PEROXIDASE ISOENZYMES AS MARKERS OF CELL DEDIFFERENTIATION IN GRAPEVINES (VITIS-VINIFERA)

The expression, and the tissue localization and the subcellular locali zation of peroxidase isoenzymes were studied during the development of mesocarp and hypodermal tissues of Vitis vinifera fruits cvs Airen an d Monastrell until fruit softening. In addition the de-differentiation process of mesocarp tissues to form callus cultures was investigated. Both grapevine cultivars contain, as the only component of peroxidase polymorphism in the whole fruit, the peroxidase isoenzyme Bg (the sol e component of the peroxidase isoenzyme group HpI BPrx in grapevines), which is both developmentally-regulated and tissue-specific. The esta blishment of cell cultures from the mesocarp of grapevine fruits is ac companied by the de novo expression of one acidic (APrx) and one basic (LpI BPrx) peroxidase isoenzyme group, whose particular isoenzyme com position is cultivar-specific and dependent on subcellular location (s oluble or bound to cell wall). These results suggest that, during the establishment of grape vine cell cultures from mesocarp tissues of gra pevine fruits, there is a differential expression of the peroxidase is oenzyme groups APrx and LpI BPrx located in both soluble and cell wall -bound fractions. This de novo gene expression probably expresses at m olecular level the totipotency of grapevine somatic cells, which is li nked to the de-differentiation process associated with the in vitro cu lture.