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