The general working topic of the group is the biogenesis of the thylakoid membrane, in particular the transport of proteins across this membrane. To date, four different transport pathways have been described at the thylakoid membrane which are addressed as Sec-dependent, Delta-pH-dependent, SRP-dependent und spontaneous protein transport. Each pathway operates with a distinct mechanism and is specific for a subset of thylakoid proteins.
Methodology:The characterization of the transport mechanism generally involves in vitro synthesized precursor proteins and isolated chloroplasts or thylakoid membranes. Cloning of components of the thylakoidal transport machinery as well as the isolation of mutants of Arabidopsis thaliana and Synechocystis PCC6803 which are affected in their transport machineries are additional points of emphasis.
The final goal is to understand the phylogeny of the thylakoidal transport pathways, i.e., how, why and from which origin such a variety of protein transport pathways was developed. The chloroplast representing a former prokaryote in an eukaryotic cell environment seems to provide an almost ideal system for this type of analysis.
In addition to this main topic, the following projects are pursued:
1. Modulation of photosynthetic electron transport by ions (Dr. Metzger)
The influence of different ions (particularly Ca2+) and their involvement in the structure and function of photosystem II
(e.g., water-splitting, regulation of electron transport, membrane structure) is analyzed with various biochemical and biophysical
methods.
2. Strategies of adaptation of unicellular green algae to various light conditions (Dr. Tschiersch)
The regulation of light harvesting and photosystem II activity is analyzed in the model organisms Euglena gracilis and Chlamydomonas
reinhardtii using a combination of fluorescence analyses and biochemical methods.
3. Analysis of zoo- and phytoplankton in arctic ponds (Dr. Zellmer)
We examine zoo- and phytoplankton of temporary arctic ponds with special emphasis on its mutual interaction and changes due to UV-radiation and variation of biotic and abiotic environmental factors.