Presentation on theme: "Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg"— Presentation transcript:
1 Julia Rausenberger Zentrum für Biosystemanalyse Universität Freiburg An integrative and quantitative model for phyB mediated photomorphogenesis: From protein dynamics to physiologyJulia RausenbergerZentrum für BiosystemanalyseUniversität FreiburgGRK Begutachtung18. Februar 2010
2 Aspects of photomorphogenesis Adapted from Quail (2002)red lightSkotomorphogenesis vs. PhotomorphogenesisAlternative developmental programs during early plant growth: light-dependent de-etiolationPhytochrome B:Dimeric protein about 125kDaAbundant in red light (660nm)Two reversibly photointerconverting formsNuclear complexesearly, transientlate, stableMediated reactions:Growth of hypocotyl lengthMagnitude of cotyledon areasTaken from Bae & Choi (2008)
3 What makes the phytochrome system interesting for theoreticians? Pr = 0.85k1, 660 nmk2, 660 nmPfrRPrPfr = 0.03k1, 730 nmk2, 730 nmFRat equilibrium:d[Pfr]/dt = 0 = k1[Pr] - k2[Pfr][Pfr]/[Ptot] = = k1 / (k1 + k2)PrPfrk1k2Adjustable parameters:spectral composition of incident lightlight intensity (photon flux)duration of irradiationprotein dynamics can be changed by switching on/off the light
4 Time resolved hypocotyl growth DarknessContinuous red lightphyB-9Col WTphyB-OXHypocotyl growth is a standard read-out for phytochrome signaling.When grown in darkness, the three phenotypes show the same S-shaped growth profile.Light-grown seedlings also exhibit an S-shaped growth curve, but the final hypocotyl length vary due to the presence of active phytochrome.No active phytochrome presentHow does active phytochromeinfluence hypocotyl growth?
5 Investigations of growth patterns Hypocotyl dark growth is characterized by:Asymmetric S-shaped growth curve LAsymmetric bell-shape of velocity function dL/dt-> growth rate is not constant over timeJ. Sachs (1874): ”large period of growth”: growth velocity increase -> maximum -> growth velocity decreaseG. Backman (1931): Integration of the growth velocity yields S- shaped growth curve: “growth cycle” γ determines the asymmetry of L and dL/dtBiological timeGrowthrateEnvironmental limitation
6 How does active phytochrome come into play? End-point-analysis (after 4 days)darknesscontinuous red lightBiological timeModified growthrateEnvironmental limitationScale bar = 10μm