title: Isolation of sealed plasma membrane vesicles from Phytophthora megasperma f. sp. glycinea: II. Partial characterization of Ca2+ transport and glyceollin effects.
abstract: Calcium uptake was examined in sealed plasma membrane vesicles isolated from the plant pathogenic fungus, Phytophthora megasperma f. sp. glycinea. Calcium uptake was ATP-dependent and by the addition of various ionophores in the presence of ATP, it was shown that Ca2+ transport was mediated by a nH+/Ca2+ antiport. Further evidence for this antiport mechanism included Ca2+ uptake driven by an imposed pH gradient and the observation that calcium could dissipate a steady-state pH gradient across the vesicle membrane. Transport mediated by the nH+/Ca2+ antiport was optimal at pH 7.0, and demonstrated saturation kinetics for Ca2+ with a Km of about 7 microM. Glyceollin, a soybean phytoalexin, was found to inhibit Ca2+ transport consistent with its ability to increase H+ conductance. In the presence of glyceollin, calcium leakage from Phytophthora membrane vesicles also increased. This study provides basic information about calcium transport in a plant pathogenic fungus as well as demonstrating a possible mode of action of a phytoalexin.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D001578:Benzopyrans / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000032:analysis / Q000378:metabolism*; D008411:Chytridiomycota / Q000378:metabolism*; D004553:Electric Conductivity / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D010838:Phytophthora / Q000378:metabolism*; D036343:Pterocarpans; D013025:Glycine max
chemical_list: D001578:Benzopyrans; D036343:Pterocarpans; D000001:Calcimycin; C017343:glyceollin; D000255:Adenosine Triphosphate; D002118:Calcium