Changes in Surface Properties of Developing Zoospores of Blastocladiella entersonii: Binding of Concanavalin A

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Abstract
Binding of concanavalin [Con] A to the cell surface of developing B. emersonii zoospores was explored by fluorescence microscopy, EM and radioactive labeling. After labeling with fluorescein isothiocyanate-conjugated Con A, the fluorescence intensity of individual non-induced zoospores varied greatly. Similarly labeled zoospores, induced with K+ ions for synchronous development, revealed a more even distribution of fluorescence intensity. The zoospore surface contained 4.3 .times. 107 Con A binding sites per cell which were randomly distributed and closely attached to the surface. The affinity constants ranged from 7.5 .times. 107 M-1 to 3.5 .times. 105 M-1, while the Scatchard plot was typical of heterogeneous binding. Further developed cells, round cells and germlings contained 3.0 .times. 107 to 2.1 .times. 107 Con A binding sites/cell which were mostly loosely associated patches protruding into the extracellular region. The affinity constants decreased appreciably compared with those measured at the zoospore stage. Specific Con A binding characteristics appeared to correlate with the respective developmental stage of the zoospore.