Involvement of JIM13-and JIM8-responsive carbohydrate epitopes in early stages of cell wall formation

We studied the possible involvement of JIM13- and JIM8-responsive epitopes in the formation of the cell wall at the surface of regenerating protoplast s of sugar beet (Beta vulgaris L). The spatial and temporal expression of b oth antigens was studied in suspension cells used as the source-tissue for protoplast isolation, in suspension- and mesophyll-derived protoplasts, and in cells which developed from both types of protoplast. Immunofluorescence and immunocytochemical-electron microscopic methods revealed that labeling was present in the cell walls of most suspension cells and also in the inc ipients of cell walls synthesized around the protoplasts. This signal becam e much more intense as rebuilding of the cell wall progressed during cultur e. Relatively weaker labeling was observed in the cytoplasm, where it was f requently associated with the vacuolar compartment. Signal intensity varied between individual cells of the same population and in successive stages o f development, but was always stronger with JIM13 than with JIM8. The role of JIM13-responsive epitope in the development of suspension-derived protop lasts was further studied by its ability to bind antibody added to cultures of different ages. Both JIM8- and JIM13-responsive epitopes were widesprea d in sugar beet cells of different origin and stage of cell wall synthesis. These epitopes may play an important role in cell wall formation and growt h under in vitro conditions.