Inhibition of mating pair formation by wheat germ agglutinin and wheat germ agglutinin-binding substances in Paramecium caudatum cells

In this study, we revealed that the lectin wheat germ agglutinin (WGA) and its specific binding sugars, N-acetylneuraminic acid (NeuAc) and Nacetylglucosamine (GlcNAc), inhibited mating pair formation in Paramecium caudatum. The concentrations that caused 50% inhibition (IC50) were 17 nM, 3 mM and 30 mM, respectively. Using FITCWGA, it was shown fluorescence-cytochemically that WGA bound to the adhesion site between conjugated cells; this binding was inhibited by NeuAc but not GlcNAc. Moreover, the binding of FITCWGA was maintained appreciably when its localization was changed in correspon-dence with progression of conjugation until exchange of gametic nuclei was completed at which point the binding between both cells disintegrated. These results strongly suggested that NeuAc plays a primary role in mating pair formation in P. caudatum as a specific WGA binding sugar. INTRODUCTION