Functional analysis of PsbS transmembrane domains through base editing in Physcomitrium patens

: Plants exposed to light fluctuations are protected from photodamage by non-photochemical quenching (NPQ), a reversible mechanism that enables dissipation of excess absorbed energy as heat, which is essential for plant fitness and crop productivity. In plants NPQ requires the presence of the membrane protein PsbS that, upon activation, interacts with antenna proteins, inducing their dissipative conformation. Here, we exploited base editing in the moss Physcomitrium patens to introduce in vivo specific amino acid changes and assess their impact on PsbS activity, targeting transmembrane regions to investigate their role in essential protein-protein interactions. This approach enabled the recognition of residues essential for protein stability and the identification of a hydrophobic cluster of amino acids impacting PsbS activity. This work provides new information on the PsbS molecular mechanism while also demonstrating the potential of base editing approaches for in planta gene function analysis.