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Biophys J. 2014 May 6;106(9):1864-70. doi: 10.1016/j.bpj.2014.03.016.

Dynamic mechanical responses of Arabidopsis thylakoid membranes during PSII-specific illumination.

Author information

1
Bioengineering Department, University of California, Berkeley, California.
2
Department of Plant and Microbial Biology, University of California, Berkeley, California; Howard Hughes Medical Institute, University of California, Berkeley, California.
3
Howard Hughes Medical Institute, University of California, Berkeley, California.
4
Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California; Molecular and Cell Biology Department, University of California, Berkeley, California; Howard Hughes Medical Institute, University of California, Berkeley, California.
5
Department of Plant and Microbial Biology, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California; Howard Hughes Medical Institute, University of California, Berkeley, California.
6
Bioengineering Department, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California. Electronic address: fletch@berkeley.edu.

Abstract

Remodeling of thylakoid membranes in response to illumination is an important process for the regulation of photosynthesis. We investigated the thylakoid network from Arabidopsis thaliana using atomic force microscopy to capture dynamic changes in height, elasticity, and viscosity of isolated thylakoid membranes caused by changes in illumination. We also correlated the mechanical response of the thylakoid network with membrane ultrastructure using electron microscopy. We find that the elasticity of the thylakoid membranes increases immediately upon PSII-specific illumination, followed by a delayed height change. Direct visualization by electron microscopy confirms that there is a significant change in the packing repeat distance of the membrane stacks in response to illumination. Although experiments with Gramicidin show that the change in elasticity depends primarily on the transmembrane pH gradient, the height change requires both the pH gradient and STN7-kinase-dependent phosphorylation of LHCII. Our studies indicate that lumen expansion in response to illumination is not simply a result of the influx of water, and we propose a dynamic model in which protein interactions within the lumen drive these changes.

PMID:
24806918
PMCID:
PMC4017268
DOI:
10.1016/j.bpj.2014.03.016
[Indexed for MEDLINE]
Free PMC Article
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