Accumulation of a fusion protein containing 2S albumin induces novel vesicles in vegetative cells of Arabidopsis

We have previously reported that precursor-accumulating (PAC) vesicles foun d exclusively in developing seeds are involved in a transport of seed stora ge proteins, such as 2S albumin, from the endoplasmic reticulum to protein- storage vacuoles, Here, we constructed chimeric genes that encode fusion pr oteins consisting of both various lengths of polypeptides derived from pump kin 2S albumin and a selectable marker enzyme, phosphinothricin acetyltrans ferase. The chimeric genes were expressed in transgenic Arabidopsis in orde r to investigate the mechanism of the PAC vesicle formation. A fusion prote in expressed by one of the chimeric genes-is accumulated as a proprotein-pr ecursor form, and localized in novel vesicles of vegetative cells, The vesi cles show distinct features that well much to the PAC vesicles, Despite of the accumulation of the fusion protein, the transgenic Arabidopsis is still sensitive to phosphinothricin. Phosphinothricin acetyltransferase containe d in the fusion protein is obviously compartmentalized in the PAC-like vesi cles that do not permit the detoxification of this herbicide. These results indicate that the PAC-like vesicle can be induced in vegetative cells by t he ectopic expression of the protein that is destined to be compartmentaliz ed into the PAC vesicles.