Considerable attention has been focused on how photosystem II (PSII) is assembled in vivo and how it is repaired following irreversible damage by visible light (so-called photoinhibition). Nixon et al. (pp. 1–16) summarize recent results on the assembly and repair of PSII in cyanobacteria, which are excellent model organisms to study higher plant photosynthesis. A model is proposed in Synechocystis in which the damaged D1 sub-unit is removed by a hetero-oligomeric complex, and it is postulated that a similar mechanism of D1 degradation also operates in chloroplasts.
