The unicellular green alga Chlamydomonas reinhardtii is a popular model organism in the field of photosynthesis research. The absence of the proteins PGRL1 and/or PGR5, being conserved in eukaryotic photosynthetic organisms, results in a severe deregulation of photosynthetic electron transport. Still, the molecular role of PGRL1 and PGR5 is elusive until today.

In her work, Laura Mosebach characterized the physiological response of the PGRL1/PGR5 knockout mutants in C. reinhardtii to high light intensities with spectroscopical and proteinbiochemical methods. Furthermore, she investigated electron transfer processes in isolated thylakoid membranes.

In the knockout mutants, photosystem I was the primary target of photodamage. This observation confirms the absence of a regulatory feedback protecting photosystem I at the expense of photosystem II in the wildtype. Moreover, the amount of membrane-associated ferredoxin:NADP+ reductase (FNR) was diminished in thylakoids isolated from the knockout mutants. This finding establishes a new perspective on the multifaceted PGRL1/PGR5 knockout related phenotypes.

Future work will focus on the question if and how PGRL1 and PGR5 contribute to the recruitment of FNR to the thylakoid membrane – and if and how recruitment of FNR to the thylakoid membrane modulates photosynthetic electron transport.

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Laura Mosebach conducted this work at the Institute Biology and Biotechnology of Plants, Chair of Plant Biochemistry and Biotechnology in the working group of Prof. Dr. Michael Hippler.