Plant Vacuolar Sorting Receptor

, is a putative receptor involved in sorting proteins such as proaleurain to the lytic vacu-ole, with its N-terminal domain recognizing the vacuolar sorting determinant. Although all VSR PS-1 characteristics and in vitro binding properties described so far favored its receptor function, this function remained to be demonstrated. Here, we used green fluorescent protein (GFP) as a reporter in a yeast mutant strain defective for its own vacuolar re-ceptor, Vps10p. By expressing VSR PS-1 together with GFP fused to the vacuolar sorting determinant of petunia proaleu-rain, we were able to efficiently redirect the reporter to the yeast vacuole. VSR PS-1 is ineffective on GFP either alone or when fused with another type of plant vacuolar sorting determinant from a chitinase. The plant VSR PS-1 therefore inter-acts specifically with the proaleurain vacuolar sorting determinant in vivo, and this interaction leads to the transport of the reporter protein through the yeast secretory pathway to the vacuole. This finding demonstrates VSR PS-1 receptor function but also emphasizes the differences in the spectrum of ligands between Vps10p and its plant equivalent