title: Involvement of mitogen-activated protein kinases in the symbiosis Bradyrhizobium-Lupinus.
abstract: In plants, mitogen-activated protein kinases (MAPKs) are involved in signalling to hormones, cell cycle regulation, stresses, and plant defence responses. In this work, several MAPKs were detected by immunobloting in roots and nodules of Lupinus albus produced by inoculation with Bradyrhizobium sp. (Lupinus). In vitro kinase assays showed that inoculation of seedling roots with B. sp. (Lupinus) activates salt stress-inducible and stress-activated MAPKs after 5 min of incubation. By contrast, inoculation with dead B. sp. (Lupinus) or the heterologous bacteria Sinorhizobium meliloti did not induce salt stress-inducible and stress-activated MAPK activities. In vivo experiments showed that inoculation with B. sp. (Lupinus) induced the activation of MAPKs in roots. The maximal activation was in the region of the root tip with emerging hairs, which corresponds to the infection zone. The p38 MAPK inhibitors SB 202190 and SB 203580 blocked these kinase activities. Experiments with SB 202190 and the MAPKK inhibitor UO 126 altered the pattern of nodulation in the main root, decreasing the number and weight of nodules produced in the upper sites while increasing the nodule number in the younger lower root zone. These data suggest that MAPK inhibition blocks early events in the susceptible root zone to rhizobial infection, delaying nodulation, and support a role for MAPKs in the infection and nodulation of L. albus by B. sp. (Lupinus).
authors.affiliation: Instituto de Recursos Naturales, Centro de Ciencias Medioambientales, Consejo Superior de Investigaciones Científicas, Serrano, 115 dpdo, E-28006 Madrid, Spain. mfernandezp@ccma.csic.es
authors.forename: Mercedes
authors.initials: M
authors.lastname: Fernandez-Pascual
authors.forename: M Mercedes
authors.initials: MM
authors.lastname: Lucas
authors.forename: Maria Rosario
authors.initials: MR
authors.lastname: de Felipe
authors.forename: Lisardo
authors.initials: L
authors.lastname: Boscá
authors.forename: Heribert
authors.initials: H
authors.lastname: Hirt
authors.forename: Maria Pilar
authors.initials: MP
authors.lastname: Golvano
mesh_terms: D020369:Bradyrhizobium / Q000502:physiology*; D004789:Enzyme Activation; D007150:Immunohistochemistry; D031297:Lupinus / Q000201:enzymology* / Q000382:microbiology* / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D010940:Plant Proteins / Q000502:physiology*; D018517:Plant Roots / Q000201:enzymology / Q000382:microbiology / Q000502:physiology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016962:Sinorhizobium meliloti / Q000502:physiology; D013559:Symbiosis / Q000187:drug effects / Q000502:physiology*
chemical_list: D010940:Plant Proteins; D047428:Protein Kinase Inhibitors; D020928:Mitogen-Activated Protein Kinases