Distinct roles of the photosystem II protein PsbS and zeaxanthin in the regulation of light harvesting in plants revealed by fluorescence lifetime snapshots

• Published in: Proceedings of the National Academy of Sciences - PNAS 2014-12, Vol.111 (49), p.17498-17503
• Main Authors: Sylak-Glassman, Emily J., Malnoë, Alizée, De Re, Eleonora, Brooks, Matthew D., Fischer, Alexandra Lee, Niyogi, Krishna K., Fleming, Graham R.
• Format: Article
• Language: English
• Subjects: Arabidopsis - enzymology; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; BASIC BIOLOGICAL SCIENCES; Bioenergetics; Biological Sciences; carotenoids; Chlorophyll; Chlorophyll - chemistry; Chlorophylls; Crop harvesting; Enzymes; Fluorescence; fluorescence lifetime; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant - genetics; Genotypes; Leaves; Light; Light-Harvesting Protein Complexes - metabolism; Luminous intensity; nonphotochemical quenching; Oxidoreductases - metabolism; Photons; photosystem II; Photosystem II Protein Complex - metabolism; Plants; Proteins; Protons; PsbS; Quenching; Thylakoids; Zeaxanthins - metabolism
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1418317111

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. Significance By comparing the form of the chlorophyll fluorescence decays in wild-type, npq1 , npq4 , and npq1 npq4 plants, we show that the presence of violaxanthin deepoxidase (VDE), but not the protein PsbS, changes the excited-state relaxation dynamics of chlorophyll. PsbS has the strongest effect during the initial induction of quenching. The presence of both zeaxanthin and PsbS is required for strong quenching. This fluorescence lifetime technique helps elucidate both the kinetics with which quenching turns on and off and the relaxation dynamics of excited-state chlorophyll.