Tissue printing for myrosinase activity in roots of turnip and Japanese radish and horseradish: a technique for localizing myrosinases

A method for analyzing the tissue distribution of myrosinase activity in Br assicaceous plants was developed. This technique is based on 'tissue printi ng' to visualize enzyme activity. The freshly-cut surface (transverse direc tion) of the root of three species, Japanese radish (Raphanus sativus). tur nip (Brassica campestris) and Japanese horseradish (wasabi: Wasabia japonic a), was pressed onto a polyvinylidene difluoride (PVDF) filter to immobiliz e the proteins onto the membrane. The sites of myrosinase activity on the m embranes were visualized by the sinigrin-glucose oxidase-peroxidase system. Signals for myrosinase activity were observed in both the epidermis and va scular cambium of the root of the Japanese radish, turnip and wasabi. Measu rement of myrosinase activity in protein extracts indicated that the level of myrosinase activity in the peeling, which consisted of the epidermis, co l tex and vascular cambium, was much higher than that in the peeled root of the three species. These results support the image that myrosinase activit y, obtained in tissue printing, corresponded well with the tissue distribut ion of myrosinase activity, (C) 2001 Elsevier Science Ireland Ltd. All righ ts reserved.