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Hydrogen peroxide released from Pyropia yezoensis induced by oligo-porphyrans: Mechanisms and effect

Hou, Yun, Wang, Jing, Simerly, Thomas, Jin, Weihua, Zhang, Hong, Zhang, Quanbin
Journal of applied phycology 2015 v.27 no.4 pp. 1639-1649
NAD(P)H oxidase (H2O2-forming), NADP (coenzyme), Rhodophyta, acid hydrolysis, anion exchange chromatography, elicitors, hydrogen peroxide, mixtures, molecular weight, oligosaccharides, oxidation, polymerization, polysaccharides
Porphyran, a sulfated galactan, is the main cellular polysaccharide in the marine red alga Pyropia yezoensis. In this study, oligo-porphyrans, obtained by acid hydrolysis of porphyran, were investigated for their H₂O₂-inducing abilities in the defense responses of P. yezoensis. Oligo-porphyrans with average molecular weights (MWs) lower than 1.43 kDa had H₂O₂-inducing abilities. In contrast, oligo-porphyrans with average MWs of 6.12 kDa triggered no response. The active oligo-porphyrans were fractioned by anion-exchange chromatography. We found that two distinct mechanisms might be involved in the oligo-porphyran-induced H₂O₂ release in P. yezoensis. Mixtures of mono-sulfated oligo-galactans with degrees of polymerization (DPs) ranging from 1 to 3 might induce the response through the oxidation of cellular oligosaccharides, which enable P. yezoensis to resist rotting caused by dense incubation. Mixtures of oligo-porphyrans, consisting of 4 ~ 7 monosaccharide residues and 2 ~ 3 sulfate groups, might induce the generation of H₂O₂ by activation of NADPH oxidase, leading to an oxidative burst in P. yezoensis. The elicitor activity of oligo-porphyrans thus depends on their molecular size.