Abstract.
The function of aspartic proteinases (EC 3.4.23) present in flowers of Cynara species is still unknown. Cardosin A, as a highly abundant aspartic proteinase from Cynara cardunculus L., a relative of the artichoke, is synthesised as a zymogen and subsequently undergoes proteolytic processing, yielding the mature and active enzyme. Here we report the study of the expression and localization of cardosin A, as a first approach to address the question of its physiological relevance. A polyclonal antibody specific for cardosin A was raised against a synthetic peptide corresponding to an amino acid sequence of the enzyme. This antibody was used to study the organ-specific, tissue-specific and subcellular localization of cardosin A by immunoblotting, tissue printing and immunogold electron microscopy. The results showed that expression of cardosin A is highly restricted to the pistils, and that the enzyme accumulates mainly in protein storage vacuoles of the stigmatic papillae. Cardosin A is also present, although much less abundantly, in the vacuoles of the cells of the epidermis of the style. In view of these results, the possible physiological roles of cardosin A are discussed, namely an involvement in defense mechanisms or pollen-pistil interaction, as well as in flower senescence.
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Received: 10 December 1996 / Accepted: 14 March 1997
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Ramalho-Santos, M., Pissarra, J., Veríssimo, P. et al. Cardosin A, an abundant aspartic proteinase, accumulates in protein storage vacuoles in the stigmatic papillae of Cynara cardunculus L.. Planta 203, 204–212 (1997). https://doi.org/10.1007/s004250050183
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DOI: https://doi.org/10.1007/s004250050183