Abstract
Seed-storage proteins are deposited in protein bodies, specialized vacuoles, as a source of nitrogen for growth after seed germination. They are synthesized on rER as larger precursors and are transported to protein-storage vacuoles in maturing seeds. We previously identified PAC (precursor-accumulating) vesicles that mediate the intracellular transport of the precursors of storage proteins in pumpkin. On the membrane of the isolated PAC vesicles, PV72 was found as a major component. In vitro binding analysis revealed that PV72 had an ability to bind the precursor of 2S albumin, one of the major storage proteins in pumpkin. Thus, PV72 was predicted as a sorting receptor for seed-storage proteins. In Arabidopsis thaliana, there are seven genes that exhibit sequence homology to pumpkin PV72. We are now analyzing whether some of them mediate the transport of the storage proteins to the protein-storage vacuoles in maturing Arabidopsis seeds.
