Two Closely Related Wheat Storage Proteins Follow a Markedly Different Subcellular Route in Xenopus laevis Oocytes

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.