  Proteins synthesized on membrane-bound ribosomes are sorted at the Golgi
apparatus level for delivery to various cellular destinations: the plasma
membrane or the extracellular space, and the lytic vacuole or lysosome. Sorting
involves the assembly of vesicles, which preferentially package soluble
proteins with a common destination. The selection of proteins for a particular
vesicle type involves the recognition of proteins by specific receptors, such
as the vacuolar sorting receptors for vacuolar targeting. Most eukaryotic
organisms have one or two receptors to target proteins to the lytic vacuole.
Surprisingly, plants have several members of the same family, seven in
Arabidopsis thaliana. Why do plants have so many proteins to sort soluble
proteins to their respective destinations? The presence of at least two types
of vacuoles, lytic and storage, seems to be a partial answer. In this review we
analyze the last experimental evidence supporting the presence of different
subfamilies of plant vacuolar sorting receptors.
