Abstract
Seed storage proteins are synthesized on rER as precursors, are transported to protein storage vacuoles (PSVs), and then are converted into the mature forms. To understand the mechanism of storage protein transport, we examined the detailed phenotypes of Arabidopsis mutant seeds that abnormally accumulate the precursors of the storage proteins. Based on their phenotypes, the mutants were divided into two classes. Class 1 mutants including atvsr1 accumulated a larger amount of pro12S globulins. They secreted storage proteins from the cells. Class 2 mutants accumulated a larger amount of 2S albumins, and had novel structures that accumulate storage proteins. The structures were similar to precursor-accumulating (PAC) vesicles found in maturing pumpkin seeds. PAC vesicles are involved in Golgi-independent transport of storage proteins.
