The proteolytic processing of seed storage proteins in Arabidopsis embryo cells starts in the multivesicular bodies.
We have investigated the transport of storage proteins, their processing proteases, and the Vacuolar Sorting Receptor-1/Epidermal Growth Factor Receptor-Like Protein1 (VSR-1/ATELP1) receptor during the formation of protein storage vacuoles in Arabidopsis thaliana embryos by means of high-pressure freezing/freeze substitution, electron tomography, immunolabeling techniques, and subcellular fractionation. The storage proteins and their processing proteases are segregated from each other within the Golgi cisternae and packaged into separate vesicles. The storage protein-containing vesicles but not the processing enzyme-containing vesicles carry the VSR-1/ATELP1 receptor. Both types of secretory vesicles appear to fuse into a type of prevacuolar multivesicular body (MVB). We have also determined that the proteolytic processing of the 2S albumins starts in the MVBs. We hypothesize that the compartmentalized processing of storage proteins in the MVBs may allow for the sequential activation of processing proteases as the MVB lumen gradually acidifies.
Otegui
Marisa S
MS
Department of Botany, University of Wisconsin, Madison, Wisconsin 53706, USA. otegui@wisc.edu
Herder
Rachel
R
Schulze
Jan
J
Jung
Rudolf
R
Staehelin
L Andrew
LA
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000196:embryology*; D006056:Golgi Apparatus / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012639:Seeds / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D010940:Plant Proteins