Plant cells assemble large protein–pigment supercomplexes, comprising photosystem I (PSI) or PSII core complexes and accessory light-harvesting complexes (LHCI or LHCII), to convert solar energy into chemical compounds. Although the composition and function of these supercomplexes are largely understood, the mechanisms that govern their assembly remain understudied. In a recent study published in Nature Plants, Zhang et al. investigated the assembly of PSI–LHCI supercomplexes in land plants, leading to the discovery of a novel assembly factor.

Using in vivo [35S]Met pulse-chase experiments, the authors traced the stepwise assembly of PSI–LHCI complexes, noting a reduced number of assembly intermediates in pbf8 mutants. Although these mutants were able to assemble low levels of PSI–LHCI complexes, the process was notably slower and less efficient compared with wild-type cells.