The isolation and characterization of a root lectin from soybean (Glycine max (L), cultivar Chippewa)

A lectin has been isolated from the roots of 5-day soybean (Glycine max (L) cultivar Chippewa) seedlings, and its properties have been compared to those of the soybean seed lectin. The sugar-binding activities of the two lectins, both in terms of specific hemagglutinating activity and sugar specificity, are indistinguishable. Molecular properties of the two lectins, measured as relative molecular weights, isoelectric and electrophoretic patterns, amino acid compositions, immunochemical cross-reactivity, and chromatographic behavior on Sepharose-concanavalin A adsorbents suggest that the seed and the root lectin are very similar but not identical. On the basis of these comparisons, we conclude that models regarding biological functions of soybean lectin derived from studies using the seed lectin can be extended to include the root lectin in this cultivar. Studies on the distribution of the lectin in the root tissue suggest that it is associated with the outer surface of the root and is concentrated in the segments of the root at which hair and early secondary roots are observed. Since this is the region at which Rhizobium binding occurs and at which nodulation probably is initiated, all the reported observations on the root lectin are consistent with its proposed role in the specific interaction of the developing soybean with its symbiont.