Journal Article

Lack of the Light-Harvesting Complex CP24 Affects the Structure and Function of the Grana Membranes of Higher Plant Chloroplasts

Kovács, László, Boekema, Egbert J, Horton, Peter, Jansson, Stefan, Kereïche, Sami, Ruban, Alexander V, Ilioaia, Cristian, Damkjær, Jakob

2006

Overview

The photosystem II (PSII) light-harvesting antenna in higher plants contains a number of highly conserved gene products whose function is unknown. Arabidopsis thaliana plants depleted of one of these, the CP24 light-harvesting complex, have been analyzed. CP24-deficient plants showed a decrease in light-limited photosynthetic rate and growth, but the pigment and protein content of the thylakoid membranes were otherwise almost unchanged. However, there was a major change in the macroorganization of PSII within these membranes; electron microscopy and image analysis revealed the complete absence of the C₂S₂M₂ light-harvesting complex II (LHCII)/PSII supercomplex predominant in wild-type plants. Instead, only C₂S₂ supercomplexes, which are deficient in the LHCIIb M-trimers, were found. Spectroscopic analysis confirmed the disruption of the wild-type macroorganization of PSII. It was found that the functions of the PSII antenna were disturbed: connectivity between PSII centers was reduced, and maximum photochemical yield was lowered; rapidly reversible nonphotochemical quenching was inhibited; and the state transitions were altered kinetically. CP24 is therefore an important factor in determining the structure and function of the PSII light-harvesting antenna, providing the linker for association of the M-trimer into the PSII complex, allowing a specific macroorganization that is necessary both for maximum quantum efficiency and for photoprotective dissipation of excess excitation energy.

• Publisher: American Society of Plant Biologists
• Subject: analysis / Arabidopsis / Arabidopsis - metabolism / Arabidopsis - radiation effects / Arabidopsis - ultrastructure / Arabidopsis Proteins / Arabidopsis Proteins - analysis / Arabidopsis Proteins - isolation & purification / Arabidopsis Proteins - metabolism / Arabidopsis Proteins/analysis/isolation & purification/metabolism / Arabidopsis thaliana / Arabidopsis/metabolism/radiation effects/ultrastructure / Chlorophylls / Chloroplasts / Chloroplasts - ultrastructure / Chromatography, Gel / Circular Dichroism / deficiency / DNA, Bacterial / DNA, Bacterial - metabolism / electron microscopy / Fluorescence / genes / Grana / image analysis / isolation & purification / Leaves / Light / light harvesting complex / Light-Harvesting Protein Complexes / Light-Harvesting Protein Complexes - analysis / Light-Harvesting Protein Complexes - deficiency / Light-Harvesting Protein Complexes - isolation & purification / Light-Harvesting Protein Complexes/analysis/deficiency/isolation & purification / metabolism / Models, Biological / Mutagenesis, Insertional / Photochemicals / Photosynthesis / Photosynthesis - radiation effects / Photosynthetic Reaction Center Complex Proteins / Photosynthetic Reaction Center Complex Proteins - metabolism / Photosystem II / Photosystem II Protein Complex / Photosystem II Protein Complex - metabolism / Pigments / Pigments, Biological / Pigments, Biological - metabolism / Plant Leaves / Plant Leaves - radiation effects / Plants / protein content / radiation effects / Radio antennas / RNA, Antisense / RNA, Antisense - metabolism / Structure-Activity Relationship / Temperature / Thylakoids / Thylakoids - ultrastructure / Trimers / ultrastructure