Cell Pairing during Mating in Tetrahymena: I. Does Phagocytosis or a Cell Surface Receptor Participate in Con A Block?

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The lectin, Concanavalin A (Con A), inhibits cell pairing during mating in Tetrahymena and binds to the surface of pairing cells via receptors concentrated around the conjugation junction. Concanavalin A is also ingested in large amounts into food vacuoles. To dispel the possibility that Con A inhibits pairing via uptake into food vacuoles or through induction of food vacuole formation and to strengthen the idea that pairing is blocked through binding of Con A to cell surface receptors, we have conducted three types of experiments: 1) attempts to inhibit pairing by feeding with nutrients and with tantalum, a non‐nutritive reagent; 2) a temporal analysis of the presence of food vacuoles in mating cells fed with tantalum; and 3) analysis of the restoration of pairing following the addition of α‐methyl mannoside to cells previously treated with inhibitory concentrations of Con A. The results of these studies support the idea that Con A inhibits pairing by binding to receptors located on the cell surface and not by induction of or uptake into food vacuoles. We also present evidence that cells grown in an enriched proteose peptone medium are able to pair and undergo morphogenesis more readily than cells grown in 2% proteose peptone. Copyright © 1988, Wiley Blackwell. All rights reserved

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The Journal of Protozoology