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An integrative and quantitative model for phyB mediated photomorphogenesis: From protein dynamics to physiology Julia Rausenberger Zentrum für Biosystemanalyse.

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Presentation on theme: "An integrative and quantitative model for phyB mediated photomorphogenesis: From protein dynamics to physiology Julia Rausenberger Zentrum für Biosystemanalyse."— Presentation transcript:

1 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

2 Adapted from Quail (2002) red light Aspects of photomorphogenesis Skotomorphogenesis vs. Photomorphogenesis Alternative developmental programs during early plant growth: light-dependent de-etiolation 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 What makes the phytochrome system interesting for theoreticians? 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 Pr Pfr = 0.03 k 1, 730 nm k 2, 730 nm FR Pr = 0.85 k 1, 660 nm k 2, 660 nm Pfr R at equilibrium: d[P fr ]/dt = 0 = k 1 [P r ] - k 2 [P fr ] [P fr ]/[P tot ] = = k 1 / (k 1 + k 2 ) Pr Pfr k 1 k 2

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

5 Investigations of growth patterns 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 γ determines the asymmetry of L and dL/dt Biological time Growth rate Environmental limitation 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

6 How does active phytochrome come into play? darknesscontinuous red light End-point-analysis (after 4 days) Scale bar = 10μm Biological time Modified growth rate Environmental limitation


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