Light-harvesting antenna composition controls the macrostructure and dynamics of thylakoid membranes in Arabidopsis.

We characterized a set of Arabidopsis mutants deficient in specific light-harvesting proteins, using freeze-fracture electron microscopy to probe the organization of complexes in the membrane and confocal fluorescence recovery after photobleaching to probe the dynamics of thylakoid membranes within intact chloroplasts. The same methods were used to characterize mutants lacking or over-expressing PsbS, a protein related to light-harvesting complexes that appears to play a role in regulation of photosynthetic light harvesting. We found that changes in the complement of light-harvesting complexes and PsbS have striking effects on the photosystem II macrostructure, and that these effects correlate with changes in the mobility of chlorophyll proteins within the thylakoid membrane.

Photoprotective energy dissipation involves the reorganization of photosystem II light-harvesting complexes in the grana membranes of spinach chloroplasts.

Plants must regulate their use of absorbed light energy on a minute-by-minute basis to maximize the efficiency of photosynthesis and to protect photosystem II (PSII) reaction centers from photooxidative damage. The regulation of light harvesting involves the photoprotective dissipation of excess absorbed light energy in the light-harvesting antenna complexes (LHCs) as heat. Here, we report an investigation into the structural basis of light-harvesting regulation in intact spinach (Spinacia oleracea) chloroplasts using freeze-fracture electron microscopy, combined with laser confocal microscopy employing the fluorescence recovery after photobleaching technique.

Visualizing the mobility and distribution of chlorophyll proteins in higher plant thylakoid membranes: effects of photoinhibition and protein phosphorylation.

The diffusion of proteins in chloroplast thylakoid membranes is believed to be important for processes including the photosystem-II repair cycle and the regulation of light harvesting. However, to date there is very little direct information on the mobility of thylakoid proteins. We have used fluorescence recovery after photobleaching in a laser-scanning confocal microscope to visualize in real time the exchange of chlorophyll proteins between grana in intact spinach (Spinacia oleracea L.