A novel PSII photosynthetic control is activated in anoxic cultures of green algae

Photosynthetic green algae face an ever-changing environment of fluctuating light as well as unstable oxygen levels, which via the production of free radicals constantly challenges the integrity of the photosynthetic complexes. To face such challenges, a complex photosynthetic control network monitors and tightly control the membrane redox potential. Here, we show that not only that the photosynthetic control set the rate limiting step of photosynthetic linear electron flow, but also, upon its ultimate dissipation, it triggers intrinsic alternations in the activity of the photosynthetic complexes. These changes have a grave and prolonged effect on the activity of photosystem II, leading to a massive 3-fold decrease in its electron output. We came into this conclusion via studying a variety of green algae species and applying advance mass-spectrometry and diverse spectroscopic techniques. Our results shed new light on the mechanism of photosynthetic regulation, and provide new target for improving photosynthesis.