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„Inovace a zvýšení atraktivity studia biofyziky “, reg. č.: CZ.1.07/2.2.00/15.0309 Phototropin signaling in chloroplast movements Prof. Halina GABRYŚ Department of Plant Biotechnology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland 14. 4. 2014, 14:00 seminar room in F2 building Centre of Region Haná To optimize conditions for photosynthesis chloroplasts are in constant motion in most plants. They accumulate in weakly illuminated regions of the cell and avoid regions exposed to strong light. In the mesophyll of vascular land plants, these orientation movements are controlled only by blue light. In Arabidopsis thaliana, two photoreceptors, phototropin1 (phot1) and phototropin2 (phot2), control the accumulation response, with the latter active at higher fluency rates. Phot2 alone controls the avoidance response. The signalling pathway downstream of phototropins is largely unknown both at the level of signalling target(s) and mediating species: signal carriers and/or modulators. Chloroplasts move passively, driven by forces operating outside the organelles. While the participation of actin cytoskeleton in the movement mechanism is unequivocal, the mode of actin involvement remains debatable. Our recent studies have been aimed at determining more exact roles of low molecular species suggested as secondary messengers in the signal transduction: Ca2+ ions and elements of the phosphoinositide system.