PhyscoQ · From algae to land plants: how antennae regulate NPQ in the moss Physcomitrium patens.

Photosynthesis powers life on Earth by capturing solar energy and converting it into chemical energy to fuel carbon fixation. However, when metabolic pathways cannot utilize all produced energy, sunlight becomes damaging. Light capture is performed by pigment-binding proteins known as Light-Harvesting Complexes (LHCs) which optimize absorption but also increase the risk of photodamage under high light conditions. To avoid this, photosynthetic organisms evolved non-photochemical quenching (NPQ), a protective mechanism that dissipates excess absorbed energy as heat.While NPQ is conserved across lineages, its molecular players differ substantially. In the green alga Chlamydomonas reinhardtii, NPQ depends on the stress-related protein LHCSR and a specific LHC subunit, LHCBM1. In contrast, land plants like Arabidopsis thaliana rely on the PSBS protein and the xanthophyll zeaxanthin, without requiring a specific LHC subunit, although quenching occurs in the LHC. These differences suggest that the role of antenna complexes in NPQ evolved during the transition from aquatic to terrestrial environments.This project investigates the contribution of LHCs to NPQ using the moss Physcomitrium patens, which is an excellent model organism because of its evolutionary position between green algae and land plants and its retention of both LHCSR- and PSBS-dependent NPQ mechanisms.Taking advantage of the unique characteristics of P. patens (short life cycle, dominant haploid phase and high efficiency of genomic editing), we will integrate genetic approaches with advanced spectroscopic techniques to investigate how LHC composition affects NPQ. Initially, changes in LHCBMs accumulation and NPQ activation will be assessed under different light conditions. Then, the most promising LHC subunits will be systematically removed in WT, PSBS- and LHCSR-deficient backgrounds, allowing us to dissect their individual roles and provide evolutionary insight into how NPQ mechanisms have diversified.