Thriving in sunlight: a structural biology approach to appraise the dynamics of Photosystem II interactome . – PHOTO_DYN

Photosystem II (PSII), a membrane embedded photosynthetic complex, is the unique catalyser of solar energy conversion into organic compounds. In the context of ever changing environmental conditions and to foresee biotechnological applications of photosynthetic organisms, it is compulsory to understand how these organisms adapt to variations in solar irradiances. This adaptation primarily relies on the interaction of the conserved PSII catalytic core with a plethora of interacting proteins - its interactome - to either optimize light harvesting or drive the disassemble/repair cycle of photo-damaged PSII. The structural association of PSII with its interactome is inevitably transient and therefore recalcitrant to classic approaches for structural determination. Therefore, PHOTO-DYN will combine leading-edge biophysical and integrative structural biology approaches, such as chemical crosslinking mass spectrometry (XL-MS) and cryo electron microscopy (cryo-EM), to first establish the PSII-interactome components in two evolutionarily and ecologically divergent model organisms for land plants (Arabidopsis thaliana, At) and marine phytoplankton (the diatom Phaeodactylum tricornutum, Pt) under reference conditions. Time-course experiments under variable light conditions will ultimately elucidate the dynamic modulation of components of the PSII interactome in response to environmental cues. Results will provide cutting-edge scientific knowledge, along with valuable directions for biotechnological improvement of light-use-efficiency in globally relevant crops to increase their productivity (thanks to data acquired in At) and to optimise CO2 sequestration and transformation in marine phytoplankton (thanks to data acquired in Pt).The technical and biological challenges set by PHOTO-DYN will be successfully accomplished by three partners, with a leading-edge expertise and instrumentation in proteomics, photosynthesis/photophysiology and structural biology.