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

Yuval Milrad, Valéria Nagy, Tamar Elman, Maria Fadeeva, Szilvia Z. Tóth, Iftach Yacoby*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Photosynthetic hydrogen production from microalgae is considered to have potential as a renewable energy source. Yet, the process has two main limitations holding it back from scaling up; (i) electron loss to competing processes, mainly carbon fixation and (ii) sensitivity to O2 which diminishes the expression and the activity of the hydrogenase enzyme catalyzing H2 production. Here we report a third, hitherto unknown challenge: We found that under anoxia, a slow-down switch is activated in photosystem II (PSII), diminishing the maximal photosynthetic productivity by three-fold. Using purified PSII and applying in vivo spectroscopic and mass spectrometric techniques on Chlamydomonas reinhardtii cultures, we show that this switch is activated under anoxia, within 10 s of illumination. Furthermore, we show that the recovery to the initial rate takes place following 15 min of dark anoxia, and propose a mechanism in which, modulation in electron transfer at the acceptor site of PSII diminishes its output. Such insights into the mechanism broaden our understanding of anoxic photosynthesis and its regulation in green algae and inspire new strategies to improve bio-energy yields.

Original languageEnglish
Article number514
JournalCommunications Biology
Issue number1
StatePublished - Dec 2023


FundersFunder number
Western Washington University
Magyar Tudományos AkadémiaLP2014/19
Israel Science Foundation941/22
Tel Aviv University
National Research, Development and Innovation OfficeFK 135633, K132600


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