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Laura Mosebach Universität Münster

Laura Mosebach's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at xxUniversity in the year 2016.

Title of awarded thesis

"Regulation of photosynthetic electron transfer via PGRL1 and PGR5 in Chlamydomonas reinhardtii"

The proteins PGRL1 and PGR5 are potentially involved in the recruitment of Ferredoxin:NADP+ Reductase (FNR) to the thylakoid membrane which is involved in the photosynthetic electron transport in the green alga.

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.


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.

The photosynthetic machinery. Linear electron flow (LEF), cyclic electron flow (CEF) and the roles of the transmembrane electrochemical proton gradient. As electron transfer is coupled to proton translocation, LEF and CEF contribute to the formation of the proton gradient. LEF involves water splitting and NADPH production. The proton gradient fuels ATP synthesis, induces non-photochemical quenching (qE) and exerts photosynthetic control. LHC = light harvesting complex; PS = photosystem; Cyt b6f = cytochrome b6f complex; PC = plastocyanin; FDX = ferredoxin; FNR = FDX:NADP+ reductase; ATPase = CF1-F0-ATP-synthase; PGRL1 = PGR5-like photosynthetic phenotype 1; PGR5 = proton gradient regulation 5. Top left: Chlamydomonas reinhardtii Source of algal cell: Pflanzenforschung.de (http://www.pflanzenforschung.de/de/themen/pflanzen-im-fokus/chlamydomonas/) (adapted from Pflanzenforschung.de) Graph: Laura Mosebach