Dr. Jiri Jablonsky

Photorespiration, its regulation and interaction with other processes

"Cyanobacteria and C4 plants have almost negligible photorespiration in contrast to C3 plants - is there a reason from the evolutionary point?"

Photorespiration occurs in all oxygen-based photosynthetic organisms. This process recycles phosphoglycolate, toxic compound and result of Rubisco oxygenase activity, to phosphoglycerate. Photorespiration is a wasteful process in the edge between the stress protection and crop productivity.
The main question arises where is the balance between the stress protection and crop yield or if the photorespiration is essential process at all. The subquestion we are focused on is: How is the photorespiration regulated and integrated among other processes in the context of carbon metabolism within the range of phylogenetically different organisms (C3 and C4 plants and cyanobacteria)?
The photorespiration itself has been described in detail. If we understand its integration and regulation within the carbon metabolism, it will be possible to minimize the photorespiratory pathway, if it is possible for C3 plants in the field conditions, and to increase the crop production significantly.
The project is in its initial stage. We started with the basic scheme model of the Calvin-Benson cycle and starch synthesis and compared the outputs of our model with the simulations based on the earlier models of the dark photosynthetic reactions. This comparison proved serious errors in the earlier models. We described these errors and suggested corrections.
The next step is to develop a model of photosynthetic reactions for cyanobacteria. This model can be one-compartmental which allows accurate evaluation of the core model (Calvin-Benson cycle) and easier analysis of the photorespiration (in comparison to 4-compartments for higher plants) with the help of experimental data. We are going to use this model for testing of photorespiratory pathways suggested only for cyanobacteria and extend this model for higher plants.

Previous publications:

Lazar D. and J. Jablonsky. 2009. On the approaches applied in formulation of a kinetic model of photosystem II: Different approaches lead to different simulations of the chlorophyll a fluorescence transients. Journal of Theoretical Biology 257: 260-269

Jablonsky J., Susila P., and D. Lazar. 2008. Impact of dimeric organization of enzyme and its function: The case of photosynthetic water splitting. Bioinformatics 24: 2755-2759

Lazar D. and J. Jablonsky. 2008. Response to Kinetic Models of photosystem II should incorporate a role for Q_B-nonreducing reaction centers. Biophysical Journal 95: 3115-3116

Jablonsky J. and D. Lazar. 2008. Evidence for intermediate S-states as initial phase in the process of Oxygen Evolving Complex oxidation. Biophysical Journal 94: 2725-2736