Abstract
Polysaccharides from marine algae are one novel source of plant defense elicitors for alternative and eco-friendly plant protection against phytopathogens. The effect of exopolysaccharides (EPS) produced by Porphyridium sordidum on elicitation of Arabidopsis thaliana defense responses against Fusarium oxysporum was evaluated. Firstly, in order to enhance EPS production, a Box–Behnken experimental design was carried out to optimize NaCl, NaNO3 and MgSO4 concentrations in the culture medium of microalgae. A maximum EPS production (2.45 g/L) higher than that of the control (0.7 g/L) was observed for 41.62 g/L NaCl, 0.63 g/L NaNO3 and 7.2 g/L MgSO4 concentrations. Structurally, the EPS contained mainly galactose, xylose and glucose. Secondly, the elicitor effect of EPS was evaluated by investigating the plant defense-related signaling pathways that include activation of Salicylic or Jasmonic Acid-dependent pathway genes. A solution of 2 mg/mL of EPS has led to the control of fungal growth by the plant. Results showed that EPS foliar application induced phenylalaline ammonia lyase and H2O2 accumulation. Expression profile analysis of the defense-related genes using qRT-PCR revealed the up-regulation of Superoxide dismutases (SOD), Peroxidase (POD), Pathogenesis-related protein 1 (PR-1) and Cytochrome P450 monooxyge-nase (CYP), while Catalase (CAT) and Plant defensin 1.2 (PDF1.2) were not induced. Results suggest that EPS may induce the elicitation of A. thaliana’s defense response against F. oxysporum, activating the Salicylic Acid pathway.
Highlights
Plants are usually exposed to a wide range of phytopathogenic microorganisms and viruses and have developed different mechanisms of defense to control their attacks
Constitutive defenses are designed by physical barriers such as rigid cell walls and wax epidermal cuticles, while inducing defense responses are activated by a wide variety of elicitors, which are made up of diverse molecular structures such as peptides, lipids and carbohydrates [1]
Tunisianseawater seawaterwas waspreliminarily preliminarily identified as being of the genus because it presented cells with identified as being of the genus Porphyridium sp. because it presented cells withdiameter diameter between between7–10
Summary
Plants are usually exposed to a wide range of phytopathogenic microorganisms and viruses and have developed different mechanisms of defense to control their attacks These mechanisms vary from constitutive to induced defenses. Constitutive defenses are designed by physical barriers such as rigid cell walls and wax epidermal cuticles, while inducing defense responses are activated by a wide variety of elicitors, which are made up of diverse molecular structures such as peptides, lipids and carbohydrates [1]. These products comprise both pathogen- and plant-derived molecules.
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