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 have examined Arabidopsis maigo mutants that abnormally accumulate the precursors of the storage proteins. Here, we report a new maigo mutant, mag4, that abnormally accumulate the precursors of 12S globulins and 2S albumins in seeds. Novel structures with high electron-dense core were found in mag4 seed cells. Some of them are surrounded with ribosomes. Immunogold analysis suggests that the high electron-dense core is an aggregate of pro2S albumins and that 12S globulins are localized around the core. MAG4 might function in membrane traffic between ER and Golgi for seed storage proteins.
