title: Phylogeny-directed structural analysis of the Arabidopsis PsbS protein.
abstract: Plant psbS proteins are essential for regulated thermal dissipation of excess light referred to as non-photochemical quenching of chlorophyll fluorescence yield (NPQ). Amino acid sequences derived from 65 psbS genes from 44 species were aligned to reveal extensive conservation consistent with of motifs that underlie intrinsic aspects of the NPQ mechanism. Site-directed mutagenesis was employed to block presumptive zeaxanthin or chlorophyll-binding sites in Arabidopsis psbS by disrupting ion-bonding between two pairs of non-adjacent glutamate and arginine residues. Transgenic Arabidopsis lines synthesizing only the altered psbS forms exhibited severely impaired NPQ capacity. In addition, the phylogenetic depth of the psbS database permitted identification of cryptic sites of adaptive evolution. Instances of localized positive selection were rare and largely limited to the family Poaceae (grasses). Specifically, adaptive evolution was detected in a hydrophilic stroma-exposed region and was correlated with the presence of the C4 pathway of carbon fixation.
authors.affiliation: Department of Biochemistry and Genetics, The Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06511, USA. Neil.Schultes@po.state.ct.us
authors.forename: Neil P
authors.initials: NP
authors.lastname: Schultes
authors.forename: Richard B
authors.initials: RB
authors.lastname: Peterson
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002734:Chlorophyll / Q000378:metabolism; D017931:DNA Primers; D017343:Genes, Plant; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D030821:Plants, Genetically Modified; D006109:Poaceae / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D029681:Arabidopsis Proteins; D017931:DNA Primers; D045342:Light-Harvesting Protein Complexes; C489731:NPQ4 protein, Arabidopsis; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; D002734:Chlorophyll