title: Physiological, structural and molecular traits activated in strawberry plants after inoculation with the plant growth-promoting bacterium Azospirillum brasilense REC3.
abstract: The plant growth-promoting strain REC3 of Azospirillum brasilense, isolated from strawberry roots, prompts growth promotion and systemic protection against anthracnose disease in this crop. Hence, we hypothesised that A. brasilense REC3 can induce different physiological, structural and molecular responses in strawberry plants. Therefore, the aim of this work was to study these traits activated in Azospirillum-colonised strawberry plants, which have not been assessed until now. Healthy, in vitro micropropagated plants were root-inoculated with REC3 under hydroponic conditions; root and leaf tissues were sampled at different times, and oxidative burst, phenolic compound content, malondialdehyde (MDA) concentration, callose deposition, cell wall fortification and gene expression were evaluated. Azospirillum inoculation enhanced levels of soluble phenolic compounds after 12 h post-inoculation (hpi), while amounts of cell wall bound phenolics were similar in inoculated and control plants. Other early responses activated by REC3 (at 24 hpi) were a decline of lipid peroxidation and up-regulation of strawberry genes involved in defence (FaPR1), bacterial recognition (FaFLS2) and H₂O₂ depuration (FaCAT and FaAPXc). The last may explain the apparent absence of oxidative burst in leaves after bacterial inoculation. Also, REC3 inoculation induced delayed structural responses such as callose deposition and cell wall fortification (at 72 hpi). Results showed that A. brasilense REC3 is capable of exerting beneficial effects on strawberry plants, reinforcing their physiological and cellular characteristics, which in turns contribute to improve plant performance.
authors.affiliation: Facultad de Agronomía y Zootecnia, Universidad Nacional de Tucumán, San Miguel de Tucumán, Tucumán, Argentina; Facultad de Bioquímica, Química y Farmacia, Instituto Superior de Investigaciones Biológicas (INSIBIO), CONICET-UNT, and Instituto de Química Biológica "Dr. Bernabé Bloj", San Miguel de Tucumán, Tucumán, Argentina.
authors.forename: M F
authors.initials: MF
authors.lastname: Guerrero-Molina
authors.forename: N C
authors.initials: NC
authors.lastname: Lovaisa
authors.forename: S M
authors.initials: SM
authors.lastname: Salazar
authors.forename: M G
authors.initials: MG
authors.lastname: Martínez-Zamora
authors.forename: J C
authors.initials: JC
authors.lastname: Díaz-Ricci
authors.forename: R O
authors.initials: RO
authors.lastname: Pedraza
mesh_terms: D015806:Azospirillum brasilense; D018533:Biomass; D002473:Cell Wall / Q000378:metabolism; D060467:Disease Resistance / Q000235:genetics; D031985:Fragaria / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology; D015870:Gene Expression; D017343:Genes, Plant; D005936:Glucans / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010636:Phenols / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D013559:Symbiosis; D015854:Up-Regulation
chemical_list: D005936:Glucans; D010636:Phenols; D008315:Malondialdehyde; C048306:callose; D006861:Hydrogen Peroxide
keywords: Azospirillum brasilense; Fragaria ananassa; callose deposition; cell wall fortification; gene expression; lipid peroxidation; phenolic compounds