EXPRESSION OF ASCORBATE OXIDASE IN CULTURED GREEN ZUCCHINI CELLS - EFFECT OF COPPER AND ABSCISIC-ACID

Cell cultures have been developed from green zucchini (Cucurbita pepo medullosa) ana used as a model system for studying the expression of a scorbate oxidase (AO). Addition of copper, the enzyme cofactor, to the culture medium increased the ascorbate oxidase activity, without chan ges in the specific mRNA and protein level. Therefore, copper presumab ly activates the apo AO present in the cell. Addition of the phytohorm one abscisic acid (ABA) to the medium led to a decrease of both AO act ivity and content, paralleled by a decrease of the specific mRNA. Thus , it is assumed that ABA modifies the AO protein net synthesis, possib ly acting at the transcriptional level.