Encystation in parasitic protozoa.

Giardia and Entamoeba parasites encase themselves in a carbohydrate-rich cyst for travel from host to host. Both parasites upregulate their Golgi apparatus during this process, yielding organelles that are now found to be similar to those of higher eukaryotes. In fact, unusual enzymes and structural proteins used for cyst wall synthesis, the complexity of the secretory pathways used to transport materials to the developing cyst walls, as well as unexpected mechanisms of gene regulation and parasite-host and parasite-parasite information exchange, are revealing a high level of sophistication in these organisms that occupy low branch points in the eukaryotic lineage.