title: Distinct roles of the photosystem II protein PsbS and zeaxanthin in the regulation of light harvesting in plants revealed by fluorescence lifetime snapshots.
abstract: The photosystem II (PSII) protein PsbS and the enzyme violaxanthin deepoxidase (VDE) are known to influence the dynamics of energy-dependent quenching (qE), the component of nonphotochemical quenching (NPQ) that allows plants to respond to fast fluctuations in light intensity. Although the absence of PsbS and VDE has been shown to change the amount of quenching, there have not been any measurements that can detect whether the presence of these proteins alters the type of quenching that occurs. The chlorophyll fluorescence lifetime probes the excited-state chlorophyll relaxation dynamics and can be used to determine the amount of quenching as well as whether two different genotypes with the same amount of NPQ have similar dynamics of excited-state chlorophyll relaxation. We measured the fluorescence lifetimes on whole leaves of Arabidopsis thaliana throughout the induction and relaxation of NPQ for wild type and the qE mutants, npq4, which lacks PsbS; npq1, which lacks VDE and cannot convert violaxanthin to zeaxanthin; and npq1 npq4, which lacks both VDE and PsbS. These measurements show that although PsbS changes the amount of quenching and the rate at which quenching turns on, it does not affect the relaxation dynamics of excited chlorophyll during quenching. In addition, the data suggest that PsbS responds not only to ΔpH but also to the Δψ across the thylakoid membrane. In contrast, the presence of VDE, which is necessary for the accumulation of zeaxanthin, affects the excited-state chlorophyll relaxation dynamics.
authors.affiliation: Departments of Chemistry and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Sylak-Glassman
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Plant and Microbial Biology.
authors.forename: Alizée
authors.initials: A
authors.lastname: Malnoë
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Graduate Group in Applied Science and Technology, and.
authors.forename: Eleonora
authors.initials: E
authors.lastname: De Re
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Plant and Microbial Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; and.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Brooks
authors.affiliation: Departments of Chemistry and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
authors.forename: Alexandra Lee
authors.initials: AL
authors.lastname: Fischer
authors.affiliation: Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Plant and Microbial Biology, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; and.
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.affiliation: Departments of Chemistry and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 Graduate Group in Applied Science and Technology, and vcrfleming@berkeley.edu.
authors.forename: Graham R
authors.initials: GR
authors.lastname: Fleming
mesh_terms: D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002734:Chlorophyll / Q000737:chemistry; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D065146:Zeaxanthins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; C489731:NPQ4 protein, Arabidopsis; D045332:Photosystem II Protein Complex; D065146:Zeaxanthins; D002734:Chlorophyll; D010088:Oxidoreductases; C023290:violaxanthin de-epoxidase
keywords: PsbS; carotenoids; fluorescence lifetime; nonphotochemical quenching; photosystem II