PARENT SESSION
Posters P6B Photosynthetic acclimation: Mechanisms and gene expression. Abstracts (531-578)

Phosphorylation of DNA binding proteins in chloroplasts of Sinapis alba after acclimation to different light qualities. Vidal Fey^*,1, Yagut Allahverdiyeva², Virpi Paakkarinen², Eva-Mari Aro², Thomas Pfannschmidt¹, ¹ FSU Jena, Dept. of Plant Physiology, Jena, Germany² University of Turku, Dept. of Plant Physiology and Molecular Biology, Turku, Finland

ABSTRACT- To adapt to changing environmental conditions such as light intensity or light quality higher plants have developed several acclimatory responses. These processes are highly regulated by protein phosphorylation and redox control. In chloroplasts of higher plants important redox signals originate in the photosynthetic electron transport chain. To date several redox-controlled thylakoid phosphoproteins are described [reviewed in (1)]. We focus on the regulation of the expression of psaAB encoding the core proteins of photosystem I (PSI). As there was shown earlier this operon is controlled by the redox state of the plastoquinone pool during photosystem stoichiometry adjustment which occurs in response to long-term excitation imbalances (2). To induce excitation imbalances between the photosystems we use special light sources exciting differentially PSI or PSII, respectively, and thereby causing a respective oxidized or reduced plastoquinone pool. In order to analyze the impact of such redox signals on proteins of the gene expression machinery we purified proteins from a lysate of intact chloroplasts of Sinapis alba by heparin-sepharose chromatography. These protein fractions were analyzed for their kinase activity by autophosphorylation with gamma-ATP, their phosphorylation state using exogenous kinase and phosphatase, as well as western analyses using anti-phospho-aminoacid antibodies. According to the data we suppose that protein phosphorylation plays an important role in the expression control of chloroplast encoded photosynthesis genes. 1. Aro, E. M., and Ohad, I. (2003) Antioxid Redox Signal 5, 55-67 2. Pfannschmidt, T., Nilsson, A., and Allen, J. F. (1999) Nature 397, 625-628

KEY WORDS: phosphorylation, redox-control, DNA binding, Sinapis alba