PERIODATE-ACID TREATMENT OF SECTIONS PERMITS ON-GRID IMMUNOGOLD LOCALIZATION OF PEA SEED VICILIN IN ER AND GOLGI

The legume seed reserve protein vicilin was localized in developing pea cotyledons by immunogold labeling on sections of glutaraldehyde-osmium-fixed, resin-embedded tissue. By treating sections with periodate and acid before antibody labeling, a 20-fold increase in specific antibody binding was observed. The densest label occurred over vacuolar contents, previously identified as the site of protein storage, and over electron-dense cisternae occassionally seen to be continuous with the vacuolar contents. Vicilin was also associated with the rough endoplasmic reticulum, the implied site of synthesis, and in electron-dense Golgi vesicles which are suggested as a vehicle by which newly synthesized protein is relocated into the vacuole.