Abstract
Secretion of pathogen proteins is crucial for the establishment of disease in animals and plants. Typically, early interactions between host and pathogen trigger regulated secretion of pathogenicity factors that function in pathogen adhesion and host penetration. During the onset of plant infection by spores of the Oomycete, Phytophthora nicotianae, proteins are secreted from three types of cortical vesicles. Following induction of spore encystment, two vesicle types undergo full fusion, releasing their entire contents onto the cell surface. However, the third vesicle type, so-called large peripheral vesicles, selectively secretes a small Sushi domain-containing protein, PnCcp, while retaining a large glycoprotein, PnLpv, before moving away from the plasma membrane. Selective secretion of PnCcp is associated with its compartmentalization within the vesicle periphery. Pharmacological inhibition of dynamin function, purportedly in vesicle fission, by dynasore treatment provides evidence that selective secretion of PnCcp requires transient fusion of the large peripheral vesicles. This is the first report of selective protein secretion via transient fusion outside mammalian cells. Selective secretion is likely to be an important aspect of plant infection by this destructive pathogen.
Highlights
Secretion is a fundamental process essential for many aspects of development including cell adhesion, migration, communication and differentiation
Our results indicate that the selective secretion of large peripheral vesicle proteins in Phytophthora zoospores utilizes a kiss-and-run, transient fusion mechanism similar to that described in mammalian cells, and they provide new information on factors that may contribute to the mechanics of selective secretion
Selective secretion of PnCcp from P. nicotianae zoospore large peripheral vesicles Immunolabelling studies using a monoclonal antibody, Lpv-1, directed towards the high molecular weight glycoprotein, PcLpv, stored in the large peripheral vesicles in P. cinnamomi zoospores indicated that large peripheral vesicles do not undergo exocytosis during zoospore encystment but instead became dispersed throughout the cyst cytoplasm (Gubler & Hardham, 1988)
Summary
Secretion is a fundamental process essential for many aspects of development including cell adhesion, migration, communication and differentiation. Secretion plays a vital role in the establishment of disease in animals and plants. During host-pathogen interactions, prokaryotic and eukaryotic pathogens release a wide range of pathogenicity factors that are required for infection. In malaria parasites such as Plasmodium and Toxoplasma species, for example, successful invasion of host cells is dependent upon the regulated secretion of proteins located in three categories of apical vesicles (Carruthers & Sibley, 1997). Secretion plays a vital role in host
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