Cell wall localization of dihydroflavonol-glucoside β-glucosidase in flowers of Petunia hybrida.

Limbs of flower buds from Petunia hybrida were investigated for β-glucosidase activity with dihydroflavonol-glucosides and 4-methyl-umbelliferyl-β-D-glucoside as substrates. Dihydroflavonol-glucoside β-glucosidase is localized in the cell wall. This activity has an acid pH optimum and is also active toward 4-methyl-umbelliferyl-β-glucoside. Besides this activity a neutral β-glucosidase is present. This activity is soluble and is not active toward dihydroflavonol-glucosides. Using starch gel electrophoresis it was shown that no difference in β-glucosidase activity is present between mutants able to convert dihydroflavonols into anthocyanins and mutants accumulating dihydroflavonol-glucosides. It is concluded that β-glucosidase activity is not involved in anthocyanin synthesis.