CELL-DIFFERENTIATION IN DICTYOSTELIUM-DISCOIDEUM CONTROLS ASSEMBLY OFPROTEIN-LINKED GLYCANS

The prestalk and prespore cells from the Dictyostelium discoideum mult icellular slug stage of development differ in assembly of glycoconjuga tes. Prespore cells are 2- to 3-fold more active than prestalk cells i n the assembly of N-linked glycans and 20-fold more active in their fu cosylation. Only prespore cells synthesize an O-linked glycan consisti ng in part of Fuc alpha-linked to N-acetylglucosamine. Incorporation o f fucose, glucosamine, mannose and galactose into large pronase-resist ant glycoconjugates was almost exclusively into prespore cells. Such g lucosamine-labelled glycoconjugates resist fragmentation by beta-elimi nation and include a glycoantigen dependent on the modB genetic locus. In contrast, large fucose-labelled glycoconjugates consisted of multi ple, small, O-linked oligosaccharides on carrier peptides. The spore c oat protein SP96 has several fucosylated O-linked oligosaccharides, on e of which correlates with a fucose epitope previously shown to locali ze in prespore vesicles and the outer layer of the spore coat.