Cytochemical localization of β-(1 → 4)-D-glucans in plant and fungal cells using an exoglucanase-gold complex

An exoglucanase (exo-1,4-β-glucanase), purified from a cellulase produced by the fungus Trichoderma harzianum, was tagged with colloidal gold particles and applied on plant and fungal tissue sections for localizing β-(1 → 4)-linked glucans. The present review reports the conditions required for the preparation of this enzyme-gold complex and for its application in transmission electron microscopy. The exoglucanase-gold complex was found to be a powerful probe for labelling accurately cellulosic glucans in tissues processed under conventional procedures. This approach represents a promising alternative to previous methods such as autoradiography or subtractive cytochemistry in the study of wall topochemistry. It will undoubtedly acquire increasing applicability and relevance in various fields of plant science including physiology and pathology.