Cardosin A, an abundant aspartic proteinase, accumulates in protein storage vacuoles in the stigmatic papillae of Cynara cardunculus L

• Published in: Planta Vol. 203; no. 2; pp. 204 - 212
• Main Authors: Ramalho-Santos, M, Pissarra, J, Verissimo, P, Pereira, S, Salema, R, Pires, E, Faro, C.J
• Format: Journal Article
• Language: English
• Published: Berlin Springer-Verlag 01.10.1997; Springer
• Subjects: ACIDE ASPARTIQUE; ACIDO ASPARTICO; Amino Acid Sequence; ANTIBODIES; ANTICORPS; ANTICUERPOS; ASPARTIC ACID; Aspartic Acid Endopeptidases - biosynthesis; Aspartic Acid Endopeptidases - isolation & purification; Aspartic Acid Endopeptidases - metabolism; Barley; Biological and medical sciences; Biotechnology; Cell walls; CYNARA CARDUNCULUS; ENZIMAS; ENZYME; ENZYMES; Epidermal cells; EXPRESION GENICA; EXPRESSION DES GENES; FISIOLOGIA VEGETAL; FLEUR; FLORES; FLOWERS; Fundamental and applied biological sciences. Psychology; GENE EXPRESSION; IMMUNOLOGICAL TECHNIQUES; Metabolism; MICROSCOPIA; MICROSCOPIE; MICROSCOPY; Microscopy, Immunoelectron; Papillae; PEPTIDE; Peptide Fragments - chemistry; Peptide Fragments - immunology; PEPTIDES; PEPTIDOS; PHYSIOLOGIE VEGETALE; PLANT PHYSIOLOGY; Plant physiology and development; Plant Proteins - biosynthesis; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Plant Stems; PLANT TISSUES; Plants; Plants - enzymology; Plants - ultrastructure; Pollen; PROTEASAS; PROTEASE; PROTEASES; PROTEINAS; PROTEINE; PROTEINS; Seeds; TECHNIQUE IMMUNOLOGIQUE; TECNICAS INMUNOLOGICAS; TEJIDOS VEGETALES; TISSU VEGETAL; Vacuoles; Vacuoles - enzymology; Vacuoles - ultrastructure; Flower; Enzyme; Tissue specificity; Compositae; Gene expression; Biological activity; Immunological method; Peptidases; Cynara cardunculus; Dicotyledones; Angiospermae; Hydrolases; Spermatophyta; Aspartic endopeptidases; Localization
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s004250050183

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.