title: Oxidative and antioxidative responses in the wheat-Azospirillum brasilense interaction.
abstract: Azospirillum is a plant growth-promoting rhizobacteria (PGPR) able to enhance the growth of wheat. The aim of this study was to test the effect of Azospirillum brasilense cell wall components on superoxide (O2·(-)) production in wheat roots and the effect of oxidative stress on A. brasilense viability. We found that inoculation with A. brasilense reduced O2·(-) levels by approx. 30 % in wheat roots. Inoculation of wheat with papain-treated A. brasilense, a Cys protease, notably increased O2·(-) production in all root tissues, as was observed by the nitro blue tetrazolium (NBT) reduction. However, a 24-h treatment with rhizobacteria lipopolysaccharides (50 and 100 μg/mL) alone did not affect the pattern of O2·(-) production. Analysis of the effect of plant cell wall components on A. brasilense oxidative enzyme activity showed no changes in catalase activity but a decrease in superoxide dismutase activity in response to polygalacturonic acid treatment. Furthermore, A. brasilense growth was only affected by high concentrations of H2O2 or paraquat, but not by sodium nitroprusside. Our results suggest that rhizobacterial cell wall components play an important role in controlling plant cell responses and developing tolerance of A. brasilense to oxidative stress produced by the plant.
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, Edif. A1', Morelia, Michoacán, CP 58040, Mexico.
authors.forename: Manuel
authors.initials: M
authors.lastname: Méndez-Gómez
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, Edif. A1', Morelia, Michoacán, CP 58040, Mexico.
authors.forename: Elda
authors.initials: E
authors.lastname: Castro-Mercado
authors.affiliation: Department of Biology and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996-0840, USA.
authors.forename: Gladys
authors.initials: G
authors.lastname: Alexandre
authors.affiliation: Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, Edif. A1', Morelia, Michoacán, CP 58040, Mexico. egpineda@umich.mx.
authors.forename: Ernesto
authors.initials: E
authors.lastname: García-Pineda
mesh_terms: D015806:Azospirillum brasilense / Q000502:physiology*; D002374:Catalase / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*; D012988:Soil Microbiology; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D013559:Symbiosis; D014908:Triticum / Q000254:growth & development / Q000378:metabolism / Q000382:microbiology*
chemical_list: D008070:Lipopolysaccharides; D010940:Plant Proteins; D013481:Superoxides; D002374:Catalase; D013482:Superoxide Dismutase
keywords: Azospirillum; Catalase (CAT); Oxidative stress; Plant growth-promoting rhizobacteria (PGPR); Superoxide; Superoxide dismutase (SOD)