A stable LHCII-PSI aggregate and suppression of photosynthetic state transitions in the psae1-1 mutant of Arabidopsis thaliana |
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Authors: | Pesaresi Paolo Lunde Christina Jahns Peter Tarantino Delia Meurer Jörg Varotto Claudio Hirtz Rolf-Dieter Soave Carlo Scheller Henrik Vibe Salamini Francesco Leister Dario |
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Institution: | Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei Arabidopsis thaliana (ZIGIA), Max-Planck-Institut für Züchtungsforschung, Carl-von-Linné-Weg 10, 50829 K?ln, Germany. |
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Abstract: | During photosynthetic state transitions, a fraction of the major light-harvesting complex (LHCII) shuttles between photosystems II (PSII) and I (PSI), depending on whether or not it is phosphorylated. Its phosphorylation state in turn depends on the relative activity of the two photosystems, which is a function of redox state and illumination parameters. In the psae1-1 mutant of Arabidopsis thaliana (L.) Heynh., amounts of the PSI subunits E, C, D, H and L are decreased. A fraction of LHCII is stably associated with PSI when plants are exposed to low light conditions, giving rise to a high-molecular-mass protein-pigment complex detectable in native protein gels. The formation of this abnormal LHCII-PSI complex is associated with an almost complete suppression of state transitions, a drastic increase in the levels of phosphorylated LHCII under all light regimes tested, and a permanent reduction in PSII antenna size. All these observations suggest that the altered polypeptide composition of PSI perturbs the docking of phosphorylated LHCII, making psae1-1 a unique mutant for the study of PSI-LHCII interactions and additional effects of the mutation, such as a decrease in grana stacking and increased adenylate kinase activity. |
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