Epigenetic control of extracellular auxin catabolism in grapevine cells cultured in suspension

Abstract

The several factors which control extracellular auxin catabolism were studied in grapevine (Vitis vinifera cv. Gamay), using cells cultured in suspension as a model system. From the results, it is concluded that, contrarily to previous observations with cultured cells, auxin catabolism in the spent medium depends on a massive sequential secretion of both basic and acidic isoperoxidases. It also depends on the secretion of phenolic compounds, characterized as of an 'auxin protector' nature, which modulate the IAA-oxidase activity of the extracellular isoperoxidases throughout the culture period. Thus, unlike observations of peroxidase activities, IAA-oxidase activities are expressed mainly during the beginning of the post-exponential growth phase of the cultured cells, giving to this highly compartmentalized catabolic process an apparent central role in the depletion of the IAA content, once the cultured cells have stopped growing.