Abstract
Wheat seed storage proteins are deposited in protein bodies (PB) inside vacuoles, but their subcellular site of aggregation and their route to vacuoles are still controversial. In the present work, an ultra structural analysis of developing wheat endosperm at early to mid maturation was performed to address these issues. Golgi complexes were rarely detected, indicating that their role in wheat storage protein transport is limited. In contrast, a considerable amount of PB was detected in the cytoplasm. Many of these PB were surrounded by RER membranes and were enlarged by fusion of smaller PB. Small, electron lucent vesicles were detected around the surfaces of the PB in the cytoplasm, or attached to them, suggesting that such attachments and subsequent fusion of the vesicles with each other lead to the formation of small vacuoles containing PB inclusions. Immunogold labeling with serum raised against yeast-BiP, an ER-localized protein, demonstrated that the wheat BiP homolog was present within the PB in the cytoplasm as well as inside vacuoles. This confirmed that the PB were formed within the RER and that the Golgi complex was not involved in their transport to vacuoles. It is concluded that a considerable part of the wheat storage proteins aggregate into PB within the RER and are then transported as intact PB to the vacuoles by a novel route that does not utilize the Golgi complex.
Full Text
The Full Text of this article is available as a PDF (5.4 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bole D. G., Hendershot L. M., Kearney J. F. Posttranslational association of immunoglobulin heavy chain binding protein with nascent heavy chains in nonsecreting and secreting hybridomas. J Cell Biol. 1986 May;102(5):1558–1566. doi: 10.1083/jcb.102.5.1558. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Chiang H. L., Schekman R. Regulated import and degradation of a cytosolic protein in the yeast vacuole. Nature. 1991 Mar 28;350(6316):313–318. doi: 10.1038/350313a0. [DOI] [PubMed] [Google Scholar]
- Denecke J., Goldman M. H., Demolder J., Seurinck J., Botterman J. The tobacco luminal binding protein is encoded by a multigene family. Plant Cell. 1991 Sep;3(9):1025–1035. doi: 10.1105/tpc.3.9.1025. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Giannella G., Pelosi-Testa E., Carlini P., Habetswallner D., Montesoro E., Camagna A., Calzini V., Ruggeri E. M., Arena M. G., Masciulli R. Fluctuations of plasma beta 2-microglobulin, soluble interleukin 2 receptor and interferon-gamma concentrations after adoptive immunotherapy with high-dose interleukin 2 and lymphokine-activated killer cells. Immunobiology. 1989 Feb;178(4-5):305–315. doi: 10.1016/s0171-2985(89)80054-3. [DOI] [PubMed] [Google Scholar]
- Haas I. G., Wabl M. Immunoglobulin heavy chain binding protein. Nature. 1983 Nov 24;306(5941):387–389. doi: 10.1038/306387a0. [DOI] [PubMed] [Google Scholar]
- Hardwick K. G., Lewis M. J., Semenza J., Dean N., Pelham H. R. ERD1, a yeast gene required for the retention of luminal endoplasmic reticulum proteins, affects glycoprotein processing in the Golgi apparatus. EMBO J. 1990 Mar;9(3):623–630. doi: 10.1002/j.1460-2075.1990.tb08154.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Herman E. M., Lamb C. J. Arabinogalactan-rich glycoproteins are localized on the cell surface and in intravacuolar multivesicular bodies. Plant Physiol. 1992 Jan;98(1):264–272. doi: 10.1104/pp.98.1.264. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Larkins B. A., Hurkman W. J. Synthesis and deposition of zein in protein bodies of maize endosperm. Plant Physiol. 1978 Aug;62(2):256–263. doi: 10.1104/pp.62.2.256. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Munro S., Pelham H. R. A C-terminal signal prevents secretion of luminal ER proteins. Cell. 1987 Mar 13;48(5):899–907. doi: 10.1016/0092-8674(87)90086-9. [DOI] [PubMed] [Google Scholar]
- Munro S., Pelham H. R. An Hsp70-like protein in the ER: identity with the 78 kd glucose-regulated protein and immunoglobulin heavy chain binding protein. Cell. 1986 Jul 18;46(2):291–300. doi: 10.1016/0092-8674(86)90746-4. [DOI] [PubMed] [Google Scholar]
- Pelham H. R. Control of protein exit from the endoplasmic reticulum. Annu Rev Cell Biol. 1989;5:1–23. doi: 10.1146/annurev.cb.05.110189.000245. [DOI] [PubMed] [Google Scholar]
- Pelham H. R. The retention signal for soluble proteins of the endoplasmic reticulum. Trends Biochem Sci. 1990 Dec;15(12):483–486. doi: 10.1016/0968-0004(90)90303-s. [DOI] [PubMed] [Google Scholar]
- Rose M. D., Misra L. M., Vogel J. P. KAR2, a karyogamy gene, is the yeast homolog of the mammalian BiP/GRP78 gene. Cell. 1989 Jun 30;57(7):1211–1221. doi: 10.1016/0092-8674(89)90058-5. [DOI] [PubMed] [Google Scholar]
- Towbin H., Staehelin T., Gordon J. Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A. 1979 Sep;76(9):4350–4354. doi: 10.1073/pnas.76.9.4350. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wallace J. C., Galili G., Kawata E. E., Cuellar R. E., Shotwell M. A., Larkins B. A. Aggregation of lysine-containing zeins into protein bodies in Xenopus oocytes. Science. 1988 Apr 29;240(4852):662–664. doi: 10.1126/science.2834822. [DOI] [PubMed] [Google Scholar]
- Yoshihisa T., Anraku Y. A novel pathway of import of alpha-mannosidase, a marker enzyme of vacuolar membrane, in Saccharomyces cerevisiae. J Biol Chem. 1990 Dec 25;265(36):22418–22425. [PubMed] [Google Scholar]