Integrative regulatory network of plant thylakoid energy transduction

•‘State transition’ cannot explain the behavior of PSII–LHCII phosphorylation.•PSI is sensitive to excess electrons from PSII.•LHCII phosphorylation prevents excess electrons from accumulating under low light.•PGR5-dependent regulation of linear electron transfer protects PSI under high light.

Highly flexible regulation of photosynthetic light reactions in plant chloroplasts is a prerequisite to provide sufficient energy flow to downstream metabolism and plant growth, to protect light reactions against photodamage, and to ensure controlled cellular signaling from the chloroplast to the nucleus. Such comprehensive regulation occurs via the control of excitation energy transfer to and between the two photosystems (PSII and PSI), of the electrochemical gradient across the thylakoid membrane (ΔpH), and of electron transfer from PSII to PSI electron acceptors. In this opinion article, we propose that these regulatory mechanisms, functioning at different levels of photosynthetic energy conversion, might be interconnected and describe how the concomitant and integrated function of these mechanisms might enable plants to acclimate to a full array of environmental changes.