title: Dissecting cardosin B trafficking pathways in heterologous systems.
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 high-mannose-type 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 Golgi-modifying enzymes are able to modify the glycans. Concerning cardosin B trafficking pathway, it is transported through the Golgi in a RAB-D2a-dependent route, and is delivered to the vacuole via the prevacuolar compartment in a RAB-F2b-dependent 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.
authors.affiliation: Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, s/nº, 4169-007, Porto, Portugal. diana.costa@fc.up.pt
authors.forename: Diana Soares
authors.initials: DS
authors.lastname: da Costa
authors.forename: Susana
authors.initials: S
authors.lastname: Pereira
authors.forename: Ian
authors.initials: I
authors.lastname: Moore
authors.forename: José
authors.initials: J
authors.lastname: Pissarra
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001692:Biological Transport; D030821:Plants, Genetically Modified
chemical_list: D029681:Arabidopsis Proteins