Dynamic feedback of the photosystem II reaction centre on photoprotection in plants (Nat Plants) $

The light reactions of photosynthesis are under constant regulation in order to continue operating efficiently and avoid photodamage in a fluctuating light environment.  One mechanism to avoid photodamage is the dissipation of excess excitation energy as heat, which can be determined by measuring non-photochemical quenching (NPQ) of chlorophyll fluorescence.  The various mechanisms responsible for NPQ are poorly understood, including the number of NPQ processes that operate in photosystem II (PSII), and differences in NPQ mechanisms for open or closed PSII reaction centres.  Here, Farooq et al used picosecond fluorescence analysis on spinach leaves to investigate NPQ processes for open and closed reaction centres.  They provide evidence for at least two quenching mechanisms, and show that one of these is only active when PSII reaction centres are closed, with subsequent rapid inactivation upon opening of reaction centres.  In addition, opening reaction centres provides an instant feedback to the antenna to reduce the rate of NPQ, improving photosynthetic efficiency.  The authors conclude by discussing the potential mechanisms responsible for these phenomena.  (Summary by Mike Page) Nat Plants 10.1038/s41477-018-0127-8