THE PLANT CELL, Vol 5, Issue 4 443-450, Copyright © 1993 by American Society of Plant Biologists
The N- and C-Terminal Regions Regulate the Transport of Wheat [gamma]-Gliadin through the Endoplasmic Reticulum in Xenopus Oocytes
Y. Altschuler, N. Rosenberg, R. Harel and G. Galili
Department of Plant Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel
Following sequestration into the endoplasmic reticulum (ER), wheat storage
proteins are naturally either retained and packaged into protein bodies
within this organelle or exported to the Golgi apparatus. To identify
protein domains that control the sorting of wheat storage proteins within
the ER, a wild-type [gamma]-gliadin storage protein as well as two of its
deletion mutants, each bearing either of the two autonomous N- and
C-terminal regions, were expressed in Xenopus oocytes. Our results
demonstrated that the N-terminal region of the gliadin, which is composed
of several tandem repeats of the consensus sequence PQQPFPQ, was entirely
retained within the ER and accumulated in dense protein bodies. In
contrast, the C-terminal autonomous region was efficiently secreted to the
medium. The wild-type [gamma]-gliadin, containing both regions, was
secreted at a lower rate and less efficiently than its C-terminal region.
These results suggest that sorting of the wheat [gamma]-gliadin within the
ER may be determined by a balance between two opposing signals: one
functions in the retention and packaging of the storage protein within the
ER, while the second renders the protein competent for export from this
organelle to the Golgi apparatus.
