Lectins as Cytochemical Probes of the Developing Wheat Grain. I. Fluorescein-Labelled Lectins Covering a Range of Specificities With Emphasis on Those That Bind D-Galactose.

Abstract

Twelve fluorescein-labelled lectins with combining sites that collectively recognize a range of sugars were used as specific cytochemical probes to study both plastic-embedded and frozen sections of developing wheat grain. Specific reactions, inhibited by preincubation of lectin with sugars complementary to the specific combining sites, were observed with all of the lectins except the L- fucose-binding agglutinins from Lotus tetragonolobus and Ulex europaeus, and the N-acetyl-D-glucosamine-binding lectin from U. europaeus. Lectins from Canavalia ensiformis, Pisum sativum and Bandeiraea simplicifolia reacted with the starch granules. Potato and wheat-germ agglutinins, both of which bind N-acetyl-D-glucosamine, stained protein bodies. The latter lectin also reacted strongly with the nucellar epidermis in the immature grain. Four D-galactose-binding lectins from Abrus precatorius, Arachis hypogaea, Bandeiraea simplicifolia and Glycine max reacted with the cell walls of both the nucellar epidermis and the nucellar projection. Fluorescent staining of the nucellar epidermis was most uniform and intense at about 14 days post-anthesis (p.a.) and declined thereafter until it had completely disappeared by 35 days p.a. However, staining of the nucellar projection persisted throughout the period of examination.