Tissue localization of beta-glucosidase in rye, maize and wheat seedlings

The localization of beta-glucosidase was determined at the tissue level in roots and shoots of rye, wheat and maize seedlings, using an immunohistoche mical approach with antibodies directed against purified maize beta-glucosi dase as the primary antibody. In the roots, the beta-glucosidase was found in the epidermis and the underlying cell layer. In the leaves, staining was seen in the epidermis (rye and wheat) and nearby vascular tissue (rye, whe at and maize). In all 3 species, beta-glucosidase activity was highest in t he coleoptile. Here the enzyme was restricted to the epidermis in wheat and to cells near the vascular tissue in maize, but was found in the whole tis sue, except the vascular tissue, in rye. Maize, wheat and rye all contain h ydroxamic acid glucosides, and results are discussed in relation to a propo sed role of beta-glucosidase as part of a defense system releasing hydroxam ic acid aglucone upon herbivore attack, pathogen penetration or aphid infes tation.