Lectins as Cytochemical Probes of the Developing Wheat Grain. Iii. Reaction of Potato and Wheat-Germ Lectins With Wheat Protein Bodies.

Abstract

Fluorescein-labelled lectins from the potato tuber and from wheat germ stained endosperm protein bodies in JB-4-embedded transverse sections cut from developing wheat grains. With potato lectin the reaction was observed in sections cut from grains at all stages between 10 and 35 days post-anthesis (p.a.). With wheat-germ lectin, staining was far less intense and the reaction was seen clearly only at 25-35 days p.a. Protein bodies isolated from wheat endosperm between 14 and 21 days p.a., and thin sections of dough prepared from mature wheat flour, also reacted with potato lectin. Intense fluorescence of aleurone granules was observed following treatment of JB-4-embedded sections with labelled potato lectin. The specificity of the reactions was further investigated by inhibition studies with monosaccharides, N,N'-diacetylchitobiose, N,N',N"-triacetylchitotriose, and some glycoproteins. We hypothesize that these reactions are mediated through specific sugar residues covalently attached to the storage proteins present in the protein bodies. Hydrophobic interactions may also be involved in the lectin binding. Experiments designed to investigate the existence of a wheat reserve glycoprotein(s) are therefore an important research priority. Potato lectin in particular should prove to be a valuable cytochemical probe in ultrastructural studies designed to examine the cytoplasmic origin and mode of transport of storage proteins to the vacuoles in the developing wheat endosperm.