Novel energy transfer pathway between light-harvesting complexes and photosystem I core identified through structural studies ($)

Plants must regulate the harvesting of light to maintain proper energy fluxes though photosystem I (PSI) and photosystem II (PSII). Under optimal conditions, the light-harvesting complex II (LHCII) is phosphorylated and forms a supercomplex with the PSI core and the light-harvesting complex I (LHCI). This phosphorylation is due to a kinase (STN7) that senses the redox status of the chloroplast. While there is some structural data of the interaction between PSI and PSII, it was unclear how the phosphorylation of the LHCII enhances its interaction with PSI. Pan and colleagues used single-particle cryo-electron microscopy (cryo-EM) on purified maize protein complexes to solve the PSI-LHCI-LHCII structure at a resolution of 3.3 Å. Specific subunits of PSI are important for relaying excitation to the PSI core thought chlorophyll molecules, revealing a novel pathway for energy transfer from LHCI and LCHII to the PSI core. (Summary by Julia Miller) Science 10.1126/science.aat1156