Light provides the energy that fuels photosynthesis to fix inorganic carbon into sugars, polysaccharides and oils that are critical for the survival of man and to generate the oxygen that we breathe. Nevertheless, excess light can lead to the formation of harmful reactive oxygen species that result in cell death. For this, light absorption and utilization are precisely managed via the photoprotective mechanism qE (energy quenching) that converts the excess absorbed light energy to heat and returns it to the biosphere.

Most of the research efforts for the elucidation of signaling pathways controlling qE focus on the role of light, leaving out a key signaling molecule: CO2. In my talk I will present evidence that CO₂ has a pivotal role in light-signaling and will propose a new view on the regulation of excess light and low-CO₂ responses in the green microalgae Chlamydomonas reinhardtii.