title: Ferredoxin limits cyclic electron flow around PSI (CEF-PSI) in higher plants--stimulation of CEF-PSI enhances non-photochemical quenching of Chl fluorescence in transplastomic tobacco.
abstract: We tested the hypothesis that ferredoxin (Fd) limits the activity of cyclic electron flow around PSI (CEF-PSI) in vivo and that the relief of this limitation promotes the non-photochemical quenching (NPQ) of Chl fluorescence. In transplastomic tobacco (Nicotiana tabacum cv Xanthi) expressing Fd from Arabidopsis (Arabidopsis thaliana) in its chloroplasts, the minimum yield (F(o)) of Chl fluorescence was higher than in the wild type. F(o) was suppressed to the wild-type level upon illumination with far-red light, implying that the transfer of electrons by Fd-quinone oxidoreductase (FQR) from the chloroplast stroma to plastoquinone was enhanced in transplastomic plants. The activity of CEF-PSI became higher in transplastomic than in wild-type plants under conditions limiting photosynthetic linear electron flow. Similarly, the NPQ of Chl fluorescence was enhanced in transplastomic plants. On the other hand, pool sizes of the pigments of the xanthophyll cycle and the amounts of PsbS protein were the same in all plants. All these results supported the hypothesis strongly. We conclude that breeding plants with an NPQ of Chl fluorescence increased by an enhancement of CEF-PSI activity might lead to improved tolerance for abiotic stresses, particularly under conditions of low light use efficiency.
authors.affiliation: Research Institute of Innovative Technology for the Earth (RITE), 9-2 Kizugawadai, Kizu-cho, Soraku-gun, Kyoto, 619-0292 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Hideki
authors.initials: H
authors.lastname: Kato
authors.forename: Yuki
authors.initials: Y
authors.lastname: Shinzaki
authors.forename: Sayaka
authors.initials: S
authors.lastname: Horiguchi
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Shikanai
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Hase
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Endo
authors.forename: Minori
authors.initials: M
authors.lastname: Nishioka
authors.forename: Amane
authors.initials: A
authors.lastname: Makino
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Tomizawa
authors.forename: Chikahiro
authors.initials: C
authors.lastname: Miyake
mesh_terms: D000595:Amino Acid Sequence; D002734:Chlorophyll / Q000737:chemistry / Q000528:radiation effects; D002736:Chloroplasts / Q000502:physiology; D004579:Electron Transport / Q000502:physiology; D005288:Ferredoxins / Q000235:genetics / Q000502:physiology*; D005453:Fluorescence; D008027:Light; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000502:physiology*; D045331:Photosystem I Protein Complex / Q000502:physiology; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects; D014026:Nicotiana / Q000737:chemistry / Q000502:physiology*
chemical_list: D005288:Ferredoxins; D045331:Photosystem I Protein Complex; D002734:Chlorophyll