Far-Red Light Photoacclimation Rewires Antenna-Photosystem Organization in Cyanobacterial Cells

Abstract

Thylakoid membrane remodeling regulates photosynthetic activity in response to changing light, but it is unknown whether such membrane-scale control exists in cyanobacteria, which lack the spatially segregated membrane domains of green algae and plants. Using cryo-electron tomography guided by single-cell hyperspectral correlative imaging, we link spectral acclimation state to thylakoid architecture in far-red light adapting cyanobacteria. We determine the native structures of phycobilisome-photosystem II supercomplexes at subnanometer resolution and show that light-dependent molecular changes propagate across scales to restructure the photosynthetic machinery throughout the thylakoids. We further reveal persistent membrane heterogeneity after prolonged far-red light acclimation and identify a low abundance phycobilisome-photosystem I supercomplex in far-red light conditions. Together, our results frame cyanobacterial thylakoids as plastic membranes that remodel antenna-photosystem structure and organization to regulate photosynthesis.