Abstract
Seed storage proteins are synthesized on the endoplasmic reticulum (ER) as precursors and then transported to protein storage vacuoles, where they are processed into mature forms. Here, we isolated and characterized an Arabidopsis mutant, maigo5 (mag5), that accumulated the precursors of storage proteins in dry seeds. mag5 seed cells developed many novel structures with high electron-dense cores. Immunoelectron microscopy revealed that these structures are MAG bodies previously found in the seeds of mag2 (1) and mag4 (2). Because MAG bodies are derived from the ER, we considered that mag5 mutant has a defect in storage proteins exit from the ER. We used map-based cloning and identified the MAG5 gene, which encodes an unknown protein. Both MAG2 and MAG4 are involved in the protein transport between ER and Golgi body: MAG2 is necessary for retrograde transport, while MAG4 is necessary for anterograde transport. Our findings suggest that MAG5 is required for intracellular transport between ER-Golgi body.
(1) Li L. et.al, Plant Cell 2006;18(12):3535-3547.
(2) Takahashi H. et.al, Plant Cell Physiol 2010;51(10):1777-1787.
