DBG · Promoting young researchers

Wilena Telman (Universität Bielefeld)

Wilena Telman's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Bielfeld University in the year 2016.

Title of awarded thesis

"Function of the 2-cystein peroxiredoxin and cyclophilin 20-3 within the redox-regulatory network in A. thaliana"

The obtained results gave evidence that the chloroplastidic 2-CysPrx-Cyp20-3 module links the redox, protein and thiol homeostasis in the context of cellular stress adaptation.

To maintain the cellular redox homeostasis under fluctuating environmental conditions, plants have developed a highly complex and dynamic redox regulatory network. Among other detoxification mechanisms, such as the Asada-Halliwell cycle, 2-cysteine peroxiredoxin (2-CysPrx) and cyclophilin 20-3 (Cyp20-3) as thiol-based en-zymes play a special role in the regulation of the cellular redox status in chloro-plasts. Depending on its redox state and conformation, the 2-CysPrx is involved in the peroxide detoxification, modulation of the redox state of interaction partners and can act as a chaperone. The stromal Cyp20-3 is involved in protein folding processes and, after binding the jasmonic acid precursor oxophytodienoic acid (OPDA), can stimulate the cysteine synthesis to increase the cellular redox potential. According to a hypothetical model these two enzymes link the redox regulation and homeostasis with the oxylipin signaling as well as the cysteine synthesis.

In this work, the postulated model was extended by using different in vitro approaches to analyze specific interactions with stromal interaction partners. Experiments with recombinant 2-CysPrx indicated a partial thylakoid association under reducing conditions. To identify other potential 2-CysPrx interaction partners, stromal protein was crosslinked to covalently fix weak interactions. Furthermore, it was possible to characterize different stromal factors, which have an inhibitory effect on the 2-CysPrx decamer dissociation.

To assess the effect of oxidative stress on protein homeostasis, A. thaliana knockout lines of Δ2-CysPrx and ΔCyp20-3 were exposed to high light and heat stress. Analysis of proteincarbonylation pattern and content gave indications on deregulation in proteindegradation by oxidative post-translational modification. Further leaf disc experiments with Δ2-CysPrx and ΔCyp20-3 mutants showed a strong decrease in photosynthetic efficiency after sulfite and sulfide incubation. These results allow con-clusions about the involvement of both proteins acting as a module in the sulfur assimilation pathway and thus maintaining the thiol homeostasis under oxidative stress conditions.

___

Wilena Telman conducted this work at the Chair of Plant Biochemistry and Physiology, Bielefeld Univerity in the working group of Prof. Dr. Karl-Josef Dietz.