Characterization of cell surface carbohydrates on asexual spores of the water moldSaprolegnia ferax

Summary In asexual reproduction of the water mold,Saprolegnia ferax, four distinct and sequentially produced spores are involved in dispersal, two of which are motile and two of which are nonmotile. Composition of cell surface glycoproteins may be important in dispersal strategies for each of these stages. Binding patterns of fluorescently labelled lectins were investigated to identify differences in glycoproteins of asexually produced dispersal stages. The pattern of lectin binding to zoospores was diverse. FITC-Con A bound to surfaces of zoospores and membranes of the water expulsion vacuole system, indicating the prescence of mannosyl and glucosyl residues. In zoospores incubated for more than 30 min in FITC-WGA and FITC-GS II. which bind N-acetyl glucosamine, fluorescence was sometimes localized in peripheral, intracellular patches. In shorter incubations, secondary zoospores bound these lectins along the groove region where K-bodies were located. Surfaces of cystospores typically bound FITC-WGA, but not FITC-GS II. FITC-GS II, however, bound to empty cystospore walls, probably because reactive sugars were available at the inner surface of the wall. Germ tubes emerging from cystospores bound labelled WGA and GS II, but not Con A. The same lectin binding pattern was found along discharge papilla of primary cystospores, indicating that modifications in cystospore walls associated with direct germination and zoospore discharge were similar. Thus, glycoproteins involved in early establishment of the hyphal system differ from those forming the cell surface of cystospores. Differences in the binding pattern of lectins to zoospores and cystospores highlight differences between cell surface carbohydrates of motile and nonmotile asexual stages.Abbreviations BPA lectin fromBauhinia purpurea - C₁ primary cystospore - C₂ secondary cystospore - Con A concanavalin A, lectin fromCanavalia ensiformis - DBA lectin fromDolichos biflorus - DIC Nomarski differential interference contrast optics - DS dilute salts - FITC fluorescein isothiocyanate - FUC fucose - Gal galactose - GalNAc N-acetyl galactosamine - Glc glucose - GlcNAc N-acetyl glucosamine - GS I Griffonia simplicifolia lectin I - GS II G. simplicifolia lectin II - Man mannose - MPA lectin fromMaclura pomifera - PC phase contrast optics - PNA lectin fromArachis hypogaea - SBA soybean agglutinin, lectin fromGlycine max - UEA-1 lectin fromUlex europaeus - WGA wheat germ agglutinin fromTriticum vulgare - WV water expulsion vacuole