Abstract
Seed storage proteins are synthesized on rER as larger precursors, are transported to protein storage vacuoles (PSVs) by vesicle-mediated machinery, and then are processed into mature forms. Recently, we have identified AtVSR1 as a sorting receptor for seed storage proteins in Arabidopsis.1) Storage protein precursors are accumulated in the extracellular space in the seeds of AtVSR1-deficient mutant. We report here A06 mutant that accumulates the precursors in addition to the mature forms of the storage proteins. Electron microscopic analysis revealed that A06 mutant abnormally secreted storage proteins from cells as the AtVSR1-deficient mutant. A06 seed cells possessed smaller and much more PSVs in the cytoplasm than those of wild-type cells. These phenotypes of A06 mutant are different from those of AtVSR1-deficient mutant. Immunoblot analysis revealed that AtVSR1 was present in the seeds of A06 mutant.
1) T. Shimada et al. Proc. Natl. Acad. Sci. USA, 100, 16095 (2003)
