Differential expression of a cell wall-localized peroxidase isoenzyme capable of oxidizing 4-hydroxystilbenes during the cell culture of grapevine (Vitis vinifera cv. Airen and Monastrell)

Differential expression and localization of peroxidase isoenzymes capable of oxidizing 4-hydroxystilbenes was studied during establishment of callus cultures from Vitis vinifera Airen (anthocyanin-non accumulating) and Monastrell (anthocyanin-accumulating) berries. Callus formation from mesocarp tissues was accompanied by differential expression of several peroxidase isoenzyemes located in cell walls, among which only peroxidase isoenzyme A₁ was capable of oxidizing 4-hydroxystilbene to any great extent. Likewise, grape cell cultures were capable of accumulating the grape stilbene phytoalexin, resveratrol. However, -viniferin, the most powerful phytoalexin in grapevines and previously considered as the product of peroxidase-mediated oxidative coupling of two resveratrol moieties, was only detectable in trace amounts. Since grapevine suspension cell cultures were unable to produce H₂O₂ as revealed by the luminol test, H₂O₂ production by the cultured cells appears to be one of the main factors which limits resveratrol oxidation in the cell walls of grapevine cells cultured in suspension.