Chloroplasts provide a number of essential processes for the plant cell, most prominently oxygenic photosynthesis. Thus, it is important that function and biogenesis of this organelle is closely coordinated with the developmental stage and metabolic requirements of the cell. As the structural platform of oxygenic photosynthesis, the thylakoid membrane is an essential component of the cellular architecture of the chloroplast and plays an important role in its function and development. Nonetheless, many aspects of thylakoid evolution, formation, maintenance and adaptation remain widely enigmatic. Aim of our project is the identification and characterization of regulatory as well as functional components of thylakoid formation and chloroplast biogenesis as well as the analysis of their evolutionary origin.
Our research is funded by:
ITN 'COSI'
ERA-PG 'CROPP'
DAAD
The Function of Vipp1 in Thylakoid Biogenesis:
Vipp1 is a protein that evolved in cyanobacteria in close correlation to the evolution of oxygenic photosynthesis. The protein is derived from the bacterial phage shock protein, PspA, with which it shares many common features, including the presence of distinct subdomains and the formation of a large homo-oligomeric complex. In addition, a Vipp1-specific C terminal domain not found in PspA provides new functionality for the Vipp1 protein. We are currently investigating the nature of the Vipp1 complex and the exact function of Vipp1 in the biogenesis of the thylakoid membrane.
Vesicle Transport in Chloroplasts of Vascular Plants:
While many of the constituents of thylakoid formation were developed in the ancestor of today’s cyanobacteria, chloroplasts have integrated new components into this process, some of which are derived from the eukaryotic host and were adapted to their new function in the chloroplast, i.e. a vesicle transport system of eukaryotic origin found in chloroplasts of land plants. Our project is foccused on the identification of proteins involved in this transport system and in the elucidation of its function.
Calcium/Calmodulin-regulated Processes in Chloroplasts and Mitochondria:
Calcium is one of the most important second messengers of eukaryotic cells. A number of external as well as internal stimuli result in a spatial and temporary increase in calcium concentration that is detected by a number of calcium-sensitive proteins, such as calmodulin. Calmodulin modulate a wide variety of cellular processes such as gene expression, phosphorylation cascades or ion transport resulting in a cellular response to the original stimulus. The whole cell is integrated into the calcium/calmodulin network and there is growing evidence that this includes both endosymbiotic organelles. In this context, we study processes in mitochondria and chloroplast that are regulated via Ca2+/Calmodulin, including the identification and characterization of calmodulins and calmodulin-targets involved in this regulation.
