THE PLANT CELL, Vol 2, Issue 9 941-950, Copyright © 1990 by American Society of Plant Biologists
Two Closely Related Wheat Storage Proteins Follow a Markedly Different Subcellular Route in Xenopus laevis Oocytes
R. Simon, Y. Altschuler, R. Rubin and G. Galili
Department of Plant Genetics, The Weizmann Institute of Science, Rehovot, Israel 76100
[alpha]-Gliadins and [gamma]-gliadins are two closely related wheat storage
proteins that evolved from a common ancestral gene. However, synthesis of
[alpha]-gliadins and [gamma]-gliadins in Xenopus laevis oocytes revealed
striking differences in their subcellular routing. The major portion of
[alpha]-gliadin accumulated inside the oocyte, whereas most of the
[gamma]-gliadin was secreted. Disruption of the Golgi apparatus by monensin
revealed that the major part of secretion of [gamma]-gliadin is Golgi
mediated. The difference in the subcellular route between [alpha]-gliadin
and [gamma]-gliadin may be attributed to differential transport from the
endoplasmic reticulum to the Golgi apparatus, a process that is generally
the rate-limiting step in protein secretion. Coinjection of the two mRNAs
had no effect on their routing, indicating no interaction between them. Our
results support the hypothesis that subcellular transport of gliadins in
wheat endosperm occurs in two separate routes; one is Golgi mediated, and
the other is not. We also show that the subcellular transport may be
markedly affected by small structural variations within closely related
storage proteins.
