Under excess light, photosynthetic organisms employ feedback mechanisms to avoid
photodamage. Photoprotection is triggered by acidification of the lumen of the
photosynthetic membrane following saturation of the metabolic activity. A low pH triggers
thermal dissipation of excess absorbed energy by the light-harvesting complexes (LHCs).
LHCs are not able to sense pH variations, and their switch to a dissipative mode depends on
stress-related proteins and allosteric cofactors. In green algae the trigger is the pigment …