title: Dynamic mechanical responses of Arabidopsis thylakoid membranes during PSII-specific illumination.
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.
authors.affiliation: Bioengineering Department, University of California, Berkeley, California.
authors.forename: Casper H
authors.initials: CH
authors.lastname: Clausen
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California; Howard Hughes Medical Institute, University of California, Berkeley, California.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Brooks
authors.affiliation: Bioengineering Department, University of California, Berkeley, California.
authors.forename: Tai-De
authors.initials: TD
authors.lastname: Li
authors.affiliation: Howard Hughes Medical Institute, University of California, Berkeley, California.
authors.forename: Patricia
authors.initials: P
authors.lastname: Grob
authors.affiliation: Howard Hughes Medical Institute, University of California, Berkeley, California.
authors.forename: Gigi
authors.initials: G
authors.lastname: Kemalyan
authors.affiliation: 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.
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
authors.affiliation: 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.
authors.forename: Krishna K
authors.initials: KK
authors.lastname: Niyogi
authors.affiliation: Bioengineering Department, University of California, Berkeley, California; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California. Electronic address: fletch@berkeley.edu.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Fletcher
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000378:metabolism; D001696:Biomechanical Phenomena / Q000528:radiation effects; D004548:Elasticity; D006863:Hydrogen-Ion Concentration; D008027:Light; D055595:Mechanical Phenomena; D018625:Microscopy, Atomic Force; D010766:Phosphorylation / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism* / Q000528:radiation effects*
chemical_list: D029681:Arabidopsis Proteins; D045332:Photosystem II Protein Complex; D017346:Protein Serine-Threonine Kinases; C497212:STN7 protein, Arabidopsis