmiophilic substances in the lumen of rER cistern ae and by the detection of a BiP analogue in the storage protein depos its contained in the young PSV. These results are discussed in terms o f the involvement of other endomembrane compartments (Golgi apparatus and clathrin coated vesicles) in the intracellular transport of storag e proteins in legumes.