Mechanisms of Photodamage and Protein Turnover in Photoinhibition.

Rapid protein degradation and replacement is an important response to photodamage and a means of photoprotection by recovering proteostasis. Protein turnover and translation efficiency studies have discovered fast turnover subunits in cytochrome b6f and the NAD(P)H dehydrogenase (NDH) complex, in addition to PSII subunit D1. Mutations of these complexes have been linked to enhanced photodamage at least partially via cyclic electron flow. Photodamage and photoprotection involving cytochrome b6f, NDH complex, cyclic electron flow, PSI, and nonphotochemical quenching proteins have been reported. Here, we propose that the rapid turnover of specific proteins in cytochrome b6f and the NDH complex need to be characterised and compared with the inhibition of PSII by excess excitation energy and PSI by excess electron flux to expand our understanding of photoinhibition mechanisms.