Authors: Diana Soares da Costa Susana Pereira Ian Moore José Pissarra
Publish Date: 2010/09/25
Volume: 232, Issue: 6, Pages: 1517-1530
Abstract
In cardoon pistils while cardosin A is detected in the vacuoles of stigmatic papillae cardosin B accumulates in the extracellular matrix of the transmitting tissue Given cardosins’ high homology and yet different cellular localisation cardosins represent a potentially useful model to understand and study the structural and functional plasticity of plant secretory pathways The vacuolar targeting of cardosin A was replicated in heterologous species so the targeting of cardosin B was examined in these systems Inducible expression in transgenic Arabidopsis and transient expression in tobacco epidermal cells were used in parallel to study cardosin B intracellular trafficking and localisation Cardosin B was successfully expressed in both systems where it accumulated mainly in the vacuole but it was also detected in the cell wall The glycosylation pattern of cardosin B in these systems was in accordance with that observed in cardoon highmannosetype glycans suggesting that either the glycans are inaccessible to the Golgi processing enzymes due to cardosin B conformation or the protein leaves the Golgi in an early step before Golgimodifying enzymes are able to modify the glycans Concerning cardosin B trafficking pathway it is transported through the Golgi in a RABD2adependent route and is delivered to the vacuole via the prevacuolar compartment in a RABF2bdependent pathway Since cardosin B is secreted in cardoon pistils its localisation in the vacuoles in cardoon ovary and in heterologous systems suggests that the differential targeting of cardosins A and B in cardoon pistils results principally from differences in the cells in which these two proteins are expressed
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