The seven rice vacuolar sorting receptors localize to prevacuolar compartments

Abstract

Vacuolar sorting is critically important in plants as it regulates the mobilization of proteins and plays a major role in important agricultural traits like yield and seed protein content. Vacuolar sorting receptors (VSRs) are integral membrane proteins that mediate protein trafficking from the Golgi apparatus to the vacuole via the intermediate membrane-bound prevacuolar compartment (PVC)/multivesicular body (MVB). VSR proteins, such as an 80 kD (BP-80) from pea, also serve as markers for PVC/MVB. Dissecting VSR-mediated protein trafficking pathways may provide ways to enhance agronomic traits and crop yield. Green fluorescence protein (GFP) fusions with the seven Arabidopsis (Arabidopsis thaliana) VSRs were previously shown to localize to PVCs in transgenic tobacco BY-2 cells. The Rice (Oryza sativa) genome contains seven VSRs (OsVSR1-7), but little is known about their subcellular localizations. Here we studied the subcellular localization of OsVSR1-7 b y using a reporter approach, in which GFP-OsVSR1-7 fusions containing the transmembrane domain (TMD) and cytoplasmic tail (CT) of individual OsVSR were expressed in the protoplasts of rice, transgenic tobacco BY-2 cells and transgenic rice plants. Immunofluorescent labelling studies and confocal laser scanning microscope observation demonstrated that the seven OsVSRs are localized to PVCs and form ring-like structures upon wortmannin treatment. Therefore, we have verified the subcellular localization of OsVSR1-7 in this study. The OsVSRs tagged with GFP can serve as PVCs/MVBs markers in rice for the future studies.