| Abstract Detail
Protein Targeting and Vesicular Trafficking Wang, Junqi [1], Li, Yubing [2], Lo, Sze Wan [2], Hillmer, Stefan [3], Sun, Samuel S. M. [2], Robinson, David [3], Jiang, Liwen [2]. Protein Mobilization in Germinating Mung Bean Seeds Involves Vacuolar Sorting Receptors and Multivesicular Bodies. Plants accumulate and store proteins in protein storage vacuoles (PSVs) during seed development and maturation. Upon seed germination, these storage proteins are mobilized to provide nutrients for seedling growth. However, little is known about the molecular mechanisms of protein degradation during seed germination. Here we test the hypothesis that vacuolar sorting receptor (VSR) proteins play a role in mediating protein degradation in germinating seeds. We demonstrate that both VSR proteins and hydrolytic enzymes are synthesized de novo during mung bean seed germination. Immunogold EM with VSR antibodies demonstrated that VSRs mainly locate to the peripheral membrane of multivesicular bodies (MVBs), presumably as recycling receptors in Day-1 germinating seeds, but become internalized to the MVB lumen, presumably for degradation at Day-3 germination. Chemical cross-linking and immunoprecipitation with VSR antibodies identified the cysteine protease aleurain as a specific VSR-interacting protein in germinating seeds. Further confocal immunofluorescence and immunogold EM studies demonstrate that VSR and aleurain colocalized to MVBs, as well as PSVs in germinating seeds. Thus, MVBs in germinating seeds exercise dual functions: as a storage compartment for proteases that are physically separated from PSVs in the mature seed, and as an intermediate compartment for VSR-mediated delivery of proteases from the Golgi apparatus to the PSV for protein degradation during seed germination. Supported by by grants from the Research Grants Council of Hong Kong (CUHK4260/02M, CUHK4307/03M and CUHK4580/05M), National Science Foundation of China (30529001), CUHK Scheme C and UGC-AoE (B-07/99) to L. Jiang.
Log in to add this item to your schedule
1 - The Chinese University of Hong Kong, Department of Biology, Room386, Department of Biology, Science centre,, The Chiese University of Hong Kong, Shatin, NT,, Hong Kong, P.R. China
2 - The Chinese University Of Hong Kong, Biology
3 - University of Heidelberg, Heidelberg Institute for plant sciences
Keywords:
VSR
MVB
seed germination.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P22004
Abstract ID:165 |
