Differential compartmentation of sucrose and gentianose in the cytosol and vacuoles of storage root protoplasts from Gentiana Lutea L.

The storage roots of perennial Gentiana lutea L.plants contain several sugars. The predominant carbohydrate reserve is gentianose (β-D-glucopyranosyl-(1 → 6)-α-D-glucopyranosyl-(1 ↔ 2)-β-D-fructofuranoside). Vacuoles were isolated from root protoplasts and purified through a betaine density gradient. The yield was about 75%. Gentianose and gentiobiose were localized to 100% in the vacuoles, fructose and glucose to about 80%, and sucrose to only about 50%. Taking the volumes of the vacuolar and extravacuolar (cytosolic) compartments into account it is inferred that gentianose is located exclusively in the vacuoles, whilst sucrose is much more concentrated in the cytosol where it may play a role as a cryoprotectant. The concentration of fructose and glucose appeared to be similar on both sides of the tonoplast.