title: An endopolygalacturonase from Sclerotinia sclerotiorum induces calcium-mediated signaling and programmed cell death in soybean cells.
abstract: A basic endopolygalacturonase (PG) isoform, produced early by Sclerotinia sclerotiorum when infecting soybean seedlings, was used to examine the signaling role of the enzyme in aequorin-expressing soybean cells. A cytosolic Ca2+ elevation was induced, with a rapid increase (phase 1) and a very slow decrease (phase 2) of Ca2+ concentration, indicating the involvement of Ca2+ ions in PG signaling. Within 1 h of PG-cell contact a remarkable level of cell death was recorded, significantly higher than the control cell culture turnover. The observed morphological and biochemical changes were indicative of the activation of programmed cell death; in particular, cytochrome c release in the cytoplasm and activation of both caspase 9-like and caspase 3-like proteases were found. When a polygalacturonase-inhibiting protein (PGIP) and the PG were simultaneously applied to cells, both the Ca2+ increase and cell death were annulled. The possible roles of prolonged sustained cytosolic Ca2+ concentrations in inducing cell death and of the PG-PGIP interaction in preventing PG signaling are discussed.
authors.affiliation: Dipartimento di Biologia, Università di Padova, via U Bassi 58/B, 35131 Padova, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Zuppini
authors.forename: Lorella
authors.initials: L
authors.lastname: Navazio
authors.forename: Luca
authors.initials: L
authors.lastname: Sella
authors.forename: Carla
authors.initials: C
authors.lastname: Castiglioni
authors.forename: Francesco
authors.initials: F
authors.lastname: Favaron
authors.forename: Paola
authors.initials: P
authors.lastname: Mariani
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001203:Ascomycota / Q000201:enzymology*; D020013:Calcium Signaling / Q000502:physiology*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D007527:Isoenzymes; D011096:Polygalacturonase / Q000235:genetics / Q000378:metabolism*; D013025:Glycine max / Q000166:cytology* / Q000378:metabolism*
chemical_list: D007527:Isoenzymes; D045304:Cytochromes c; D011096:Polygalacturonase; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases