Ioannis Dikaios

Molecular analysis of key-factors for light use efficiency in plant and algae.

Photosynthesis is driven by the energy absorbed by the green pigment chlorophyll.  Chlorophyll performs this task efficiently because upon absorption it builds long lasting excited states that store the energy until it can be used by reaction centers for photosynthesis. However, this property can be a weak point in the present-day, oxygen-rich atmosphere because a type of excited states - called triplets - reacts with oxygen and produce ROS (Reactive Oxygen Species) which are poisonous for the cell. Of course, triplet level should be kept very low and this is performed by the action of special proteins called PSBS and LHCSR, respectively in plants and algae. What these proteins do is transform the energy of the triplet states into heat thus making them safe. The productivity of plant and algae depends on the capacity of preventing damage without slowing photosynthesis too much. LHCSR and PSBS accomplish this by detecting the presence of excess energy from the acidification of the chloroplast (lumen) and activating energy dissipation. This makes chloroplasts less acidic and inactivates the proteins allowing for optimal photosynthetic yield. In general, organisms privilege survival vs. growth: Algae do that very well, thus dissipating more energy than needed. Engineering LHCSR and PSBS would allow tuning energy dissipation and maximizing productivity. This is what we want to do in our research: Identify the key component of the molecular switch between photosynthesis and heat dissipation in order to understand how it works and modify it for the best.