In the photosynthetic process solar energy is con- verted to chemical energy. The energy-rich products of photosynthesis are utilised directly or indirectly by all vertebrates on this planet; the by-product of the light reaction, oxygen, is a vital constituent of the atmosphere and has enabled the diversity of life as we know it today. The world’s growing population consumes ever-increasing amounts of food and energy. Therefore, there are two key objectives in plant research: increasing biomass production and generating new sustainable energy sources. The foundation to address these important objectives is a detailed understanding of the process of photo- synthesis. Despite their fundamental importance, our knowledge of the molecular mechanisms involved
in the biogenesis and turnover of the photosynthetic complexes is still limited. I focus on the photosyn- thetic light reaction with the aim to optimize plant growth for enhanced food and biomass production.
Wolfgang Schroder 1150 766The chloroplast, an organelle with a complex architecture, consists of several distinct compartments that contain both nu- clear- and plastid-encoded proteins. Photosynthetic electron transport occurs in the thylakoid membrane, while CO2  xa- tion takes place in the stroma. In 1997 we started to develop a method for the isolation of a highly puri ed thylakoid lumen using spinach chloroplasts.We carried out the  rst systemat- ic characterisation of the lumen content and showed that it contained at least 25 proteins.These data changed the common understanding of the thylakoid lumen from being mainly proton storage for the generation of the proton motive force.We were able to show that the lumen instead plays an important role in the proper function of the photosynthetic complexes and the integrity of the thylakoid membrane.
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We characterised several of the novel lumen proteins. As the genome for the model organism Arabidopsis thaliana was getting available we continued our research on this organism and published the  rst 2D-gels of Arabidopsis in 2000 and the complete map was published (Schubert et al. 2002). Our analysis showed that the thylakoid lumen of Arabidopsis contains at least 46 unique proteins. These include 11 immunophilins, Deg (P1, P5 and P8) proteases, 3 pentapeptiderepeat proteins, 10 PsbP domain proteins, 2 PsbQ-domain proteins, extra copies of the Photo- system II extrinsic proteins PsbO, P and Q,TL29,VDE and  ve proteins with unknown function. It is thus clear that there is a very speci c group of proteins that are localized in the thylakoid lumen.The “empty” space contains proteins and thus is bound to have various enzymatic activities important for the photosynthetic process. A large program for antibody produc- tion, overexpression, crystalisation and anti-sense of these lumen proteins is now in progress.The published maps of the thylakoid lumen content are used for analysis of various stress factors such as temperature, light and nutrition. The protein changes are quanti ed with the EttanTM DIGE, and DeCyderTM image analysis platform, in combination with various MS techniques.
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