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High light induced disassembly of photosystem II supercomplexes in Arabidopsis requires STN7-dependent phosphorylation of CP29
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
2011 (English)In: PLoS ONE, ISSN 1932-6203, Vol. 6, no 9Article in journal (Refereed) Published
Abstract [en]

Photosynthetic oxidation of water and production of oxygen by photosystem II (PSII) in thylakoid membranes of plant chloroplasts is highly affected by changes in light intensities. To minimize damage imposed by excessive sunlight and sustain the photosynthetic activity PSII, organized in supercomplexes with its light harvesting antenna, undergoes conformational changes, disassembly and repair via not clearly understood mechanisms. We characterized the phosphoproteome of the thylakoid membranes from Arabidopsis thaliana wild type, stn7, stn8 and stn7stn8 mutant plants exposed to high light. The high light treatment of the wild type and stn8 caused specific increase in phosphorylation of Lhcb4.1 and Lhcb4.2 isoforms of the PSII linker protein CP29 at five different threonine residues. Phosphorylation of CP29 at four of these residues was not found in stn7 and stn7stn8 lacking the STN7 protein kinase. Blue native gel electrophoresis followed by immunological and mass spectrometric analyses of the protein complexes revealed that the high light treatment of the wild type caused migration of CP29 from the PSII supercomplexes to PSII dimers and monomers. A similar high-light-induced disassembly of the PSII supercomplexes occurred in stn8, but not in stn7 and stn7stn8. Transfer of the high-light-treated wild type plants to normal light relocated CP29 back to PSII supercomplexes. We postulate that disassembly of the PSII supercomplexes in plants exposed to high light operate via the STN7-kinase-dependent phosphorylation of the linker protein CP29. Disruption of this adaptive mechanism can explain dramatically retarded growth of the stn7 and stn7stn8 mutants under fluctuating normal/high light conditions.

Place, publisher, year, edition, pages
PloS , 2011. Vol. 6, no 9
Keyword [en]
Photosynthesis, chloroplast, thylakoid, protein phosphorylation, photosystem II supercomplexes, CP29
National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-62302DOI: 10.1371/journal.pone.0024565ISI: 000294802500061OAI: diva2:372574
Funding agencies|Swedish Research Council||Swedish Research Council for Environment, Agriculture and Spatial Planning||Available from: 2010-11-26 Created: 2010-11-26 Last updated: 2011-10-03Bibliographically approved
In thesis
1. Regulatory Functions of Protein Phosphorylation in Plant Photosynthetic Membranes
Open this publication in new window or tab >>Regulatory Functions of Protein Phosphorylation in Plant Photosynthetic Membranes
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Oxygenic photosynthesis is the process in plants, algae and cyanobacteria which converts light energy from the sun into carbohydrates and at the same time produces oxygen from water. Both carbohydrates and oxygen are essential to sustain life on earth. Sunlight is thus a necessity for life, but it can also cause severe problems for photosynthetic organisms, which have evolved several remarkable acclimation systems to cope with light fluctuations in the environment. In higher plants the light driven reactions of photosynthesis proceed in the chloroplast thylakoid membranes highly organized into stacked regions of grana and interconnecting stroma  lamellae. The grana structure is thought to provide functional benefits in the processes of acclimation of the photosynthetic apparatus, particularly in the quality control of photosystem II (PSII) were photodamaged PSII is repaired in a stepwise manner. These processes in the thylakoid membranes were suggested to be regulated by reversible phosphorylation of several proteins in PSII and in its light harvesting antennae complexes (LHCII). Two thylakoid protein kinases, called STN8 and STN7, have been previously identified as responsible for the phosphorylation of PSII and LHCII, respectively. However, molecular mechanisms and the exact functions of these protein phosphorylation events remained largely unknown.

In this thesis research I have demonstrated that the PSII protein phosphorylation is needed for the maintenance of the thylakoid structure in Arabidopsis thaliana chloroplasts. A big part of the work on characterization of proteins and their phosphorylation has been done using novel mass spectrometry techniques, and we further developed a label-free method for quantitative studies of protein phosphorylation. The phosphorylation of PSII proteins was found to be diurnal regulated and required for maintenance of the cation-dependent functional stacking of the thylakoid membranes. This phosphorylation was further shown to be important for the regulated turnover of the D1 protein of PSII.

Phosphorylation of the plant specific TSP9 protein was found to be dependent on STN7 kinase, and plants deficient in TSP9 showed reduced ability to perform the photosynthetic state transitions and to execute thermal dissipation of excess light energy under high light conditions. I also accomplished characterization of the protein phosphorylation in thylakoids from Arabidopsis plants subjected to high light treatment and discovered STN7-dependent phosphorylation of the antenna protein CP29 required for the adaptive disassembly of PSII supercomplexes in conditions of high light stress.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 42 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1212
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-62303 (URN)978-91-7393-301-8 (ISBN)
Public defence
2010-12-17, Linden, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (English)
Available from: 2010-11-26 Created: 2010-11-26 Last updated: 2010-11-26Bibliographically approved

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