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Ubiquitin ligase switch in plant photomorphogenesis: A hypothesis.

Pokhilko A, Ramos JA, Holtan H, Maszle DR, Khanna R, Millar AJ - J. Theor. Biol. (2010)

Bottom Line: This leads to accumulation of COP1's target transcription factors, which initiates photomorphogenesis, resulting in dramatic changes of the seedling's physiology.CUL4 activity is predicted to increase in the presence of light.We propose that the ubiquitin ligase switch is important for the complex regulation of multiple transcription factors during plants development.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JH, United Kingdom. apokhilk@staffmail.ed.ac.uk

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The simulated kinetics of the full model (Scheme 2) upon dark-to-light transition. A: The activities of COP1 and CUL4 ligases are shown by green and magenta lines, respectively. The kinetics of HFR1 and HY5 proteins and HY5 mRNA are shown by blue, black and red lines, respectively. Experimental data points—as in Fig. 3. B: The kinetics of different forms of COP1 (red) and CUL4 (blue): Active forms are shown by dotted lines, inactive forms—by dashed lines, free COP1—by dashed-dotted line, total content—by solid lines. The simulation was run starting from initial conditions, which correspond to the steady state of the system in darkness: cCOP1i=0; cCOP1a=0.737; cI=0; cP=1; cCOP1f=0.28; cCULi=0.911; cCULa=0.089; ; cHY5=0.266; cHFR1=0.1.
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f0020: The simulated kinetics of the full model (Scheme 2) upon dark-to-light transition. A: The activities of COP1 and CUL4 ligases are shown by green and magenta lines, respectively. The kinetics of HFR1 and HY5 proteins and HY5 mRNA are shown by blue, black and red lines, respectively. Experimental data points—as in Fig. 3. B: The kinetics of different forms of COP1 (red) and CUL4 (blue): Active forms are shown by dotted lines, inactive forms—by dashed lines, free COP1—by dashed-dotted line, total content—by solid lines. The simulation was run starting from initial conditions, which correspond to the steady state of the system in darkness: cCOP1i=0; cCOP1a=0.737; cI=0; cP=1; cCOP1f=0.28; cCULi=0.911; cCULa=0.089; ; cHY5=0.266; cHFR1=0.1.

Mentions: After fitting the model parameters (Table A2 of the Appendix), Scheme 2 closely matched experimental data during the transition of dark-grown seedlings to light. The description of the output module was improved compared to Scheme 1 through the better simulation of the experimentally observed immediate fall of HY5 mRNA after its initial rise (Fig. 4A). The model explained this fall by the restoration of COP1 activity, which potentially had negative impact on HY5 expression. Scheme 2 also described correctly the observed kinetics of HFR1 and HY5 proteins (Fig. 4A) through the mechanism, analogous to Scheme 1 (Fig. 3), which is based upon higher activity of COP1 towards HFR1 than HY5. In contrast with Scheme 1, Scheme 2 described the experimentally observed slow fall in the total COP1 content after the transition of plants to light (von Arnim et al., 1997). Fig. 4B shows the kinetics of the different forms of COP1 and CUL4 together with their total contents. Importantly, the sharp changes in the ligase activities after lights-on were related with their re-distribution between different forms, while the total ligase content changed more slowly. The substantial decline in the simulated COP1 content after 24 h of light corresponded to the experimental observation (von Arnim and Deng, 1994; von Arnim et al., 1997).


Ubiquitin ligase switch in plant photomorphogenesis: A hypothesis.

Pokhilko A, Ramos JA, Holtan H, Maszle DR, Khanna R, Millar AJ - J. Theor. Biol. (2010)

The simulated kinetics of the full model (Scheme 2) upon dark-to-light transition. A: The activities of COP1 and CUL4 ligases are shown by green and magenta lines, respectively. The kinetics of HFR1 and HY5 proteins and HY5 mRNA are shown by blue, black and red lines, respectively. Experimental data points—as in Fig. 3. B: The kinetics of different forms of COP1 (red) and CUL4 (blue): Active forms are shown by dotted lines, inactive forms—by dashed lines, free COP1—by dashed-dotted line, total content—by solid lines. The simulation was run starting from initial conditions, which correspond to the steady state of the system in darkness: cCOP1i=0; cCOP1a=0.737; cI=0; cP=1; cCOP1f=0.28; cCULi=0.911; cCULa=0.089; ; cHY5=0.266; cHFR1=0.1.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3021735&req=5

f0020: The simulated kinetics of the full model (Scheme 2) upon dark-to-light transition. A: The activities of COP1 and CUL4 ligases are shown by green and magenta lines, respectively. The kinetics of HFR1 and HY5 proteins and HY5 mRNA are shown by blue, black and red lines, respectively. Experimental data points—as in Fig. 3. B: The kinetics of different forms of COP1 (red) and CUL4 (blue): Active forms are shown by dotted lines, inactive forms—by dashed lines, free COP1—by dashed-dotted line, total content—by solid lines. The simulation was run starting from initial conditions, which correspond to the steady state of the system in darkness: cCOP1i=0; cCOP1a=0.737; cI=0; cP=1; cCOP1f=0.28; cCULi=0.911; cCULa=0.089; ; cHY5=0.266; cHFR1=0.1.
Mentions: After fitting the model parameters (Table A2 of the Appendix), Scheme 2 closely matched experimental data during the transition of dark-grown seedlings to light. The description of the output module was improved compared to Scheme 1 through the better simulation of the experimentally observed immediate fall of HY5 mRNA after its initial rise (Fig. 4A). The model explained this fall by the restoration of COP1 activity, which potentially had negative impact on HY5 expression. Scheme 2 also described correctly the observed kinetics of HFR1 and HY5 proteins (Fig. 4A) through the mechanism, analogous to Scheme 1 (Fig. 3), which is based upon higher activity of COP1 towards HFR1 than HY5. In contrast with Scheme 1, Scheme 2 described the experimentally observed slow fall in the total COP1 content after the transition of plants to light (von Arnim et al., 1997). Fig. 4B shows the kinetics of the different forms of COP1 and CUL4 together with their total contents. Importantly, the sharp changes in the ligase activities after lights-on were related with their re-distribution between different forms, while the total ligase content changed more slowly. The substantial decline in the simulated COP1 content after 24 h of light corresponded to the experimental observation (von Arnim and Deng, 1994; von Arnim et al., 1997).

Bottom Line: This leads to accumulation of COP1's target transcription factors, which initiates photomorphogenesis, resulting in dramatic changes of the seedling's physiology.CUL4 activity is predicted to increase in the presence of light.We propose that the ubiquitin ligase switch is important for the complex regulation of multiple transcription factors during plants development.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JH, United Kingdom. apokhilk@staffmail.ed.ac.uk

Show MeSH
Related in: MedlinePlus