title: A pigment-binding protein essential for regulation of photosynthetic light harvesting.
abstract: Photosynthetic light harvesting in plants is regulated in response to changes in incident light intensity. Absorption of light that exceeds a plant's capacity for fixation of CO2 results in thermal dissipation of excitation energy in the pigment antenna of photosystem II by a poorly understood mechanism. This regulatory process, termed nonphotochemical quenching, maintains the balance between dissipation and utilization of light energy to minimize generation of oxidizing molecules, thereby protecting the plant against photo-oxidative damage. To identify specific proteins that are involved in nonphotochemical quenching, we have isolated mutants of Arabidopsis thaliana that cannot dissipate excess absorbed light energy. Here we show that the gene encoding PsbS, an intrinsic chlorophyll-binding protein of photosystem II, is necessary for nonphotochemical quenching but not for efficient light harvesting and photosynthesis. These results indicate that PsbS may be the site for nonphotochemical quenching, a finding that has implications for the functional evolution of pigment-binding proteins.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley 94720-3102, USA.
authors.forename: X P
authors.initials: XP
authors.lastname: Li
authors.forename: O
authors.initials: O
authors.lastname: Björkman
authors.forename: C
authors.initials: C
authors.lastname: Shih
authors.forename: A R
authors.initials: AR
authors.lastname: Grossman
authors.forename: M
authors.initials: M
authors.lastname: Rosenquist
authors.forename: S
authors.initials: S
authors.lastname: Jansson
authors.forename: K K
authors.initials: KK
authors.lastname: Niyogi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis; D029681:Arabidopsis Proteins; D017343:Genes, Plant; D008027:Light; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D011487:Protein Conformation
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; C489731:NPQ4 protein, Arabidopsis; D009687:Nuclear Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins