Photosynthetic organisms are occasionally exposed to excess sunlight, which cannot be productively used and becomes detrimental. To counteract this, plants and algae activate regulatory mechanisms that dissipate the surplus absorbed energy. Such mechanisms, known as non-photochemical quenching (NPQ) of excess energy, prevent the formation of reactive oxygen species (ROS), such as singlet oxygen (1O2), which can damage or inhibit critical components of the photosynthetic apparatus. Since O2 is produced in the chloroplast as a byproduct of photosynthesis, the balance between light-harvesting and protective response to excess light is crucial to maximise the productivity of plants and algae.

NPQ involves multiple mechanisms functioning across different time scales, all of which work together to reduce the risk of photoinhibition. Our research team employs genome-editing techniques in model plant and algal species, and collaborates with experts in physical chemistry and ultrafast spectroscopy to investigate how NPQ responses are mediated by pigment-binding antenna proteins. Our recent work has revealed two distinct mechanisms for dissipating excess light, one originating from the monomeric antenna complexes and another from the trimeric complexes – both involving chlorophyll and carotenoid molecules which catalyze the photoprotective reactions within the Photosystem II.
In particular, the high-light-induced carotenoid zeaxanthin plays a critical role by binding to specific antenna complexes. This modulates the formation of potentially harmful chlorophyll excited states in vivo, thereby preventing ROS production. Overall, our ongoing work aims to deepen the understanding of the evolutionary conservation, structural features, and biophysical mechanisms underpinning NPQ responses.