title: Protective action of spermine and spermidine against photoinhibition of photosystem I in isolated thylakoid membranes.
abstract: The photo-stability of photosystem I (PSI) is of high importance for the photosynthetic processes. For this reason, we studied the protective action of two biogenic polyamines (PAs) spermine (Spm) and spermidine (Spd) on PSI activity in isolated thylakoid membranes subjected to photoinhibition. Our results show that pre-loading thylakoid membranes with Spm and Spd reduced considerably the inhibition of O2 uptake rates, P700 photooxidation and the accumulation of superoxide anions (O2(-)) induced by light stress. Spm seems to be more effective than Spd in preserving PSI photo-stability. The correlation of the extent of PSI protection, photosystem II (PSII) inhibition and O2(-) generation with increasing Spm doses revealed that PSI photo-protection is assumed by two mechanisms depending on the PAs concentration. Given their antioxidant character, PAs scavenge directly the O2(-) generated in thylakoid membranes at physiological concentration (1 mM). However, for non-physiological concentration, the ability of PAs to protect PSI is due to their inhibitory effect on PSII electron transfer.
authors.affiliation: Groupe de Recherche en Biologie-Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors.forename: Hnia
authors.initials: H
authors.lastname: Yaakoubi
authors.affiliation: Groupe de Recherche en Biologie-Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors.forename: Saber
authors.initials: S
authors.lastname: Hamdani
authors.affiliation: Groupe de Recherche en Biologie-Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors.forename: Laurent
authors.initials: L
authors.lastname: Bekalé
authors.affiliation: Groupe de Recherche en Biologie-Végétale, Université du Québec à Trois-Rivières, Trois-Rivières, Québec, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Carpentier
mesh_terms: D001692:Biological Transport / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D008027:Light; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D010100:Oxygen / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D011837:Radiation-Protective Agents / Q000494:pharmacology; D013095:Spermidine / Q000494:pharmacology*; D013096:Spermine / Q000494:pharmacology*; D018724:Spinacia oleracea / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D020524:Thylakoids / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D013997:Time Factors
chemical_list: D045331:Photosystem I Protein Complex; D011837:Radiation-Protective Agents; D013481:Superoxides; D013096:Spermine; D010100:Oxygen; D013095:Spermidine