THE GOLGI-APPARATUS OF PHYTOPHTHORA-CINNAMOMI MAKES 3 TYPES OF SECRETORY OR STORAGE-VESICLES CONCURRENTLY

The formation of three types of vesicles in the oomycete Phytophthora cinnamomi was investigated using ultrastructural and immunocytochemica l techniques. All three vesicles are synthesised at the same time; one type serves a storage role; the others undergo regulated secretion. A monoclonal antibody Lpv-1 that is specific for glycoproteins containe d in the storage vesicles labelled the endoplasmic reticulum (ER), ele ments in the transition region between ER and Golgi stack, and cis, me dial and trans Golgi cisternae. Cpa-2, a monoclonal antibody specific for glycoproteins contained within secretory dorsal vesicles labelled the transition region, cis cisternae and a trans-Golgi network. Vesicl es possessing a structure characteristic of mature secretory ventral v esicles were observed in close association with the trans face of Golg i stacks. The results suggest that all three vesicles are formed by th e Golgi apparatus. Double immunogold labelling with Lpv-1 and Cpa-2 sh owed that these two sets of glycoproteins occurred within the same Gol gi cisternae, indicating that both products pass through and are sorte d concurrently within a single Golgi stack.