BPS2026 – Computational insights into the molecular basis of high-light adaptation in cyanobacteria and cyanophages within Photosystem II

In cyanobacteria, the Photosystem II (PSII) complex catalyzes the light-driven oxidation of water, converting light energy into chemical energy and initiating the photosynthetic electron transport chain. In Prochlorococcus , a well-defined phylogenetic hierarchy of ecotypes exists, including high-light (HL)-adapted and low-light (LL)-adapted strains. HL conditions are known to induce photodamage to the D1/D2 proteins of PSII, and HL-adapted strains may have evolved enhanced resistance to this damage. To understand the molecular basis of this adaptation, we employed bioinformatic analyses and structural predictions to investigate HL- and LL-adapted Prochlorococcus . Our study identified three co-evolving residues in the D2 protein, at positions I29, L39, and C39, which may enhance known photosynthetic pathways and facilitate more efficient electron transfer in PSII. Furthermore, D2–Y180 and D1–Y182 may act as auxiliary electron donors to chlorophyll a (Chl-a) in Synechococcus , enhancing photodamage resistance by improving the electron transfer process. This function may enhance electron transfer rates and reduce the accumulation of the oxidized state of Chl-a. This work is supported by the NW-BRaVE for Biopreparedness project funded by the US Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, under FWP 81832.