title: Effects of Ca2+ on phytoalexin induction by fungal elicitor in soybean cells.
abstract: A glucan elicitor from the cell walls of the fungus Phytophthora megasperma f.sp. glycinea caused increases in the activities of the phytoalexin biosynthetic enzymes, phenylalanine ammonia-lyase and chalcone synthase, and induced the production of the phytoalexin, glyceollin, in soybean (Glycine max) cell suspension cultures when tested in culture medium containing 1.2 mmol/liter Ca2+. Removal of extracellular Ca2+ by treatment with ethylene glycol bis(beta-aminoethyl ether)-N, N'-tetraacetic acid followed by washing the cells with Ca2+-free culture medium abolished the elicitor-mediated phytoalexin response. This suppression was largely reversed on readdition of Ca2+. Elicitor-mediated enhancement of biosynthetic enzyme activities and accumulation of glyceollin was strongly inhibited by La3+; effective concentrations for 50% inhibition were (mumol/liter) 40 for phenylalanine ammonia-lyase, 100 for chalcone synthase, and 30 for glyceollin. Verapamil caused similar effects only at concentrations higher than 0.1 mmol/liter, whereas trifluoperazine and 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate did not affect enzyme induction by the elicitor in the concentration range tested. Uptake of alpha-amino isobutyric acid into soybean cells, which was rapidly inhibited in the presence of the glucan elicitor, was not affected by La3+ nor was uptake inhibition by the elicitor relieved by La3+. The Ca2+ ionophore, A23187, enhanced phytoalexin biosynthetic enzyme activities and glyceollin accumulation in a dose-dependent manner, with 50% stimulation (relative to the elicitor) occurring at about 5 mumol/liter. The results suggest that the glucan elicitor causes changes in metabolite fluxes across the plasma membrane of soybean cells, among which changes in Ca2+ fluxes appear to be important for the stimulation of the phytoalexin response.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000621:Aminoisobutyric Acids / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D008411:Chytridiomycota / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D005419:Flavonoids / Q000378:metabolism*; D005936:Glucans / Q000302:isolation & purification / Q000494:pharmacology*; D007529:Isoflavones / Q000378:metabolism*; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism; D010838:Phytophthora / Q000502:physiology*; D010936:Plant Extracts; D010944:Plants / Q000378:metabolism*; D012717:Sesquiterpenes; D013025:Glycine max / Q000378:metabolism; D013729:Terpenes; D000094162:Phytoalexins
chemical_list: D000621:Aminoisobutyric Acids; D005419:Flavonoids; D005936:Glucans; D007529:Isoflavones; D010936:Plant Extracts; D012717:Sesquiterpenes; D013729:Terpenes; C100049:2-aminoisobutyric acid; D000001:Calcimycin; D004533:Egtazic Acid; D000217:Acyltransferases; C020141:flavanone synthetase; D010650:Phenylalanine Ammonia-Lyase; D002118:Calcium; D000094162:Phytoalexins