Comparative Effects of Azospirillum brasilense Sp245 and Pseudomonas aeruginosa PAO1 Lipopolysaccharides on Wheat Seedli
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Comparative Effects of Azospirillum brasilense Sp245 and Pseudomonas aeruginosa PAO1 Lipopolysaccharides on Wheat Seedling Growth and Peroxidase Activity Alma Alejandra Hernández‑Esquivel1 · Elda Castro‑Mercado1 · Ernesto García‑Pineda1 Received: 14 May 2020 / Accepted: 1 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The effects of lipopolysaccharides (LPS) from Azospirillum brasilense Sp245, a plant growth-promoting rhizobacteria, and Pseudomonas aeruginosa PAO1, a pathogenic bacterium, on plant growth and peroxidase (POD) activity were assessed on wheat seedlings. A. brasilense LPS (100 µg/mL) increased total length, and total fresh weight in wheat seedlings 4 days after treatment. P. aeruginosa LPS did not show effect on plant growth. A. brasilense LPS increased root hairs length similar to whole cells, while P. aeruginosa LPS increased root hairs density and slightly root hairs length. Both LPS increased POD activity and hydrogen peroxide (H2O2) content in root; however, the LPS from the pathogenic bacterium generated higher increments. The peroxidase inhibitor salicylhydroxamic acid (SHAM) inhibited plant growth, which was not recovered by the addition of LPS neither A. brasilense nor P. aeruginosa. POD activity stimulated by LPS was calcium-dependent as confirmed by the addition of the calcium channel blocker LaCl3. The results suggest that plant cells sense differentially LPS from beneficial or pathogenic bacteria and that calcium is needed to respond to the presence of both LPS. Keywords Azospirillum brasilense · Pseudomonas aeruginosa · Lipopolysaccharides · Wheat · Peroxidase · Plant growth
Introduction Lipopolysaccharides (LPS) are major components of the outer membrane (OM) of Gram-negative bacteria that contribute to membrane integrity and stability. LPS also contribute to cell defense against external stress factors by providing a permeability barrier against many different classes of molecules including antibiotics and metals (Silipo and Molinaro 2017; Molinaro et al. 2009). LPS are involved in adhesion and colonization in hostbacterium interactions. In addition, LPS are potent elicitors of innate immune responses during pathogenesis of Gramnegative infections in both plant and animal hosts (Takeuchi and Akira 2010; Ranf 2016; Ranf et al. 2016). All LPS share three common structural components: a lipophilic moiety termed lipid A, a core oligosaccharide, and an O-specific * Ernesto García‑Pineda [email protected] 1
Instituto de Investigaciones Químico Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Ciudad Universitaria, Edif. A1, CP 58040 Morelia, Michoacán, Mexico
polysaccharide (also known as O-chain or O-antigen), a hydrophilic glycan. The core oligosaccharide contains a carbohydrate that is specific to LPS: 3-deoxy-d-manno-oct2-ulosonic acid (Kdo), as well as several heptose moieties. The O-specific polysaccharide is joined to the Kdo domain and is oriented outwards, whereas lipid A is embedded in the OM to anchor LPS to the mem
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