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Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg

An integrative and quantitative model for phyB mediated photomorphogenesis: From protein dynamics to physiology. Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg. GRK Begutachtung 18. Februar 2010. Aspects of photomorphogenesis. red light.

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Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg

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  1. An integrative and quantitative modelforphyBmediated photomorphogenesis:Fromproteindynamics to physiology Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg GRK Begutachtung 18. Februar 2010

  2. Aspects of photomorphogenesis red light Skotomorphogenesisvs. Photomorphogenesis Alternativedevelopmental programs duringearlyplant growth: light-dependentde-etiolation Adapted from Quail (2002) Taken from Bae & Choi (2008) Phytochrome B: • Dimeric protein about 125kDa • Abundant in red light (660nm) • Two reversibly photointerconverting forms • Nuclear complexes • early, transient • late, stable • Mediated reactions: • Growth of hypocotyl length • Magnitude of cotyledon areas

  3. Pfr Pr Pr Pr Pr Pr Pfr Pfr Pfr Pfr What makes the phytochrome system interesting for theoreticians? at equilibrium: d[Pfr]/dt = 0 = k1[Pr] - k2[Pfr] [Pfr]/[Ptot] =  = k1 / (k1 + k2) R FR  = 0.85  = 0.03 k2 k1 k2, 660 nm k1, 660 nm k2, 730 nm k1, 730 nm • Adjustable parameters: • spectral composition of incident light • light intensity (photon flux) • duration of irradiation • protein dynamics can be changed by switching on/off the light

  4. Time resolved hypocotyl growth Darkness Continuous red light phyB-9 Col WT phyB-OX No active phytochrome present How does active phytochrome influence hypocotyl growth?

  5. Investigations of growth patterns • J. Sachs (1874): ”large period of growth”: growth velocity increase -> maximum -> growth velocity decrease • G. Backman (1931): Integration of the growth velocity yields S- shaped growth curve: “growth cycle” • Hypocotyl dark growth is characterized by: • Asymmetric S-shaped growth curve L • Asymmetric bell-shape of velocity function dL/dt -> growth rate is not constant over time Biological time Growth rate Environmentallimitation  γ determines the asymmetry of L and dL/dt

  6. Howdoesactivephytochrome come intoplay? darkness continuous red light End-point-analysis (after 4 days) Biological time Environmentallimitation Modifiedgrowth rate Scale bar = 10μm

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