title: Reactive oxygen species from type-I photosensitized reactions contribute to the light-induced wilting of dark-grown pea (Pisum sativum) epicotyls.
abstract: Type-II, singlet oxygen-mediated photosensitized damage has already been shown to occur in epicotyls of dark-germinated pea (Pisum sativum L.) seedlings upon illumination, resulting in fast turgor loss and wilting. In this study we show evidence that the palette of reactive oxygen species (ROS) is more complex. Hydrogen peroxide, superoxide and hydroxyl radicals are also formed, suggesting the occurrence of type-I reactions as well. Moreover, hydrogen peroxide injection into the epicotyls in the dark was able to provoke wilting directly. Formation of hydroxyl radicals could also be triggered by the addition of hydrogen peroxide in the dark, preferentially in the mid-sections where wilting occurs, showing that potential mediators of a Fenton reaction are present in the epicotyls, but unevenly distributed. Localization of light-inducible ROS formation fully (hydrogen peroxide) or partially (superoxide radicals) overlaps with the distribution of monomer protochlorophyllide complexes, showing that these pigment forms are capable of provoking both type-I and type-II reactions.
authors.affiliation: Institute of Plant Biology, Biological Research Centre, Szeged, Hungary. ehideg@brc.hu
authors.forename: Eva
authors.initials: E
authors.lastname: Hideg
authors.forename: Beáta
authors.initials: B
authors.lastname: Vitányi
authors.forename: Annamária
authors.initials: A
authors.lastname: Kósa
authors.forename: Katalin
authors.initials: K
authors.lastname: Solymosi
authors.forename: Károly
authors.initials: K
authors.lastname: Bóka
authors.forename: Sungae
authors.initials: S
authors.lastname: Won
authors.forename: Yumi
authors.initials: Y
authors.lastname: Inoue
authors.forename: Robert W
authors.initials: RW
authors.lastname: Ridge
authors.forename: Béla
authors.initials: B
authors.lastname: Böddi
mesh_terms: D003624:Darkness; D004578:Electron Spin Resonance Spectroscopy; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D008027:Light; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D016877:Oxidants / Q000378:metabolism / Q000494:pharmacology; D018532:Pisum sativum / Q000378:metabolism / Q000502:physiology / Q000528:radiation effects*; D011521:Protochlorophyllide / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D036226:Seedlings / Q000502:physiology / Q000528:radiation effects* / Q000648:ultrastructure
chemical_list: D016877:Oxidants; D017382:Reactive Oxygen Species; D011521:Protochlorophyllide; D006861:Hydrogen Peroxide