Abstract
Microalgal polysaccharides (PSs) may be an effective elicitor agent that can efficiently protect plants against biotic stresses. In this study, wee investigates, the effect of PS obtained from microalgae and cyanobacteria (D. salina MS002, P. tricorontum MS023, Porphyridium sp. MS081, Desmodesmus sp., D. salina MS067 and A. platensis MS001) on the biochemical and metabolomics markers linked to defense pathways in tomato plants. The phenylalanine ammonia lyase (PAL), chitinase, 1,3-beta-glucanase and peroxidase (POX) activities have been improved in tomato plants leaves treated by polysaccharides extracted from P. triocnutum (238.26%); Desmodesmus sp. (19.95%); P. triocnutum (137.50%) and Porphyridium sp. (47.28%) respectively. For proteins, polyphenols and H2O2, the maximum effect was induced by D. salina 067 (55.01%), Porphyridium sp. (3.97%) and A. platensis (35.08%) respectively. On the other hand, Gas Chromatography-mass spectrometry (GC–MS) metabolomics analysis showed that PSs induced the modification of metabolite profile involved in the wax construction of tomato leaves, such as fatty acids, alkanes, alkenes and phytosterol. PS treatments improved the accumulation of fatty acids C16:3, C18:2 and C18:3 released from the membrane lipids as precursors of oxylipin biosynthesis which are signaling molecules of plant defense. In addition, PS treatment induced the accumulation of C18:0 and Azelaic acid which is a regulator of salicylic acid-dependent systemic acquired resistance. However, molecular and metabolic studies can determine more precisely the mode of action of microalgal polysaccharides as biostimulants/elicitors plant defense.
Highlights
Microalgal polysaccharides (PSs) may be an effective elicitor agent that can efficiently protect plants against biotic stresses
The microalgae polysaccharide content was recorded as 12,7%, 5.52%, 4.10% and 2.58% for P. tricornutum, Porphyridium sp., D. salina 002 and A. platensis respectively, while their partial characterization indicated that they were composed of neutral sugars (5.0–35.350%), sulfates (4.051–11.541%), uronic acids (3.602–42.865%), proteins (2.701–22.068%), amino acids (0.017–0.206%) and β-glucans (0.008–0.698%)
P. tricornutum exhibited the maximum production of polysaccharides (12.7%) composed of 32,3%, 6,75% and 0,698% of uronic acid, sulfate content and beta-glucan content respectively
Summary
Microalgal polysaccharides (PSs) may be an effective elicitor agent that can efficiently protect plants against biotic stresses. Molecular and metabolic studies can determine more precisely the mode of action of microalgal polysaccharides as biostimulants/elicitors plant defense Plants in their environment are exposed to divers biotic and abiotic s tresses[1]. Detailed reports are available on the induction of defense resistance in plants via a variety of biological inducers such as plant extracts, essential oils, bacteria and fungus, algal extracts and p olysaccharides[11] These elicitors have no direct toxic effect on pathogens and pests, but they have the ability to induce signaling. In the same w ay[24], have demonstrated that D. salina exopolysaccharide have the potential to induce the metabolic and biochemical pathways related to natural plant defense in tomato plants under salt stress. These molecules are rapidly detected by the membrane receptors of the host plant, in order to induce various defense r esponses[30]
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