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We have constructed Arabidopsis thaliana plants that are virtually devoid of the major light-harvesting complex, LHC II. This was accomplished by introducing the Lhcb2.1 coding region in the antisense orientation into the genome by Agrobacterium-mediated transformation. Lhcb1 and Lhcb2 were absent, while Lhcb3, a protein present in LHC II associated with(More)
Photosystem II (PSII) is a key component of photosynthesis, the process of converting sunlight into the chemical energy of life. In plant cells, it forms a unique oligomeric macrostructure in membranes of the chloroplasts. Several light-harvesting antenna complexes are organized precisely in the PSII macrostructure-the major trimeric complexes (LHCII) that(More)
Dissipation of excess excitation energy within the photosystem II light-harvesting antenna (LHCII) by non-photochemical quenching (NPQ) is an important photoprotective process in plants. An update to a hypothesis for the mechanism of NPQ [FEBS Letters 292, 1991] is presented. The impact of recent advances in understanding the structure, organisation and(More)
Xanthophylls have a crucial role in the structure and function of the light harvesting complexes of photosystem II (LHCII) in plants. The binding of xanthophylls to LHCII has been investigated, particularly with respect to the xanthophyll cycle carotenoids violaxanthin and zeaxanthin. It was found that most of the violaxanthin pool was loosely bound to the(More)
The main chlorophyll a/b light-harvesting complex of photosystem II, LHCIIb, has earlier been shown to be capable of undergoing light-induced reversible structural changes and chlorophyll a fluorescence quenching in a way resembling those observed in granal thylakoids when exposed to excess light [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. The(More)
Non-photochemical quenching of chlorophyll fluorescence (NPQ) is symptomatic of the regulation of energy dissipation by the light-harvesting antenna of photosystem II (PS II). The kinetics of NPQ in both leaves and isolated chloroplasts are determined by the transthylakoid delta pH and the de-epoxidation state of the xanthophyll cycle. In order to(More)
Non-photochemical quenching of chlorophyll fluorescence in plants occurs in the light harvesting antenna of photosystem II and is regulated by the xanthophyll cycle. A new in vitro model for this process has been developed. Purified light harvesting complexes above the detergent critical micelle concentration have a stable high fluorescence yield but a(More)
Chlorophyll fluorescence quenching can be stimulated in vitro in purified photosystem II antenna complexes. It has been shown to resemble nonphotochemical quenching observed in isolated chloroplasts and leaves in several important respects, providing a model system for study of the mechanism of photoprotective energy dissipation. The effect of temperature(More)
Nonphotochemical quenching of chlorophyll fluorescence in plants is indicative of a process that dissipates excess excitation energy from the light-harvesting antenna of photosystem II. The major fraction of quenching is obligatorily dependent upon the thylakoid DeltapH and is regulated by the de-epoxidation state of the xanthophyll cycle carotenoids(More)
The chlorophyll fluorescence yield of purified photosystem II light-harvesting complexes can be lowered by manipulation of experimental conditions. In several important respects, this quenching resembles the nonphotochemical quenching observed in isolated chloroplasts and leaves, therefore providing a model system for investigating the underlying mechanism.(More)