Lectin in five soybean cultivars previously considered to be lectin-negative

Hemagglutinating proteins were isolated by affinity chromatography from seeds of each of five cultivars of soybeans (Glycine max (L.) Merr.) previously reported to lack detectable lectin (S.P. Pull et al., 1978; Science 200, 1277). Quantities were between 1,000 and 10,000 times less than that found in the seeds of the reference cultivar, Chippewa. The sensitivity of the hemagglutinating assay was 0.05 μg ml-1. Hemagglutinating activity was demonstrated in affinity-purified fractions from bulk seeds and seeds from individual plants in two cultivars, 30—70% ammonium-sulfate-precipitable fractions of seeds from individual plants of all five cultivars, and in whole crude extracts of individual seeds from each cultivar. In all instances, hemagglutinating activity was inhibited by galactose, anti-soybean agglutinin (SBA), and lectin-binding polysaccharide produced by Rhizobium japonicum. Affinity-purified lectin from seeds of a single Columbia plant was labeled with fluorescein isothiocyanate (FITC) and observed by fluorescence microscopy to bind to R. japonicum cells with specificity, intensity and localization indistinguishable from FITC-SBA. Lectins from three cultivars in sufficiently high concentration for study had molecular properties very similar to Chippewa SBA.